From 56770893a61b865084f4c855fc6cdb40197a955b Mon Sep 17 00:00:00 2001
From: Jang Jiseob <ragmani0216@gmail.com>
Date: Wed, 12 Feb 2025 16:38:16 +0900
Subject: [PATCH] [onert] Apply nested namespace in backend directory (#14643)

This commit applies nested namepsace in backend directory.

ONE-DCO-1.0-Signed-off-by: ragmani <ragmani0216@gmail.com>
---
 runtime/onert/backend/acl_cl/Backend.h        | 10 ++--------
 runtime/onert/backend/acl_cl/BackendContext.h | 10 ++--------
 runtime/onert/backend/acl_cl/CLTimer.h        | 10 ++--------
 runtime/onert/backend/acl_cl/Config.cc        | 10 ++--------
 runtime/onert/backend/acl_cl/Config.h         | 10 ++--------
 .../backend/acl_cl/ConstantInitializer.cc     | 10 ++--------
 .../backend/acl_cl/ConstantInitializer.h      | 10 ++--------
 .../onert/backend/acl_cl/KernelGenerator.cc   | 10 ++--------
 .../onert/backend/acl_cl/KernelGenerator.h    | 10 ++--------
 runtime/onert/backend/acl_cl/Optimizer.cc     | 10 ++--------
 runtime/onert/backend/acl_cl/Optimizer.h      | 10 ++--------
 runtime/onert/backend/acl_cl/TensorBuilder.h  | 10 ++--------
 runtime/onert/backend/acl_cl/TensorManager.h  | 10 ++--------
 .../backend/acl_cl/operand/CLSubTensor.cc     | 13 ++----------
 .../backend/acl_cl/operand/CLSubTensor.h      | 13 ++----------
 .../onert/backend/acl_cl/operand/CLTensor.cc  | 13 ++----------
 .../onert/backend/acl_cl/operand/CLTensor.h   | 13 ++----------
 .../onert/backend/acl_cl/operand/ICLTensor.cc | 13 ++----------
 .../onert/backend/acl_cl/operand/ICLTensor.h  | 13 ++----------
 .../backend/acl_common/AclActivationBuilder.h | 10 ++--------
 .../backend/acl_common/AclBackendContext.h    | 10 ++--------
 .../acl_common/AclConstantInitializer.cc      | 10 ++--------
 .../acl_common/AclConstantInitializer.h       | 10 ++--------
 .../onert/backend/acl_common/AclFunction.h    | 10 ++--------
 .../acl_common/AclInternalBufferManager.h     | 10 ++--------
 .../onert/backend/acl_common/AclKernelGen.h   | 10 ++--------
 .../acl_common/AclLinearMemoryManager.h       | 10 ++--------
 .../backend/acl_common/AclMemoryManager.h     | 10 ++--------
 .../backend/acl_common/AclSubTensorAnalyzer.h | 10 ++--------
 .../backend/acl_common/AclTensorBuilder.h     | 20 ++++---------------
 .../backend/acl_common/AclTensorManager.h     | 20 ++++---------------
 .../backend/acl_common/AclTensorRegistry.h    | 10 ++--------
 runtime/onert/backend/acl_common/Convert.cc   | 10 ++--------
 runtime/onert/backend/acl_common/Convert.h    | 10 ++--------
 .../onert/backend/acl_common/IACLTensor.cc    | 10 ++--------
 runtime/onert/backend/acl_common/IACLTensor.h | 10 ++--------
 runtime/onert/backend/acl_common/Swizzle.h    | 10 ++--------
 runtime/onert/backend/acl_neon/Backend.h      | 10 ++--------
 .../onert/backend/acl_neon/BackendContext.h   | 10 ++--------
 runtime/onert/backend/acl_neon/Config.cc      | 10 ++--------
 runtime/onert/backend/acl_neon/Config.h       | 10 ++--------
 .../backend/acl_neon/ConstantInitializer.cc   | 10 ++--------
 .../backend/acl_neon/ConstantInitializer.h    | 10 ++--------
 .../onert/backend/acl_neon/KernelGenerator.cc | 10 ++--------
 .../onert/backend/acl_neon/KernelGenerator.h  | 10 ++--------
 runtime/onert/backend/acl_neon/Optimizer.cc   | 10 ++--------
 runtime/onert/backend/acl_neon/Optimizer.h    | 10 ++--------
 .../onert/backend/acl_neon/TensorBuilder.h    | 10 ++--------
 .../onert/backend/acl_neon/TensorManager.h    | 10 ++--------
 .../backend/acl_neon/operand/INETensor.cc     | 13 ++----------
 .../backend/acl_neon/operand/INETensor.h      | 13 ++----------
 .../backend/acl_neon/operand/NESubTensor.cc   | 13 ++----------
 .../backend/acl_neon/operand/NESubTensor.h    | 13 ++----------
 .../backend/acl_neon/operand/NETensor.cc      | 13 ++----------
 .../onert/backend/acl_neon/operand/NETensor.h | 13 ++----------
 .../include/cl_common/BackendContext.h        | 10 ++--------
 .../cl_common/include/cl_common/LifetimeMap.h | 10 ++--------
 .../cl_common/include/cl_common/ParentInfo.h  | 10 ++--------
 .../backend/cl_common/src/LifetimeMap.cc      | 10 ++--------
 runtime/onert/backend/cpu/Backend.h           | 10 ++--------
 runtime/onert/backend/cpu/BackendContext.cc   | 10 ++--------
 runtime/onert/backend/cpu/BackendContext.h    | 10 ++--------
 runtime/onert/backend/cpu/Config.cc           | 10 ++--------
 runtime/onert/backend/cpu/Config.h            | 10 ++--------
 runtime/onert/backend/cpu/ExternalContext.cc  | 10 ++--------
 runtime/onert/backend/cpu/ExternalContext.h   | 10 ++--------
 runtime/onert/backend/cpu/KernelGenerator.cc  | 10 ++--------
 runtime/onert/backend/cpu/KernelGenerator.h   | 10 ++--------
 .../onert/backend/cpu/SharedMemoryOperands.cc | 10 ++--------
 .../onert/backend/cpu/SharedMemoryOperands.h  | 10 ++--------
 .../onert/backend/cpu/StaticTensorManager.h   | 10 ++--------
 runtime/onert/backend/cpu/Tensor.h            | 10 ++--------
 runtime/onert/backend/cpu/TensorBuilder.h     | 10 ++--------
 runtime/onert/backend/cpu/ops/AddNLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/AddNLayer.h     | 13 ++----------
 .../onert/backend/cpu/ops/ArgMinMaxLayer.cc   | 13 ++----------
 .../onert/backend/cpu/ops/ArgMinMaxLayer.h    | 13 ++----------
 .../onert/backend/cpu/ops/BatchMatMulLayer.cc | 13 ++----------
 .../onert/backend/cpu/ops/BatchMatMulLayer.h  | 20 ++++---------------
 .../backend/cpu/ops/BatchToSpaceNDLayer.cc    | 13 ++----------
 .../backend/cpu/ops/BatchToSpaceNDLayer.h     | 13 ++----------
 .../backend/cpu/ops/BinaryArithmeticLayer.cc  | 13 ++----------
 .../backend/cpu/ops/BinaryArithmeticLayer.h   | 13 ++----------
 .../onert/backend/cpu/ops/BroadcastToLayer.cc | 13 ++----------
 .../onert/backend/cpu/ops/BroadcastToLayer.h  | 13 ++----------
 runtime/onert/backend/cpu/ops/CompareLayer.cc | 13 ++----------
 runtime/onert/backend/cpu/ops/CompareLayer.h  | 13 ++----------
 runtime/onert/backend/cpu/ops/ConcatLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/ConcatLayer.h   | 13 ++----------
 .../onert/backend/cpu/ops/ConvolutionLayer.cc | 13 ++----------
 .../onert/backend/cpu/ops/ConvolutionLayer.h  | 20 ++++---------------
 .../backend/cpu/ops/DepthToSpaceLayer.cc      | 13 ++----------
 .../onert/backend/cpu/ops/DepthToSpaceLayer.h | 13 ++----------
 .../cpu/ops/DepthwiseConvolutionLayer.cc      | 13 ++----------
 .../cpu/ops/DepthwiseConvolutionLayer.h       | 13 ++----------
 .../cpu/ops/DetectionPostProcessLayer.cc      | 13 ++----------
 .../cpu/ops/DetectionPostProcessLayer.h       | 13 ++----------
 runtime/onert/backend/cpu/ops/EinsumLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/EinsumLayer.h   | 20 ++++---------------
 .../cpu/ops/ElementwiseActivationLayer.cc     | 13 ++----------
 .../cpu/ops/ElementwiseActivationLayer.h      | 13 ++----------
 .../backend/cpu/ops/ElementwiseBinaryLayer.cc | 13 ++----------
 .../backend/cpu/ops/ElementwiseBinaryLayer.h  | 13 ++----------
 .../backend/cpu/ops/ElementwiseUnaryLayer.cc  | 13 ++----------
 .../backend/cpu/ops/ElementwiseUnaryLayer.h   | 13 ++----------
 .../onert/backend/cpu/ops/ExpandDimsLayer.cc  | 13 ++----------
 .../onert/backend/cpu/ops/ExpandDimsLayer.h   | 13 ++----------
 runtime/onert/backend/cpu/ops/FillLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/FillLayer.h     | 13 ++----------
 .../backend/cpu/ops/FullyConnectedLayer.cc    | 13 ++----------
 .../backend/cpu/ops/FullyConnectedLayer.h     | 20 ++++---------------
 .../backend/cpu/ops/FusedBatchNormLayer.cc    | 13 ++----------
 .../backend/cpu/ops/FusedBatchNormLayer.h     | 20 ++++---------------
 runtime/onert/backend/cpu/ops/GGMLHelper.cc   | 13 ++----------
 runtime/onert/backend/cpu/ops/GGMLHelper.h    | 13 ++----------
 runtime/onert/backend/cpu/ops/GatherLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/GatherLayer.h   | 13 ++----------
 runtime/onert/backend/cpu/ops/L2NormLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/L2NormLayer.h   | 13 ++----------
 runtime/onert/backend/cpu/ops/LSTMLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/LSTMLayer.h     | 20 ++++---------------
 .../onert/backend/cpu/ops/LogSoftMaxLayer.cc  | 13 ++----------
 .../onert/backend/cpu/ops/LogSoftMaxLayer.h   | 13 ++----------
 .../backend/cpu/ops/MatrixBandPartLayer.cc    | 13 ++----------
 .../backend/cpu/ops/MatrixBandPartLayer.h     | 13 ++----------
 runtime/onert/backend/cpu/ops/MeanLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/MeanLayer.h     | 13 ++----------
 runtime/onert/backend/cpu/ops/OneHotLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/OneHotLayer.h   | 13 ++----------
 .../onert/backend/cpu/ops/OperationUtils.cc   | 13 ++----------
 .../onert/backend/cpu/ops/OperationUtils.h    | 13 ++----------
 runtime/onert/backend/cpu/ops/PackLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/PackLayer.h     | 13 ++----------
 runtime/onert/backend/cpu/ops/PadLayer.cc     | 13 ++----------
 runtime/onert/backend/cpu/ops/PadLayer.h      | 13 ++----------
 runtime/onert/backend/cpu/ops/PoolLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/PoolLayer.h     | 13 ++----------
 runtime/onert/backend/cpu/ops/PowLayer.cc     | 13 ++----------
 runtime/onert/backend/cpu/ops/PowLayer.h      | 13 ++----------
 .../onert/backend/cpu/ops/QuantizeLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/QuantizeLayer.h | 13 ++----------
 runtime/onert/backend/cpu/ops/RangeLayer.cc   | 13 ++----------
 runtime/onert/backend/cpu/ops/RangeLayer.h    | 13 ++----------
 runtime/onert/backend/cpu/ops/RankLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/RankLayer.h     | 13 ++----------
 runtime/onert/backend/cpu/ops/ReduceLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/ReduceLayer.h   | 20 ++++---------------
 runtime/onert/backend/cpu/ops/ReshapeLayer.cc | 13 ++----------
 runtime/onert/backend/cpu/ops/ReshapeLayer.h  | 13 ++----------
 .../backend/cpu/ops/ResizeBilinearLayer.cc    | 13 ++----------
 .../backend/cpu/ops/ResizeBilinearLayer.h     | 13 ++----------
 runtime/onert/backend/cpu/ops/ReverseLayer.cc | 13 ++----------
 runtime/onert/backend/cpu/ops/ReverseLayer.h  | 13 ++----------
 runtime/onert/backend/cpu/ops/RmsNormLayer.cc | 13 ++----------
 runtime/onert/backend/cpu/ops/RmsNormLayer.h  | 13 ++----------
 runtime/onert/backend/cpu/ops/RoPELayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/RoPELayer.h     | 13 ++----------
 runtime/onert/backend/cpu/ops/SelectLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/SelectLayer.h   | 13 ++----------
 runtime/onert/backend/cpu/ops/ShapeLayer.cc   | 13 ++----------
 runtime/onert/backend/cpu/ops/ShapeLayer.h    | 13 ++----------
 runtime/onert/backend/cpu/ops/SliceLayer.cc   | 13 ++----------
 runtime/onert/backend/cpu/ops/SliceLayer.h    | 13 ++----------
 runtime/onert/backend/cpu/ops/SoftMaxLayer.cc | 13 ++----------
 runtime/onert/backend/cpu/ops/SoftMaxLayer.h  | 13 ++----------
 .../backend/cpu/ops/SpaceToBatchNDLayer.cc    | 13 ++----------
 .../backend/cpu/ops/SpaceToBatchNDLayer.h     | 13 ++----------
 .../backend/cpu/ops/SpaceToDepthLayer.cc      | 13 ++----------
 .../onert/backend/cpu/ops/SpaceToDepthLayer.h | 13 ++----------
 runtime/onert/backend/cpu/ops/SplitLayer.cc   | 13 ++----------
 runtime/onert/backend/cpu/ops/SplitLayer.h    | 13 ++----------
 runtime/onert/backend/cpu/ops/SplitVLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/SplitVLayer.h   | 13 ++----------
 .../onert/backend/cpu/ops/SquaredDiffLayer.cc | 13 ++----------
 .../onert/backend/cpu/ops/SquaredDiffLayer.h  | 13 ++----------
 .../cpu/ops/StatelessRandomUniformLayer.cc    | 13 ++----------
 .../cpu/ops/StatelessRandomUniformLayer.h     | 13 ++----------
 .../backend/cpu/ops/StridedSliceLayer.cc      | 13 ++----------
 .../onert/backend/cpu/ops/StridedSliceLayer.h | 13 ++----------
 runtime/onert/backend/cpu/ops/TileLayer.cc    | 13 ++----------
 runtime/onert/backend/cpu/ops/TileLayer.h     | 13 ++----------
 .../onert/backend/cpu/ops/TransposeLayer.cc   | 13 ++----------
 .../onert/backend/cpu/ops/TransposeLayer.h    | 13 ++----------
 runtime/onert/backend/cpu/ops/UnpackLayer.cc  | 13 ++----------
 runtime/onert/backend/cpu/ops/UnpackLayer.h   | 13 ++----------
 runtime/onert/backend/ruy/Backend.h           | 10 ++--------
 runtime/onert/backend/ruy/BackendContext.cc   | 10 ++--------
 runtime/onert/backend/ruy/BackendContext.h    | 10 ++--------
 runtime/onert/backend/ruy/Config.cc           | 10 ++--------
 runtime/onert/backend/ruy/Config.h            | 10 ++--------
 runtime/onert/backend/ruy/ExternalContext.h   | 10 ++--------
 runtime/onert/backend/ruy/KernelGenerator.cc  | 10 ++--------
 runtime/onert/backend/ruy/KernelGenerator.h   | 10 ++--------
 .../onert/backend/ruy/StaticTensorManager.h   | 10 ++--------
 runtime/onert/backend/ruy/Tensor.h            | 10 ++--------
 runtime/onert/backend/ruy/TensorBuilder.h     | 10 ++--------
 .../onert/backend/ruy/ops/ConvolutionLayer.cc | 13 ++----------
 .../onert/backend/ruy/ops/ConvolutionLayer.h  | 13 ++----------
 .../backend/ruy/ops/FullyConnectedLayer.cc    | 13 ++----------
 .../backend/ruy/ops/FullyConnectedLayer.h     | 13 ++----------
 .../onert/backend/ruy/ops/OperationUtils.cc   | 13 ++----------
 .../onert/backend/ruy/ops/OperationUtils.h    | 13 ++----------
 runtime/onert/backend/train/Backend.h         | 10 ++--------
 runtime/onert/backend/train/BackendContext.cc | 10 ++--------
 runtime/onert/backend/train/BackendContext.h  | 10 ++--------
 runtime/onert/backend/train/Config.cc         | 10 ++--------
 runtime/onert/backend/train/Config.h          | 10 ++--------
 .../backend/train/DisposableTensorIndex.h     | 10 ++--------
 runtime/onert/backend/train/ExternalContext.h | 10 ++--------
 .../onert/backend/train/KernelGenerator.cc    | 10 ++--------
 runtime/onert/backend/train/KernelGenerator.h | 10 ++--------
 .../backend/train/LayerScopeTensorIndex.h     | 10 ++--------
 runtime/onert/backend/train/MemoryManager.cc  | 10 ++--------
 runtime/onert/backend/train/MemoryManager.h   | 10 ++--------
 runtime/onert/backend/train/MemoryPlanner.cc  | 10 ++--------
 runtime/onert/backend/train/MemoryPlanner.h   | 10 ++--------
 .../backend/train/MemoryPlannerFactory.cc     | 10 ++--------
 .../backend/train/MemoryPlannerFactory.h      | 10 ++--------
 runtime/onert/backend/train/Tensor.h          | 10 ++--------
 runtime/onert/backend/train/TensorBuilder.cc  | 10 ++--------
 runtime/onert/backend/train/TensorBuilder.h   | 10 ++--------
 runtime/onert/backend/train/TensorManager.cc  | 10 ++--------
 runtime/onert/backend/train/TensorManager.h   | 10 ++--------
 runtime/onert/backend/train/TensorPlanner.cc  | 10 ++--------
 runtime/onert/backend/train/TensorPlanner.h   | 10 ++--------
 runtime/onert/backend/train/TensorRegistry.h  | 10 ++--------
 .../backend/train/ops/BackPropAccumulator.cc  | 13 ++----------
 .../backend/train/ops/BackPropAccumulator.h   | 13 ++----------
 .../backend/train/ops/BackPropInitializer.cc  | 13 ++----------
 .../backend/train/ops/BackPropInitializer.h   | 13 ++----------
 .../train/ops/BinaryArithmeticLayer.cc        | 13 ++----------
 .../backend/train/ops/BinaryArithmeticLayer.h | 13 ++----------
 .../backend/train/ops/ConvolutionLayer.cc     | 13 ++----------
 .../backend/train/ops/ConvolutionLayer.h      | 13 ++----------
 .../train/ops/DepthwiseConvolutionLayer.cc    | 13 ++----------
 .../train/ops/DepthwiseConvolutionLayer.h     | 13 ++----------
 .../train/ops/ElementwiseActivationLayer.cc   | 13 ++----------
 .../train/ops/ElementwiseActivationLayer.h    | 13 ++----------
 .../backend/train/ops/FullyConnectedLayer.cc  | 13 ++----------
 .../backend/train/ops/FullyConnectedLayer.h   | 13 ++----------
 .../backend/train/ops/GradientApplier.cc      | 13 ++----------
 .../onert/backend/train/ops/GradientApplier.h | 13 ++----------
 .../ops/LossCategoricalCrossentropyLayer.cc   | 13 ++----------
 .../ops/LossCategoricalCrossentropyLayer.h    | 13 ++----------
 runtime/onert/backend/train/ops/LossLayer.cc  | 13 ++----------
 runtime/onert/backend/train/ops/LossLayer.h   | 13 ++----------
 .../train/ops/LossMeanSquaredErrorLayer.cc    | 13 ++----------
 .../train/ops/LossMeanSquaredErrorLayer.h     | 13 ++----------
 runtime/onert/backend/train/ops/MeanLayer.cc  | 13 ++----------
 runtime/onert/backend/train/ops/MeanLayer.h   | 13 ++----------
 .../onert/backend/train/ops/OperationUtils.cc | 13 ++----------
 .../onert/backend/train/ops/OperationUtils.h  | 13 ++----------
 runtime/onert/backend/train/ops/PadLayer.cc   | 13 ++----------
 runtime/onert/backend/train/ops/PadLayer.h    | 13 ++----------
 runtime/onert/backend/train/ops/PoolLayer.cc  | 13 ++----------
 runtime/onert/backend/train/ops/PoolLayer.h   | 13 ++----------
 .../onert/backend/train/ops/ReshapeLayer.cc   | 13 ++----------
 .../onert/backend/train/ops/ReshapeLayer.h    | 13 ++----------
 .../onert/backend/train/ops/SoftMaxLayer.cc   | 13 ++----------
 .../onert/backend/train/ops/SoftMaxLayer.h    | 13 ++----------
 runtime/onert/backend/train/optimizer/Adam.cc | 13 ++----------
 runtime/onert/backend/train/optimizer/Adam.h  | 13 ++----------
 .../backend/train/optimizer/Optimizers.h      | 10 ++--------
 runtime/onert/backend/train/optimizer/SGD.cc  | 13 ++----------
 runtime/onert/backend/train/optimizer/SGD.h   | 13 ++----------
 runtime/onert/backend/trix/Backend.h          | 10 ++--------
 runtime/onert/backend/trix/BackendContext.cc  | 10 ++--------
 runtime/onert/backend/trix/BackendContext.h   | 10 ++--------
 runtime/onert/backend/trix/BatchThreadPool.cc | 10 ++--------
 runtime/onert/backend/trix/BatchThreadPool.h  | 10 ++--------
 runtime/onert/backend/trix/Config.cc          | 10 ++--------
 runtime/onert/backend/trix/Config.h           | 10 ++--------
 runtime/onert/backend/trix/Convert.cc         | 10 ++--------
 runtime/onert/backend/trix/Convert.h          | 10 ++--------
 runtime/onert/backend/trix/DevContext.cc      | 10 ++--------
 runtime/onert/backend/trix/DevContext.h       | 10 ++--------
 runtime/onert/backend/trix/KernelGenerator.cc | 10 ++--------
 runtime/onert/backend/trix/KernelGenerator.h  | 10 ++--------
 runtime/onert/backend/trix/Tensor.h           | 10 ++--------
 runtime/onert/backend/trix/TensorBuilder.h    | 10 ++--------
 runtime/onert/backend/trix/ops/BulkLayer.cc   | 13 ++----------
 runtime/onert/backend/trix/ops/BulkLayer.h    | 13 ++----------
 runtime/onert/backend/xnnpack/Backend.h       | 10 ++--------
 .../onert/backend/xnnpack/BackendContext.cc   | 10 ++--------
 .../onert/backend/xnnpack/BackendContext.h    | 10 ++--------
 runtime/onert/backend/xnnpack/Config.cc       | 10 ++--------
 runtime/onert/backend/xnnpack/Config.h        | 10 ++--------
 .../onert/backend/xnnpack/ExternalContext.cc  | 10 ++--------
 .../onert/backend/xnnpack/ExternalContext.h   | 10 ++--------
 .../onert/backend/xnnpack/KernelGenerator.cc  | 10 ++--------
 .../onert/backend/xnnpack/KernelGenerator.h   | 10 ++--------
 .../backend/xnnpack/StaticTensorManager.h     | 10 ++--------
 runtime/onert/backend/xnnpack/Tensor.h        | 10 ++--------
 runtime/onert/backend/xnnpack/TensorBuilder.h | 10 ++--------
 .../backend/xnnpack/ops/ConvolutionLayer.cc   | 13 ++----------
 .../backend/xnnpack/ops/ConvolutionLayer.h    | 13 ++----------
 .../xnnpack/ops/DepthwiseConvolutionLayer.cc  | 13 ++----------
 .../xnnpack/ops/DepthwiseConvolutionLayer.h   | 13 ++----------
 .../xnnpack/ops/FullyConnectedLayer.cc        | 13 ++----------
 .../backend/xnnpack/ops/FullyConnectedLayer.h | 13 ++----------
 runtime/onert/backend/xnnpack/ops/Layer.h     | 13 ++----------
 .../backend/xnnpack/ops/OperationUtils.h      | 13 ++----------
 302 files changed, 622 insertions(+), 3001 deletions(-)

diff --git a/runtime/onert/backend/acl_cl/Backend.h b/runtime/onert/backend/acl_cl/Backend.h
index 301ded01f64..14b1a36a7e4 100644
--- a/runtime/onert/backend/acl_cl/Backend.h
+++ b/runtime/onert/backend/acl_cl/Backend.h
@@ -28,11 +28,7 @@
 #include "Optimizer.h"
 #include "AclTensorRegistry.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 class Backend : public ::onert::backend::Backend
@@ -64,8 +60,6 @@ class Backend : public ::onert::backend::Backend
   std::shared_ptr<IConfig> _config;
 };
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_BACKEND_H__
diff --git a/runtime/onert/backend/acl_cl/BackendContext.h b/runtime/onert/backend/acl_cl/BackendContext.h
index 5da9158250e..40d074a0cff 100644
--- a/runtime/onert/backend/acl_cl/BackendContext.h
+++ b/runtime/onert/backend/acl_cl/BackendContext.h
@@ -23,11 +23,7 @@
 #include "KernelGenerator.h"
 #include "TensorBuilder.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 class Optimizer;
@@ -35,8 +31,6 @@ class Optimizer;
 using BackendContext =
   acl_common::AclBackendContext<TensorBuilder, ConstantInitializer, KernelGenerator, Optimizer>;
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/acl_cl/CLTimer.h b/runtime/onert/backend/acl_cl/CLTimer.h
index a9158e1af5f..0bb73b14818 100644
--- a/runtime/onert/backend/acl_cl/CLTimer.h
+++ b/runtime/onert/backend/acl_cl/CLTimer.h
@@ -24,11 +24,7 @@
 #include <list>
 #include <sstream>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 /**
@@ -101,8 +97,6 @@ class CLTimer : public util::ITimer
   std::list<::cl::Event> _measured_events;
 };
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_CLTIMER_H__
diff --git a/runtime/onert/backend/acl_cl/Config.cc b/runtime/onert/backend/acl_cl/Config.cc
index 52196f35db6..9a2ff462c68 100644
--- a/runtime/onert/backend/acl_cl/Config.cc
+++ b/runtime/onert/backend/acl_cl/Config.cc
@@ -25,11 +25,7 @@
 
 #include "Config.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 bool Config::initialize()
@@ -47,6 +43,4 @@ bool Config::initialize()
   return true;
 }
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
diff --git a/runtime/onert/backend/acl_cl/Config.h b/runtime/onert/backend/acl_cl/Config.h
index 9e77fce63b7..1d4ba722e4a 100644
--- a/runtime/onert/backend/acl_cl/Config.h
+++ b/runtime/onert/backend/acl_cl/Config.h
@@ -22,11 +22,7 @@
 #include <backend/IConfig.h>
 #include <arm_compute/runtime/CL/CLScheduler.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 class Config : public IConfig
@@ -42,8 +38,6 @@ class Config : public IConfig
   std::unique_ptr<util::ITimer> timer() override { return std::make_unique<CLTimer>(); }
 };
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_CONFIG_H__
diff --git a/runtime/onert/backend/acl_cl/ConstantInitializer.cc b/runtime/onert/backend/acl_cl/ConstantInitializer.cc
index 88885352745..379b02b5b22 100644
--- a/runtime/onert/backend/acl_cl/ConstantInitializer.cc
+++ b/runtime/onert/backend/acl_cl/ConstantInitializer.cc
@@ -21,11 +21,7 @@
 
 #include "ConstantInitializer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 ConstantInitializer::ConstantInitializer(const ir::Operands &operands,
@@ -119,6 +115,4 @@ void ConstantInitializer::visit(const ir::operation::Reverse &node)
   }
 }
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
diff --git a/runtime/onert/backend/acl_cl/ConstantInitializer.h b/runtime/onert/backend/acl_cl/ConstantInitializer.h
index fc0eca84fad..c5e4e4e69a0 100644
--- a/runtime/onert/backend/acl_cl/ConstantInitializer.h
+++ b/runtime/onert/backend/acl_cl/ConstantInitializer.h
@@ -19,11 +19,7 @@
 
 #include "AclConstantInitializer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 class ConstantInitializer : public acl_common::AclConstantInitializer
@@ -41,8 +37,6 @@ class ConstantInitializer : public acl_common::AclConstantInitializer
   void visit(const ir::operation::Reverse &) final;
 };
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_CONSTANT_INITIALIZER_H__
diff --git a/runtime/onert/backend/acl_cl/KernelGenerator.cc b/runtime/onert/backend/acl_cl/KernelGenerator.cc
index 69378a0ee00..1cb815baf97 100644
--- a/runtime/onert/backend/acl_cl/KernelGenerator.cc
+++ b/runtime/onert/backend/acl_cl/KernelGenerator.cc
@@ -32,11 +32,7 @@
 #include "util/logging.h"
 #include "AclKernelGen.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 using ::onert::backend::acl_common::asAclFunction;
@@ -1546,6 +1542,4 @@ void KernelGenerator::visit(const ir::operation::Reverse &node)
   _return_fn = asAclFunction(std::move(fn));
 }
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
diff --git a/runtime/onert/backend/acl_cl/KernelGenerator.h b/runtime/onert/backend/acl_cl/KernelGenerator.h
index d8f580f854f..9556e7b5256 100644
--- a/runtime/onert/backend/acl_cl/KernelGenerator.h
+++ b/runtime/onert/backend/acl_cl/KernelGenerator.h
@@ -23,11 +23,7 @@
 #include "AclTensorRegistry.h"
 #include "TensorManager.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 class KernelGenerator : public basic::KernelGeneratorBase
@@ -93,8 +89,6 @@ class KernelGenerator : public basic::KernelGeneratorBase
   std::shared_ptr<acl_common::AclTensorRegistry<TensorManager>> _tensor_reg;
 };
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_KERNEL_GENERATOR_H__
diff --git a/runtime/onert/backend/acl_cl/Optimizer.cc b/runtime/onert/backend/acl_cl/Optimizer.cc
index 1eeeeec48ba..bbd624c22cb 100644
--- a/runtime/onert/backend/acl_cl/Optimizer.cc
+++ b/runtime/onert/backend/acl_cl/Optimizer.cc
@@ -23,11 +23,7 @@
 
 #include <cassert>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 Optimizer::Optimizer(BackendContext *context)
@@ -50,6 +46,4 @@ void Optimizer::optimize()
   }
 }
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
diff --git a/runtime/onert/backend/acl_cl/Optimizer.h b/runtime/onert/backend/acl_cl/Optimizer.h
index ad515486069..e0caf407c53 100644
--- a/runtime/onert/backend/acl_cl/Optimizer.h
+++ b/runtime/onert/backend/acl_cl/Optimizer.h
@@ -20,11 +20,7 @@
 #include "BackendContext.h"
 #include "TensorBuilder.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 class Optimizer
@@ -39,8 +35,6 @@ class Optimizer
   std::shared_ptr<TensorBuilder> _tensor_builder;
 };
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_OPTIMIZER_H__
diff --git a/runtime/onert/backend/acl_cl/TensorBuilder.h b/runtime/onert/backend/acl_cl/TensorBuilder.h
index 5492929fec7..8301b60b151 100644
--- a/runtime/onert/backend/acl_cl/TensorBuilder.h
+++ b/runtime/onert/backend/acl_cl/TensorBuilder.h
@@ -22,18 +22,12 @@
 #include "operand/CLTensor.h"
 #include "operand/CLSubTensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 using TensorBuilder =
   acl_common::AclTensorBuilder<operand::ICLTensor, operand::CLTensor, operand::CLSubTensor>;
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/acl_cl/TensorManager.h b/runtime/onert/backend/acl_cl/TensorManager.h
index 2860f51f3df..a601c3b5599 100644
--- a/runtime/onert/backend/acl_cl/TensorManager.h
+++ b/runtime/onert/backend/acl_cl/TensorManager.h
@@ -33,11 +33,7 @@
 
 #include "util/logging.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
+namespace onert::backend::acl_cl
 {
 
 using MemoryManager =
@@ -71,8 +67,6 @@ inline TensorManager *createTensorManager(bool is_linear_executor)
   }
 }
 
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl
 
 #endif // __ONERT_BACKEND_ACL_CL_TENSOR_MANAGER_H__
diff --git a/runtime/onert/backend/acl_cl/operand/CLSubTensor.cc b/runtime/onert/backend/acl_cl/operand/CLSubTensor.cc
index 2c435734900..65930088bad 100644
--- a/runtime/onert/backend/acl_cl/operand/CLSubTensor.cc
+++ b/runtime/onert/backend/acl_cl/operand/CLSubTensor.cc
@@ -16,13 +16,7 @@
 
 #include "CLSubTensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
-{
-namespace operand
+namespace onert::backend::acl_cl::operand
 {
 
 CLSubTensor::CLSubTensor(ICLTensor *parent, const arm_compute::TensorShape &tensor_shape,
@@ -37,7 +31,4 @@ const arm_compute::CLSubTensor *CLSubTensor::handle() const { return _cl_sub_ten
 
 arm_compute::CLSubTensor *CLSubTensor::handle() { return _cl_sub_tensor.get(); }
 
-} // namespace operand
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl::operand
diff --git a/runtime/onert/backend/acl_cl/operand/CLSubTensor.h b/runtime/onert/backend/acl_cl/operand/CLSubTensor.h
index 0a26e48227b..87eadc9ee50 100644
--- a/runtime/onert/backend/acl_cl/operand/CLSubTensor.h
+++ b/runtime/onert/backend/acl_cl/operand/CLSubTensor.h
@@ -20,13 +20,7 @@
 #include <arm_compute/runtime/CL/CLSubTensor.h>
 #include "ICLTensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
-{
-namespace operand
+namespace onert::backend::acl_cl::operand
 {
 
 class CLSubTensor : public ICLTensor
@@ -51,9 +45,6 @@ class CLSubTensor : public ICLTensor
   std::shared_ptr<arm_compute::CLSubTensor> _cl_sub_tensor;
 };
 
-} // namespace operand
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl::operand
 
 #endif // __ONERT_BACKEND_ACL_CL_OPERAND_CL_SUB_TENSOR_H__
diff --git a/runtime/onert/backend/acl_cl/operand/CLTensor.cc b/runtime/onert/backend/acl_cl/operand/CLTensor.cc
index 38ce4647f85..6f09932a622 100644
--- a/runtime/onert/backend/acl_cl/operand/CLTensor.cc
+++ b/runtime/onert/backend/acl_cl/operand/CLTensor.cc
@@ -22,13 +22,7 @@
 
 #include <Convert.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
-{
-namespace operand
+namespace onert::backend::acl_cl::operand
 {
 
 CLTensor::CLTensor(const arm_compute::TensorInfo &info, size_t rank, size_t num_uses)
@@ -52,7 +46,4 @@ void CLTensor::setBuffer(void *host_ptr)
   allocator()->import_memory(buffer);
 }
 
-} // namespace operand
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl::operand
diff --git a/runtime/onert/backend/acl_cl/operand/CLTensor.h b/runtime/onert/backend/acl_cl/operand/CLTensor.h
index 487d04662b0..bf0f49baa90 100644
--- a/runtime/onert/backend/acl_cl/operand/CLTensor.h
+++ b/runtime/onert/backend/acl_cl/operand/CLTensor.h
@@ -23,13 +23,7 @@
 #include "arm_compute/runtime/CL/CLTensorAllocator.h"
 #include "ICLTensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
-{
-namespace operand
+namespace onert::backend::acl_cl::operand
 {
 
 class CLTensor : public ICLTensor
@@ -61,9 +55,6 @@ class CLTensor : public ICLTensor
   size_t _num_uses;
 };
 
-} // namespace operand
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl::operand
 
 #endif // __ONERT_BACKEND_ACL_CL_OPERAND_CL_TENSOR_H__
diff --git a/runtime/onert/backend/acl_cl/operand/ICLTensor.cc b/runtime/onert/backend/acl_cl/operand/ICLTensor.cc
index 2cee0b47445..0b2303c550b 100644
--- a/runtime/onert/backend/acl_cl/operand/ICLTensor.cc
+++ b/runtime/onert/backend/acl_cl/operand/ICLTensor.cc
@@ -19,13 +19,7 @@
 #include <arm_compute/runtime/CL/CLScheduler.h>
 #include <arm_compute/core/CL/OpenCL.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
-{
-namespace operand
+namespace onert::backend::acl_cl::operand
 {
 
 void ICLTensor::access(const std::function<void(ITensor &tensor)> &fn)
@@ -54,7 +48,4 @@ void ICLTensor::enqueueReadBuffer(void *ptr, bool blocking)
   queue.enqueueReadBuffer(handle()->cl_buffer(), blocking ? CL_TRUE : CL_FALSE, 0,
                           info()->total_size(), ptr);
 }
-} // namespace operand
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl::operand
diff --git a/runtime/onert/backend/acl_cl/operand/ICLTensor.h b/runtime/onert/backend/acl_cl/operand/ICLTensor.h
index 51152a3183b..479825d81b1 100644
--- a/runtime/onert/backend/acl_cl/operand/ICLTensor.h
+++ b/runtime/onert/backend/acl_cl/operand/ICLTensor.h
@@ -21,13 +21,7 @@
 
 #include <IACLTensor.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_cl
-{
-namespace operand
+namespace onert::backend::acl_cl::operand
 {
 
 class ICLTensor : public acl_common::IACLTensor
@@ -48,9 +42,6 @@ class ICLTensor : public acl_common::IACLTensor
   void unmap(cl::CommandQueue &q) { return handle()->unmap(q); }
 };
 
-} // namespace operand
-} // namespace acl_cl
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_cl::operand
 
 #endif // __ONERT_BACKEND_ACL_CL_OPERAND_I_CL_TENSOR_H__
diff --git a/runtime/onert/backend/acl_common/AclActivationBuilder.h b/runtime/onert/backend/acl_common/AclActivationBuilder.h
index 5d92a78566b..93a97a2a8ad 100644
--- a/runtime/onert/backend/acl_common/AclActivationBuilder.h
+++ b/runtime/onert/backend/acl_common/AclActivationBuilder.h
@@ -25,11 +25,7 @@
 
 #include "Convert.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T_Tensor, typename T_ActivationLayer, typename T_ExecFunction>
@@ -118,8 +114,6 @@ AclActivationBuilder<T_Tensor, T_ActivationLayer, T_ExecFunction>::generate(ir::
   }
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_ACL_ACTIVATION_BUILDER_H__
diff --git a/runtime/onert/backend/acl_common/AclBackendContext.h b/runtime/onert/backend/acl_common/AclBackendContext.h
index 2ca75a67a3f..be177794147 100644
--- a/runtime/onert/backend/acl_common/AclBackendContext.h
+++ b/runtime/onert/backend/acl_common/AclBackendContext.h
@@ -25,11 +25,7 @@
 
 #include <cl_common/BackendContext.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 // TODO Find better way to handle common code (reduce template)
@@ -96,8 +92,6 @@ class AclBackendContext
   std::shared_ptr<T_Optimizer> optimizer;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_ACLBACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/acl_common/AclConstantInitializer.cc b/runtime/onert/backend/acl_common/AclConstantInitializer.cc
index 66ff59b00b4..24e5b318f1a 100644
--- a/runtime/onert/backend/acl_common/AclConstantInitializer.cc
+++ b/runtime/onert/backend/acl_common/AclConstantInitializer.cc
@@ -16,11 +16,7 @@
 
 #include "AclConstantInitializer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 AclConstantInitializer::AclConstantInitializer(const ir::Operands &operands,
@@ -162,6 +158,4 @@ void AclConstantInitializer::registerCopyInitializer(const ir::OperandIndex &ind
   }
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
diff --git a/runtime/onert/backend/acl_common/AclConstantInitializer.h b/runtime/onert/backend/acl_common/AclConstantInitializer.h
index 2da16093dd1..8016db5a1ce 100644
--- a/runtime/onert/backend/acl_common/AclConstantInitializer.h
+++ b/runtime/onert/backend/acl_common/AclConstantInitializer.h
@@ -30,11 +30,7 @@
 #include <backend/ITensorRegistry.h>
 #include <util/logging.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T>
@@ -198,8 +194,6 @@ class AclConstantInitializer : public ir::OperationVisitor
   std::unordered_map<ir::OperandIndex, Initializer> _init_map;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_COMPILER_ACL_COMMON_ACLCONSTANT_INITIALIZER_H__
diff --git a/runtime/onert/backend/acl_common/AclFunction.h b/runtime/onert/backend/acl_common/AclFunction.h
index 94b65863af4..f825ba7b8cd 100644
--- a/runtime/onert/backend/acl_common/AclFunction.h
+++ b/runtime/onert/backend/acl_common/AclFunction.h
@@ -21,11 +21,7 @@
 #include <arm_compute/runtime/IFunction.h>
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 class AclFunction : public ::onert::exec::IFunction
@@ -47,8 +43,6 @@ class AclFunction : public ::onert::exec::IFunction
   std::unique_ptr<::arm_compute::IFunction> _func;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_KERNEL_ACL_FUNCTION_H__
diff --git a/runtime/onert/backend/acl_common/AclInternalBufferManager.h b/runtime/onert/backend/acl_common/AclInternalBufferManager.h
index cca5778d4f6..d1e9c166a92 100644
--- a/runtime/onert/backend/acl_common/AclInternalBufferManager.h
+++ b/runtime/onert/backend/acl_common/AclInternalBufferManager.h
@@ -21,11 +21,7 @@
 #include <cassert>
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 // NOTE. If any backend can use something like InternalBufferManager,
@@ -92,8 +88,6 @@ class AclInternalBufferManager : public IInternalBufferManager
   std::shared_ptr<T_MemoryManager> _internal_manager;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_INTERNAL_BUFFER_MANAGER_H__
diff --git a/runtime/onert/backend/acl_common/AclKernelGen.h b/runtime/onert/backend/acl_common/AclKernelGen.h
index 91d548597ac..bff8e23593e 100644
--- a/runtime/onert/backend/acl_common/AclKernelGen.h
+++ b/runtime/onert/backend/acl_common/AclKernelGen.h
@@ -23,11 +23,7 @@
 #include <ir/operation/LSTM.h>
 #include <arm_compute/runtime/CL/CLFunctions.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 void enableDimCorrection(IACLTensor *tensor)
@@ -330,8 +326,6 @@ kernelGenPool2D(const T_PoolOp &node, const ir::Operands &operands,
   return fn;
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_ACL_KERNEL_GEN_H_
diff --git a/runtime/onert/backend/acl_common/AclLinearMemoryManager.h b/runtime/onert/backend/acl_common/AclLinearMemoryManager.h
index 5c546b77a02..228a5f9a7b2 100644
--- a/runtime/onert/backend/acl_common/AclLinearMemoryManager.h
+++ b/runtime/onert/backend/acl_common/AclLinearMemoryManager.h
@@ -23,11 +23,7 @@
 #include "ir/OperandIndexMap.h"
 #include "util/logging.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T_MemoryManager, typename T_PoolManager, typename T_LifetimeManager>
@@ -98,8 +94,6 @@ class AclLinearMemoryManager : public AclMemoryManager<T_ITensor, T_Tensor, T_Su
   std::shared_ptr<T_MemoryGroup> _io_group;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_LINEAR_MEMORY_MANAGER_H__
diff --git a/runtime/onert/backend/acl_common/AclMemoryManager.h b/runtime/onert/backend/acl_common/AclMemoryManager.h
index 8e6bdd86aef..6ba5b60bfb6 100644
--- a/runtime/onert/backend/acl_common/AclMemoryManager.h
+++ b/runtime/onert/backend/acl_common/AclMemoryManager.h
@@ -25,11 +25,7 @@
 #include "Convert.h"
 #include "util/logging.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T_ITensor, typename T_Tensor, typename T_SubTensor> class AclMemoryManager
@@ -93,8 +89,6 @@ template <typename T_ITensor, typename T_Tensor, typename T_SubTensor> class Acl
   ir::OperandIndexMap<std::shared_ptr<T_SubTensor>> _subtensors;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_MEMORY_MANAGER_H__
diff --git a/runtime/onert/backend/acl_common/AclSubTensorAnalyzer.h b/runtime/onert/backend/acl_common/AclSubTensorAnalyzer.h
index 36e59df1611..568fa32da3e 100644
--- a/runtime/onert/backend/acl_common/AclSubTensorAnalyzer.h
+++ b/runtime/onert/backend/acl_common/AclSubTensorAnalyzer.h
@@ -22,11 +22,7 @@
 #include <ir/OperationVisitor.h>
 #include <ir/Graph.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 /**
@@ -110,8 +106,6 @@ class AclSubTensorAnalyzer : public ir::OperationVisitor
   bool usePadding{false};
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_ACL_SUB_TENSOR_ANALYZER_H__
diff --git a/runtime/onert/backend/acl_common/AclTensorBuilder.h b/runtime/onert/backend/acl_common/AclTensorBuilder.h
index b6e7488b368..484cea90d15 100644
--- a/runtime/onert/backend/acl_common/AclTensorBuilder.h
+++ b/runtime/onert/backend/acl_common/AclTensorBuilder.h
@@ -32,11 +32,7 @@
 #include <memory>
 #include <queue>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T_ITensor, typename T_Tensor, typename T_SubTensor> class AclTensorBuilder
@@ -107,9 +103,7 @@ template <typename T_ITensor, typename T_Tensor, typename T_SubTensor> class Acl
   ir::OperandIndexMap<cl_common::ParentInfo> _parent_map;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #include <cassert>
 #include <stack>
@@ -118,11 +112,7 @@ template <typename T_ITensor, typename T_Tensor, typename T_SubTensor> class Acl
 
 #include "util/logging.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T_ITensor, typename T_Tensor, typename T_SubTensor>
@@ -327,8 +317,6 @@ AclTensorBuilder<T_ITensor, T_Tensor, T_SubTensor>::findRootParent(ir::OperandIn
   return findRootParent(parent_ind);
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_TEMPL_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/acl_common/AclTensorManager.h b/runtime/onert/backend/acl_common/AclTensorManager.h
index 41a89fbf281..3fb51bb6f9e 100644
--- a/runtime/onert/backend/acl_common/AclTensorManager.h
+++ b/runtime/onert/backend/acl_common/AclTensorManager.h
@@ -23,11 +23,7 @@
 #include "AclInternalBufferManager.h"
 #include "ir/OperandIndexMap.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T_ITensor, typename T_Tensor, typename T_SubTensor> class AclTensorManager
@@ -79,18 +75,12 @@ template <typename T_ITensor, typename T_Tensor, typename T_SubTensor> class Acl
   ir::OperandIndexMap<T_AclMemoryManager &> _ind_to_mgr;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #include <cassert>
 #include "util/logging.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 template <typename T_ITensor, typename T_Tensor, typename T_SubTensor>
@@ -297,8 +287,6 @@ void AclTensorManager<T_ITensor, T_Tensor, T_SubTensor>::tryDeallocConstants(voi
   }
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_TENSOR_MANAGER_H__
diff --git a/runtime/onert/backend/acl_common/AclTensorRegistry.h b/runtime/onert/backend/acl_common/AclTensorRegistry.h
index 02d66db99af..9e9b997eec7 100644
--- a/runtime/onert/backend/acl_common/AclTensorRegistry.h
+++ b/runtime/onert/backend/acl_common/AclTensorRegistry.h
@@ -19,11 +19,7 @@
 
 #include "backend/ITensorRegistry.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 /**
@@ -46,8 +42,6 @@ template <typename T_AclTensorManager> class AclTensorRegistry : public ITensorR
   T_AclTensorManager *_tensor_mgr;
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_ACL_TENSOR_REGISTRY_H__
diff --git a/runtime/onert/backend/acl_common/Convert.cc b/runtime/onert/backend/acl_common/Convert.cc
index f0904a685d9..3a6ee6832b3 100644
--- a/runtime/onert/backend/acl_common/Convert.cc
+++ b/runtime/onert/backend/acl_common/Convert.cc
@@ -21,11 +21,7 @@
 #include "ir/operation/ElementwiseActivation.h"
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 ::arm_compute::TensorShape asTensorShape(const ir::Shape &shape, bool apply_dim_correction)
@@ -339,6 +335,4 @@ arm_compute::Size2D asDilation(uint32_t dilation_width, uint32_t dilation_height
   return arm_compute::Size2D(dilation_width, dilation_height);
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
diff --git a/runtime/onert/backend/acl_common/Convert.h b/runtime/onert/backend/acl_common/Convert.h
index 6dd8d01ab06..5dfe59c06ef 100644
--- a/runtime/onert/backend/acl_common/Convert.h
+++ b/runtime/onert/backend/acl_common/Convert.h
@@ -40,11 +40,7 @@
 
 #include <set>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 ::arm_compute::TensorShape asTensorShape(const ir::Shape &shape, bool apply_dim_correction = true);
@@ -81,8 +77,6 @@ arm_compute::ReductionOperation convertReduceType(ir::operation::Reduce::ReduceT
 arm_compute::PixelValue asPixelValue(const ir::Operand &operand);
 arm_compute::Size2D asDilation(uint32_t dilation_width, uint32_t dilation_height);
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_CONVERT_H__
diff --git a/runtime/onert/backend/acl_common/IACLTensor.cc b/runtime/onert/backend/acl_common/IACLTensor.cc
index 50fef459daf..820dc2105b3 100644
--- a/runtime/onert/backend/acl_common/IACLTensor.cc
+++ b/runtime/onert/backend/acl_common/IACLTensor.cc
@@ -18,11 +18,7 @@
 #include "Convert.h"
 #include "Swizzle.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 size_t IACLTensor::calcOffset(const ir::Coordinates &coords) const
@@ -68,6 +64,4 @@ const std::vector<int32_t> &IACLTensor::data_zero_points() const
   throw std::runtime_error("IACLTensor::data_zero_points() is not supported.");
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
diff --git a/runtime/onert/backend/acl_common/IACLTensor.h b/runtime/onert/backend/acl_common/IACLTensor.h
index e43a4cbdac8..b3a80cdeb31 100644
--- a/runtime/onert/backend/acl_common/IACLTensor.h
+++ b/runtime/onert/backend/acl_common/IACLTensor.h
@@ -21,11 +21,7 @@
 #include <arm_compute/core/ITensor.h>
 #include "Swizzle.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 /**
@@ -88,8 +84,6 @@ class IACLTensor : public ITensor
   size_t _rank; // Actual rank (reflects extended rank)
 };
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif //__ONERT_BACKEND_ACL_COMMON_I_ACL_TENSOR_H__
diff --git a/runtime/onert/backend/acl_common/Swizzle.h b/runtime/onert/backend/acl_common/Swizzle.h
index a1575aab9f3..2d0a1dde0cb 100644
--- a/runtime/onert/backend/acl_common/Swizzle.h
+++ b/runtime/onert/backend/acl_common/Swizzle.h
@@ -20,11 +20,7 @@
 #include <cassert>
 #include <ir/Layout.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_common
+namespace onert::backend::acl_common
 {
 
 class ARMComputeAxis
@@ -103,8 +99,6 @@ template <typename T> inline T ReorderBits(T in, size_t numOfBits)
   return out;
 }
 
-} // namespace acl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_common
 
 #endif // __ONERT_BACKEND_ACL_COMMON_SWIZZLE_H__
diff --git a/runtime/onert/backend/acl_neon/Backend.h b/runtime/onert/backend/acl_neon/Backend.h
index 1c7713055c0..bab834f0b49 100644
--- a/runtime/onert/backend/acl_neon/Backend.h
+++ b/runtime/onert/backend/acl_neon/Backend.h
@@ -28,11 +28,7 @@
 #include "TensorManager.h"
 #include "Optimizer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 class Backend : public ::onert::backend::Backend
@@ -64,8 +60,6 @@ class Backend : public ::onert::backend::Backend
   std::shared_ptr<IConfig> _config;
 };
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_BACKEND_H__
diff --git a/runtime/onert/backend/acl_neon/BackendContext.h b/runtime/onert/backend/acl_neon/BackendContext.h
index b73dd188ee8..71e91755b2c 100644
--- a/runtime/onert/backend/acl_neon/BackendContext.h
+++ b/runtime/onert/backend/acl_neon/BackendContext.h
@@ -23,11 +23,7 @@
 #include "KernelGenerator.h"
 #include "TensorBuilder.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 class Optimizer;
@@ -35,8 +31,6 @@ class Optimizer;
 using BackendContext =
   acl_common::AclBackendContext<TensorBuilder, ConstantInitializer, KernelGenerator, Optimizer>;
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/acl_neon/Config.cc b/runtime/onert/backend/acl_neon/Config.cc
index 380ebc10a8b..7813373c0c3 100644
--- a/runtime/onert/backend/acl_neon/Config.cc
+++ b/runtime/onert/backend/acl_neon/Config.cc
@@ -18,15 +18,9 @@
 
 #include <util/ConfigSource.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 bool Config::initialize() { return true; }
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
diff --git a/runtime/onert/backend/acl_neon/Config.h b/runtime/onert/backend/acl_neon/Config.h
index 86748bb2f3d..806442d28e8 100644
--- a/runtime/onert/backend/acl_neon/Config.h
+++ b/runtime/onert/backend/acl_neon/Config.h
@@ -21,11 +21,7 @@
 #include <memory>
 #include <util/ITimer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 class Config : public IConfig
@@ -40,8 +36,6 @@ class Config : public IConfig
   std::unique_ptr<util::ITimer> timer() override { return std::make_unique<util::CPUTimer>(); }
 };
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_CONFIG_H__
diff --git a/runtime/onert/backend/acl_neon/ConstantInitializer.cc b/runtime/onert/backend/acl_neon/ConstantInitializer.cc
index 1bd702756da..4ea7b234628 100644
--- a/runtime/onert/backend/acl_neon/ConstantInitializer.cc
+++ b/runtime/onert/backend/acl_neon/ConstantInitializer.cc
@@ -16,11 +16,7 @@
 
 #include "ConstantInitializer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 ConstantInitializer::ConstantInitializer(const ir::Operands &operands,
@@ -71,6 +67,4 @@ void ConstantInitializer::visit(const ir::operation::SpaceToBatchND &node)
   }
 }
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
diff --git a/runtime/onert/backend/acl_neon/ConstantInitializer.h b/runtime/onert/backend/acl_neon/ConstantInitializer.h
index 9723ba0126c..0986beb6081 100644
--- a/runtime/onert/backend/acl_neon/ConstantInitializer.h
+++ b/runtime/onert/backend/acl_neon/ConstantInitializer.h
@@ -19,11 +19,7 @@
 
 #include "AclConstantInitializer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 class ConstantInitializer : public acl_common::AclConstantInitializer
@@ -37,8 +33,6 @@ class ConstantInitializer : public acl_common::AclConstantInitializer
   void visit(const ir::operation::SpaceToBatchND &node) final;
 };
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_CONSTANT_INITIALIZER_H__
diff --git a/runtime/onert/backend/acl_neon/KernelGenerator.cc b/runtime/onert/backend/acl_neon/KernelGenerator.cc
index b8cef544c9e..db1ed3b800a 100644
--- a/runtime/onert/backend/acl_neon/KernelGenerator.cc
+++ b/runtime/onert/backend/acl_neon/KernelGenerator.cc
@@ -31,11 +31,7 @@
 #include "util/logging.h"
 #include "AclKernelGen.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 using ::onert::backend::acl_common::asAclFunction;
@@ -1348,6 +1344,4 @@ void KernelGenerator::visit(const ir::operation::OneHot &node)
   _return_fn = asAclFunction(std::move(fn));
 }
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
diff --git a/runtime/onert/backend/acl_neon/KernelGenerator.h b/runtime/onert/backend/acl_neon/KernelGenerator.h
index 5721cb123ea..999501972f3 100644
--- a/runtime/onert/backend/acl_neon/KernelGenerator.h
+++ b/runtime/onert/backend/acl_neon/KernelGenerator.h
@@ -24,11 +24,7 @@
 #include "AclTensorRegistry.h"
 #include "TensorManager.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 class KernelGenerator : public basic::KernelGeneratorBase
@@ -88,8 +84,6 @@ class KernelGenerator : public basic::KernelGeneratorBase
   std::shared_ptr<acl_common::AclTensorRegistry<TensorManager>> _tensor_reg;
 };
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_KERNEL_GENERATOR_H__
diff --git a/runtime/onert/backend/acl_neon/Optimizer.cc b/runtime/onert/backend/acl_neon/Optimizer.cc
index 3e5921d0ebd..cdf721b16f4 100644
--- a/runtime/onert/backend/acl_neon/Optimizer.cc
+++ b/runtime/onert/backend/acl_neon/Optimizer.cc
@@ -23,11 +23,7 @@
 
 #include <cassert>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 Optimizer::Optimizer(BackendContext *context)
@@ -48,6 +44,4 @@ void Optimizer::optimize()
   }
 }
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
diff --git a/runtime/onert/backend/acl_neon/Optimizer.h b/runtime/onert/backend/acl_neon/Optimizer.h
index b8fb343e9d5..3481c8ec08c 100644
--- a/runtime/onert/backend/acl_neon/Optimizer.h
+++ b/runtime/onert/backend/acl_neon/Optimizer.h
@@ -20,11 +20,7 @@
 #include "BackendContext.h"
 #include "TensorBuilder.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 class Optimizer
@@ -39,8 +35,6 @@ class Optimizer
   std::shared_ptr<TensorBuilder> _tensor_builder;
 };
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_OPTIMIZER_H__
diff --git a/runtime/onert/backend/acl_neon/TensorBuilder.h b/runtime/onert/backend/acl_neon/TensorBuilder.h
index 7b6e8406bad..c702b841030 100644
--- a/runtime/onert/backend/acl_neon/TensorBuilder.h
+++ b/runtime/onert/backend/acl_neon/TensorBuilder.h
@@ -22,18 +22,12 @@
 #include "operand/NETensor.h"
 #include "operand/NESubTensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 using TensorBuilder =
   acl_common::AclTensorBuilder<operand::INETensor, operand::NETensor, operand::NESubTensor>;
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/acl_neon/TensorManager.h b/runtime/onert/backend/acl_neon/TensorManager.h
index 5ecc0fbb3d2..cfd608d4ab7 100644
--- a/runtime/onert/backend/acl_neon/TensorManager.h
+++ b/runtime/onert/backend/acl_neon/TensorManager.h
@@ -33,11 +33,7 @@
 
 #include "util/logging.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
+namespace onert::backend::acl_neon
 {
 
 using MemoryManager =
@@ -70,8 +66,6 @@ inline TensorManager *createTensorManager(bool is_linear_executor)
   }
 }
 
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon
 
 #endif // __ONERT_BACKEND_ACL_NEON_TENSOR_MANAGER_H__
diff --git a/runtime/onert/backend/acl_neon/operand/INETensor.cc b/runtime/onert/backend/acl_neon/operand/INETensor.cc
index fddcff0f441..89fd5844fad 100644
--- a/runtime/onert/backend/acl_neon/operand/INETensor.cc
+++ b/runtime/onert/backend/acl_neon/operand/INETensor.cc
@@ -16,13 +16,7 @@
 
 #include "INETensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
-{
-namespace operand
+namespace onert::backend::acl_neon::operand
 {
 
 void INETensor::access(const std::function<void(ITensor &tensor)> &fn)
@@ -34,7 +28,4 @@ void INETensor::access(const std::function<void(ITensor &tensor)> &fn)
   fn(*this);
 }
 
-} // namespace operand
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon::operand
diff --git a/runtime/onert/backend/acl_neon/operand/INETensor.h b/runtime/onert/backend/acl_neon/operand/INETensor.h
index 3747b12b7b1..301089d3682 100644
--- a/runtime/onert/backend/acl_neon/operand/INETensor.h
+++ b/runtime/onert/backend/acl_neon/operand/INETensor.h
@@ -21,13 +21,7 @@
 
 #include <IACLTensor.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
-{
-namespace operand
+namespace onert::backend::acl_neon::operand
 {
 
 class INETensor : public acl_common::IACLTensor
@@ -39,9 +33,6 @@ class INETensor : public acl_common::IACLTensor
   void access(const std::function<void(ITensor &tensor)> &fn) final;
 };
 
-} // namespace operand
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon::operand
 
 #endif // __ONERT_BACKEND_ACL_NEON_OPERAND_I_NE_TENSOR_H__
diff --git a/runtime/onert/backend/acl_neon/operand/NESubTensor.cc b/runtime/onert/backend/acl_neon/operand/NESubTensor.cc
index fe82f620646..a693d9d68b8 100644
--- a/runtime/onert/backend/acl_neon/operand/NESubTensor.cc
+++ b/runtime/onert/backend/acl_neon/operand/NESubTensor.cc
@@ -16,13 +16,7 @@
 
 #include "NESubTensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
-{
-namespace operand
+namespace onert::backend::acl_neon::operand
 {
 
 NESubTensor::NESubTensor(INETensor *parent, const arm_compute::TensorShape &tensor_shape,
@@ -37,7 +31,4 @@ const arm_compute::SubTensor *NESubTensor::handle() const { return _ne_sub_tenso
 
 arm_compute::SubTensor *NESubTensor::handle() { return _ne_sub_tensor.get(); }
 
-} // namespace operand
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon::operand
diff --git a/runtime/onert/backend/acl_neon/operand/NESubTensor.h b/runtime/onert/backend/acl_neon/operand/NESubTensor.h
index 74dbe901103..81c7f1deac4 100644
--- a/runtime/onert/backend/acl_neon/operand/NESubTensor.h
+++ b/runtime/onert/backend/acl_neon/operand/NESubTensor.h
@@ -20,13 +20,7 @@
 #include <arm_compute/runtime/SubTensor.h>
 #include "INETensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
-{
-namespace operand
+namespace onert::backend::acl_neon::operand
 {
 
 class NESubTensor : public INETensor
@@ -51,9 +45,6 @@ class NESubTensor : public INETensor
   std::shared_ptr<arm_compute::SubTensor> _ne_sub_tensor;
 };
 
-} // namespace operand
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon::operand
 
 #endif // __ONERT_BACKEND_ACL_NEON_OPERAND_NE_SUB_TENSOR_H__
diff --git a/runtime/onert/backend/acl_neon/operand/NETensor.cc b/runtime/onert/backend/acl_neon/operand/NETensor.cc
index 4b237d731f1..b7fa345efb3 100644
--- a/runtime/onert/backend/acl_neon/operand/NETensor.cc
+++ b/runtime/onert/backend/acl_neon/operand/NETensor.cc
@@ -18,13 +18,7 @@
 #include <arm_compute/runtime/MemoryRegion.h>
 #include "NETensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
-{
-namespace operand
+namespace onert::backend::acl_neon::operand
 {
 
 NETensor::NETensor(const arm_compute::TensorInfo &info, size_t rank, size_t num_uses)
@@ -39,7 +33,4 @@ arm_compute::Tensor *NETensor::handle() { return _ne_tensor.get(); }
 
 arm_compute::TensorAllocator *NETensor::allocator() { return _ne_tensor->allocator(); }
 
-} // namespace operand
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon::operand
diff --git a/runtime/onert/backend/acl_neon/operand/NETensor.h b/runtime/onert/backend/acl_neon/operand/NETensor.h
index 69f8b211145..33076a16812 100644
--- a/runtime/onert/backend/acl_neon/operand/NETensor.h
+++ b/runtime/onert/backend/acl_neon/operand/NETensor.h
@@ -22,13 +22,7 @@
 #include "arm_compute/runtime/TensorAllocator.h"
 #include "INETensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace acl_neon
-{
-namespace operand
+namespace onert::backend::acl_neon::operand
 {
 
 class NETensor : public INETensor
@@ -52,9 +46,6 @@ class NETensor : public INETensor
   size_t _num_uses;
 };
 
-} // namespace operand
-} // namespace acl_neon
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::acl_neon::operand
 
 #endif // __ONERT_BACKEND_ACL_NEON_OPERAND_NE_TENSOR_H__
diff --git a/runtime/onert/backend/cl_common/include/cl_common/BackendContext.h b/runtime/onert/backend/cl_common/include/cl_common/BackendContext.h
index 79031d656a5..90a1db194da 100644
--- a/runtime/onert/backend/cl_common/include/cl_common/BackendContext.h
+++ b/runtime/onert/backend/cl_common/include/cl_common/BackendContext.h
@@ -23,11 +23,7 @@
 #include <ir/OperandIndexSequence.h>
 #include <util/logging.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cl_common
+namespace onert::backend::cl_common
 {
 
 // TODO Find better way to handle common code (reduce template)
@@ -225,8 +221,6 @@ class BackendContext : public onert::backend::BackendContext
   std::shared_ptr<T_KernelGenerator> kernel_gen;
 };
 
-} // namespace cl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cl_common
 
 #endif // __ONERT_BACKEND_CL_COMMON_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/cl_common/include/cl_common/LifetimeMap.h b/runtime/onert/backend/cl_common/include/cl_common/LifetimeMap.h
index 5fe5eec7932..3f36d01dedd 100644
--- a/runtime/onert/backend/cl_common/include/cl_common/LifetimeMap.h
+++ b/runtime/onert/backend/cl_common/include/cl_common/LifetimeMap.h
@@ -24,11 +24,7 @@
 #include <map>
 #include <vector>
 
-namespace onert
-{
-namespace backend
-{
-namespace cl_common
+namespace onert::backend::cl_common
 {
 
 // TODO Abstract UserType into LifetimeMap and LifetimeSeq
@@ -44,8 +40,6 @@ using LifetimeSeq = std::vector<std::pair<UsesType, ir::OperandIndex>>;
 
 LifetimeMap createLifetimeMap(LifetimeSeq &seq, ir::OperandIndexMap<ParentInfo> &parent_map);
 
-} // namespace cl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cl_common
 
 #endif // __ONERT_BACKEND_CL_COMMON_LIFETIME_MAP_H__
diff --git a/runtime/onert/backend/cl_common/include/cl_common/ParentInfo.h b/runtime/onert/backend/cl_common/include/cl_common/ParentInfo.h
index e0d8982f566..90897dcf44c 100644
--- a/runtime/onert/backend/cl_common/include/cl_common/ParentInfo.h
+++ b/runtime/onert/backend/cl_common/include/cl_common/ParentInfo.h
@@ -20,11 +20,7 @@
 #include <ir/Index.h>
 #include <ir/Coordinates.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cl_common
+namespace onert::backend::cl_common
 {
 
 /**
@@ -36,8 +32,6 @@ struct ParentInfo
   ir::Coordinates coordinates;
 };
 
-} // namespace cl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cl_common
 
 #endif // __ONERT_BACKEND_CL_COMMON_PARENT_INFO_H__
diff --git a/runtime/onert/backend/cl_common/src/LifetimeMap.cc b/runtime/onert/backend/cl_common/src/LifetimeMap.cc
index 2b689ab057c..bec1420a18e 100644
--- a/runtime/onert/backend/cl_common/src/LifetimeMap.cc
+++ b/runtime/onert/backend/cl_common/src/LifetimeMap.cc
@@ -18,11 +18,7 @@
 
 #include <unordered_map>
 
-namespace onert
-{
-namespace backend
-{
-namespace cl_common
+namespace onert::backend::cl_common
 {
 
 LifetimeMap createLifetimeMap(LifetimeSeq &lifetime_seq,
@@ -80,6 +76,4 @@ LifetimeMap createLifetimeMap(LifetimeSeq &lifetime_seq,
   return lifetime_map;
 }
 
-} // namespace cl_common
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cl_common
diff --git a/runtime/onert/backend/cpu/Backend.h b/runtime/onert/backend/cpu/Backend.h
index a4199f98d37..149fe9a2be9 100644
--- a/runtime/onert/backend/cpu/Backend.h
+++ b/runtime/onert/backend/cpu/Backend.h
@@ -26,11 +26,7 @@
 
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 class Backend : public ::onert::backend::Backend
@@ -58,8 +54,6 @@ class Backend : public ::onert::backend::Backend
   std::shared_ptr<IConfig> _config;
 };
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_BACKEND_H__
diff --git a/runtime/onert/backend/cpu/BackendContext.cc b/runtime/onert/backend/cpu/BackendContext.cc
index 16904d86a86..dd10d447fcd 100644
--- a/runtime/onert/backend/cpu/BackendContext.cc
+++ b/runtime/onert/backend/cpu/BackendContext.cc
@@ -27,11 +27,7 @@
 
 #include <misc/polymorphic_downcast.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 ITensorRegistry *BackendContext::genTensors()
@@ -73,6 +69,4 @@ FunctionMap BackendContext::genKernels()
   return ret;
 }
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
diff --git a/runtime/onert/backend/cpu/BackendContext.h b/runtime/onert/backend/cpu/BackendContext.h
index 69ab30c827f..44df9ae9282 100644
--- a/runtime/onert/backend/cpu/BackendContext.h
+++ b/runtime/onert/backend/cpu/BackendContext.h
@@ -22,11 +22,7 @@
 #include "KernelGenerator.h"
 #include "ExternalContext.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 class BackendContext : public onert::backend::BackendContext
@@ -58,8 +54,6 @@ class BackendContext : public onert::backend::BackendContext
   std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/cpu/Config.cc b/runtime/onert/backend/cpu/Config.cc
index cea8095b15c..6f6603e1166 100644
--- a/runtime/onert/backend/cpu/Config.cc
+++ b/runtime/onert/backend/cpu/Config.cc
@@ -16,15 +16,9 @@
 
 #include "Config.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 bool Config::initialize() { return true; }
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
diff --git a/runtime/onert/backend/cpu/Config.h b/runtime/onert/backend/cpu/Config.h
index 7245e1ca35e..5a2aa1e8565 100644
--- a/runtime/onert/backend/cpu/Config.h
+++ b/runtime/onert/backend/cpu/Config.h
@@ -21,11 +21,7 @@
 #include <memory>
 #include <util/ITimer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 class Config : public IConfig
@@ -40,8 +36,6 @@ class Config : public IConfig
   std::unique_ptr<util::ITimer> timer() override { return std::make_unique<util::CPUTimer>(); }
 };
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_CONFIG_H__
diff --git a/runtime/onert/backend/cpu/ExternalContext.cc b/runtime/onert/backend/cpu/ExternalContext.cc
index 8de7e5b1038..7df60c0f61e 100644
--- a/runtime/onert/backend/cpu/ExternalContext.cc
+++ b/runtime/onert/backend/cpu/ExternalContext.cc
@@ -56,11 +56,7 @@ int32_t countPhysicalCores()
 
 } // namespace
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 ExternalContext::ExternalContext() : _ruy_context(new ruy::Context)
@@ -81,6 +77,4 @@ void ExternalContext::initGgmlContext()
       ggml_init({.mem_size = 0, .mem_buffer = nullptr, .no_alloc = true}), &ggml_free);
 }
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
diff --git a/runtime/onert/backend/cpu/ExternalContext.h b/runtime/onert/backend/cpu/ExternalContext.h
index b5f753ce9ac..2f0fa7dcf7c 100644
--- a/runtime/onert/backend/cpu/ExternalContext.h
+++ b/runtime/onert/backend/cpu/ExternalContext.h
@@ -23,11 +23,7 @@
 
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 class ExternalContext
@@ -50,8 +46,6 @@ class ExternalContext
   std::unique_ptr<ggml_context, decltype(&ggml_free)> _ggml_context{nullptr, &ggml_free};
 };
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_EXTERNAL_CONTEXT_H__
diff --git a/runtime/onert/backend/cpu/KernelGenerator.cc b/runtime/onert/backend/cpu/KernelGenerator.cc
index 1a9f6e7c547..d8c5ddf0a12 100644
--- a/runtime/onert/backend/cpu/KernelGenerator.cc
+++ b/runtime/onert/backend/cpu/KernelGenerator.cc
@@ -81,11 +81,7 @@
 
 #include <stdexcept>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 namespace
@@ -1583,6 +1579,4 @@ void KernelGenerator::visit(const ir::operation::RoPE &node)
   _return_fn = std::move(fn);
 }
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
diff --git a/runtime/onert/backend/cpu/KernelGenerator.h b/runtime/onert/backend/cpu/KernelGenerator.h
index e403ab796df..b8ed5cb0a4a 100644
--- a/runtime/onert/backend/cpu/KernelGenerator.h
+++ b/runtime/onert/backend/cpu/KernelGenerator.h
@@ -27,11 +27,7 @@
 #include <ir/Operands.h>
 #include <ir/Operations.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 class KernelGenerator : public basic::KernelGeneratorBase
@@ -108,8 +104,6 @@ class KernelGenerator : public basic::KernelGeneratorBase
   const std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_KERNEL_GENERATOR_H__
diff --git a/runtime/onert/backend/cpu/SharedMemoryOperands.cc b/runtime/onert/backend/cpu/SharedMemoryOperands.cc
index 2f357b6b380..d9ecce223a5 100644
--- a/runtime/onert/backend/cpu/SharedMemoryOperands.cc
+++ b/runtime/onert/backend/cpu/SharedMemoryOperands.cc
@@ -16,11 +16,7 @@
 
 #include "SharedMemoryOperands.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 namespace
@@ -89,6 +85,4 @@ ir::OperandIndexMap<ir::OperandIndex> findSharedMemoryOperandIndexes(const ir::I
   return shared_memory_operand_map;
 }
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
diff --git a/runtime/onert/backend/cpu/SharedMemoryOperands.h b/runtime/onert/backend/cpu/SharedMemoryOperands.h
index 3e4289592ef..3bb1e1d35fe 100644
--- a/runtime/onert/backend/cpu/SharedMemoryOperands.h
+++ b/runtime/onert/backend/cpu/SharedMemoryOperands.h
@@ -20,11 +20,7 @@
 #include "ir/IGraph.h"
 #include "ir/OperandIndexMap.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 /*
  * Find indexed of operands assigned to tensors which can share memory (indicate the same buffer).
@@ -32,8 +28,6 @@ namespace cpu
  */
 ir::OperandIndexMap<ir::OperandIndex> findSharedMemoryOperandIndexes(const ir::IGraph &graph);
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_SHARED_MEMORY_OPERANDS_H__
diff --git a/runtime/onert/backend/cpu/StaticTensorManager.h b/runtime/onert/backend/cpu/StaticTensorManager.h
index bcbb569ea17..b0eabf3eb84 100644
--- a/runtime/onert/backend/cpu/StaticTensorManager.h
+++ b/runtime/onert/backend/cpu/StaticTensorManager.h
@@ -19,17 +19,11 @@
 
 #include "backend/basic/StaticTensorManager.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 using StaticTensorManager = basic::StaticTensorManager;
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_STATICTENSOR_MANAGER_H__
diff --git a/runtime/onert/backend/cpu/Tensor.h b/runtime/onert/backend/cpu/Tensor.h
index f42d3d06829..7c00eb89ec9 100644
--- a/runtime/onert/backend/cpu/Tensor.h
+++ b/runtime/onert/backend/cpu/Tensor.h
@@ -20,18 +20,12 @@
 #include <backend/basic/Tensor.h>
 #include <ir/Data.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 using Tensor = basic::Tensor;
 using ExternalTensor = basic::ExternalTensor;
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_TENSOR_H__
diff --git a/runtime/onert/backend/cpu/TensorBuilder.h b/runtime/onert/backend/cpu/TensorBuilder.h
index a7a410f1742..ea8d9a8d968 100644
--- a/runtime/onert/backend/cpu/TensorBuilder.h
+++ b/runtime/onert/backend/cpu/TensorBuilder.h
@@ -19,17 +19,11 @@
 
 #include <backend/basic/TensorBuilder.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
+namespace onert::backend::cpu
 {
 
 using TensorBuilder = basic::TensorBuilder;
 
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu
 
 #endif // __ONERT_BACKEND_CPU_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/cpu/ops/AddNLayer.cc b/runtime/onert/backend/cpu/ops/AddNLayer.cc
index 96799129554..5d9985c3ffb 100644
--- a/runtime/onert/backend/cpu/ops/AddNLayer.cc
+++ b/runtime/onert/backend/cpu/ops/AddNLayer.cc
@@ -21,13 +21,7 @@
 #include <cker/operation/AddN.h>
 #include <assert.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 void AddNLayer::configure(std::vector<const IPortableTensor *> &&inputs, IPortableTensor *output)
@@ -63,7 +57,4 @@ void AddNLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/AddNLayer.h b/runtime/onert/backend/cpu/ops/AddNLayer.h
index b7639d149a5..a8c14b18ab8 100644
--- a/runtime/onert/backend/cpu/ops/AddNLayer.h
+++ b/runtime/onert/backend/cpu/ops/AddNLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class AddNLayer : public ::onert::exec::IFunction
@@ -45,9 +39,6 @@ class AddNLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_ADDNLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.cc b/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.cc
index a1b8bfce360..68191ab35f1 100644
--- a/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.cc
@@ -21,13 +21,7 @@
 #include <cker/operation/ArgMinMax.h>
 #include <assert.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 namespace
 {
@@ -117,7 +111,4 @@ void ArgMinMaxLayer::run()
 #undef TF_LITE_ARG_MIN_MAX
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.h b/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.h
index 4c864cb98f1..250db4e78b9 100644
--- a/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.h
+++ b/runtime/onert/backend/cpu/ops/ArgMinMaxLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ArgMinMaxLayer : public ::onert::exec::IFunction
@@ -48,9 +42,6 @@ class ArgMinMaxLayer : public ::onert::exec::IFunction
   bool _is_arg_max;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_ARGMINMAXLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/BatchMatMulLayer.cc b/runtime/onert/backend/cpu/ops/BatchMatMulLayer.cc
index 3b08fd5b15d..efbb8ece467 100644
--- a/runtime/onert/backend/cpu/ops/BatchMatMulLayer.cc
+++ b/runtime/onert/backend/cpu/ops/BatchMatMulLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/BatchMatMul.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 BatchMatMulLayer::BatchMatMulLayer()
@@ -78,7 +72,4 @@ void BatchMatMulLayer::run()
 
 #undef AVGPOOLING_PARAMETERS
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/BatchMatMulLayer.h b/runtime/onert/backend/cpu/ops/BatchMatMulLayer.h
index 6770e218b9a..f1bb79673ca 100644
--- a/runtime/onert/backend/cpu/ops/BatchMatMulLayer.h
+++ b/runtime/onert/backend/cpu/ops/BatchMatMulLayer.h
@@ -22,21 +22,12 @@
 
 #include <exec/IFunction.h>
 
-namespace nnfw
-{
-namespace cker
+namespace nnfw::cker
 {
 class BatchMatMul;
-}
-} // namespace nnfw
+} // namespace nnfw::cker
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class BatchMatMulLayer : public ::onert::exec::IFunction
@@ -64,9 +55,6 @@ class BatchMatMulLayer : public ::onert::exec::IFunction
   std::unique_ptr<nnfw::cker::BatchMatMul> _kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_BATCH_MATMUL_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.cc b/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.cc
index 2609481fb85..8d61592e9f7 100644
--- a/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.cc
+++ b/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/BatchToSpaceND.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 BatchToSpaceNDLayer::BatchToSpaceNDLayer()
@@ -76,7 +70,4 @@ void BatchToSpaceNDLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.h b/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.h
index 6e25b241bf7..f5102011480 100644
--- a/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.h
+++ b/runtime/onert/backend/cpu/ops/BatchToSpaceNDLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class BatchToSpaceNDLayer : public ::onert::exec::IFunction
@@ -51,9 +45,6 @@ class BatchToSpaceNDLayer : public ::onert::exec::IFunction
   IPortableTensor *_crops;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_BATCHTOSPACEND_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.cc b/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.cc
index 5ef506978f6..9d95aa4d525 100644
--- a/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.cc
+++ b/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/BinaryArithmeticOps.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -282,7 +276,4 @@ void BinaryArithmeticLayer::configure(const IPortableTensor *lhs, const IPortabl
 
 void BinaryArithmeticLayer::run() { _kernel(_lhs, _rhs, _output); }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.h b/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.h
index c7ed89187c5..3f655e3c898 100644
--- a/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.h
+++ b/runtime/onert/backend/cpu/ops/BinaryArithmeticLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 enum class ArithmeticType
@@ -61,9 +55,6 @@ class BinaryArithmeticLayer : public ::onert::exec::IFunction
   std::function<void(const IPortableTensor *, const IPortableTensor *, IPortableTensor *)> _kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_BINARYARITHMETICLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/BroadcastToLayer.cc b/runtime/onert/backend/cpu/ops/BroadcastToLayer.cc
index d31b814bbc4..d11e7cebe35 100644
--- a/runtime/onert/backend/cpu/ops/BroadcastToLayer.cc
+++ b/runtime/onert/backend/cpu/ops/BroadcastToLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/BroadcastTo.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 BroadcastToLayer::BroadcastToLayer() : _input(nullptr), _shape(nullptr), _output(nullptr)
@@ -67,7 +61,4 @@ void BroadcastToLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/BroadcastToLayer.h b/runtime/onert/backend/cpu/ops/BroadcastToLayer.h
index 8e8433fc9c7..144052bf8ff 100644
--- a/runtime/onert/backend/cpu/ops/BroadcastToLayer.h
+++ b/runtime/onert/backend/cpu/ops/BroadcastToLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class BroadcastToLayer : public ::onert::exec::IFunction
@@ -48,9 +42,6 @@ class BroadcastToLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_BROADCASTLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/CompareLayer.cc b/runtime/onert/backend/cpu/ops/CompareLayer.cc
index 07b74029127..0945b21cf77 100644
--- a/runtime/onert/backend/cpu/ops/CompareLayer.cc
+++ b/runtime/onert/backend/cpu/ops/CompareLayer.cc
@@ -20,13 +20,7 @@
 #include <assert.h>
 #include <cker/operation/Comparison.h>
 using namespace nnfw::cker;
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -166,7 +160,4 @@ void CompareLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/CompareLayer.h b/runtime/onert/backend/cpu/ops/CompareLayer.h
index add360ef852..3f440e6c727 100644
--- a/runtime/onert/backend/cpu/ops/CompareLayer.h
+++ b/runtime/onert/backend/cpu/ops/CompareLayer.h
@@ -22,13 +22,7 @@
 #include <exec/IFunction.h>
 #include <ir/operation/Comparison.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class CompareLayer : public ::onert::exec::IFunction
@@ -49,9 +43,6 @@ class CompareLayer : public ::onert::exec::IFunction
   ir::operation::Comparison::ComparisonType _op_type;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_COMPARELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ConcatLayer.cc b/runtime/onert/backend/cpu/ops/ConcatLayer.cc
index 5d48b0e7f99..bf86526a0aa 100644
--- a/runtime/onert/backend/cpu/ops/ConcatLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ConcatLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Concatenation.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 ConcatLayer::ConcatLayer() : _inputs(), _output(nullptr), _axis(0)
@@ -138,7 +132,4 @@ void ConcatLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ConcatLayer.h b/runtime/onert/backend/cpu/ops/ConcatLayer.h
index 0787199d69e..37cbf0a9071 100644
--- a/runtime/onert/backend/cpu/ops/ConcatLayer.h
+++ b/runtime/onert/backend/cpu/ops/ConcatLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ConcatLayer : public ::onert::exec::IFunction
@@ -51,9 +45,6 @@ class ConcatLayer : public ::onert::exec::IFunction
   int32_t _axis;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_CONCATLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ConvolutionLayer.cc b/runtime/onert/backend/cpu/ops/ConvolutionLayer.cc
index 717f2dc8ba2..b9862002733 100644
--- a/runtime/onert/backend/cpu/ops/ConvolutionLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ConvolutionLayer.cc
@@ -22,13 +22,7 @@
 #include "ir/Padding.h"
 #include <cker/operation/Conv.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 ConvolutionLayer::ConvolutionLayer()
   : _input(nullptr), _kernel(nullptr), _bias(nullptr), _output(nullptr),
@@ -358,7 +352,4 @@ void ConvolutionLayer::prepare()
   _prepare = true;
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ConvolutionLayer.h b/runtime/onert/backend/cpu/ops/ConvolutionLayer.h
index c5bab1a9205..62a879c534f 100644
--- a/runtime/onert/backend/cpu/ops/ConvolutionLayer.h
+++ b/runtime/onert/backend/cpu/ops/ConvolutionLayer.h
@@ -24,23 +24,14 @@
 #include <functional>
 #include <memory>
 
-namespace nnfw
-{
-namespace cker
+namespace nnfw::cker
 {
 class Conv;
 struct ConvHybridTempArena;
 class Shape;
-} // namespace cker
-} // namespace nnfw
+} // namespace nnfw::cker
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ConvolutionLayer : public ::onert::exec::IFunction
@@ -94,9 +85,6 @@ class ConvolutionLayer : public ::onert::exec::IFunction
   bool _is_hybrid;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_CONVOLUTIONLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.cc b/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.cc
index e23b7c14ad0..fdba608b61a 100644
--- a/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.cc
+++ b/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/DepthToSpace.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 DepthToSpaceLayer::DepthToSpaceLayer() : _input(nullptr), _block_size(0), _output(nullptr)
 {
@@ -71,7 +65,4 @@ void DepthToSpaceLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.h b/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.h
index 32e0171ceab..e31891fa803 100644
--- a/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.h
+++ b/runtime/onert/backend/cpu/ops/DepthToSpaceLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 class DepthToSpaceLayer : public ::onert::exec::IFunction
 {
@@ -46,9 +40,6 @@ class DepthToSpaceLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_DEPTH_TO_SPACE_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.cc b/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.cc
index 9ebaa9b14f7..ef347c9c321 100644
--- a/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.cc
+++ b/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.cc
@@ -19,13 +19,7 @@
 #include "cker/PortableTensorUtils.h"
 #include <cker/operation/DepthwiseConv.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 void DepthwiseConvolutionLayer::prepareF32()
@@ -367,7 +361,4 @@ void DepthwiseConvolutionLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.h b/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.h
index 62eabe17849..08336fa91e8 100644
--- a/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.h
+++ b/runtime/onert/backend/cpu/ops/DepthwiseConvolutionLayer.h
@@ -24,13 +24,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class DepthwiseConvolutionLayer : public ::onert::exec::IFunction
@@ -105,9 +99,6 @@ class DepthwiseConvolutionLayer : public ::onert::exec::IFunction
   std::vector<int32_t> _input_offsets;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_KERNEL_CPU_DEPTHWISECONVOLUTIONLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.cc b/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.cc
index dc9e20e0a76..fbbdde6a905 100644
--- a/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.cc
+++ b/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.cc
@@ -22,13 +22,7 @@
 #include <utility>
 #include <cmath>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -302,7 +296,4 @@ void DetectionPostProcessLayer::run()
 
 DetectionPostProcessLayer::~DetectionPostProcessLayer() { delete[] _allocations.selections_buffer; }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.h b/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.h
index 836a70caca5..b5696076b23 100644
--- a/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.h
+++ b/runtime/onert/backend/cpu/ops/DetectionPostProcessLayer.h
@@ -21,13 +21,7 @@
 
 #include "OperationUtils.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class DetectionPostProcessLayer : public ::onert::exec::IFunction
@@ -97,9 +91,6 @@ class DetectionPostProcessLayer : public ::onert::exec::IFunction
   Allocations _allocations;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_DPP_H__
diff --git a/runtime/onert/backend/cpu/ops/EinsumLayer.cc b/runtime/onert/backend/cpu/ops/EinsumLayer.cc
index 8e10c464211..14c4ccca650 100644
--- a/runtime/onert/backend/cpu/ops/EinsumLayer.cc
+++ b/runtime/onert/backend/cpu/ops/EinsumLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/Einsum.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 EinsumLayer::EinsumLayer()
@@ -77,7 +71,4 @@ void EinsumLayer::configure(const std::vector<const IPortableTensor *> &inputs,
   _output = output;
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/EinsumLayer.h b/runtime/onert/backend/cpu/ops/EinsumLayer.h
index a93f87e77e5..e05aad4661a 100644
--- a/runtime/onert/backend/cpu/ops/EinsumLayer.h
+++ b/runtime/onert/backend/cpu/ops/EinsumLayer.h
@@ -24,21 +24,12 @@
 #include <functional>
 #include <memory>
 
-namespace nnfw
-{
-namespace cker
+namespace nnfw::cker
 {
 class Einsum;
-}
-} // namespace nnfw
+} // namespace nnfw::cker
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class EinsumLayer : public ::onert::exec::IFunction
@@ -64,9 +55,6 @@ class EinsumLayer : public ::onert::exec::IFunction
   std::unique_ptr<nnfw::cker::Einsum> _einsum_kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_EINSUM_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.cc b/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.cc
index bf511415164..73c931b9091 100644
--- a/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.cc
@@ -25,13 +25,7 @@
 #include <cker/operation/ReLU6.h>
 #include <cker/operation/Tanh.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 ElementwiseActivationLayer::ElementwiseActivationLayer()
@@ -193,7 +187,4 @@ void ElementwiseActivationLayer::configure(const IPortableTensor *input, IPortab
 
 void ElementwiseActivationLayer::run() { _kernel(_input, _output); }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.h b/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.h
index d8a90148f3d..982e19c36da 100644
--- a/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.h
+++ b/runtime/onert/backend/cpu/ops/ElementwiseActivationLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 enum class ElementwiseActivationType
@@ -61,9 +55,6 @@ class ElementwiseActivationLayer : public ::onert::exec::IFunction
   std::function<void(const IPortableTensor *input, IPortableTensor *output)> _kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_ElementwiseActivationLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.cc b/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.cc
index 4dc039498c3..441fadd8309 100644
--- a/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.cc
@@ -24,13 +24,7 @@
 #include <cker/operation/LogicalOr.h>
 #include <cker/operation/MaxMin.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -232,7 +226,4 @@ void ElementwiseBinaryLayer::configure(const IPortableTensor *lhs, const IPortab
 
 void ElementwiseBinaryLayer::run() { _kernel(_lhs, _rhs, _output); }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.h b/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.h
index a6007ecd0e8..ebdd946a4cb 100644
--- a/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.h
+++ b/runtime/onert/backend/cpu/ops/ElementwiseBinaryLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 enum class ElementwiseBinaryType
@@ -61,9 +55,6 @@ class ElementwiseBinaryLayer : public ::onert::exec::IFunction
   std::function<void(const IPortableTensor *, const IPortableTensor *, IPortableTensor *)> _kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_ELEMENTWISEBINARYLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.cc b/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.cc
index f8e26e19a94..aa07f0844da 100644
--- a/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.cc
@@ -25,13 +25,7 @@
 #include <cker/operation/LogicalNot.h>
 #include <cker/operation/Round.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -396,7 +390,4 @@ void ElementwiseUnaryLayer::configure(const IPortableTensor *input, IPortableTen
 
 void ElementwiseUnaryLayer::run() { _kernel(_input, _output); }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.h b/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.h
index 54a6fc02a6c..a560c5807e4 100644
--- a/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.h
+++ b/runtime/onert/backend/cpu/ops/ElementwiseUnaryLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 enum class ElementwiseUnaryType
@@ -71,9 +65,6 @@ class ElementwiseUnaryLayer : public ::onert::exec::IFunction
   std::function<void(const IPortableTensor *, IPortableTensor *)> _kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_ELEMENTWISEUNARYLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ExpandDimsLayer.cc b/runtime/onert/backend/cpu/ops/ExpandDimsLayer.cc
index 543c402dd22..7d04a29a885 100644
--- a/runtime/onert/backend/cpu/ops/ExpandDimsLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ExpandDimsLayer.cc
@@ -16,13 +16,7 @@
 
 #include "ExpandDimsLayer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 ExpandDimsLayer::ExpandDimsLayer() : _input(nullptr), _output(nullptr)
@@ -46,7 +40,4 @@ void ExpandDimsLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ExpandDimsLayer.h b/runtime/onert/backend/cpu/ops/ExpandDimsLayer.h
index 1b7ead0c303..df49eddd4f2 100644
--- a/runtime/onert/backend/cpu/ops/ExpandDimsLayer.h
+++ b/runtime/onert/backend/cpu/ops/ExpandDimsLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ExpandDimsLayer : public ::onert::exec::IFunction
@@ -45,9 +39,6 @@ class ExpandDimsLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // ExpandDi__ONERT_BACKEND_CPU_OPS_EXPANDDIMS_LAYER_H__ms
diff --git a/runtime/onert/backend/cpu/ops/FillLayer.cc b/runtime/onert/backend/cpu/ops/FillLayer.cc
index cc12fcbd893..128caa79496 100644
--- a/runtime/onert/backend/cpu/ops/FillLayer.cc
+++ b/runtime/onert/backend/cpu/ops/FillLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Fill.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 FillLayer::FillLayer() : _value(nullptr), _output(nullptr)
@@ -65,7 +59,4 @@ void FillLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/FillLayer.h b/runtime/onert/backend/cpu/ops/FillLayer.h
index ce843654a93..732d3658de9 100644
--- a/runtime/onert/backend/cpu/ops/FillLayer.h
+++ b/runtime/onert/backend/cpu/ops/FillLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class FillLayer : public ::onert::exec::IFunction
@@ -44,9 +38,6 @@ class FillLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_FILLLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/FullyConnectedLayer.cc b/runtime/onert/backend/cpu/ops/FullyConnectedLayer.cc
index c2decaf6ca1..4f7e6bdca78 100644
--- a/runtime/onert/backend/cpu/ops/FullyConnectedLayer.cc
+++ b/runtime/onert/backend/cpu/ops/FullyConnectedLayer.cc
@@ -23,13 +23,7 @@
 #include <cker/TensorUtils.h>
 #include <misc/polymorphic_downcast.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 FullyConnectedLayer::FullyConnectedLayer()
@@ -326,7 +320,4 @@ void FullyConnectedLayer::prepare()
 #endif
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/FullyConnectedLayer.h b/runtime/onert/backend/cpu/ops/FullyConnectedLayer.h
index 34b4985608f..912b946a8bb 100644
--- a/runtime/onert/backend/cpu/ops/FullyConnectedLayer.h
+++ b/runtime/onert/backend/cpu/ops/FullyConnectedLayer.h
@@ -23,21 +23,12 @@
 
 #include <exec/IFunction.h>
 
-namespace nnfw
-{
-namespace cker
+namespace nnfw::cker
 {
 class FCTempArena;
-}
-} // namespace nnfw
+} // namespace nnfw::cker
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class FullyConnectedLayer : public ::onert::exec::IFunction
@@ -88,9 +79,6 @@ class FullyConnectedLayer : public ::onert::exec::IFunction
 #endif
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_FULLYCONNECTEDLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.cc b/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.cc
index 1bec15a08ae..6fc8824943a 100644
--- a/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.cc
+++ b/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/FusedBatchNorm.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 FusedBatchNormLayer::FusedBatchNormLayer()
@@ -87,7 +81,4 @@ void FusedBatchNormLayer::configure(const std::vector<const IPortableTensor *> &
   _data_format = data_format;
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.h b/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.h
index d42b0c900b7..0f62b23ffc6 100644
--- a/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.h
+++ b/runtime/onert/backend/cpu/ops/FusedBatchNormLayer.h
@@ -24,21 +24,12 @@
 #include <functional>
 #include <memory>
 
-namespace nnfw
-{
-namespace cker
+namespace nnfw::cker
 {
 class FusedBatchNorm;
-}
-} // namespace nnfw
+} // namespace nnfw::cker
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class FusedBatchNormLayer : public ::onert::exec::IFunction
@@ -65,9 +56,6 @@ class FusedBatchNormLayer : public ::onert::exec::IFunction
   std::unique_ptr<nnfw::cker::FusedBatchNorm> _fusedbatchnorm_kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_FUSEDBATCHNORM_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/GGMLHelper.cc b/runtime/onert/backend/cpu/ops/GGMLHelper.cc
index 17bc9b018b1..8b66f024171 100644
--- a/runtime/onert/backend/cpu/ops/GGMLHelper.cc
+++ b/runtime/onert/backend/cpu/ops/GGMLHelper.cc
@@ -16,13 +16,7 @@
 
 #include "GGMLHelper.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 ggml_type getGGMLType(ir::DataType type)
@@ -70,7 +64,4 @@ struct ggml_tensor getGGMLTensor(const IPortableTensor *tensor)
   return res;
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/GGMLHelper.h b/runtime/onert/backend/cpu/ops/GGMLHelper.h
index 3f559c7eadc..d692dc23d7d 100644
--- a/runtime/onert/backend/cpu/ops/GGMLHelper.h
+++ b/runtime/onert/backend/cpu/ops/GGMLHelper.h
@@ -21,20 +21,11 @@
 
 #include <ggml.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 struct ggml_tensor getGGMLTensor(const IPortableTensor *tensor);
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif
diff --git a/runtime/onert/backend/cpu/ops/GatherLayer.cc b/runtime/onert/backend/cpu/ops/GatherLayer.cc
index 2b23546488c..18a3464447a 100644
--- a/runtime/onert/backend/cpu/ops/GatherLayer.cc
+++ b/runtime/onert/backend/cpu/ops/GatherLayer.cc
@@ -21,13 +21,7 @@
 
 #include <cker/operation/Gather.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 void GatherLayer::configure(const IPortableTensor *input, const IPortableTensor *indices,
@@ -142,7 +136,4 @@ void GatherLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/GatherLayer.h b/runtime/onert/backend/cpu/ops/GatherLayer.h
index be2ae40a0f8..0761b0a8b5c 100644
--- a/runtime/onert/backend/cpu/ops/GatherLayer.h
+++ b/runtime/onert/backend/cpu/ops/GatherLayer.h
@@ -23,13 +23,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class GatherLayer : public ::onert::exec::IFunction
@@ -59,9 +53,6 @@ class GatherLayer : public ::onert::exec::IFunction
   ExternalContext *_ctx;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_GATHERLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/L2NormLayer.cc b/runtime/onert/backend/cpu/ops/L2NormLayer.cc
index fe5019de60c..0ff9b24f390 100644
--- a/runtime/onert/backend/cpu/ops/L2NormLayer.cc
+++ b/runtime/onert/backend/cpu/ops/L2NormLayer.cc
@@ -21,13 +21,7 @@
 #include <cker/operation/L2Normalize.h>
 #include <cker/Types.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 void L2NormLayer::configure(const IPortableTensor *input, IPortableTensor *output)
@@ -63,7 +57,4 @@ void L2NormLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/L2NormLayer.h b/runtime/onert/backend/cpu/ops/L2NormLayer.h
index 63f2d11330b..51d31476501 100644
--- a/runtime/onert/backend/cpu/ops/L2NormLayer.h
+++ b/runtime/onert/backend/cpu/ops/L2NormLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 class L2NormLayer : public ::onert::exec::IFunction
 {
@@ -47,9 +41,6 @@ class L2NormLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_L2NORM_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/LSTMLayer.cc b/runtime/onert/backend/cpu/ops/LSTMLayer.cc
index 16b0feec87e..c3986efecf7 100644
--- a/runtime/onert/backend/cpu/ops/LSTMLayer.cc
+++ b/runtime/onert/backend/cpu/ops/LSTMLayer.cc
@@ -21,13 +21,7 @@
 
 #include <cker/operation/LSTM.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -313,7 +307,4 @@ void LSTMLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/LSTMLayer.h b/runtime/onert/backend/cpu/ops/LSTMLayer.h
index 72ac2ed0412..c6a44bec7bf 100644
--- a/runtime/onert/backend/cpu/ops/LSTMLayer.h
+++ b/runtime/onert/backend/cpu/ops/LSTMLayer.h
@@ -23,21 +23,12 @@
 #include <ir/operation/LSTM.h>
 #include <exec/IFunction.h>
 
-namespace nnfw
-{
-namespace cker
+namespace nnfw::cker
 {
 class FCTempArena;
-}
-} // namespace nnfw
+} // namespace nnfw::cker
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 // TODO Support LSTM, BiDirectionalSequenceLSTM
@@ -121,9 +112,6 @@ class LSTMLayer : public ::onert::exec::IFunction
   bool _has_cell_state_data{false};
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_LSTMLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.cc b/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.cc
index a544dd97055..fe204a1edba 100644
--- a/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.cc
+++ b/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/LogSoftMax.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 LogSoftMaxLayer::LogSoftMaxLayer() : _input(nullptr), _output(nullptr), _beta(0.0), _axis(0)
@@ -95,7 +89,4 @@ void LogSoftMaxLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.h b/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.h
index 1533f336186..4c23fb1c34e 100644
--- a/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.h
+++ b/runtime/onert/backend/cpu/ops/LogSoftMaxLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class LogSoftMaxLayer : public ::onert::exec::IFunction
@@ -56,9 +50,6 @@ class LogSoftMaxLayer : public ::onert::exec::IFunction
   float _table[256];
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_LOGSOFTMAXLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.cc b/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.cc
index 7220a2bab40..f42b8cdeaab 100644
--- a/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.cc
+++ b/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/MatrixBandPart.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 MatrixBandPartLayer::MatrixBandPartLayer()
@@ -84,7 +78,4 @@ void MatrixBandPartLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.h b/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.h
index 9dcc6b2775e..992e04093a8 100644
--- a/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.h
+++ b/runtime/onert/backend/cpu/ops/MatrixBandPartLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class MatrixBandPartLayer : public ::onert::exec::IFunction
@@ -52,9 +46,6 @@ class MatrixBandPartLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_MATRIXBANDPARTLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/MeanLayer.cc b/runtime/onert/backend/cpu/ops/MeanLayer.cc
index c86a9d12649..f773f02b526 100644
--- a/runtime/onert/backend/cpu/ops/MeanLayer.cc
+++ b/runtime/onert/backend/cpu/ops/MeanLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/ReduceMean.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 MeanLayer::MeanLayer() : _input(nullptr), _axes(nullptr), _output(nullptr), _keep_dims(false)
@@ -90,7 +84,4 @@ void MeanLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/MeanLayer.h b/runtime/onert/backend/cpu/ops/MeanLayer.h
index 7ad81e1e2dd..0ec26d78061 100644
--- a/runtime/onert/backend/cpu/ops/MeanLayer.h
+++ b/runtime/onert/backend/cpu/ops/MeanLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class MeanLayer : public ::onert::exec::IFunction
@@ -52,9 +46,6 @@ class MeanLayer : public ::onert::exec::IFunction
   bool _keep_dims;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_MEANLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/OneHotLayer.cc b/runtime/onert/backend/cpu/ops/OneHotLayer.cc
index 66773a608f1..83acc564163 100644
--- a/runtime/onert/backend/cpu/ops/OneHotLayer.cc
+++ b/runtime/onert/backend/cpu/ops/OneHotLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/OneHot.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 template <typename T> void OneHotLayer::oneHotImpl()
@@ -61,7 +55,4 @@ void OneHotLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/OneHotLayer.h b/runtime/onert/backend/cpu/ops/OneHotLayer.h
index b0f03a261df..e286bb6f2f5 100644
--- a/runtime/onert/backend/cpu/ops/OneHotLayer.h
+++ b/runtime/onert/backend/cpu/ops/OneHotLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class OneHotLayer : public ::onert::exec::IFunction
@@ -59,9 +53,6 @@ class OneHotLayer : public ::onert::exec::IFunction
   int32_t _axis;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_ONEHOTLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/OperationUtils.cc b/runtime/onert/backend/cpu/ops/OperationUtils.cc
index de88ba0255e..f6db75d9df5 100644
--- a/runtime/onert/backend/cpu/ops/OperationUtils.cc
+++ b/runtime/onert/backend/cpu/ops/OperationUtils.cc
@@ -20,13 +20,7 @@
 #include <cassert>
 #include <cmath>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 uint32_t getNumberOfDimensions(const IPortableTensor *tensor)
@@ -322,7 +316,4 @@ nnfw::cker::RoPEMode getRoPEMode(ir::operation::RoPE::RoPEMode rope_mode)
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/OperationUtils.h b/runtime/onert/backend/cpu/ops/OperationUtils.h
index c354dc49bab..f0bfd7e79ec 100644
--- a/runtime/onert/backend/cpu/ops/OperationUtils.h
+++ b/runtime/onert/backend/cpu/ops/OperationUtils.h
@@ -33,13 +33,7 @@
 using OperandType = onert::ir::DataType;
 using namespace onert::util;
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 union DataPtr {
@@ -194,9 +188,6 @@ template <> inline bool *getBuffer(IPortableTensor *tensor)
   return reinterpret_cast<bool *>(tensor->buffer());
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __NNFW_SUPPORT_NNAPI_OPERATION_UTILS_H__
diff --git a/runtime/onert/backend/cpu/ops/PackLayer.cc b/runtime/onert/backend/cpu/ops/PackLayer.cc
index beac6c73be3..69791ac4294 100644
--- a/runtime/onert/backend/cpu/ops/PackLayer.cc
+++ b/runtime/onert/backend/cpu/ops/PackLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Pack.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 PackLayer::PackLayer() : _inputs(), _output(nullptr), _axis(0)
@@ -89,7 +83,4 @@ void PackLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/PackLayer.h b/runtime/onert/backend/cpu/ops/PackLayer.h
index b92c8d48c23..9aa98217757 100644
--- a/runtime/onert/backend/cpu/ops/PackLayer.h
+++ b/runtime/onert/backend/cpu/ops/PackLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class PackLayer : public ::onert::exec::IFunction
@@ -48,9 +42,6 @@ class PackLayer : public ::onert::exec::IFunction
   int32_t _axis;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_PACKLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/PadLayer.cc b/runtime/onert/backend/cpu/ops/PadLayer.cc
index aceb42de3ae..8035ea2fb11 100644
--- a/runtime/onert/backend/cpu/ops/PadLayer.cc
+++ b/runtime/onert/backend/cpu/ops/PadLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/Pad.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 PadLayer::PadLayer()
@@ -92,7 +86,4 @@ void PadLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/PadLayer.h b/runtime/onert/backend/cpu/ops/PadLayer.h
index b6caddaea14..c0049dceb00 100644
--- a/runtime/onert/backend/cpu/ops/PadLayer.h
+++ b/runtime/onert/backend/cpu/ops/PadLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 // Note, this is pad with mode=`CONSTANT`: it doesn't support `REFLECT` and
@@ -54,9 +48,6 @@ class PadLayer : public ::onert::exec::IFunction
   ConstDataPtr _constantValueData;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_PADLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/PoolLayer.cc b/runtime/onert/backend/cpu/ops/PoolLayer.cc
index 088ca5fd7fc..326c0a2850d 100644
--- a/runtime/onert/backend/cpu/ops/PoolLayer.cc
+++ b/runtime/onert/backend/cpu/ops/PoolLayer.cc
@@ -21,13 +21,7 @@
 
 #include <unordered_map>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -143,7 +137,4 @@ void PoolLayer::run() { _kernel(_input, _output); }
 
 #undef AVGPOOLING_PARAMETERS
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/PoolLayer.h b/runtime/onert/backend/cpu/ops/PoolLayer.h
index adc89550596..6d63ea059e2 100644
--- a/runtime/onert/backend/cpu/ops/PoolLayer.h
+++ b/runtime/onert/backend/cpu/ops/PoolLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 enum class PoolType
@@ -61,9 +55,6 @@ class PoolLayer : public ::onert::exec::IFunction
   std::function<void(const IPortableTensor *, IPortableTensor *)> _kernel;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_POOLLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/PowLayer.cc b/runtime/onert/backend/cpu/ops/PowLayer.cc
index efd024dee28..fb78bcfe61d 100644
--- a/runtime/onert/backend/cpu/ops/PowLayer.cc
+++ b/runtime/onert/backend/cpu/ops/PowLayer.cc
@@ -19,13 +19,7 @@
 #include <cker/operation/Pow.h>
 #include <cker/operation/BinaryArithmeticOps.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 void PowLayer::powFloat32()
@@ -65,7 +59,4 @@ void PowLayer::run()
     throw std::runtime_error{"Pow: unsupportted data type"};
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/PowLayer.h b/runtime/onert/backend/cpu/ops/PowLayer.h
index 2689aad17ed..d282a479959 100644
--- a/runtime/onert/backend/cpu/ops/PowLayer.h
+++ b/runtime/onert/backend/cpu/ops/PowLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class PowLayer : public ::onert::exec::IFunction
@@ -55,9 +49,6 @@ class PowLayer : public ::onert::exec::IFunction
   ir::Activation _activation{ir::Activation::NONE};
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_POWLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/QuantizeLayer.cc b/runtime/onert/backend/cpu/ops/QuantizeLayer.cc
index 08550e7c93a..2e5e53d0b82 100644
--- a/runtime/onert/backend/cpu/ops/QuantizeLayer.cc
+++ b/runtime/onert/backend/cpu/ops/QuantizeLayer.cc
@@ -24,13 +24,7 @@
 #include <cker/operation/Quantize.h>
 #include <cker/operation/Round.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 template <typename InputT, typename OutputT>
 void affineQuantize(const IPortableTensor *input, IPortableTensor *output)
@@ -94,7 +88,4 @@ void QuantizeLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/QuantizeLayer.h b/runtime/onert/backend/cpu/ops/QuantizeLayer.h
index 112d315623c..ef3f79a997a 100644
--- a/runtime/onert/backend/cpu/ops/QuantizeLayer.h
+++ b/runtime/onert/backend/cpu/ops/QuantizeLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 class QuantizeLayer : public ::onert::exec::IFunction
 {
@@ -47,9 +41,6 @@ class QuantizeLayer : public ::onert::exec::IFunction
   int32_t _output_multiplier;
   int _output_shift;
 };
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_QUANTIZELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/RangeLayer.cc b/runtime/onert/backend/cpu/ops/RangeLayer.cc
index a41b31b3fca..f14f6a9f6bc 100644
--- a/runtime/onert/backend/cpu/ops/RangeLayer.cc
+++ b/runtime/onert/backend/cpu/ops/RangeLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Range.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 RangeLayer::RangeLayer() : _start(nullptr), _limit(nullptr), _delta(nullptr), _output(nullptr)
 {
@@ -60,7 +54,4 @@ void RangeLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/RangeLayer.h b/runtime/onert/backend/cpu/ops/RangeLayer.h
index 2d83b39b159..5ab4063dd9f 100644
--- a/runtime/onert/backend/cpu/ops/RangeLayer.h
+++ b/runtime/onert/backend/cpu/ops/RangeLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 class RangeLayer : public ::onert::exec::IFunction
 {
@@ -46,9 +40,6 @@ class RangeLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_RANGELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/RankLayer.cc b/runtime/onert/backend/cpu/ops/RankLayer.cc
index 765c595ff20..78325d7fc91 100644
--- a/runtime/onert/backend/cpu/ops/RankLayer.cc
+++ b/runtime/onert/backend/cpu/ops/RankLayer.cc
@@ -18,13 +18,7 @@
 
 #include "OperationUtils.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 RankLayer::RankLayer() : _input(nullptr), _output(nullptr)
@@ -44,7 +38,4 @@ void RankLayer::run()
   output_data[0] = _input->getShape().rank();
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/RankLayer.h b/runtime/onert/backend/cpu/ops/RankLayer.h
index 6282ceb074f..d7ffb1e8cf7 100644
--- a/runtime/onert/backend/cpu/ops/RankLayer.h
+++ b/runtime/onert/backend/cpu/ops/RankLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class RankLayer : public ::onert::exec::IFunction
@@ -45,9 +39,6 @@ class RankLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_RANKLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ReduceLayer.cc b/runtime/onert/backend/cpu/ops/ReduceLayer.cc
index 8c2bc1b3e4a..e9abe4ff10d 100644
--- a/runtime/onert/backend/cpu/ops/ReduceLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ReduceLayer.cc
@@ -21,13 +21,7 @@
 #include "cker/neon/neon_check.h"
 #include <cker/operation/Reduce.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 namespace
@@ -221,7 +215,4 @@ void ReduceLayer::run()
   _kernel(_input, _output, axes);
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ReduceLayer.h b/runtime/onert/backend/cpu/ops/ReduceLayer.h
index e70f0fcb21a..1fed24c0437 100644
--- a/runtime/onert/backend/cpu/ops/ReduceLayer.h
+++ b/runtime/onert/backend/cpu/ops/ReduceLayer.h
@@ -24,21 +24,12 @@
 #include <exec/IFunction.h>
 #include <memory>
 
-namespace nnfw
-{
-namespace cker
+namespace nnfw::cker
 {
 class Reduce;
-}
-} // namespace nnfw
+} // namespace nnfw::cker
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 enum class ReduceType
@@ -77,9 +68,6 @@ class ReduceLayer : public ::onert::exec::IFunction
   ReduceType _reduceType;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_REDUCESUMLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ReshapeLayer.cc b/runtime/onert/backend/cpu/ops/ReshapeLayer.cc
index a50cf0eaceb..53f43a079df 100644
--- a/runtime/onert/backend/cpu/ops/ReshapeLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ReshapeLayer.cc
@@ -16,13 +16,7 @@
 
 #include "ReshapeLayer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 ReshapeLayer::ReshapeLayer() : _input(nullptr), _shape(nullptr), _output(nullptr)
@@ -51,7 +45,4 @@ void ReshapeLayer::configure(const IPortableTensor *input, const IPortableTensor
 
 void ReshapeLayer::run() { reshapeGeneric(); }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ReshapeLayer.h b/runtime/onert/backend/cpu/ops/ReshapeLayer.h
index b49c0bf7d73..c61fc18d8e9 100644
--- a/runtime/onert/backend/cpu/ops/ReshapeLayer.h
+++ b/runtime/onert/backend/cpu/ops/ReshapeLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ReshapeLayer : public ::onert::exec::IFunction
@@ -49,9 +43,6 @@ class ReshapeLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_RESHAPELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.cc b/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.cc
index c32015fdc34..9b46d049b7a 100644
--- a/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.cc
@@ -18,13 +18,7 @@
 #include "cker/operation/ResizeBilinear.h"
 #include <cker/Types.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 ResizeBilinearLayer::ResizeBilinearLayer()
@@ -116,7 +110,4 @@ void ResizeBilinearLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.h b/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.h
index d7ae1c62015..cc20845f2ee 100644
--- a/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.h
+++ b/runtime/onert/backend/cpu/ops/ResizeBilinearLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ResizeBilinearLayer : public ::onert::exec::IFunction
@@ -54,9 +48,6 @@ class ResizeBilinearLayer : public ::onert::exec::IFunction
   bool _half_pixel_centers;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_RESIZEBILINEAR_H__
diff --git a/runtime/onert/backend/cpu/ops/ReverseLayer.cc b/runtime/onert/backend/cpu/ops/ReverseLayer.cc
index cddab302ae3..8ae4c39ca0f 100644
--- a/runtime/onert/backend/cpu/ops/ReverseLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ReverseLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Reverse.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 void ReverseLayer::run()
@@ -61,7 +55,4 @@ void ReverseLayer::configure(const IPortableTensor *input, const IPortableTensor
   _output = output;
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ReverseLayer.h b/runtime/onert/backend/cpu/ops/ReverseLayer.h
index 9591dae3250..6af20016e18 100644
--- a/runtime/onert/backend/cpu/ops/ReverseLayer.h
+++ b/runtime/onert/backend/cpu/ops/ReverseLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ReverseLayer : public ::onert::exec::IFunction
@@ -50,9 +44,6 @@ class ReverseLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_REVERSE_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/RmsNormLayer.cc b/runtime/onert/backend/cpu/ops/RmsNormLayer.cc
index 4dcfa9d1045..a8dad9b59df 100644
--- a/runtime/onert/backend/cpu/ops/RmsNormLayer.cc
+++ b/runtime/onert/backend/cpu/ops/RmsNormLayer.cc
@@ -21,13 +21,7 @@
 #include <cker/operation/RmsNorm.h>
 #include <cker/Types.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 void RmsNormLayer::configure(const IPortableTensor *input, const IPortableTensor *gamma,
@@ -58,7 +52,4 @@ void RmsNormLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/RmsNormLayer.h b/runtime/onert/backend/cpu/ops/RmsNormLayer.h
index 134c39b6513..8e570299044 100644
--- a/runtime/onert/backend/cpu/ops/RmsNormLayer.h
+++ b/runtime/onert/backend/cpu/ops/RmsNormLayer.h
@@ -21,13 +21,7 @@
 #include "OperationUtils.h"
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 class RmsNormLayer : public ::onert::exec::IFunction
 {
@@ -50,9 +44,6 @@ class RmsNormLayer : public ::onert::exec::IFunction
   float _epsilon;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_RMSNORM_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/RoPELayer.cc b/runtime/onert/backend/cpu/ops/RoPELayer.cc
index 7e3f7d84dbb..009a52f8d6f 100644
--- a/runtime/onert/backend/cpu/ops/RoPELayer.cc
+++ b/runtime/onert/backend/cpu/ops/RoPELayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/RoPE.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 RoPELayer::RoPELayer()
@@ -86,7 +80,4 @@ void RoPELayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/RoPELayer.h b/runtime/onert/backend/cpu/ops/RoPELayer.h
index ee16c75c050..ee3a6fbb51a 100644
--- a/runtime/onert/backend/cpu/ops/RoPELayer.h
+++ b/runtime/onert/backend/cpu/ops/RoPELayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class RoPELayer : public ::onert::exec::IFunction
@@ -55,9 +49,6 @@ class RoPELayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_ROPE_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SelectLayer.cc b/runtime/onert/backend/cpu/ops/SelectLayer.cc
index 4c28d14719a..814103b4ebf 100644
--- a/runtime/onert/backend/cpu/ops/SelectLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SelectLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Select.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 SelectLayer::SelectLayer()
@@ -82,7 +76,4 @@ void SelectLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SelectLayer.h b/runtime/onert/backend/cpu/ops/SelectLayer.h
index 2ef50f369b2..180ff1bf1d9 100644
--- a/runtime/onert/backend/cpu/ops/SelectLayer.h
+++ b/runtime/onert/backend/cpu/ops/SelectLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class SelectLayer : public ::onert::exec::IFunction
@@ -48,9 +42,6 @@ class SelectLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SELECT_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/ShapeLayer.cc b/runtime/onert/backend/cpu/ops/ShapeLayer.cc
index 46294e948c8..13e32d58978 100644
--- a/runtime/onert/backend/cpu/ops/ShapeLayer.cc
+++ b/runtime/onert/backend/cpu/ops/ShapeLayer.cc
@@ -18,13 +18,7 @@
 
 #include "OperationUtils.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 ShapeLayer::ShapeLayer() : _input(nullptr), _output(nullptr)
@@ -67,7 +61,4 @@ void ShapeLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/ShapeLayer.h b/runtime/onert/backend/cpu/ops/ShapeLayer.h
index bd2a7abde17..37bb1503c7d 100644
--- a/runtime/onert/backend/cpu/ops/ShapeLayer.h
+++ b/runtime/onert/backend/cpu/ops/ShapeLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class ShapeLayer : public ::onert::exec::IFunction
@@ -45,9 +39,6 @@ class ShapeLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SHAPELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SliceLayer.cc b/runtime/onert/backend/cpu/ops/SliceLayer.cc
index 6332fbb56d9..23c9af95c7f 100644
--- a/runtime/onert/backend/cpu/ops/SliceLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SliceLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Slice.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 SliceLayer::SliceLayer() : _input(nullptr), _begin(nullptr), _size(nullptr), _output(nullptr)
@@ -113,7 +107,4 @@ void SliceLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SliceLayer.h b/runtime/onert/backend/cpu/ops/SliceLayer.h
index 650e2c97a3e..edc04253fa7 100644
--- a/runtime/onert/backend/cpu/ops/SliceLayer.h
+++ b/runtime/onert/backend/cpu/ops/SliceLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class SliceLayer : public ::onert::exec::IFunction
@@ -56,9 +50,6 @@ class SliceLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SLICELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SoftMaxLayer.cc b/runtime/onert/backend/cpu/ops/SoftMaxLayer.cc
index 320914dae0b..a40d7f4f29a 100644
--- a/runtime/onert/backend/cpu/ops/SoftMaxLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SoftMaxLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/SoftMax.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 SoftMaxLayer::SoftMaxLayer() : _input(nullptr), _output(nullptr), _beta(0.0)
@@ -124,7 +118,4 @@ void SoftMaxLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SoftMaxLayer.h b/runtime/onert/backend/cpu/ops/SoftMaxLayer.h
index fd20136d8e1..32a789c7b02 100644
--- a/runtime/onert/backend/cpu/ops/SoftMaxLayer.h
+++ b/runtime/onert/backend/cpu/ops/SoftMaxLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class SoftMaxLayer : public ::onert::exec::IFunction
@@ -56,9 +50,6 @@ class SoftMaxLayer : public ::onert::exec::IFunction
   uint8_t _uint8_table2[256];
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SOFTMAXLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.cc b/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.cc
index 8dd0a01a5a6..d4b7478e581 100644
--- a/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/SpaceToBatchND.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 SpaceToBatchNDLayer::SpaceToBatchNDLayer()
   : _input(nullptr), _block_shape(nullptr), _padding(nullptr), _output(nullptr)
@@ -106,7 +100,4 @@ void SpaceToBatchNDLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.h b/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.h
index 6f46387194c..2eae8ef8d78 100644
--- a/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.h
+++ b/runtime/onert/backend/cpu/ops/SpaceToBatchNDLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 class SpaceToBatchNDLayer : public ::onert::exec::IFunction
 {
@@ -52,9 +46,6 @@ class SpaceToBatchNDLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SPACE_TO_BATCH_ND_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.cc b/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.cc
index 8271daf4238..b5011ce4e68 100644
--- a/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/SpaceToDepth.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 SpaceToDepthLayer::SpaceToDepthLayer() : _input(nullptr), _block_size(0), _output(nullptr)
 {
@@ -67,7 +61,4 @@ void SpaceToDepthLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.h b/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.h
index c11ef2b0aed..59f9b3fa590 100644
--- a/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.h
+++ b/runtime/onert/backend/cpu/ops/SpaceToDepthLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 class SpaceToDepthLayer : public ::onert::exec::IFunction
 {
@@ -46,9 +40,6 @@ class SpaceToDepthLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SPACE_TO_BATCH_ND_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SplitLayer.cc b/runtime/onert/backend/cpu/ops/SplitLayer.cc
index 6e4eaccd4e6..05ab632b2a5 100644
--- a/runtime/onert/backend/cpu/ops/SplitLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SplitLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Split.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 SplitLayer::SplitLayer() : _input(nullptr), _axis(nullptr), _num_splits(0), _outputs()
@@ -97,7 +91,4 @@ void SplitLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SplitLayer.h b/runtime/onert/backend/cpu/ops/SplitLayer.h
index 090f8716669..94c92efefa4 100644
--- a/runtime/onert/backend/cpu/ops/SplitLayer.h
+++ b/runtime/onert/backend/cpu/ops/SplitLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class SplitLayer : public ::onert::exec::IFunction
@@ -50,9 +44,6 @@ class SplitLayer : public ::onert::exec::IFunction
   std::vector<IPortableTensor *> _outputs;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SPLITLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SplitVLayer.cc b/runtime/onert/backend/cpu/ops/SplitVLayer.cc
index 166e6e6fda0..3fa41be44f9 100644
--- a/runtime/onert/backend/cpu/ops/SplitVLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SplitVLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/SplitV.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 SplitVLayer::SplitVLayer()
@@ -93,7 +87,4 @@ void SplitVLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SplitVLayer.h b/runtime/onert/backend/cpu/ops/SplitVLayer.h
index 98f2f4406e8..1e7a0421612 100644
--- a/runtime/onert/backend/cpu/ops/SplitVLayer.h
+++ b/runtime/onert/backend/cpu/ops/SplitVLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class SplitVLayer : public ::onert::exec::IFunction
@@ -52,9 +46,6 @@ class SplitVLayer : public ::onert::exec::IFunction
   std::vector<IPortableTensor *> _outputs;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SPLIT_V_LAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/SquaredDiffLayer.cc b/runtime/onert/backend/cpu/ops/SquaredDiffLayer.cc
index 78984c5a93e..8202d01486e 100644
--- a/runtime/onert/backend/cpu/ops/SquaredDiffLayer.cc
+++ b/runtime/onert/backend/cpu/ops/SquaredDiffLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/SqDiff.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 SqDiffLayer::SqDiffLayer() : _input1(nullptr), _input2(nullptr), _output(nullptr)
@@ -59,7 +53,4 @@ void SqDiffLayer::run()
     throw std::runtime_error{"SquaredDiff: unsupported data type"};
   }
 }
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/SquaredDiffLayer.h b/runtime/onert/backend/cpu/ops/SquaredDiffLayer.h
index 386eea9ae30..a8c9dd6a55e 100644
--- a/runtime/onert/backend/cpu/ops/SquaredDiffLayer.h
+++ b/runtime/onert/backend/cpu/ops/SquaredDiffLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class SqDiffLayer : public ::onert::exec::IFunction
@@ -49,9 +43,6 @@ class SqDiffLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_SQDIFFLAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.cc b/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.cc
index 587582e8f93..ffd0b7fb5ed 100644
--- a/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.cc
+++ b/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/operation/StatelessRandomUniform.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 StatelessRandomUniformLayer::StatelessRandomUniformLayer()
@@ -61,7 +55,4 @@ void StatelessRandomUniformLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.h b/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.h
index ef11d623d1c..ae1c3700230 100644
--- a/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.h
+++ b/runtime/onert/backend/cpu/ops/StatelessRandomUniformLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class StatelessRandomUniformLayer : public ::onert::exec::IFunction
@@ -51,9 +45,6 @@ class StatelessRandomUniformLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_STATELESS_RANDOM_UNIFORM_H__
diff --git a/runtime/onert/backend/cpu/ops/StridedSliceLayer.cc b/runtime/onert/backend/cpu/ops/StridedSliceLayer.cc
index bb8550ad022..dbeb59cc898 100644
--- a/runtime/onert/backend/cpu/ops/StridedSliceLayer.cc
+++ b/runtime/onert/backend/cpu/ops/StridedSliceLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/StridedSlice.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 StridedSliceLayer::StridedSliceLayer()
@@ -87,7 +81,4 @@ void StridedSliceLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/StridedSliceLayer.h b/runtime/onert/backend/cpu/ops/StridedSliceLayer.h
index 46840815242..9619a5f268a 100644
--- a/runtime/onert/backend/cpu/ops/StridedSliceLayer.h
+++ b/runtime/onert/backend/cpu/ops/StridedSliceLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class StridedSliceLayer : public ::onert::exec::IFunction
@@ -60,9 +54,6 @@ class StridedSliceLayer : public ::onert::exec::IFunction
   int32_t _shrink_axis_mask;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_STRIDEDSLICELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/TileLayer.cc b/runtime/onert/backend/cpu/ops/TileLayer.cc
index 1f018db93ea..9b0b1dad947 100644
--- a/runtime/onert/backend/cpu/ops/TileLayer.cc
+++ b/runtime/onert/backend/cpu/ops/TileLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Tile.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 TileLayer::TileLayer() : _input(nullptr), _multipliers(nullptr), _output(nullptr)
@@ -70,7 +64,4 @@ void TileLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/TileLayer.h b/runtime/onert/backend/cpu/ops/TileLayer.h
index d7b793ecc88..40376dc4a5f 100644
--- a/runtime/onert/backend/cpu/ops/TileLayer.h
+++ b/runtime/onert/backend/cpu/ops/TileLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class TileLayer : public ::onert::exec::IFunction
@@ -51,9 +45,6 @@ class TileLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_TILELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/TransposeLayer.cc b/runtime/onert/backend/cpu/ops/TransposeLayer.cc
index 850c07ab838..a2592cdcbb8 100644
--- a/runtime/onert/backend/cpu/ops/TransposeLayer.cc
+++ b/runtime/onert/backend/cpu/ops/TransposeLayer.cc
@@ -21,13 +21,7 @@
 #include <cker/operation/Transpose.h>
 #include <numeric>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 TransposeLayer::TransposeLayer() : _input(nullptr), _perm(nullptr), _output(nullptr)
@@ -105,7 +99,4 @@ void TransposeLayer::run()
   }
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/TransposeLayer.h b/runtime/onert/backend/cpu/ops/TransposeLayer.h
index c8e9f8ae7f8..289d3bf5d49 100644
--- a/runtime/onert/backend/cpu/ops/TransposeLayer.h
+++ b/runtime/onert/backend/cpu/ops/TransposeLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class TransposeLayer : public ::onert::exec::IFunction
@@ -51,9 +45,6 @@ class TransposeLayer : public ::onert::exec::IFunction
   IPortableTensor *_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_TRANSPOSELAYER_H__
diff --git a/runtime/onert/backend/cpu/ops/UnpackLayer.cc b/runtime/onert/backend/cpu/ops/UnpackLayer.cc
index f18fb948329..bb592b8e953 100644
--- a/runtime/onert/backend/cpu/ops/UnpackLayer.cc
+++ b/runtime/onert/backend/cpu/ops/UnpackLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/operation/Unpack.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 UnpackLayer::UnpackLayer() : _input(nullptr), _outputs(), _axis(0), _num_output(0)
@@ -85,7 +79,4 @@ void UnpackLayer::run()
     throw std::runtime_error{"Unpack: Unsupported data type"};
 }
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
diff --git a/runtime/onert/backend/cpu/ops/UnpackLayer.h b/runtime/onert/backend/cpu/ops/UnpackLayer.h
index a185b31a040..6609bbdac37 100644
--- a/runtime/onert/backend/cpu/ops/UnpackLayer.h
+++ b/runtime/onert/backend/cpu/ops/UnpackLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace cpu
-{
-namespace ops
+namespace onert::backend::cpu::ops
 {
 
 class UnpackLayer : public ::onert::exec::IFunction
@@ -50,9 +44,6 @@ class UnpackLayer : public ::onert::exec::IFunction
   int32_t _num_output;
 };
 
-} // namespace ops
-} // namespace cpu
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::cpu::ops
 
 #endif // __ONERT_BACKEND_CPU_OPS_UNPACKLAYER_H__
diff --git a/runtime/onert/backend/ruy/Backend.h b/runtime/onert/backend/ruy/Backend.h
index 4077965c450..45638565ea4 100644
--- a/runtime/onert/backend/ruy/Backend.h
+++ b/runtime/onert/backend/ruy/Backend.h
@@ -25,11 +25,7 @@
 
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 class Backend : public ::onert::backend::Backend
@@ -57,8 +53,6 @@ class Backend : public ::onert::backend::Backend
   std::shared_ptr<IConfig> _config;
 };
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_BACKEND_H__
diff --git a/runtime/onert/backend/ruy/BackendContext.cc b/runtime/onert/backend/ruy/BackendContext.cc
index 43e37031e1b..52b0da2cba9 100644
--- a/runtime/onert/backend/ruy/BackendContext.cc
+++ b/runtime/onert/backend/ruy/BackendContext.cc
@@ -24,11 +24,7 @@
 #include "ir/OperandIndexSequence.h"
 #include "backend/basic/BackendContextHelpers.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 ITensorRegistry *BackendContext::genTensors() { return basic::genTensors(*this); }
@@ -59,6 +55,4 @@ FunctionMap BackendContext::genKernels()
   return ret;
 }
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
diff --git a/runtime/onert/backend/ruy/BackendContext.h b/runtime/onert/backend/ruy/BackendContext.h
index e29f2685fa4..53e04bf589e 100644
--- a/runtime/onert/backend/ruy/BackendContext.h
+++ b/runtime/onert/backend/ruy/BackendContext.h
@@ -24,11 +24,7 @@
 #include <backend/BackendContext.h>
 #include <compiler/GraphLowerInfo.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 class BackendContext : public onert::backend::BackendContext
@@ -65,8 +61,6 @@ class BackendContext : public onert::backend::BackendContext
   std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/ruy/Config.cc b/runtime/onert/backend/ruy/Config.cc
index bf07aa71924..a6a0968e37f 100644
--- a/runtime/onert/backend/ruy/Config.cc
+++ b/runtime/onert/backend/ruy/Config.cc
@@ -16,15 +16,9 @@
 
 #include "Config.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 bool Config::initialize() { return true; }
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
diff --git a/runtime/onert/backend/ruy/Config.h b/runtime/onert/backend/ruy/Config.h
index a5b4c41a8c5..657ee20e283 100644
--- a/runtime/onert/backend/ruy/Config.h
+++ b/runtime/onert/backend/ruy/Config.h
@@ -21,11 +21,7 @@
 #include <memory>
 #include <util/ITimer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 class Config : public IConfig
@@ -40,8 +36,6 @@ class Config : public IConfig
   std::unique_ptr<util::ITimer> timer() override { return std::make_unique<util::CPUTimer>(); }
 };
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_CONFIG_H__
diff --git a/runtime/onert/backend/ruy/ExternalContext.h b/runtime/onert/backend/ruy/ExternalContext.h
index e8502378a00..10ba119320c 100644
--- a/runtime/onert/backend/ruy/ExternalContext.h
+++ b/runtime/onert/backend/ruy/ExternalContext.h
@@ -22,11 +22,7 @@
 
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 class ExternalContext
@@ -53,8 +49,6 @@ class ExternalContext
   const std::unique_ptr<::ruy::Context> _ruy_context;
 };
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_EXTERNAL_CONTEXT_H__
diff --git a/runtime/onert/backend/ruy/KernelGenerator.cc b/runtime/onert/backend/ruy/KernelGenerator.cc
index 1a665dcae33..88bca1b581d 100644
--- a/runtime/onert/backend/ruy/KernelGenerator.cc
+++ b/runtime/onert/backend/ruy/KernelGenerator.cc
@@ -28,11 +28,7 @@
 
 #include <stdexcept>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 std::unique_ptr<exec::FunctionSequence> KernelGenerator::generate(ir::OperationIndex ind)
@@ -153,6 +149,4 @@ void KernelGenerator::visit(const ir::operation::FullyConnected &node)
   _return_fn = std::move(fn);
 }
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
diff --git a/runtime/onert/backend/ruy/KernelGenerator.h b/runtime/onert/backend/ruy/KernelGenerator.h
index c6c9438bd30..6320c8391a2 100644
--- a/runtime/onert/backend/ruy/KernelGenerator.h
+++ b/runtime/onert/backend/ruy/KernelGenerator.h
@@ -27,11 +27,7 @@
 #include <ir/Operands.h>
 #include <ir/Operations.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 class KernelGenerator : public basic::KernelGeneratorBase
@@ -57,8 +53,6 @@ class KernelGenerator : public basic::KernelGeneratorBase
   const std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_KERNEL_GENERATOR_H__
diff --git a/runtime/onert/backend/ruy/StaticTensorManager.h b/runtime/onert/backend/ruy/StaticTensorManager.h
index 867e4dedbe3..be765b9370b 100644
--- a/runtime/onert/backend/ruy/StaticTensorManager.h
+++ b/runtime/onert/backend/ruy/StaticTensorManager.h
@@ -19,17 +19,11 @@
 
 #include "backend/basic/StaticTensorManager.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 using StaticTensorManager = basic::StaticTensorManager;
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_STATICTENSOR_MANAGER_H__
diff --git a/runtime/onert/backend/ruy/Tensor.h b/runtime/onert/backend/ruy/Tensor.h
index 658086018c9..7efa2baa25a 100644
--- a/runtime/onert/backend/ruy/Tensor.h
+++ b/runtime/onert/backend/ruy/Tensor.h
@@ -20,18 +20,12 @@
 #include <backend/basic/Tensor.h>
 #include <ir/Data.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 using Tensor = basic::Tensor;
 using ExternalTensor = basic::ExternalTensor;
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_TENSOR_H__
diff --git a/runtime/onert/backend/ruy/TensorBuilder.h b/runtime/onert/backend/ruy/TensorBuilder.h
index 15d4e5b29a7..8b0e4c4de39 100644
--- a/runtime/onert/backend/ruy/TensorBuilder.h
+++ b/runtime/onert/backend/ruy/TensorBuilder.h
@@ -19,17 +19,11 @@
 
 #include <backend/basic/TensorBuilder.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
+namespace onert::backend::ruy
 {
 
 using TensorBuilder = basic::TensorBuilder;
 
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy
 
 #endif // __ONERT_BACKEND_RUY_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/ruy/ops/ConvolutionLayer.cc b/runtime/onert/backend/ruy/ops/ConvolutionLayer.cc
index f51b94568fb..d0761e78631 100644
--- a/runtime/onert/backend/ruy/ops/ConvolutionLayer.cc
+++ b/runtime/onert/backend/ruy/ops/ConvolutionLayer.cc
@@ -19,13 +19,7 @@
 #include "../Tensor.h"
 #include "ir/Padding.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
-{
-namespace ops
+namespace onert::backend::ruy::ops
 {
 ConvolutionLayer::ConvolutionLayer()
   : _input(nullptr), _kernel(nullptr), _bias(nullptr), _output(nullptr),
@@ -147,7 +141,4 @@ void ConvolutionLayer::prepare()
   _prepare = true;
 }
 
-} // namespace ops
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy::ops
diff --git a/runtime/onert/backend/ruy/ops/ConvolutionLayer.h b/runtime/onert/backend/ruy/ops/ConvolutionLayer.h
index a55387b936e..8965c754e61 100644
--- a/runtime/onert/backend/ruy/ops/ConvolutionLayer.h
+++ b/runtime/onert/backend/ruy/ops/ConvolutionLayer.h
@@ -26,13 +26,7 @@
 #include <functional>
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
-{
-namespace ops
+namespace onert::backend::ruy::ops
 {
 
 class ConvolutionLayer : public ::onert::exec::IFunction
@@ -82,9 +76,6 @@ class ConvolutionLayer : public ::onert::exec::IFunction
   std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace ops
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy::ops
 
 #endif // __ONERT_BACKEND_RUY_OPS_CONVOLUTIONLAYER_H__
diff --git a/runtime/onert/backend/ruy/ops/FullyConnectedLayer.cc b/runtime/onert/backend/ruy/ops/FullyConnectedLayer.cc
index 9935747ad24..cddefc4dbf4 100644
--- a/runtime/onert/backend/ruy/ops/FullyConnectedLayer.cc
+++ b/runtime/onert/backend/ruy/ops/FullyConnectedLayer.cc
@@ -20,13 +20,7 @@
 #include <ruy/operation/FullyConnected.h>
 #include <ruy/TensorUtils.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
-{
-namespace ops
+namespace onert::backend::ruy::ops
 {
 
 FullyConnectedLayer::FullyConnectedLayer()
@@ -95,7 +89,4 @@ void FullyConnectedLayer::prepare()
   }
 }
 
-} // namespace ops
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy::ops
diff --git a/runtime/onert/backend/ruy/ops/FullyConnectedLayer.h b/runtime/onert/backend/ruy/ops/FullyConnectedLayer.h
index 9e45a7024ae..7de20ef7667 100644
--- a/runtime/onert/backend/ruy/ops/FullyConnectedLayer.h
+++ b/runtime/onert/backend/ruy/ops/FullyConnectedLayer.h
@@ -23,13 +23,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
-{
-namespace ops
+namespace onert::backend::ruy::ops
 {
 
 class FullyConnectedLayer : public ::onert::exec::IFunction
@@ -60,9 +54,6 @@ class FullyConnectedLayer : public ::onert::exec::IFunction
   std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace ops
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy::ops
 
 #endif // __ONERT_BACKEND_RUY_OPS_FULLYCONNECTEDLAYER_H__
diff --git a/runtime/onert/backend/ruy/ops/OperationUtils.cc b/runtime/onert/backend/ruy/ops/OperationUtils.cc
index 929107b1a05..0d8fe0d359d 100644
--- a/runtime/onert/backend/ruy/ops/OperationUtils.cc
+++ b/runtime/onert/backend/ruy/ops/OperationUtils.cc
@@ -16,13 +16,7 @@
 
 #include "OperationUtils.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
-{
-namespace ops
+namespace onert::backend::ruy::ops
 {
 
 nnfw::ruy::PaddingType getPaddingType(ir::PaddingType ir_padding_type)
@@ -41,7 +35,4 @@ nnfw::ruy::PaddingType getPaddingType(ir::PaddingType ir_padding_type)
   }
 }
 
-} // namespace ops
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy::ops
diff --git a/runtime/onert/backend/ruy/ops/OperationUtils.h b/runtime/onert/backend/ruy/ops/OperationUtils.h
index 5f00a240871..cba5806f1fc 100644
--- a/runtime/onert/backend/ruy/ops/OperationUtils.h
+++ b/runtime/onert/backend/ruy/ops/OperationUtils.h
@@ -30,13 +30,7 @@
 using OperandType = onert::ir::DataType;
 using namespace onert::util;
 
-namespace onert
-{
-namespace backend
-{
-namespace ruy
-{
-namespace ops
+namespace onert::backend::ruy::ops
 {
 
 inline nnfw::ruy::Shape getTensorShape(const IPortableTensor *tensor)
@@ -78,9 +72,6 @@ inline nnfw::ruy::FusedActivationFunctionType convertActivationType(const ir::Ac
 
 nnfw::ruy::PaddingType getPaddingType(ir::PaddingType ir_padding_type);
 
-} // namespace ops
-} // namespace ruy
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::ruy::ops
 
 #endif // __ONERT_BACKEND_RUY_OPS_OPERATION_UTILS_H__
diff --git a/runtime/onert/backend/train/Backend.h b/runtime/onert/backend/train/Backend.h
index debde889329..ad2c320f7dc 100644
--- a/runtime/onert/backend/train/Backend.h
+++ b/runtime/onert/backend/train/Backend.h
@@ -27,11 +27,7 @@
 
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 // TODO Unify TensorBuilder
@@ -68,8 +64,6 @@ class Backend : public ::onert::backend::Backend, public backend::train::ITraina
   std::shared_ptr<IConfig> _config;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_BACKEND_H__
diff --git a/runtime/onert/backend/train/BackendContext.cc b/runtime/onert/backend/train/BackendContext.cc
index d0a634b1460..9e20472f7a4 100644
--- a/runtime/onert/backend/train/BackendContext.cc
+++ b/runtime/onert/backend/train/BackendContext.cc
@@ -26,11 +26,7 @@
 
 #include <cassert>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 namespace
@@ -306,6 +302,4 @@ void BackendContext::planLayerScopeTensors([[maybe_unused]] const FunctionMap &f
   return;
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/BackendContext.h b/runtime/onert/backend/train/BackendContext.h
index 7017d7e3175..01218b05644 100644
--- a/runtime/onert/backend/train/BackendContext.h
+++ b/runtime/onert/backend/train/BackendContext.h
@@ -23,11 +23,7 @@
 #include "KernelGenerator.h"
 #include "TensorBuilder.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 // TODO Remove this class if ExecutorFactory creates trainable context only once instead of
@@ -100,8 +96,6 @@ class BackendContext : public onert::backend::train::TrainableBackendContext
   std::unique_ptr<exec::train::optimizer::Optimizer> _optimizer;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/train/Config.cc b/runtime/onert/backend/train/Config.cc
index 2b65a29de40..6196580e20d 100644
--- a/runtime/onert/backend/train/Config.cc
+++ b/runtime/onert/backend/train/Config.cc
@@ -16,15 +16,9 @@
 
 #include "Config.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 bool Config::initialize() { return true; }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/Config.h b/runtime/onert/backend/train/Config.h
index a8751b369c3..92a754ec7b8 100644
--- a/runtime/onert/backend/train/Config.h
+++ b/runtime/onert/backend/train/Config.h
@@ -20,11 +20,7 @@
 #include <backend/IConfig.h>
 #include <util/ITimer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 class Config : public IConfig
@@ -39,8 +35,6 @@ class Config : public IConfig
   std::unique_ptr<util::ITimer> timer() override { return std::make_unique<util::CPUTimer>(); }
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_CONFIG_H__
diff --git a/runtime/onert/backend/train/DisposableTensorIndex.h b/runtime/onert/backend/train/DisposableTensorIndex.h
index 4505dc65739..10f2d929336 100644
--- a/runtime/onert/backend/train/DisposableTensorIndex.h
+++ b/runtime/onert/backend/train/DisposableTensorIndex.h
@@ -23,11 +23,7 @@
 
 #include "ir/Index.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 /**
@@ -93,9 +89,7 @@ inline std::ostream &operator<<(std::ostream &o, const DisposableTensorIndex &i)
   return operator<<(o, i.operand_index());
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 namespace std
 {
diff --git a/runtime/onert/backend/train/ExternalContext.h b/runtime/onert/backend/train/ExternalContext.h
index c24010ea2ec..ba46e9380ec 100644
--- a/runtime/onert/backend/train/ExternalContext.h
+++ b/runtime/onert/backend/train/ExternalContext.h
@@ -19,17 +19,11 @@
 
 #include <ExternalContext.h> // From cpu backend
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 using ExternalContext = cpu::ExternalContext;
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_EXTERNAL_CONTEXT_H__
diff --git a/runtime/onert/backend/train/KernelGenerator.cc b/runtime/onert/backend/train/KernelGenerator.cc
index 6d676045550..5046de640f3 100644
--- a/runtime/onert/backend/train/KernelGenerator.cc
+++ b/runtime/onert/backend/train/KernelGenerator.cc
@@ -39,11 +39,7 @@
 
 #include <stdexcept>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 namespace
@@ -640,6 +636,4 @@ IPortableTensor *KernelGenerator::getBackPropOut(const ir::OperandIndex &output_
   return _tensor_reg->getBackPropTensor(output_index);
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/KernelGenerator.h b/runtime/onert/backend/train/KernelGenerator.h
index 77f47e2588e..898991d7b3c 100644
--- a/runtime/onert/backend/train/KernelGenerator.h
+++ b/runtime/onert/backend/train/KernelGenerator.h
@@ -28,11 +28,7 @@
 #include <ir/Operands.h>
 #include <ir/Operations.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 // TODO Unify TensorRegistry
@@ -70,8 +66,6 @@ class KernelGenerator : public backend::train::KernelGeneratorBase
   std::unordered_map<const ir::IOperation *, ir::OperationIndex> _node_to_idx;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_KERNEL_GENERATOR_H__
diff --git a/runtime/onert/backend/train/LayerScopeTensorIndex.h b/runtime/onert/backend/train/LayerScopeTensorIndex.h
index c7cc4088431..52a00c86a26 100644
--- a/runtime/onert/backend/train/LayerScopeTensorIndex.h
+++ b/runtime/onert/backend/train/LayerScopeTensorIndex.h
@@ -21,11 +21,7 @@
 
 #include <cassert>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 class LayerScopeTensorIndex
@@ -58,9 +54,7 @@ inline std::ostream &operator<<(std::ostream &o, const LayerScopeTensorIndex &i)
   return o;
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 namespace std
 {
diff --git a/runtime/onert/backend/train/MemoryManager.cc b/runtime/onert/backend/train/MemoryManager.cc
index 64a665dd620..968d29bf5fb 100644
--- a/runtime/onert/backend/train/MemoryManager.cc
+++ b/runtime/onert/backend/train/MemoryManager.cc
@@ -22,11 +22,7 @@
 
 #include <cassert>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 TrainableMemoryManager::TrainableMemoryManager(uint32_t optim_vars_count)
@@ -129,6 +125,4 @@ void LayerScopeMemoryManager::releasePlan(const LayerScopeTensorIndex &ind)
   _mem_planner->release(ind);
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/MemoryManager.h b/runtime/onert/backend/train/MemoryManager.h
index 8333c838bce..3bb9756b3e8 100644
--- a/runtime/onert/backend/train/MemoryManager.h
+++ b/runtime/onert/backend/train/MemoryManager.h
@@ -22,11 +22,7 @@
 #include "DisposableTensorIndex.h"
 #include "LayerScopeTensorIndex.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 using MemoryManager = backend::basic::MemoryManager;
@@ -88,8 +84,6 @@ class LayerScopeMemoryManager
   std::shared_ptr<basic::Allocator> _mem_alloc;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_MEMORY_MANAGER_H__
diff --git a/runtime/onert/backend/train/MemoryPlanner.cc b/runtime/onert/backend/train/MemoryPlanner.cc
index 5ecc7278eb2..2be075858f1 100644
--- a/runtime/onert/backend/train/MemoryPlanner.cc
+++ b/runtime/onert/backend/train/MemoryPlanner.cc
@@ -23,11 +23,7 @@
 
 #include <cassert>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 template <typename Index> void BumpPlanner<Index>::claim(const Index &ind, size_t size)
@@ -215,6 +211,4 @@ template class FirstFitPlanner<LayerScopeTensorIndex>;
 template class WICPlanner<DisposableTensorIndex>;
 template class WICPlanner<LayerScopeTensorIndex>;
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/MemoryPlanner.h b/runtime/onert/backend/train/MemoryPlanner.h
index 67915bfb860..46cb065cc8f 100644
--- a/runtime/onert/backend/train/MemoryPlanner.h
+++ b/runtime/onert/backend/train/MemoryPlanner.h
@@ -31,11 +31,7 @@
 #include <unordered_set>
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 /**
@@ -162,8 +158,6 @@ template <typename Index> class WICPlanner : public basic::IMemoryPlanner<Index>
   std::multimap<uint32_t, Index, std::greater<uint32_t>> _indices;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_MEMORY_PLANNER_H__
diff --git a/runtime/onert/backend/train/MemoryPlannerFactory.cc b/runtime/onert/backend/train/MemoryPlannerFactory.cc
index 258feafad35..2002500d2b5 100644
--- a/runtime/onert/backend/train/MemoryPlannerFactory.cc
+++ b/runtime/onert/backend/train/MemoryPlannerFactory.cc
@@ -19,11 +19,7 @@
 #include "DisposableTensorIndex.h"
 #include "LayerScopeTensorIndex.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 template <typename Index> MemoryPlannerFactory<Index> &MemoryPlannerFactory<Index>::get()
@@ -53,6 +49,4 @@ basic::IMemoryPlanner<Index> *MemoryPlannerFactory<Index>::create(const std::str
 template class MemoryPlannerFactory<DisposableTensorIndex>;
 template class MemoryPlannerFactory<LayerScopeTensorIndex>;
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/MemoryPlannerFactory.h b/runtime/onert/backend/train/MemoryPlannerFactory.h
index 7d005b01c2e..7f6a1b06b40 100644
--- a/runtime/onert/backend/train/MemoryPlannerFactory.h
+++ b/runtime/onert/backend/train/MemoryPlannerFactory.h
@@ -21,11 +21,7 @@
 
 #include <string>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 template <typename Index> class MemoryPlannerFactory
@@ -41,8 +37,6 @@ template <typename Index> class MemoryPlannerFactory
   basic::IMemoryPlanner<Index> *create(const std::string &key);
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_MEMORY_PLANNER_FACTORY_H__
diff --git a/runtime/onert/backend/train/Tensor.h b/runtime/onert/backend/train/Tensor.h
index 08850678d0b..b435c2c4fcc 100644
--- a/runtime/onert/backend/train/Tensor.h
+++ b/runtime/onert/backend/train/Tensor.h
@@ -20,11 +20,7 @@
 #include <backend/basic/Tensor.h>
 #include <backend/basic/train/TrainableTensor.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 // NOTE This class can be replaced with basic::Tensor if this backend supports dynamic tensors.
@@ -47,8 +43,6 @@ using TrainableTensor = basic::train::TrainableTensor;
 using BackPropTensor = Tensor;
 using GradientTensor = Tensor;
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_TENSOR_H__
diff --git a/runtime/onert/backend/train/TensorBuilder.cc b/runtime/onert/backend/train/TensorBuilder.cc
index 55472f3dd92..e8d3feb3ad4 100644
--- a/runtime/onert/backend/train/TensorBuilder.cc
+++ b/runtime/onert/backend/train/TensorBuilder.cc
@@ -18,11 +18,7 @@
 
 #include "Tensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 TensorBuilder::TensorBuilder(const std::shared_ptr<TensorRegistry> &tensor_reg,
@@ -239,6 +235,4 @@ void TensorBuilder::allocateBackward(void)
 
 void TensorBuilder::allocateLayerScope(void) { _tensor_mgr->allocateLayerScopeTensors(); }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/TensorBuilder.h b/runtime/onert/backend/train/TensorBuilder.h
index c15d2393209..3115f36ecdb 100644
--- a/runtime/onert/backend/train/TensorBuilder.h
+++ b/runtime/onert/backend/train/TensorBuilder.h
@@ -26,11 +26,7 @@
 #include <ir/OperationIndexMap.h>
 #include <exec/train/optimizer/Optimizer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 // TODO Support dynamic tensors
@@ -94,8 +90,6 @@ class TensorBuilder
   const exec::train::optimizer::Optimizer *_optimizer;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/train/TensorManager.cc b/runtime/onert/backend/train/TensorManager.cc
index 22ed48cc02f..0d4b3bc0114 100644
--- a/runtime/onert/backend/train/TensorManager.cc
+++ b/runtime/onert/backend/train/TensorManager.cc
@@ -46,11 +46,7 @@ inline size_t alignedSize(const size_t size, const uint64_t align)
 
 } // namespace
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 TensorManager::TensorManager(const std::shared_ptr<TensorRegistry> &reg, uint32_t optim_vars_count)
@@ -208,6 +204,4 @@ void TensorManager::releaseLayerScopePlan(const LayerScopeTensorIndex &index)
   _layer_scope_mgr->releasePlan(index);
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/TensorManager.h b/runtime/onert/backend/train/TensorManager.h
index faec36b8016..3c2e6676f4c 100644
--- a/runtime/onert/backend/train/TensorManager.h
+++ b/runtime/onert/backend/train/TensorManager.h
@@ -24,11 +24,7 @@
 #include <ir/OperandIndexMap.h>
 #include <ir/OperandInfo.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 class TensorManager
@@ -75,8 +71,6 @@ class TensorManager
   const std::shared_ptr<TensorRegistry> _tensors;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_TENSOR_MANAGER_H__
diff --git a/runtime/onert/backend/train/TensorPlanner.cc b/runtime/onert/backend/train/TensorPlanner.cc
index 26e3d00fa53..7e082ca5a5e 100644
--- a/runtime/onert/backend/train/TensorPlanner.cc
+++ b/runtime/onert/backend/train/TensorPlanner.cc
@@ -18,11 +18,7 @@
 
 #include <util/logging.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 TensorPlanner::TensorPlanner(const ir::train::TrainableGraph &tgraph,
@@ -563,6 +559,4 @@ void TensorPlanner::planLayerScopeTensors(TensorBuilder *tensor_builder)
   VERBOSE(TensorPlanner) << "Finish planning layerscope tensors" << std::endl;
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
diff --git a/runtime/onert/backend/train/TensorPlanner.h b/runtime/onert/backend/train/TensorPlanner.h
index 5bdb0d70803..8b4bebd1b30 100644
--- a/runtime/onert/backend/train/TensorPlanner.h
+++ b/runtime/onert/backend/train/TensorPlanner.h
@@ -22,11 +22,7 @@
 #include <ir/train/TrainableGraph.h>
 #include <util/Set.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 class TensorPlanner
@@ -56,8 +52,6 @@ class TensorPlanner
   const util::Set<ir::OperandIndex> &_external_operands;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_TENSOR_PLANNER_H__
diff --git a/runtime/onert/backend/train/TensorRegistry.h b/runtime/onert/backend/train/TensorRegistry.h
index 2d1c034dbc4..f59e8b7666f 100644
--- a/runtime/onert/backend/train/TensorRegistry.h
+++ b/runtime/onert/backend/train/TensorRegistry.h
@@ -24,11 +24,7 @@
 #include "LayerScopeTensorIndex.h"
 #include "Tensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 class TensorRegistry
@@ -95,8 +91,6 @@ class TensorRegistry
   std::unordered_map<LayerScopeTensorIndex, std::shared_ptr<LayerScopeTensor>> _layer_scope;
 };
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_TENSOR_REGISTRY__
diff --git a/runtime/onert/backend/train/ops/BackPropAccumulator.cc b/runtime/onert/backend/train/ops/BackPropAccumulator.cc
index ecf63024da0..dc8fcdfb704 100644
--- a/runtime/onert/backend/train/ops/BackPropAccumulator.cc
+++ b/runtime/onert/backend/train/ops/BackPropAccumulator.cc
@@ -21,13 +21,7 @@
 #include <cker/operation/BinaryArithmeticOps.h>
 #include <util/CalculateActivationRange.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 BackPropAccumulator::BackPropAccumulator(const IPortableTensor *disposable_tensor,
@@ -57,7 +51,4 @@ void BackPropAccumulator::backward()
     getBuffer<float>(_back_prop_tensor));
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/BackPropAccumulator.h b/runtime/onert/backend/train/ops/BackPropAccumulator.h
index f7c1c66c6ae..593e759fa2a 100644
--- a/runtime/onert/backend/train/ops/BackPropAccumulator.h
+++ b/runtime/onert/backend/train/ops/BackPropAccumulator.h
@@ -21,13 +21,7 @@
 #include <cker/Types.h>
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 // TODO Introduce IFunction for only backwarding
@@ -47,9 +41,6 @@ class BackPropAccumulator : public exec::train::ITrainableFunction
   nnfw::cker::BinaryArithmeticOpParam _op_params;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_BACKPROP_ACCUMULATOR_H__
diff --git a/runtime/onert/backend/train/ops/BackPropInitializer.cc b/runtime/onert/backend/train/ops/BackPropInitializer.cc
index e8a4d9fbf6d..48198c0f294 100644
--- a/runtime/onert/backend/train/ops/BackPropInitializer.cc
+++ b/runtime/onert/backend/train/ops/BackPropInitializer.cc
@@ -16,13 +16,7 @@
 
 #include "BackPropInitializer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 BackPropInitializer::BackPropInitializer(const std::vector<BackPropTensor *> back_props)
@@ -46,7 +40,4 @@ void BackPropInitializer::backward()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/BackPropInitializer.h b/runtime/onert/backend/train/ops/BackPropInitializer.h
index 90e17faf74a..9eb7894cef4 100644
--- a/runtime/onert/backend/train/ops/BackPropInitializer.h
+++ b/runtime/onert/backend/train/ops/BackPropInitializer.h
@@ -22,13 +22,7 @@
 
 #include "../Tensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 // TODO Introduce IFunction for only backwarding
@@ -45,9 +39,6 @@ class BackPropInitializer : public exec::train::ITrainableFunction
   const std::vector<BackPropTensor *> _back_props;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_BACKPROP_INITIALIZER_H__
diff --git a/runtime/onert/backend/train/ops/BinaryArithmeticLayer.cc b/runtime/onert/backend/train/ops/BinaryArithmeticLayer.cc
index 3c4ce2f7ce1..61ed838b8c6 100644
--- a/runtime/onert/backend/train/ops/BinaryArithmeticLayer.cc
+++ b/runtime/onert/backend/train/ops/BinaryArithmeticLayer.cc
@@ -24,13 +24,7 @@
 #include <cker/train/operation/BinaryArithmetic.h>
 #include <cker/train/operation/ReLU.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 BinaryArithmeticLayer::BinaryArithmeticLayer()
@@ -87,7 +81,4 @@ void BinaryArithmeticLayer::backward()
     static_cast<nnfw::cker::train::ArithmeticType>(_arithmetic_type));
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/BinaryArithmeticLayer.h b/runtime/onert/backend/train/ops/BinaryArithmeticLayer.h
index 60d6e8be1cc..88bb9a3c4b9 100644
--- a/runtime/onert/backend/train/ops/BinaryArithmeticLayer.h
+++ b/runtime/onert/backend/train/ops/BinaryArithmeticLayer.h
@@ -23,13 +23,7 @@
 #include "../Tensor.h"
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 enum class ArithmeticType
@@ -63,9 +57,6 @@ class BinaryArithmeticLayer : public ::onert::exec::train::ITrainableFunction,
   std::unique_ptr<BackPropTensor> _act_back_prop_output;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_BINARYARITHMETICLAYER_H__
diff --git a/runtime/onert/backend/train/ops/ConvolutionLayer.cc b/runtime/onert/backend/train/ops/ConvolutionLayer.cc
index 41ff7fd1c43..eeb56ffc244 100644
--- a/runtime/onert/backend/train/ops/ConvolutionLayer.cc
+++ b/runtime/onert/backend/train/ops/ConvolutionLayer.cc
@@ -47,13 +47,7 @@ std::unique_ptr<Tensor> createTransposedWeights(const backend::IPortableTensor *
 
 } // namespace
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 ConvolutionLayer::ConvolutionLayer()
@@ -189,7 +183,4 @@ void ConvolutionLayer::backwardFloat32()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/ConvolutionLayer.h b/runtime/onert/backend/train/ops/ConvolutionLayer.h
index ef11f68bf57..f6bcb0a2752 100644
--- a/runtime/onert/backend/train/ops/ConvolutionLayer.h
+++ b/runtime/onert/backend/train/ops/ConvolutionLayer.h
@@ -22,13 +22,7 @@
 #include "../Tensor.h"
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class ConvolutionLayer : public ::onert::exec::train::ITrainableFunction,
@@ -60,9 +54,6 @@ class ConvolutionLayer : public ::onert::exec::train::ITrainableFunction,
   std::unique_ptr<GradientTensor> _transposed_grad_weights;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_CONVOLUTIONLAYER_H__
diff --git a/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.cc b/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.cc
index 6a6c8684679..eef45552cf4 100644
--- a/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.cc
+++ b/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.cc
@@ -22,13 +22,7 @@
 #include <cker/train/operation/DepthwiseConv.h>
 #include <cker/train/operation/ReLU.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 DepthwiseConvolutionLayer::DepthwiseConvolutionLayer()
@@ -155,7 +149,4 @@ void DepthwiseConvolutionLayer::backwardFloat32()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.h b/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.h
index 8f286b8040d..d8ba2032282 100644
--- a/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.h
+++ b/runtime/onert/backend/train/ops/DepthwiseConvolutionLayer.h
@@ -24,13 +24,7 @@
 #include "../ExternalContext.h"
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class DepthwiseConvolutionLayer : public ::onert::exec::train::ITrainableFunction,
@@ -59,9 +53,6 @@ class DepthwiseConvolutionLayer : public ::onert::exec::train::ITrainableFunctio
   std::unique_ptr<Tensor> _filter_dim_buffers;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_DEPTHWISECONVOLUTIONLAYER_H__
diff --git a/runtime/onert/backend/train/ops/ElementwiseActivationLayer.cc b/runtime/onert/backend/train/ops/ElementwiseActivationLayer.cc
index ba823616e01..8e2ce254e8d 100644
--- a/runtime/onert/backend/train/ops/ElementwiseActivationLayer.cc
+++ b/runtime/onert/backend/train/ops/ElementwiseActivationLayer.cc
@@ -21,13 +21,7 @@
 #include <cker/train/operation/ReLU.h>
 #include <cker/train/operation/ReLU6.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 ElementwiseActivationLayer::ElementwiseActivationLayer() : cpu::ops::ElementwiseActivationLayer()
@@ -96,7 +90,4 @@ void ElementwiseActivationLayer::backward()
   _backward_kernel(_output, _back_prop_output, _back_prop_input);
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/ElementwiseActivationLayer.h b/runtime/onert/backend/train/ops/ElementwiseActivationLayer.h
index a6b195540f0..a4bec312758 100644
--- a/runtime/onert/backend/train/ops/ElementwiseActivationLayer.h
+++ b/runtime/onert/backend/train/ops/ElementwiseActivationLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 enum class ElementwiseActivationType
@@ -58,9 +52,6 @@ class ElementwiseActivationLayer : public ::onert::exec::train::ITrainableFuncti
     _backward_kernel;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_ELEMENTWISEACTIVATIONLAYER_H__
diff --git a/runtime/onert/backend/train/ops/FullyConnectedLayer.cc b/runtime/onert/backend/train/ops/FullyConnectedLayer.cc
index 9d35655b26f..c581742ea4f 100644
--- a/runtime/onert/backend/train/ops/FullyConnectedLayer.cc
+++ b/runtime/onert/backend/train/ops/FullyConnectedLayer.cc
@@ -43,13 +43,7 @@ createTransposedTensor(const backend::IPortableTensor *origin_tensor)
 
 } // namespace
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 FullyConnectedLayer::FullyConnectedLayer()
@@ -195,7 +189,4 @@ void FullyConnectedLayer::backwardFloat32()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/FullyConnectedLayer.h b/runtime/onert/backend/train/ops/FullyConnectedLayer.h
index 190bfbffe42..78852d1d179 100644
--- a/runtime/onert/backend/train/ops/FullyConnectedLayer.h
+++ b/runtime/onert/backend/train/ops/FullyConnectedLayer.h
@@ -23,13 +23,7 @@
 #include <exec/train/ITrainableFunction.h>
 #include <ops/FullyConnectedLayer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class FullyConnectedLayer : public exec::train::ITrainableFunction,
@@ -65,9 +59,6 @@ class FullyConnectedLayer : public exec::train::ITrainableFunction,
   std::unique_ptr<Tensor> _act_back_prop_output;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_FULLYCONNECTEDLAYER_H__
diff --git a/runtime/onert/backend/train/ops/GradientApplier.cc b/runtime/onert/backend/train/ops/GradientApplier.cc
index 534a43ef306..148d5103582 100644
--- a/runtime/onert/backend/train/ops/GradientApplier.cc
+++ b/runtime/onert/backend/train/ops/GradientApplier.cc
@@ -18,13 +18,7 @@
 
 #include <exec/train/optimizer/Optimizer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 GradientApplier::GradientApplier() : _optimizer{nullptr}, _gradient_tensor{}, _trainable_tensor{}
@@ -46,7 +40,4 @@ void GradientApplier::applyGradient(uint32_t training_step)
     std::forward_as_tuple(*_gradient_tensor, *_trainable_tensor, training_step));
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/GradientApplier.h b/runtime/onert/backend/train/ops/GradientApplier.h
index b5725239c65..40b477ab33d 100644
--- a/runtime/onert/backend/train/ops/GradientApplier.h
+++ b/runtime/onert/backend/train/ops/GradientApplier.h
@@ -21,13 +21,7 @@
 
 #include <exec/train/optimizer/Optimizer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class GradientApplier : public ::onert::exec::train::IGradientApplier
@@ -46,9 +40,6 @@ class GradientApplier : public ::onert::exec::train::IGradientApplier
   ITrainableTensor *_trainable_tensor;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_GRADIENT_APPLIER_H__
diff --git a/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.cc b/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.cc
index a751dd163dd..17b54d2333a 100644
--- a/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.cc
+++ b/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.cc
@@ -19,13 +19,7 @@
 
 #include <cker/train/operation/Loss.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 void LossCategoricalCrossentropyLayer::configure(
@@ -82,7 +76,4 @@ void LossCategoricalCrossentropyLayer::backward()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.h b/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.h
index dfd5ef93167..054dbbf392b 100644
--- a/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.h
+++ b/runtime/onert/backend/train/ops/LossCategoricalCrossentropyLayer.h
@@ -20,13 +20,7 @@
 #include "LossLayer.h"
 #include "../Tensor.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class LossCategoricalCrossentropyLayer : public LossLayer
@@ -47,9 +41,6 @@ class LossCategoricalCrossentropyLayer : public LossLayer
   bool _is_normalization_required{false};
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_LOSS_CATEGORICALCROSSENTROPY_LAYER_H__
diff --git a/runtime/onert/backend/train/ops/LossLayer.cc b/runtime/onert/backend/train/ops/LossLayer.cc
index e5a026ba863..d4623939db8 100644
--- a/runtime/onert/backend/train/ops/LossLayer.cc
+++ b/runtime/onert/backend/train/ops/LossLayer.cc
@@ -16,13 +16,7 @@
 
 #include "LossLayer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 LossLayer::LossLayer()
@@ -48,7 +42,4 @@ void LossLayer::configure(const IPortableTensor *y_pred, const IPortableTensor *
   _reduction_type = reduction_type;
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/LossLayer.h b/runtime/onert/backend/train/ops/LossLayer.h
index f2bb3b38ee0..15eb06e29b6 100644
--- a/runtime/onert/backend/train/ops/LossLayer.h
+++ b/runtime/onert/backend/train/ops/LossLayer.h
@@ -23,13 +23,7 @@
 #include <exec/train/ITrainableFunction.h>
 #include <ir/train/LossInfo.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 enum class LossType
@@ -54,9 +48,6 @@ class LossLayer : public ::onert::exec::train::ITrainableFunction
   ir::train::LossReductionType _reduction_type;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_LOSSLAYER_H__
diff --git a/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.cc b/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.cc
index 03d3196c335..95ab2e376f0 100644
--- a/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.cc
+++ b/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.cc
@@ -19,13 +19,7 @@
 
 #include <cker/train/operation/Loss.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 void LossMeanSquaredErrorLayer::configure(const IPortableTensor *y_pred,
@@ -67,7 +61,4 @@ void LossMeanSquaredErrorLayer::backward()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.h b/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.h
index a3ed41ec804..9a08ce4924e 100644
--- a/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.h
+++ b/runtime/onert/backend/train/ops/LossMeanSquaredErrorLayer.h
@@ -19,13 +19,7 @@
 
 #include "LossLayer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class LossMeanSquaredErrorLayer : public LossLayer
@@ -40,9 +34,6 @@ class LossMeanSquaredErrorLayer : public LossLayer
   void backward() override;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_LOSS_MEANSQUAREDERROR_LAYER_H__
diff --git a/runtime/onert/backend/train/ops/MeanLayer.cc b/runtime/onert/backend/train/ops/MeanLayer.cc
index c6744e62cfa..82de9007e14 100644
--- a/runtime/onert/backend/train/ops/MeanLayer.cc
+++ b/runtime/onert/backend/train/ops/MeanLayer.cc
@@ -22,13 +22,7 @@
 #include <cker/train/operation/ReduceMean.h>
 #include <cker/operation/BinaryArithmeticOps.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 MeanLayer::MeanLayer()
@@ -79,7 +73,4 @@ void MeanLayer::backward()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/MeanLayer.h b/runtime/onert/backend/train/ops/MeanLayer.h
index 71be42f00f3..175fc0effd9 100644
--- a/runtime/onert/backend/train/ops/MeanLayer.h
+++ b/runtime/onert/backend/train/ops/MeanLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class MeanLayer : public ::onert::exec::train::ITrainableFunction, public cpu::ops::MeanLayer
@@ -46,9 +40,6 @@ class MeanLayer : public ::onert::exec::train::ITrainableFunction, public cpu::o
   const IPortableTensor *_back_prop_output;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_MEANLAYER_H__
diff --git a/runtime/onert/backend/train/ops/OperationUtils.cc b/runtime/onert/backend/train/ops/OperationUtils.cc
index 5dd41f05858..4a643763cb2 100644
--- a/runtime/onert/backend/train/ops/OperationUtils.cc
+++ b/runtime/onert/backend/train/ops/OperationUtils.cc
@@ -20,13 +20,7 @@
 #include <cker/train/operation/ReLU.h>
 #include <cker/train/operation/ReLU6.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 nnfw::cker::Shape getShape(const IPortableTensor *tensor)
@@ -110,7 +104,4 @@ nnfw::cker::train::LossReductionType convertLossReductionType(ir::train::LossRed
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/OperationUtils.h b/runtime/onert/backend/train/ops/OperationUtils.h
index f2c3b6b6029..6bcf8e0652d 100644
--- a/runtime/onert/backend/train/ops/OperationUtils.h
+++ b/runtime/onert/backend/train/ops/OperationUtils.h
@@ -21,13 +21,7 @@
 #include <cker/train/Types.h>
 #include <ir/train/LossInfo.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 using OperandType = onert::ir::DataType;
@@ -87,9 +81,6 @@ void biasGrad(const IPortableTensor *input_backprop, IPortableTensor *bias_grad)
  */
 nnfw::cker::train::LossReductionType convertLossReductionType(ir::train::LossReductionType type);
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_OPERATION_UTILS_H__
diff --git a/runtime/onert/backend/train/ops/PadLayer.cc b/runtime/onert/backend/train/ops/PadLayer.cc
index 0ac917bdf38..8851dcd97a8 100644
--- a/runtime/onert/backend/train/ops/PadLayer.cc
+++ b/runtime/onert/backend/train/ops/PadLayer.cc
@@ -18,13 +18,7 @@
 
 #include <cker/train/operation/Pad.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 PadLayer::PadLayer() : cpu::ops::PadLayer(), _back_prop_input{nullptr}, _back_prop_output{nullptr}
@@ -70,7 +64,4 @@ void PadLayer::backward()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/PadLayer.h b/runtime/onert/backend/train/ops/PadLayer.h
index 2e6f2c77403..5bb2e05b492 100644
--- a/runtime/onert/backend/train/ops/PadLayer.h
+++ b/runtime/onert/backend/train/ops/PadLayer.h
@@ -23,13 +23,7 @@
 
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 // Note, this is pad with mode=`CONSTANT`: it doesn't support `REFLECT` and
@@ -51,9 +45,6 @@ class PadLayer : public ::onert::exec::train::ITrainableFunction, public cpu::op
   const IPortableTensor *_back_prop_output;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_PADLAYER_H__
diff --git a/runtime/onert/backend/train/ops/PoolLayer.cc b/runtime/onert/backend/train/ops/PoolLayer.cc
index 09d6bd16a62..44e88b8d955 100644
--- a/runtime/onert/backend/train/ops/PoolLayer.cc
+++ b/runtime/onert/backend/train/ops/PoolLayer.cc
@@ -24,13 +24,7 @@
 #include <cker/train/operation/MaxPool.h>
 #include <cker/train/operation/ReLU.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 namespace
@@ -239,7 +233,4 @@ void PoolLayer::forward(bool training)
 
 void PoolLayer::backward() { _kernel->backward(_back_prop_output, _back_prop_input); }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/PoolLayer.h b/runtime/onert/backend/train/ops/PoolLayer.h
index 2b0c9e2a00b..7d2825bfb63 100644
--- a/runtime/onert/backend/train/ops/PoolLayer.h
+++ b/runtime/onert/backend/train/ops/PoolLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 /**
@@ -72,9 +66,6 @@ class PoolLayer : public ::onert::exec::train::ITrainableFunction, public cpu::o
   std::unique_ptr<TrainingKernelRegistry> _kernel;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_POOLLAYER_H__
diff --git a/runtime/onert/backend/train/ops/ReshapeLayer.cc b/runtime/onert/backend/train/ops/ReshapeLayer.cc
index 1c8a019bc85..d7e45b42997 100644
--- a/runtime/onert/backend/train/ops/ReshapeLayer.cc
+++ b/runtime/onert/backend/train/ops/ReshapeLayer.cc
@@ -16,13 +16,7 @@
 
 #include "ReshapeLayer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 ReshapeLayer::ReshapeLayer()
@@ -58,7 +52,4 @@ void ReshapeLayer::forward(bool) { reshapeGeneric(_input, _output); }
 
 void ReshapeLayer::backward() { reshapeGeneric(_back_prop_output, _back_prop_input); }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/ReshapeLayer.h b/runtime/onert/backend/train/ops/ReshapeLayer.h
index 2cd098d4685..658026ad6ed 100644
--- a/runtime/onert/backend/train/ops/ReshapeLayer.h
+++ b/runtime/onert/backend/train/ops/ReshapeLayer.h
@@ -21,13 +21,7 @@
 
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class ReshapeLayer : public ::onert::exec::train::ITrainableFunction
@@ -54,9 +48,6 @@ class ReshapeLayer : public ::onert::exec::train::ITrainableFunction
   const IPortableTensor *_back_prop_output;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_RESHAPELAYER_H__
diff --git a/runtime/onert/backend/train/ops/SoftMaxLayer.cc b/runtime/onert/backend/train/ops/SoftMaxLayer.cc
index 0d98f2950df..a13c64eb91a 100644
--- a/runtime/onert/backend/train/ops/SoftMaxLayer.cc
+++ b/runtime/onert/backend/train/ops/SoftMaxLayer.cc
@@ -20,13 +20,7 @@
 
 #include <cker/train/operation/SoftMax.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 SoftMaxLayer::SoftMaxLayer()
@@ -62,7 +56,4 @@ void SoftMaxLayer::backward()
   }
 }
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
diff --git a/runtime/onert/backend/train/ops/SoftMaxLayer.h b/runtime/onert/backend/train/ops/SoftMaxLayer.h
index 1b7b402ee61..e5b2071e1fc 100644
--- a/runtime/onert/backend/train/ops/SoftMaxLayer.h
+++ b/runtime/onert/backend/train/ops/SoftMaxLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/train/ITrainableFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace ops
+namespace onert::backend::train::ops
 {
 
 class SoftMaxLayer : public ::onert::exec::train::ITrainableFunction, public cpu::ops::SoftMaxLayer
@@ -46,9 +40,6 @@ class SoftMaxLayer : public ::onert::exec::train::ITrainableFunction, public cpu
   const IPortableTensor *_back_prop_output;
 };
 
-} // namespace ops
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::ops
 
 #endif // __ONERT_BACKEND_TRAIN_OPS_SOFTMAXLAYER_H__
diff --git a/runtime/onert/backend/train/optimizer/Adam.cc b/runtime/onert/backend/train/optimizer/Adam.cc
index 02954b1633b..9443b56bcd2 100644
--- a/runtime/onert/backend/train/optimizer/Adam.cc
+++ b/runtime/onert/backend/train/optimizer/Adam.cc
@@ -21,13 +21,7 @@
 #include <cmath>
 #include <misc/polymorphic_downcast.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace optimizer
+namespace onert::backend::train::optimizer
 {
 
 double Adam::getLearningRate(uint32_t training_step) const
@@ -73,7 +67,4 @@ void Adam::applyGradient(const UpdateFactors &factors) const
   }
 }
 
-} // namespace optimizer
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::optimizer
diff --git a/runtime/onert/backend/train/optimizer/Adam.h b/runtime/onert/backend/train/optimizer/Adam.h
index 1a43fe4a1be..0c8f5d1feb8 100644
--- a/runtime/onert/backend/train/optimizer/Adam.h
+++ b/runtime/onert/backend/train/optimizer/Adam.h
@@ -22,13 +22,7 @@
 #include "backend/basic/Tensor.h"
 #include "ir/OperandIndexMap.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace optimizer
+namespace onert::backend::train::optimizer
 {
 
 /**
@@ -89,9 +83,6 @@ class Adam : public exec::train::optimizer::Optimizer
   double _learning_rate;
 };
 
-} // namespace optimizer
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::optimizer
 
 #endif // __ONERT_BACKEND_TRAIN_OPTIMIZER_ADAM_H__
diff --git a/runtime/onert/backend/train/optimizer/Optimizers.h b/runtime/onert/backend/train/optimizer/Optimizers.h
index dae8e9382b5..b042b862ee4 100644
--- a/runtime/onert/backend/train/optimizer/Optimizers.h
+++ b/runtime/onert/backend/train/optimizer/Optimizers.h
@@ -22,11 +22,7 @@
 
 #include <ir/train/OptimizerInfo.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
+namespace onert::backend::train
 {
 
 std::unique_ptr<exec::train::optimizer::Optimizer>
@@ -46,8 +42,6 @@ createOptimizer(const ir::train::OptimizerInfo &optim_info)
                              ir::train::toString(optim_info.optim_code));
 }
 
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train
 
 #endif // __ONERT_BACKEND_TRAIN_OPTIMIZER_OPTIMIZERS_H__
diff --git a/runtime/onert/backend/train/optimizer/SGD.cc b/runtime/onert/backend/train/optimizer/SGD.cc
index ccc783ae3ed..826617f561d 100644
--- a/runtime/onert/backend/train/optimizer/SGD.cc
+++ b/runtime/onert/backend/train/optimizer/SGD.cc
@@ -20,13 +20,7 @@
 
 #include <cker/train/optimizer/SGD.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace optimizer
+namespace onert::backend::train::optimizer
 {
 
 double SGD::getLearningRate(uint32_t) const
@@ -58,7 +52,4 @@ void SGD::applyGradient(const UpdateFactors &factors) const
   }
 }
 
-} // namespace optimizer
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::optimizer
diff --git a/runtime/onert/backend/train/optimizer/SGD.h b/runtime/onert/backend/train/optimizer/SGD.h
index 37968c2a867..0c40bb075be 100644
--- a/runtime/onert/backend/train/optimizer/SGD.h
+++ b/runtime/onert/backend/train/optimizer/SGD.h
@@ -19,13 +19,7 @@
 
 #include <exec/train/optimizer/Optimizer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace train
-{
-namespace optimizer
+namespace onert::backend::train::optimizer
 {
 
 /**
@@ -85,9 +79,6 @@ class SGD : public exec::train::optimizer::Optimizer
   double _learning_rate;
 };
 
-} // namespace optimizer
-} // namespace train
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::train::optimizer
 
 #endif // __ONERT_BACKEND_TRAIN_OPTIMIZER_SGD_H__
diff --git a/runtime/onert/backend/trix/Backend.h b/runtime/onert/backend/trix/Backend.h
index a63839720e8..8f666cff55e 100644
--- a/runtime/onert/backend/trix/Backend.h
+++ b/runtime/onert/backend/trix/Backend.h
@@ -25,11 +25,7 @@
 
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 class Backend : public ::onert::backend::Backend
@@ -55,8 +51,6 @@ class Backend : public ::onert::backend::Backend
   std::shared_ptr<IConfig> _config;
 };
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_BACKEND_H__
diff --git a/runtime/onert/backend/trix/BackendContext.cc b/runtime/onert/backend/trix/BackendContext.cc
index f71853e0d2a..6ae185ebff2 100644
--- a/runtime/onert/backend/trix/BackendContext.cc
+++ b/runtime/onert/backend/trix/BackendContext.cc
@@ -24,11 +24,7 @@
 #include "ir/OperandIndexSequence.h"
 #include "backend/basic/BackendContextHelpers.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 ITensorRegistry *BackendContext::genTensors() { return basic::genTensors(*this); }
@@ -59,6 +55,4 @@ FunctionMap BackendContext::genKernels()
   return ret;
 }
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
diff --git a/runtime/onert/backend/trix/BackendContext.h b/runtime/onert/backend/trix/BackendContext.h
index c0734c46d3f..1852de156c1 100644
--- a/runtime/onert/backend/trix/BackendContext.h
+++ b/runtime/onert/backend/trix/BackendContext.h
@@ -22,11 +22,7 @@
 #include "KernelGenerator.h"
 #include "DevContext.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 class BackendContext : public onert::backend::BackendContext
@@ -55,8 +51,6 @@ class BackendContext : public onert::backend::BackendContext
   std::shared_ptr<DevContext> _dev_context;
 };
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/trix/BatchThreadPool.cc b/runtime/onert/backend/trix/BatchThreadPool.cc
index 3c2001d75d4..a627474c567 100644
--- a/runtime/onert/backend/trix/BatchThreadPool.cc
+++ b/runtime/onert/backend/trix/BatchThreadPool.cc
@@ -16,11 +16,7 @@
 
 #include "BatchThreadPool.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 BatchThreadPool::BatchThreadPool(size_t num_threads) : _num_threads(num_threads), _stop_all(false)
@@ -64,6 +60,4 @@ BatchThreadPool::~BatchThreadPool()
   }
 }
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
diff --git a/runtime/onert/backend/trix/BatchThreadPool.h b/runtime/onert/backend/trix/BatchThreadPool.h
index e1e2257efb0..1f4aa18e9e2 100644
--- a/runtime/onert/backend/trix/BatchThreadPool.h
+++ b/runtime/onert/backend/trix/BatchThreadPool.h
@@ -26,11 +26,7 @@
 #include <thread>
 #include <vector>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 /**
@@ -122,8 +118,6 @@ class BatchThreadPool
   bool _stop_all;
 };
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_BATCH_THREAD_POOL_H__
diff --git a/runtime/onert/backend/trix/Config.cc b/runtime/onert/backend/trix/Config.cc
index e3a7a3034d0..98b60c6ba70 100644
--- a/runtime/onert/backend/trix/Config.cc
+++ b/runtime/onert/backend/trix/Config.cc
@@ -16,15 +16,9 @@
 
 #include "Config.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 bool Config::initialize() { return true; }
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
diff --git a/runtime/onert/backend/trix/Config.h b/runtime/onert/backend/trix/Config.h
index d29b319f1bc..468890cccb0 100644
--- a/runtime/onert/backend/trix/Config.h
+++ b/runtime/onert/backend/trix/Config.h
@@ -21,11 +21,7 @@
 #include <memory>
 #include <util/ITimer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 class Config : public IConfig
@@ -40,8 +36,6 @@ class Config : public IConfig
   std::unique_ptr<util::ITimer> timer() override { return std::make_unique<util::CPUTimer>(); }
 };
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_CONFIG_H__
diff --git a/runtime/onert/backend/trix/Convert.cc b/runtime/onert/backend/trix/Convert.cc
index 684dc80dd53..26992c9e932 100644
--- a/runtime/onert/backend/trix/Convert.cc
+++ b/runtime/onert/backend/trix/Convert.cc
@@ -16,11 +16,7 @@
 
 #include "Convert.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 data_type convertDataType(const ir::DataType type)
@@ -36,6 +32,4 @@ data_type convertDataType(const ir::DataType type)
   }
 }
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
diff --git a/runtime/onert/backend/trix/Convert.h b/runtime/onert/backend/trix/Convert.h
index 12d7eea1943..2285986e450 100644
--- a/runtime/onert/backend/trix/Convert.h
+++ b/runtime/onert/backend/trix/Convert.h
@@ -24,11 +24,7 @@
 #include <libnpuhost.h>
 #include <type_traits>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 /**
@@ -78,8 +74,6 @@ void setBuffers(const std::vector<T *> &tensors, generic_buffers *buf)
   }
 }
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_CONVERT_H__
diff --git a/runtime/onert/backend/trix/DevContext.cc b/runtime/onert/backend/trix/DevContext.cc
index f8f248463ce..e815e63f85d 100644
--- a/runtime/onert/backend/trix/DevContext.cc
+++ b/runtime/onert/backend/trix/DevContext.cc
@@ -20,11 +20,7 @@
 
 #include <stdexcept>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 // All things related to npu device handle are gathered this Class, but when implementing npu
@@ -308,6 +304,4 @@ void DevContext::setBufferByBatch(const generic_buffer &origin_buf, uint32_t bat
   batch_buf->type = BUFFER_MAPPED;
 }
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
diff --git a/runtime/onert/backend/trix/DevContext.h b/runtime/onert/backend/trix/DevContext.h
index cd8de97e62c..27f0e22e743 100644
--- a/runtime/onert/backend/trix/DevContext.h
+++ b/runtime/onert/backend/trix/DevContext.h
@@ -24,11 +24,7 @@
 #include <string>
 #include <unordered_map>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 using ModelID = uint32_t;
@@ -144,8 +140,6 @@ class DevContext
   std::exception_ptr _eptr;
 };
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_DEV_CONTEXT_H__
diff --git a/runtime/onert/backend/trix/KernelGenerator.cc b/runtime/onert/backend/trix/KernelGenerator.cc
index 49437f93b49..c33dd8ce5d6 100644
--- a/runtime/onert/backend/trix/KernelGenerator.cc
+++ b/runtime/onert/backend/trix/KernelGenerator.cc
@@ -27,11 +27,7 @@
 
 #include <stdexcept>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 KernelGenerator::KernelGenerator(const ir::Graph &graph,
@@ -77,6 +73,4 @@ void KernelGenerator::visit(const ir::operation::Bulk &node)
   _return_fn = std::move(fn);
 }
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
diff --git a/runtime/onert/backend/trix/KernelGenerator.h b/runtime/onert/backend/trix/KernelGenerator.h
index 4f3de01870d..0f555d36515 100644
--- a/runtime/onert/backend/trix/KernelGenerator.h
+++ b/runtime/onert/backend/trix/KernelGenerator.h
@@ -26,11 +26,7 @@
 #include <ir/Operands.h>
 #include <ir/Operations.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 class KernelGenerator : public basic::KernelGeneratorBase
@@ -53,8 +49,6 @@ class KernelGenerator : public basic::KernelGeneratorBase
   const std::shared_ptr<DevContext> _dev_context;
 };
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_KERNEL_GENERATOR_H__
diff --git a/runtime/onert/backend/trix/Tensor.h b/runtime/onert/backend/trix/Tensor.h
index 5138cee7124..2f8243d1ff1 100644
--- a/runtime/onert/backend/trix/Tensor.h
+++ b/runtime/onert/backend/trix/Tensor.h
@@ -20,18 +20,12 @@
 #include <backend/basic/Tensor.h>
 #include <ir/Data.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 using Tensor = basic::Tensor;
 using ExternalTensor = basic::ExternalTensor;
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_TENSOR_H__
diff --git a/runtime/onert/backend/trix/TensorBuilder.h b/runtime/onert/backend/trix/TensorBuilder.h
index ac6ca0f9a35..d9577f4327f 100644
--- a/runtime/onert/backend/trix/TensorBuilder.h
+++ b/runtime/onert/backend/trix/TensorBuilder.h
@@ -19,17 +19,11 @@
 
 #include <backend/basic/TensorBuilder.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
+namespace onert::backend::trix
 {
 
 using TensorBuilder = basic::TensorBuilder;
 
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix
 
 #endif // __ONERT_BACKEND_TRIX_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/trix/ops/BulkLayer.cc b/runtime/onert/backend/trix/ops/BulkLayer.cc
index db5c81ba737..3c307a41cb2 100644
--- a/runtime/onert/backend/trix/ops/BulkLayer.cc
+++ b/runtime/onert/backend/trix/ops/BulkLayer.cc
@@ -18,13 +18,7 @@
 
 #include "../Convert.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
-{
-namespace ops
+namespace onert::backend::trix::ops
 {
 
 BulkLayer::BulkLayer() : _inputs(), _outputs(), _model_id(0), _dev_context(nullptr)
@@ -70,7 +64,4 @@ void BulkLayer::prepare()
   // DO NOTHING
 }
 
-} // namespace ops
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix::ops
diff --git a/runtime/onert/backend/trix/ops/BulkLayer.h b/runtime/onert/backend/trix/ops/BulkLayer.h
index 6590b698984..c3221c47caa 100644
--- a/runtime/onert/backend/trix/ops/BulkLayer.h
+++ b/runtime/onert/backend/trix/ops/BulkLayer.h
@@ -22,13 +22,7 @@
 
 #include <exec/IFunction.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace trix
-{
-namespace ops
+namespace onert::backend::trix::ops
 {
 
 class BulkLayer : public ::onert::exec::IFunction
@@ -54,9 +48,6 @@ class BulkLayer : public ::onert::exec::IFunction
   std::shared_ptr<DevContext> _dev_context;
 };
 
-} // namespace ops
-} // namespace trix
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::trix::ops
 
 #endif // __ONERT_BACKEND_TRIX_OPS_BULKLAYER_H__
diff --git a/runtime/onert/backend/xnnpack/Backend.h b/runtime/onert/backend/xnnpack/Backend.h
index 67494a534cd..a4459d60e93 100644
--- a/runtime/onert/backend/xnnpack/Backend.h
+++ b/runtime/onert/backend/xnnpack/Backend.h
@@ -25,11 +25,7 @@
 
 #include <memory>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 class Backend : public ::onert::backend::Backend
@@ -57,8 +53,6 @@ class Backend : public ::onert::backend::Backend
   std::shared_ptr<IConfig> _config;
 };
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_BACKEND_H__
diff --git a/runtime/onert/backend/xnnpack/BackendContext.cc b/runtime/onert/backend/xnnpack/BackendContext.cc
index df6efdbc29f..ee2a7d4ea1b 100644
--- a/runtime/onert/backend/xnnpack/BackendContext.cc
+++ b/runtime/onert/backend/xnnpack/BackendContext.cc
@@ -24,11 +24,7 @@
 #include "ir/OperandIndexSequence.h"
 #include "backend/basic/BackendContextHelpers.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 ITensorRegistry *BackendContext::genTensors() { return basic::genTensors(*this); }
@@ -59,6 +55,4 @@ FunctionMap BackendContext::genKernels()
   return ret;
 }
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
diff --git a/runtime/onert/backend/xnnpack/BackendContext.h b/runtime/onert/backend/xnnpack/BackendContext.h
index a88e0b9a6d2..20fa34ccf02 100644
--- a/runtime/onert/backend/xnnpack/BackendContext.h
+++ b/runtime/onert/backend/xnnpack/BackendContext.h
@@ -25,11 +25,7 @@
 
 const int kDefaultNumThreadpoolThreads = 1;
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 class BackendContext : public onert::backend::BackendContext
@@ -62,8 +58,6 @@ class BackendContext : public onert::backend::BackendContext
   std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_BACKEND_CONTEXT_H__
diff --git a/runtime/onert/backend/xnnpack/Config.cc b/runtime/onert/backend/xnnpack/Config.cc
index 85f96486958..8f89a553b50 100644
--- a/runtime/onert/backend/xnnpack/Config.cc
+++ b/runtime/onert/backend/xnnpack/Config.cc
@@ -18,11 +18,7 @@
 
 #include <xnnpack.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 Config::~Config() { xnn_deinitialize(); }
@@ -37,6 +33,4 @@ bool Config::initialize()
   return true;
 }
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
diff --git a/runtime/onert/backend/xnnpack/Config.h b/runtime/onert/backend/xnnpack/Config.h
index ea59479bad9..857f94fc7ed 100644
--- a/runtime/onert/backend/xnnpack/Config.h
+++ b/runtime/onert/backend/xnnpack/Config.h
@@ -21,11 +21,7 @@
 #include <memory>
 #include <util/ITimer.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 class Config : public IConfig
@@ -43,8 +39,6 @@ class Config : public IConfig
   std::unique_ptr<util::ITimer> timer() override { return std::make_unique<util::CPUTimer>(); }
 };
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_CONFIG_H__
diff --git a/runtime/onert/backend/xnnpack/ExternalContext.cc b/runtime/onert/backend/xnnpack/ExternalContext.cc
index 1fbcd4f02a3..96eef7d2e5f 100644
--- a/runtime/onert/backend/xnnpack/ExternalContext.cc
+++ b/runtime/onert/backend/xnnpack/ExternalContext.cc
@@ -18,11 +18,7 @@
 
 #include <cassert>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 ExternalContext::ExternalContext(size_t num_threads)
@@ -31,6 +27,4 @@ ExternalContext::ExternalContext(size_t num_threads)
   assert(_threadpool);
 }
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
diff --git a/runtime/onert/backend/xnnpack/ExternalContext.h b/runtime/onert/backend/xnnpack/ExternalContext.h
index 682fd2e4ee7..daa91fb5273 100644
--- a/runtime/onert/backend/xnnpack/ExternalContext.h
+++ b/runtime/onert/backend/xnnpack/ExternalContext.h
@@ -20,11 +20,7 @@
 #include <memory>
 #include <xnnpack.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 class ExternalContext
@@ -39,8 +35,6 @@ class ExternalContext
   std::unique_ptr<pthreadpool, decltype(&pthreadpool_destroy)> _threadpool;
 };
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_EXTERNAL_CONTEXT_H__
diff --git a/runtime/onert/backend/xnnpack/KernelGenerator.cc b/runtime/onert/backend/xnnpack/KernelGenerator.cc
index 51c9cf320e9..963db5aa35b 100644
--- a/runtime/onert/backend/xnnpack/KernelGenerator.cc
+++ b/runtime/onert/backend/xnnpack/KernelGenerator.cc
@@ -29,11 +29,7 @@
 
 #include <stdexcept>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 KernelGenerator::KernelGenerator(
@@ -177,6 +173,4 @@ void KernelGenerator::visit(const ir::operation::FullyConnected &node)
   _return_fn = std::move(fn);
 }
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
diff --git a/runtime/onert/backend/xnnpack/KernelGenerator.h b/runtime/onert/backend/xnnpack/KernelGenerator.h
index f4d8dcb84cd..aa8cb27b861 100644
--- a/runtime/onert/backend/xnnpack/KernelGenerator.h
+++ b/runtime/onert/backend/xnnpack/KernelGenerator.h
@@ -27,11 +27,7 @@
 #include <ir/Operands.h>
 #include <ir/Operations.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 class KernelGenerator : public basic::KernelGeneratorBase
@@ -58,8 +54,6 @@ class KernelGenerator : public basic::KernelGeneratorBase
   const std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_KERNEL_GENERATOR_H__
diff --git a/runtime/onert/backend/xnnpack/StaticTensorManager.h b/runtime/onert/backend/xnnpack/StaticTensorManager.h
index adaa3623d46..8d9be03bcaa 100644
--- a/runtime/onert/backend/xnnpack/StaticTensorManager.h
+++ b/runtime/onert/backend/xnnpack/StaticTensorManager.h
@@ -19,17 +19,11 @@
 
 #include "backend/basic/StaticTensorManager.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 using StaticTensorManager = basic::StaticTensorManager;
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_STATICTENSOR_MANAGER_H__
diff --git a/runtime/onert/backend/xnnpack/Tensor.h b/runtime/onert/backend/xnnpack/Tensor.h
index 147361109fe..a47ba719b45 100644
--- a/runtime/onert/backend/xnnpack/Tensor.h
+++ b/runtime/onert/backend/xnnpack/Tensor.h
@@ -20,18 +20,12 @@
 #include <backend/basic/Tensor.h>
 #include <ir/Data.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 using Tensor = basic::Tensor;
 using ExternalTensor = basic::ExternalTensor;
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_TENSOR_H__
diff --git a/runtime/onert/backend/xnnpack/TensorBuilder.h b/runtime/onert/backend/xnnpack/TensorBuilder.h
index cbb7c9e1867..ebb653191e5 100644
--- a/runtime/onert/backend/xnnpack/TensorBuilder.h
+++ b/runtime/onert/backend/xnnpack/TensorBuilder.h
@@ -19,17 +19,11 @@
 
 #include <backend/basic/TensorBuilder.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
+namespace onert::backend::xnnpack
 {
 
 using TensorBuilder = basic::TensorBuilder;
 
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack
 
 #endif // __ONERT_BACKEND_XNNPACK_TENSOR_BUILDER_H__
diff --git a/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.cc b/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.cc
index e2e4e38253f..4e69750ca49 100644
--- a/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.cc
+++ b/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.cc
@@ -18,13 +18,7 @@
 
 #include "ir/Padding.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 ConvolutionLayer::ConvolutionLayer(const std::shared_ptr<ExternalContext> external_context)
   : Layer(external_context), _input(nullptr), _kernel(nullptr), _bias(nullptr), _output(nullptr),
@@ -149,7 +143,4 @@ bool ConvolutionLayer::setup()
   return true;
 }
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
diff --git a/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.h b/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.h
index 6cbaa9f3ad9..5e8b84a86aa 100644
--- a/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.h
+++ b/runtime/onert/backend/xnnpack/ops/ConvolutionLayer.h
@@ -21,13 +21,7 @@
 
 #include <xnnpack.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 
 class ConvolutionLayer : public Layer
@@ -69,9 +63,6 @@ class ConvolutionLayer : public Layer
   ir::Activation _activation;
 };
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
 
 #endif // __ONERT_BACKEND_XNNPACK_OPS_CONVOLUTION_LAYER_H__
diff --git a/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.cc b/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.cc
index 1fc04b32b6d..51b8cc90266 100644
--- a/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.cc
+++ b/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.cc
@@ -18,13 +18,7 @@
 
 #include "ir/Padding.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 
 DepthwiseConvolutionLayer::DepthwiseConvolutionLayer(
@@ -150,7 +144,4 @@ bool DepthwiseConvolutionLayer::setup()
   return true;
 }
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
diff --git a/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.h b/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.h
index 10f840ae798..6bd970c9558 100644
--- a/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.h
+++ b/runtime/onert/backend/xnnpack/ops/DepthwiseConvolutionLayer.h
@@ -19,13 +19,7 @@
 
 #include "Layer.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 
 class DepthwiseConvolutionLayer : public Layer
@@ -69,9 +63,6 @@ class DepthwiseConvolutionLayer : public Layer
   ir::Activation _activation;
 };
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
 
 #endif // __ONERT_BACKEND_XNNPACK_OPS_DEPTHWISE_CONVOLUTION_LAYER_H__
diff --git a/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.cc b/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.cc
index 71f02b11091..4ef575bb278 100644
--- a/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.cc
+++ b/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.cc
@@ -18,13 +18,7 @@
 
 #include "ir/Padding.h"
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 
 FullyConnectedLayer::FullyConnectedLayer(const std::shared_ptr<ExternalContext> external_context)
@@ -136,7 +130,4 @@ bool FullyConnectedLayer::setup()
   return true;
 }
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
diff --git a/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.h b/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.h
index 883607ef9f9..ea7db95ded1 100644
--- a/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.h
+++ b/runtime/onert/backend/xnnpack/ops/FullyConnectedLayer.h
@@ -21,13 +21,7 @@
 
 #include <xnnpack.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 
 class FullyConnectedLayer : public Layer
@@ -53,9 +47,6 @@ class FullyConnectedLayer : public Layer
   ir::Activation _activation;
 };
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
 
 #endif // __ONERT_BACKEND_XNNPACK_OPS_FULLY_CONNECTED_LAYER_H__
diff --git a/runtime/onert/backend/xnnpack/ops/Layer.h b/runtime/onert/backend/xnnpack/ops/Layer.h
index ec07e874f72..23fd76407d8 100644
--- a/runtime/onert/backend/xnnpack/ops/Layer.h
+++ b/runtime/onert/backend/xnnpack/ops/Layer.h
@@ -28,13 +28,7 @@
 
 #include <xnnpack.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 
 class Layer : public ::onert::exec::IFunction
@@ -73,9 +67,6 @@ class Layer : public ::onert::exec::IFunction
   const std::shared_ptr<ExternalContext> _external_context;
 };
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
 
 #endif // __ONERT_BACKEND_XNNPACK_OPS_LAYER_H__
diff --git a/runtime/onert/backend/xnnpack/ops/OperationUtils.h b/runtime/onert/backend/xnnpack/ops/OperationUtils.h
index fe93fccc037..f82bc39811c 100644
--- a/runtime/onert/backend/xnnpack/ops/OperationUtils.h
+++ b/runtime/onert/backend/xnnpack/ops/OperationUtils.h
@@ -22,21 +22,12 @@
 #include <ir/Padding.h>
 #include <util/CalculateActivationRange.h>
 
-namespace onert
-{
-namespace backend
-{
-namespace xnnpack
-{
-namespace ops
+namespace onert::backend::xnnpack::ops
 {
 
 using OperandType = ir::DataType;
 using namespace onert::util; // CalculateActivationRange
 
-} // namespace ops
-} // namespace xnnpack
-} // namespace backend
-} // namespace onert
+} // namespace onert::backend::xnnpack::ops
 
 #endif // __ONERT_BACKEND_XNNPACK_OPS_OPERATION_UTILS_H__