chore: Fix docs and example

Author: peri044

Diff for: examples/distributed_inference/README.md

@@ -2,49 +2,46 @@
 
 Examples in this folder demonstrates doing distributed inference on multiple devices with Torch-TensorRT backend.
 
-1. Data parallel distributed inference based on [Accelerate](https://huggingface.co/docs/accelerate/usage_guides/distributed_inference)
+## Data parallel distributed inference based on [Accelerate](https://huggingface.co/docs/accelerate/usage_guides/distributed_inference)
 
 Using Accelerate users can achieve data parallel distributed inference with Torch-TensorRt backend. In this case, the entire model
 will be loaded onto each GPU and different chunks of batch input is processed on each device.
 
-See the examples started with `data_parallel` for more details.
+See the examples [data_parallel_gpt2.py](https://github.com/pytorch/TensorRT/blob/main/examples/distributed_inference/data_parallel_gpt2.py) and [data_parallel_stable_diffusion.py](https://github.com/pytorch/TensorRT/blob/main/examples/distributed_inference/data_parallel_stable_diffusion.py) for more details.
 
-2. Tensor parallel distributed inference
+## Tensor parallel distributed inference
 
 Here we use torch.distributed as an example, but compilation with tensor parallelism is agnostic to the implementation framework as long as the module is properly sharded.
 
 torchrun --nproc_per_node=2 tensor_parallel_llama2.py
 
-3. Tensor parallel distributed inference using nccl ops plugin
+## Tensor parallel distributed inference on a simple model using nccl ops plugin
 
- apt install libmpich-dev
+ 
+We use [torch.distributed](https://pytorch.org/docs/stable/distributed.html) package to add shard the model with Tensor parallelism. The distributed ops (`all_gather` and `all_reduce`) are then expressed as TensorRT-LLM plugins to avoid graph breaks during Torch-TensorRT compilation. The [converters for these operators](https://github.com/pytorch/TensorRT/blob/main/py/torch_tensorrt/dynamo/conversion/custom_ops_converters.py#L25-L55) are already available in Torch-TensorRT. The functional implementation of ops is imported from `tensorrt_llm` package (to be more specific, only `libnvinfer_plugin_tensorrt_llm.so` is required). So we have two options here 
 
- apt install libopenmpi-dev
+### Option 1: Install TensorRT-LLM
 
- #For python3.10
+Follow the instructions to [install TensorRT-LLM](https://nvidia.github.io/TensorRT-LLM/installation/linux.html)
 
- pip install tensorrt-llm
+If the default installation fails due to issues like library version mismatches or Python compatibility, it is recommended to use Option 2. After a successful installation, ensure you test by running `import torch_tensorrt` to confirm it works without errors. The import might fail if the `tensorrt_llm` installation overrides `torch_tensorrt` dependencies. Option 2 is particularly advisable if you prefer not to install `tensorrt_llm` and its associated dependencies.
 
- For other python versions, you need to load the libnvinfer_plugin_tensorrt_llm.so. Please set that in the environment variable export TRTLLM_PLUGINS_PATH={lib_path}. For example, we have already set the variable in initialize_distributed_env(). You can replace this with your TRTLLM_PLUGINS_PATH and unset it there
+### Option 2: Link the TensorRT-LLM directly.
 
- #then pip install the tensorrt and torch version compatible with installed torchTRT
+ Another alternative is to load the `libnvinfer_plugin_tensorrt_llm.so` directly. You can do this by 
+  * Downloading the [tensorrt_llm-0.16.0](https://pypi.nvidia.com/tensorrt-llm/tensorrt_llm-0.16.0-cp310-cp310-linux_x86_64.whl#sha256=f86c6b89647802f49b26b4f6e40824701da14c0f053dbda3e1e7a8709d6939c7) wheel file from the NVIDIA python index. 
+  * Extract the wheel file to a directory and you can find the `libnvinfer_plugin_tensorrt_llm.so` library under `tensorrt_llm/libs` directory.
+  * Please set the environment variable TRTLLM_PLUGINS_PATH to the above extracted path at the [initialize_distributed_env()](https://github.com/pytorch/TensorRT/blob/54e36dbafe567c75f36b3edb22d6f49d4278c12a/examples/distributed_inference/tensor_parallel_initialize_dist.py#L45) call.
 
- mpirun -n 2 --allow-run-as-root python tensor_parallel_simple_example.py
 
- #For other python
+After configuring the TensorRT-LLM or the TensorRT-LLM plugin library path, please run the following command which illustrates tensor parallelism of a simple model and compilation with Torch-TensorRT
 
-4. Tensor parallel distributed llama3 inference using nccl ops plugin
+```py
+mpirun -n 2 --allow-run-as-root python tensor_parallel_simple_example.py
+```
 
- apt install libmpich-dev
+We also provide a tensor paralellism compilation example on a more advanced model like `Llama-3`. Here's the command to run it
 
- apt install libopenmpi-dev
-
-#For python3.10
-
- pip install tensorrt-llm
-
- For other python versions, you need to load the libnvinfer_plugin_tensorrt_llm.so
-
- #then pip install the tensorrt and torch version compatible with installed torchTRT
-
- mpirun -n 2 --allow-run-as-root python tensor_parallel_llama3.py
+```py
+mpirun -n 2 --allow-run-as-root python tensor_parallel_llama3.py
+```

Diff for: examples/distributed_inference/tensor_parallel_llama3.py

@@ -17,8 +17,8 @@
 device_mesh, _world_size, _rank, logger = initialize_distributed_env(
     "./tensor_parallel_llama3"
 )
-# Import should be after initialization of the TRT-LLM plugin .so path
-import tensorrt_llm
+
+import torch_tensorrt
 
 logger.info(f"Starting PyTorch TP example on rank {_rank}.")
 assert (

Diff for: examples/distributed_inference/tensor_parallel_simple_example.py

@@ -15,7 +15,6 @@
 device_mesh, _world_size, _rank, logger = initialize_distributed_env(
     "./tensor_parallel_simple_example"
 )
-import tensorrt_llm
 
 """
 This example copies some code from https://github.com/pytorch/examples/blob/main/distributed/tensor_parallelism/tensor_parallel_example.py