Build clusters associator with clustered point size (#305)

* Define heterogeneous `count_if` algorithm

* Build clusters associator with true value size

Author: sbaldu

include/CLUEstering/internal/algorithm/count_if/count_if.hpp

@@ -0,0 +1,52 @@
+
+#pragma once
+
+#include <alpaka/alpaka.hpp>
+
+#if defined(ALPAKA_ACC_GPU_CUDA_ENABLED) and not defined(ALPAKA_HOST_ONLY)
+#include <thrust/count.h>
+#include <thrust/execution_policy.h>
+#elif defined(ALPAKA_ACC_GPU_HIP_ENABLED) and not defined(ALPAKA_HOST_ONLY)
+#include <thrust/count.h>
+#include <thrust/execution_policy.h>
+#elif defined(ALPAKA_ACC_SYCL_ENABLED)
+#include <oneapi/dpl/algorithm>
+#include <oneapi/dpl/execution>
+#else
+#include <algorithm>
+#endif
+
+namespace clue::internal::algorithm {
+
+  template <typename InputIterator, typename Predicate>
+  ALPAKA_FN_HOST inline constexpr auto count_if(InputIterator first,
+                                                InputIterator last,
+                                                Predicate pred) {
+#if defined(ALPAKA_ACC_GPU_CUDA_ENABLED) and not defined(ALPAKA_HOST_ONLY)
+    return thrust::count_if(thrust::device, first, last, pred);
+#elif defined(ALPAKA_ACC_GPU_HIP_ENABLED) and not defined(ALPAKA_HOST_ONLY)
+    return thrust::count_if(thrust::hip::par, first, last, pred);
+#elif defined(ALPAKA_ACC_SYCL_ENABLED)
+    return oneapi::dpl::count_if(oneapi::dpl::execution::dpcpp_default, first, last, pred);
+#else
+    return std::count_if(first, last, pred);
+#endif
+  }
+
+  template <typename ExecutionPolicy, typename InputIterator, typename Predicate>
+  ALPAKA_FN_HOST inline constexpr auto count_if(ExecutionPolicy&& policy,
+                                                InputIterator first,
+                                                InputIterator last,
+                                                Predicate pred) {
+#if defined(ALPAKA_ACC_GPU_CUDA_ENABLED) and not defined(ALPAKA_HOST_ONLY)
+    return thrust::count_if(std::forward<ExecutionPolicy>(policy), first, last, pred);
+#elif defined(ALPAKA_ACC_GPU_HIP_ENABLED) and not defined(ALPAKA_HOST_ONLY)
+    return thrust::count_if(std::forward<ExecutionPolicy>(policy), first, last, pred);
+#elif defined(ALPAKA_ACC_SYCL_ENABLED)
+    return oneapi::dpl::count_if(std::forward<ExecutionPolicy>(policy), first, last, pred);
+#else
+    return std::count_if(std::forward<ExecutionPolicy>(policy), first, last, pred);
+#endif
+  }
+
+}  // namespace clue::internal::algorithm

include/CLUEstering/utils/detail/get_clusters.hpp

@@ -1,21 +1,35 @@
 
 #pragma once
 
-#include "CLUEstering/utils/get_clusters.hpp"
+#include "CLUEstering/data_structures/PointsHost.hpp"
+#include "CLUEstering/data_structures/PointsDevice.hpp"
 #include "CLUEstering/data_structures/internal/MakeAssociator.hpp"
+#include "CLUEstering/detail/concepts.hpp"
+#include "CLUEstering/internal/algorithm/count_if/count_if.hpp"
+#include "CLUEstering/utils/get_clusters.hpp"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
 #include <span>
 
 namespace clue {
   namespace detail {
 
+    template <typename T>
+    struct non_negative {
+      ALPAKA_FN_HOST_ACC constexpr auto operator()(T value) const { return value >= -1; }
+    };
+
     inline auto get_clusters(std::span<const int> cluster_ids) {
-      return internal::make_associator(cluster_ids, static_cast<int32_t>(cluster_ids.size()));
+      auto clustered_points = std::ranges::count_if(cluster_ids, non_negative<int>{});
+      return internal::make_associator(cluster_ids, static_cast<int>(clustered_points));
     }
 
     template <concepts::queue TQueue>
     inline auto get_clusters(TQueue& queue, std::span<const int> cluster_ids) {
-      return internal::make_associator(
-          queue, cluster_ids, static_cast<int32_t>(cluster_ids.size()));
+      auto clustered_points = internal::algorithm::count_if(
+          cluster_ids.begin(), cluster_ids.end(), non_negative<int>{});
+      return internal::make_associator(queue, cluster_ids, clustered_points);
     }
 
   }  // namespace detail

include/CLUEstering/utils/get_clusters.hpp

@@ -4,9 +4,10 @@
 
 #pragma once
 
-#include "CLUEstering/data_structures/AssociationMap.hpp"
 #include "CLUEstering/data_structures/PointsHost.hpp"
 #include "CLUEstering/data_structures/PointsDevice.hpp"
+#include "CLUEstering/detail/concepts.hpp"
+#include <cstddef>
 
 namespace clue {