distributed_tree.h

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// -----------------------------------------------------------------------------
//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception OR LGPL-2.1-or-later
// Copyright (C) 2022 - 2026 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Detailed license information governing the source code and contributions
// can be found in LICENSE.md and CONTRIBUTING.md at the top level directory.
//
// -----------------------------------------------------------------------------
 
#ifndef dealii_arborx_distributed_tree_h
#define dealii_arborx_distributed_tree_h
 
#include <deal.II/base/config.h>
 
#if defined(DEAL_II_ARBORX_WITH_MPI) && defined(DEAL_II_WITH_MPI)
#  include <deal.II/arborx/access_traits.h>
 
#  include <deal.II/base/mpi.h>
 
#  include <ArborX_DistributedTree.hpp>
#  include <Kokkos_Core.hpp>
 
#endif
 
DEAL_II_NAMESPACE_OPEN
 
#if defined(DEAL_II_ARBORX_WITH_MPI) && defined(DEAL_II_WITH_MPI)
namespace ArborXWrappers
{
#  if ARBORX_VERSION_MAJOR < 2
  class DistributedTree
  {
  public:
    template <int dim, typename Number>
    DistributedTree(
      const MPI_Comm                               comm,
      const std::vector<BoundingBox<dim, Number>> &bounding_boxes);
 
    template <int dim, typename Number>
    DistributedTree(const MPI_Comm                         comm,
                    const std::vector<Point<dim, Number>> &points);
 
    template <typename QueryType>
    std::pair<std::vector<std::pair<int, int>>, std::vector<int>>
    query(const QueryType &queries);
 
  private:
    ArborX::DistributedTree<Kokkos::HostSpace> distributed_tree;
  };
 
 
 
  template <int dim, typename Number>
  DistributedTree::DistributedTree(
    const MPI_Comm                               comm,
    const std::vector<BoundingBox<dim, Number>> &bounding_boxes)
    : distributed_tree(comm,
                       Kokkos::DefaultHostExecutionSpace{},
                       bounding_boxes)
  {}
 
 
 
  template <int dim, typename Number>
  DistributedTree::DistributedTree(
    const MPI_Comm                         comm,
    const std::vector<Point<dim, Number>> &points)
    : distributed_tree(comm, Kokkos::DefaultHostExecutionSpace{}, points)
  {}
 
 
 
  template <typename QueryType>
  std::pair<std::vector<std::pair<int, int>>, std::vector<int>>
  DistributedTree::query(const QueryType &queries)
  {
    Kokkos::View<int *, Kokkos::HostSpace> offsets("offsets", 0);
    Kokkos::View<Kokkos::pair<int, int> *, Kokkos::HostSpace> indices_ranks(
      "indices_ranks", 0);
    distributed_tree.query(Kokkos::DefaultHostExecutionSpace{},
                           queries,
                           indices_ranks,
                           offsets);
 
    std::vector<std::pair<int, int>> indices_ranks_vector;
    for (unsigned int i = 0; i < indices_ranks.extent(0); ++i)
      {
        indices_ranks_vector.emplace_back(indices_ranks(i).first,
                                          indices_ranks(i).second);
      }
 
    std::vector<int> offsets_vector;
    offsets_vector.insert(offsets_vector.begin(),
                          offsets.data(),
                          offsets.data() + offsets.extent(0));
 
    return {indices_ranks_vector, offsets_vector};
  }
#  else
  template <typename Value>
  class DistributedTree
  {
  public:
    DistributedTree(const MPI_Comm comm, const std::vector<Value> &values);
 
    template <typename QueryType>
    std::pair<std::vector<std::pair<int, int>>, std::vector<int>>
    query(const QueryType &queries);
 
  private:
    ArborX::DistributedTree<Kokkos::HostSpace,
                            ArborX::PairValueIndex<Value, unsigned int>,
                            internal::IndexableGetter>
      distributed_tree;
    internal::ExtractIndexRank callback;
  };
 
 
 
  template <typename Value>
  DistributedTree<Value>::DistributedTree(const MPI_Comm            comm,
                                          const std::vector<Value> &values)
    : distributed_tree(comm,
                       Kokkos::DefaultHostExecutionSpace{},
                       ArborX::Experimental::attach_indices(values),
                       internal::IndexableGetter{})
    , callback{Utilities::MPI::this_mpi_process(comm)}
  {}
 
  template <typename Value>
  template <typename QueryType>
  std::pair<std::vector<std::pair<int, int>>, std::vector<int>>
  DistributedTree<Value>::query(const QueryType &queries)
  {
    Kokkos::View<int *, Kokkos::HostSpace> offsets("offsets", 0);
    Kokkos::View<Kokkos::pair<unsigned int, unsigned int> *, Kokkos::HostSpace>
      indices_ranks("indices_ranks", 0);
    if constexpr (QueryType::is_nearest)
      {
        distributed_tree.query(
          Kokkos::DefaultHostExecutionSpace{},
          queries,
          ArborX::Experimental::declare_callback_constrained(callback),
          indices_ranks,
          offsets);
      }
    else
      {
        distributed_tree.query(Kokkos::DefaultHostExecutionSpace{},
                               queries,
                               callback,
                               indices_ranks,
                               offsets);
      }
 
    std::vector<std::pair<int, int>> indices_ranks_vector;
    for (unsigned int i = 0; i < indices_ranks.extent(0); ++i)
      {
        indices_ranks_vector.emplace_back(indices_ranks(i).first,
                                          indices_ranks(i).second);
      }
 
    std::vector<int> offsets_vector;
    offsets_vector.insert(offsets_vector.begin(),
                          offsets.data(),
                          offsets.data() + offsets.extent(0));
 
    return {indices_ranks_vector, offsets_vector};
  }
 
#  endif
} // namespace ArborXWrappers
 
#endif
 
DEAL_II_NAMESPACE_CLOSE
#endif