mesh_loop.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 2017 - 2023 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE.md at
// the top level directory of deal.II.
//
// ---------------------------------------------------------------------
 
 
#ifndef dealii_mesh_worker_mesh_loop_h
#define dealii_mesh_worker_mesh_loop_h
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/template_constraints.h>
#include <deal.II/base/types.h>
#include <deal.II/base/work_stream.h>
 
#include <deal.II/grid/filtered_iterator.h>
#include <deal.II/grid/tria.h>
 
#include <deal.II/meshworker/assemble_flags.h>
#include <deal.II/meshworker/dof_info.h>
#include <deal.II/meshworker/integration_info.h>
#include <deal.II/meshworker/local_integrator.h>
#include <deal.II/meshworker/loop.h>
 
#include <functional>
#include <type_traits>
 
DEAL_II_NAMESPACE_OPEN
 
// Forward declaration
#ifndef DOXYGEN
template <typename>
class TriaActiveIterator;
#endif
 
namespace MeshWorker
{
  namespace internal
  {
    template <class CellIteratorType>
    struct CellIteratorBaseType
    {
      using type = CellIteratorType;
    };
 
    template <class CellIteratorType>
    struct CellIteratorBaseType<IteratorOverIterators<CellIteratorType>>
    {
      // Since we can have filtered iterators and the like as template
      // arguments, we recursivelyremove the template layers to retrieve the
      // underlying iterator type.
      using type = typename CellIteratorBaseType<CellIteratorType>::type;
    };
 
    template <class CellIteratorType>
    struct CellIteratorBaseType<FilteredIterator<CellIteratorType>>
    {
      // Since we can have nested filtered iterators, we recursively
      // remove the template layers to retrieve the underlying iterator type.
      using type = typename CellIteratorBaseType<CellIteratorType>::type;
    };
  } // namespace internal
 
#ifdef DOXYGEN
  using CellWorkerFunctionType = std::function<
    void(const CellIteratorBaseType &, ScratchData &, CopyData &)>;
 
  using CopierFunctionType = std::function<void(const CopyData &)>;
 
  using BoundaryWorkerFunctionType =
    std::function<void(const CellIteratorBaseType &,
                       const unsigned int,
                       ScratchData &,
                       CopyData &)>;
 
  using FaceWorkerFunctionType =
    std::function<void(const CellIteratorBaseType &,
                       const unsigned int,
                       const unsigned int,
                       const CellIteratorBaseType &,
                       const unsigned int,
                       const unsigned int,
                       ScratchData &,
                       CopyData &)>;
#endif
 
  template <class CellIteratorType,
            class ScratchData,
            class CopyData,
            class CellIteratorBaseType =
              typename internal::CellIteratorBaseType<CellIteratorType>::type>
  void
  mesh_loop(
#ifdef DOXYGEN
    const CellIteratorType &begin,
    const CellIteratorType &end,
 
    const CellWorkerFunctionType &cell_worker,
    const CopierType &            copier,
 
    const ScratchData &sample_scratch_data,
    const CopyData &   sample_copy_data,
 
    const AssembleFlags flags = assemble_own_cells,
 
    const BoundaryWorkerFunctionType &boundary_worker =
      BoundaryWorkerFunctionType(),
 
    const FaceWorkerFunctionType &face_worker = FaceWorkerFunctionType(),
    const unsigned int queue_length = 2 * MultithreadInfo::n_threads(),
    const unsigned int chunk_size   = 8
#else
    const CellIteratorType &                            begin,
    const std_cxx20::type_identity_t<CellIteratorType> &end,
 
    const std_cxx20::type_identity_t<std::function<
      void(const CellIteratorBaseType &, ScratchData &, CopyData &)>>
      &cell_worker,
    const std_cxx20::type_identity_t<std::function<void(const CopyData &)>>
      &copier,
 
    const ScratchData &sample_scratch_data,
    const CopyData &   sample_copy_data,
 
    const AssembleFlags flags = assemble_own_cells,
 
    const std_cxx20::type_identity_t<
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>> &boundary_worker =
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>(),
 
    const std_cxx20::type_identity_t<
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>> &face_worker =
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>(),
 
    const unsigned int queue_length = 2 * MultithreadInfo::n_threads(),
    const unsigned int chunk_size   = 8
#endif
  )
  {
    Assert(
      (!cell_worker) == !(flags & work_on_cells),
      ExcMessage(
        "If you provide a cell worker function, you also need to request "
        "that work should be done on cells by setting the 'work_on_cells' flag. "
        "Conversely, if you don't provide a cell worker function, you "
        "cannot set the 'work_on_cells' flag. One of these two "
        "conditions is not satisfied."));
 
    Assert((flags & (assemble_own_interior_faces_once |
                     assemble_own_interior_faces_both)) !=
             (assemble_own_interior_faces_once |
              assemble_own_interior_faces_both),
           ExcMessage(
             "If you provide a face worker function, you also need to request "
             "that work should be done on interior faces by setting either the "
             "'assemble_own_interior_faces_once' flag or the "
             "'assemble_own_interior_faces_both' flag. "
             "Conversely, if you don't provide a face worker function, you "
             "cannot set either of these two flags. One of these two "
             "conditions is not satisfied."));
 
    Assert((flags & (assemble_ghost_faces_once | assemble_ghost_faces_both)) !=
             (assemble_ghost_faces_once | assemble_ghost_faces_both),
           ExcMessage(
             "You can only 'specify assemble_ghost_faces_once' "
             "OR 'assemble_ghost_faces_both', but not both of these flags."));
 
    Assert(
      !(flags & cells_after_faces) ||
        (flags & (assemble_own_cells | assemble_ghost_cells)),
      ExcMessage(
        "The option 'cells_after_faces' only makes sense if you assemble on cells."));
 
    Assert(
      (!face_worker) == !(flags & work_on_faces),
      ExcMessage(
        "If you provide a face worker function, you also need to request "
        "that work should be done on faces by setting the 'work_on_faces' flag. "
        "Conversely, if you don't provide a face worker function, you "
        "cannot set the 'work_on_faces' flag. One of these two "
        "conditions is not satisfied."));
 
    Assert(
      (!boundary_worker) == !(flags & assemble_boundary_faces),
      ExcMessage(
        "If you provide a boundary face worker function, you also need to request "
        "that work should be done on boundary faces by setting the 'assemble_boundary_faces' flag. "
        "Conversely, if you don't provide a boundary face worker function, you "
        "cannot set the 'assemble_boundary_faces' flag. One of these two "
        "conditions is not satisfied."));
 
    auto cell_action = [&](const CellIteratorBaseType &cell,
                           ScratchData &               scratch,
                           CopyData &                  copy) {
      // First reset the CopyData class to the empty copy_data given by the
      // user.
      copy = sample_copy_data;
 
      // Store the dimension in which we are working for later use
      const auto dim = cell->get_triangulation().dimension;
 
      const bool ignore_subdomain =
        (cell->get_triangulation().locally_owned_subdomain() ==
         numbers::invalid_subdomain_id);
 
      types::subdomain_id current_subdomain_id =
        (cell->is_level_cell() ? cell->level_subdomain_id() :
                                 cell->subdomain_id());
 
      const bool own_cell =
        ignore_subdomain ||
        (current_subdomain_id ==
         cell->get_triangulation().locally_owned_subdomain());
 
      if ((!ignore_subdomain) &&
          (current_subdomain_id == numbers::artificial_subdomain_id))
        return;
 
      if (!(flags & (cells_after_faces)) &&
          (((flags & (assemble_own_cells)) && own_cell) ||
           ((flags & assemble_ghost_cells) && !own_cell)))
        cell_worker(cell, scratch, copy);
 
      if (flags & (work_on_faces | work_on_boundary))
        for (const unsigned int face_no : cell->face_indices())
          {
            if (cell->at_boundary(face_no) &&
                !cell->has_periodic_neighbor(face_no))
              {
                // only integrate boundary faces of own cells
                if ((flags & assemble_boundary_faces) && own_cell)
                  boundary_worker(cell, face_no, scratch, copy);
              }
            else
              {
                // interior face, potentially assemble
                TriaIterator<typename CellIteratorBaseType::AccessorType>
                  neighbor = cell->neighbor_or_periodic_neighbor(face_no);
 
                types::subdomain_id neighbor_subdomain_id =
                  numbers::artificial_subdomain_id;
                if (neighbor->is_level_cell())
                  neighbor_subdomain_id = neighbor->level_subdomain_id();
                // subdomain id is only valid for active cells
                else if (neighbor->is_active())
                  neighbor_subdomain_id = neighbor->subdomain_id();
 
                const bool own_neighbor =
                  ignore_subdomain ||
                  (neighbor_subdomain_id ==
                   cell->get_triangulation().locally_owned_subdomain());
 
                // skip all faces between two ghost cells
                if (!own_cell && !own_neighbor)
                  continue;
 
                // skip if the user doesn't want faces between own cells
                if (own_cell && own_neighbor &&
                    !(flags & (assemble_own_interior_faces_both |
                               assemble_own_interior_faces_once)))
                  continue;
 
                // skip face to ghost
                if (own_cell != own_neighbor &&
                    !(flags &
                      (assemble_ghost_faces_both | assemble_ghost_faces_once)))
                  continue;
 
                // Deal with refinement edges from the refined side. Assuming
                // one-irregular meshes, this situation should only occur if
                // both cells are active.
                const bool periodic_neighbor =
                  cell->has_periodic_neighbor(face_no);
 
                if (dim > 1 && ((!periodic_neighbor &&
                                 cell->neighbor_is_coarser(face_no) &&
                                 neighbor->is_active()) ||
                                (periodic_neighbor &&
                                 cell->periodic_neighbor_is_coarser(face_no) &&
                                 neighbor->is_active())))
                  {
                    Assert(cell->is_active(), ExcInternalError());
 
                    // skip if only one processor needs to assemble the face
                    // to a ghost cell and the fine cell is not ours.
                    if (!own_cell && (flags & assemble_ghost_faces_once))
                      continue;
 
                    const std::pair<unsigned int, unsigned int>
                      neighbor_face_no =
                        periodic_neighbor ?
                          cell->periodic_neighbor_of_coarser_periodic_neighbor(
                            face_no) :
                          cell->neighbor_of_coarser_neighbor(face_no);
 
                    face_worker(cell,
                                face_no,
                                numbers::invalid_unsigned_int,
                                neighbor,
                                neighbor_face_no.first,
                                neighbor_face_no.second,
                                scratch,
                                copy);
 
                    if (flags & assemble_own_interior_faces_both)
                      {
                        // If own faces are to be assembled from both sides,
                        // call the faceworker again with swapped arguments.
                        // This is because we won't be looking at an adaptively
                        // refined edge coming from the other side.
                        face_worker(neighbor,
                                    neighbor_face_no.first,
                                    neighbor_face_no.second,
                                    cell,
                                    face_no,
                                    numbers::invalid_unsigned_int,
                                    scratch,
                                    copy);
                      }
                  }
                else if (dim == 1 && cell->level() > neighbor->level())
                  {
                    // In one dimension, there is no other check to do
                    const unsigned int neighbor_face_no =
                      periodic_neighbor ?
                        cell->periodic_neighbor_face_no(face_no) :
                        cell->neighbor_face_no(face_no);
                    Assert(periodic_neighbor ||
                             neighbor->face(neighbor_face_no) ==
                               cell->face(face_no),
                           ExcInternalError());
 
                    face_worker(cell,
                                face_no,
                                numbers::invalid_unsigned_int,
                                neighbor,
                                neighbor_face_no,
                                numbers::invalid_unsigned_int,
                                scratch,
                                copy);
 
                    if (flags & assemble_own_interior_faces_both)
                      {
                        // If own faces are to be assembled from both sides,
                        // call the faceworker again with swapped arguments.
                        face_worker(neighbor,
                                    neighbor_face_no,
                                    numbers::invalid_unsigned_int,
                                    cell,
                                    face_no,
                                    numbers::invalid_unsigned_int,
                                    scratch,
                                    copy);
                      }
                  }
                else
                  {
                    // If iterator is active and neighbor is refined, skip
                    // internal face.
                    if (::internal::is_active_iterator(cell) &&
                        neighbor->has_children())
                      continue;
 
                    // Now neighbor is on the same refinement level.
                    // Double check.
                    Assert((!periodic_neighbor &&
                            !cell->neighbor_is_coarser(face_no)) ||
                             (periodic_neighbor &&
                              !cell->periodic_neighbor_is_coarser(face_no)),
                           ExcInternalError());
 
                    // If we own both cells only do faces from one side (unless
                    // AssembleFlags says otherwise). Here, we rely on cell
                    // comparison that will look at cell->index().
                    if (own_cell && own_neighbor &&
                        (flags & assemble_own_interior_faces_once) &&
                        (neighbor < cell))
                      continue;
 
                    // We only look at faces to ghost on the same level once
                    // (only where own_cell=true and own_neighbor=false)
                    if (!own_cell)
                      continue;
 
                    // now only one processor assembles faces_to_ghost. We let
                    // the processor with the smaller (level-)subdomain id
                    // assemble the face.
                    if (own_cell && !own_neighbor &&
                        (flags & assemble_ghost_faces_once) &&
                        (neighbor_subdomain_id < current_subdomain_id))
                      continue;
 
                    const unsigned int neighbor_face_no =
                      periodic_neighbor ?
                        cell->periodic_neighbor_face_no(face_no) :
                        cell->neighbor_face_no(face_no);
                    Assert(periodic_neighbor ||
                             neighbor->face(neighbor_face_no) ==
                               cell->face(face_no),
                           ExcInternalError());
 
                    face_worker(cell,
                                face_no,
                                numbers::invalid_unsigned_int,
                                neighbor,
                                neighbor_face_no,
                                numbers::invalid_unsigned_int,
                                scratch,
                                copy);
                  }
              }
          } // faces
 
      // Execute the cell_worker if faces are handled before cells
      if ((flags & cells_after_faces) &&
          (((flags & assemble_own_cells) && own_cell) ||
           ((flags & assemble_ghost_cells) && !own_cell)))
        cell_worker(cell, scratch, copy);
    };
 
    // Submit to workstream
    WorkStream::run(begin,
                    end,
                    cell_action,
                    copier,
                    sample_scratch_data,
                    sample_copy_data,
                    queue_length,
                    chunk_size);
  }
 
  template <class CellIteratorType,
            class ScratchData,
            class CopyData,
            class CellIteratorBaseType =
              typename internal::CellIteratorBaseType<CellIteratorType>::type>
  void
  mesh_loop(
    IteratorRange<CellIteratorType> iterator_range,
    const std_cxx20::type_identity_t<std::function<
      void(const CellIteratorBaseType &, ScratchData &, CopyData &)>>
      &cell_worker,
    const std_cxx20::type_identity_t<std::function<void(const CopyData &)>>
      &copier,
 
    const ScratchData &sample_scratch_data,
    const CopyData &   sample_copy_data,
 
    const AssembleFlags flags = assemble_own_cells,
 
    const std_cxx20::type_identity_t<
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>> &boundary_worker =
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>(),
 
    const std_cxx20::type_identity_t<
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>> &face_worker =
      std::function<void(const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         const CellIteratorBaseType &,
                         const unsigned int,
                         const unsigned int,
                         ScratchData &,
                         CopyData &)>(),
 
    const unsigned int queue_length = 2 * MultithreadInfo::n_threads(),
    const unsigned int chunk_size   = 8)
  {
    // Call the function above
    mesh_loop<typename IteratorRange<CellIteratorType>::IteratorOverIterators,
              ScratchData,
              CopyData,
              CellIteratorBaseType>(iterator_range.begin(),
                                    iterator_range.end(),
                                    cell_worker,
                                    copier,
                                    sample_scratch_data,
                                    sample_copy_data,
                                    flags,
                                    boundary_worker,
                                    face_worker,
                                    queue_length,
                                    chunk_size);
  }
 
  template <class CellIteratorType,
            class ScratchData,
            class CopyData,
            class MainClass>
  void
  mesh_loop(const CellIteratorType &                            begin,
            const std_cxx20::type_identity_t<CellIteratorType> &end,
            MainClass &                                         main_class,
            void (MainClass::*cell_worker)(const CellIteratorType &,
                                           ScratchData &,
                                           CopyData &),
            void (MainClass::*copier)(const CopyData &),
            const ScratchData & sample_scratch_data,
            const CopyData &    sample_copy_data,
            const AssembleFlags flags                      = assemble_own_cells,
            void (MainClass::*boundary_worker)(const CellIteratorType &,
                                               const unsigned int,
                                               ScratchData &,
                                               CopyData &) = nullptr,
            void (MainClass::*face_worker)(const CellIteratorType &,
                                           const unsigned int,
                                           const unsigned int,
                                           const CellIteratorType &,
                                           const unsigned int,
                                           const unsigned int,
                                           ScratchData &,
                                           CopyData &)     = nullptr,
            const unsigned int queue_length = 2 * MultithreadInfo::n_threads(),
            const unsigned int chunk_size   = 8)
  {
    std::function<void(const CellIteratorType &, ScratchData &, CopyData &)>
      f_cell_worker;
 
    std::function<void(
      const CellIteratorType &, const unsigned int, ScratchData &, CopyData &)>
      f_boundary_worker;
 
    std::function<void(const CellIteratorType &,
                       const unsigned int,
                       const unsigned int,
                       const CellIteratorType &,
                       const unsigned int,
                       const unsigned int,
                       ScratchData &,
                       CopyData &)>
      f_face_worker;
 
    if (cell_worker != nullptr)
      f_cell_worker = [&main_class,
                       cell_worker](const CellIteratorType &cell_iterator,
                                    ScratchData &           scratch_data,
                                    CopyData &              copy_data) {
        (main_class.*cell_worker)(cell_iterator, scratch_data, copy_data);
      };
 
    if (boundary_worker != nullptr)
      f_boundary_worker =
        [&main_class, boundary_worker](const CellIteratorType &cell_iterator,
                                       const unsigned int      face_no,
                                       ScratchData &           scratch_data,
                                       CopyData &              copy_data) {
          (main_class.*
           boundary_worker)(cell_iterator, face_no, scratch_data, copy_data);
        };
 
    if (face_worker != nullptr)
      f_face_worker = [&main_class,
                       face_worker](const CellIteratorType &cell_iterator_1,
                                    const unsigned int      face_index_1,
                                    const unsigned int      subface_index_1,
                                    const CellIteratorType &cell_iterator_2,
                                    const unsigned int      face_index_2,
                                    const unsigned int      subface_index_2,
                                    ScratchData &           scratch_data,
                                    CopyData &              copy_data) {
        (main_class.*face_worker)(cell_iterator_1,
                                  face_index_1,
                                  subface_index_1,
                                  cell_iterator_2,
                                  face_index_2,
                                  subface_index_2,
                                  scratch_data,
                                  copy_data);
      };
 
    mesh_loop(
      begin,
      end,
      f_cell_worker,
      [&main_class, copier](const CopyData &copy_data) {
        (main_class.*copier)(copy_data);
      },
      sample_scratch_data,
      sample_copy_data,
      flags,
      f_boundary_worker,
      f_face_worker,
      queue_length,
      chunk_size);
  }
 
  template <class CellIteratorType,
            class ScratchData,
            class CopyData,
            class MainClass,
            class CellIteratorBaseType =
              typename internal::CellIteratorBaseType<CellIteratorType>::type>
  void
  mesh_loop(IteratorRange<CellIteratorType> iterator_range,
            MainClass &                     main_class,
            void (MainClass::*cell_worker)(const CellIteratorBaseType &,
                                           ScratchData &,
                                           CopyData &),
            void (MainClass::*copier)(const CopyData &),
            const ScratchData & sample_scratch_data,
            const CopyData &    sample_copy_data,
            const AssembleFlags flags                      = assemble_own_cells,
            void (MainClass::*boundary_worker)(const CellIteratorBaseType &,
                                               const unsigned int,
                                               ScratchData &,
                                               CopyData &) = nullptr,
            void (MainClass::*face_worker)(const CellIteratorBaseType &,
                                           const unsigned int,
                                           const unsigned int,
                                           const CellIteratorBaseType &,
                                           const unsigned int,
                                           const unsigned int,
                                           ScratchData &,
                                           CopyData &)     = nullptr,
            const unsigned int queue_length = 2 * MultithreadInfo::n_threads(),
            const unsigned int chunk_size   = 8)
  {
    // Call the function above
    mesh_loop<typename IteratorRange<CellIteratorType>::IteratorOverIterators,
              ScratchData,
              CopyData,
              MainClass,
              CellIteratorBaseType>(iterator_range.begin(),
                                    iterator_range.end(),
                                    main_class,
                                    cell_worker,
                                    copier,
                                    sample_scratch_data,
                                    sample_copy_data,
                                    flags,
                                    boundary_worker,
                                    face_worker,
                                    queue_length,
                                    chunk_size);
  }
} // namespace MeshWorker
 
DEAL_II_NAMESPACE_CLOSE
 
#endif