cell_data_transfer.h

// ---------------------------------------------------------------------
//
// Copyright (C) 2018 - 2019 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_distributed_cell_data_transfer_h
#define dealii_distributed_cell_data_transfer_h

#include <deal.II/base/config.h>

#include <deal.II/base/smartpointer.h>

#include <deal.II/distributed/tria.h>

#include <boost/range/iterator_range.hpp>

#include <functional>


DEAL_II_NAMESPACE_OPEN

namespace parallel
{
  namespace distributed
  {
    template <int dim, int spacedim = dim, typename VectorType = Vector<double>>
    class CellDataTransfer
    {
    public:
      struct CoarseningStrategies
      {
        static typename VectorType::value_type
        check_equality(const typename parallel::distributed::
                         Triangulation<dim, spacedim>::cell_iterator &parent,
                       const VectorType &input_vector)
        {
          const typename VectorType::value_type value =
            input_vector[parent->child(0)->active_cell_index()];

          for (unsigned int child_index = 1; child_index < parent->n_children();
               ++child_index)
            Assert(
              value ==
                input_vector[parent->child(child_index)->active_cell_index()],
              ExcMessage(
                "Values on cells that will be coarsened are not equal!"));

          return value;
        }

        static typename VectorType::value_type
        sum(const typename parallel::distributed::Triangulation<dim, spacedim>::
              cell_iterator & parent,
            const VectorType &input_vector)
        {
          typename VectorType::value_type sum = 0;

          for (unsigned int child_index = 0; child_index < parent->n_children();
               ++child_index)
            sum +=
              input_vector[parent->child(child_index)->active_cell_index()];

          return sum;
        }

        static typename VectorType::value_type
        mean(const typename parallel::distributed::
               Triangulation<dim, spacedim>::cell_iterator &parent,
             const VectorType &                             input_vector)
        {
          return sum(parent, input_vector) / parent->n_children();
        }
      };

      CellDataTransfer(const parallel::distributed::Triangulation<dim, spacedim>
                         &        triangulation,
                       const bool transfer_variable_size_data = false,
                       const std::function<typename VectorType::value_type(
                         const typename parallel::distributed::
                           Triangulation<dim, spacedim>::cell_iterator &parent,
                         const VectorType &input_vector)> coarsening_strategy =
                         &CoarseningStrategies::check_equality);

      void
      prepare_for_coarsening_and_refinement(const VectorType &in);

      void
      prepare_for_coarsening_and_refinement(
        const std::vector<const VectorType *> &all_in);

      void
      prepare_for_serialization(const VectorType &in);

      void
      prepare_for_serialization(const std::vector<const VectorType *> &all_in);

      void
      unpack(VectorType &out);

      void
      unpack(std::vector<VectorType *> &all_out);

      void
      deserialize(VectorType &out);

      void
      deserialize(std::vector<VectorType *> &all_out);

    private:
      SmartPointer<const parallel::distributed::Triangulation<dim, spacedim>,
                   CellDataTransfer<dim, spacedim, VectorType>>
        triangulation;

      const bool transfer_variable_size_data;

      const std::function<typename VectorType::value_type(
        const typename parallel::distributed::Triangulation<dim, spacedim>::
          cell_iterator & parent,
        const VectorType &input_vector)>
        coarsening_strategy;

      std::vector<const VectorType *> input_vectors;

      unsigned int handle;

      void
      register_data_attach();

      std::vector<char>
      pack_callback(const typename parallel::distributed::
                      Triangulation<dim, spacedim>::cell_iterator &cell,
                    const typename parallel::distributed::
                      Triangulation<dim, spacedim>::CellStatus status);

      void
      unpack_callback(
        const typename parallel::distributed::Triangulation<dim, spacedim>::
          cell_iterator &cell,
        const typename parallel::distributed::Triangulation<dim, spacedim>::
          CellStatus status,
        const boost::iterator_range<std::vector<char>::const_iterator>
          &                        data_range,
        std::vector<VectorType *> &all_out);
    };
  } // namespace distributed
} // namespace parallel


DEAL_II_NAMESPACE_CLOSE

#endif