process_grid.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 2017 - 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_process_grid_h
#define dealii_process_grid_h

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

#include <deal.II/base/exceptions.h>
#include <deal.II/base/mpi.h>

#ifdef DEAL_II_WITH_SCALAPACK

DEAL_II_NAMESPACE_OPEN


// Forward declaration of class ScaLAPACKMatrix for ProcessGrid
#  ifndef DOXYGEN
template <typename NumberType>
class ScaLAPACKMatrix;
#  endif

namespace Utilities
{
  namespace MPI
  {
    class ProcessGrid
    {
    public:
      // Declare class ScaLAPACK as friend to provide access to private members.
      template <typename NumberType>
      friend class ::ScaLAPACKMatrix;

      ProcessGrid(MPI_Comm           mpi_communicator,
                  const unsigned int n_rows,
                  const unsigned int n_columns);

      ProcessGrid(MPI_Comm           mpi_communicator,
                  const unsigned int n_rows_matrix,
                  const unsigned int n_columns_matrix,
                  const unsigned int row_block_size,
                  const unsigned int column_block_size);

      ~ProcessGrid();

      unsigned int
      get_process_grid_rows() const;

      unsigned int
      get_process_grid_columns() const;

      int
      get_this_process_row() const;

      int
      get_this_process_column() const;

      template <typename NumberType>
      void
      send_to_inactive(NumberType *value, const int count = 1) const;

      bool
      is_process_active() const;

    private:
      ProcessGrid(MPI_Comm                                     mpi_communicator,
                  const std::pair<unsigned int, unsigned int> &grid_dimensions);

      MPI_Comm mpi_communicator;

      MPI_Comm mpi_communicator_inactive_with_root;

      int blacs_context;

      const unsigned int this_mpi_process;

      const unsigned int n_mpi_processes;

      int n_process_rows;

      int n_process_columns;

      int this_process_row;

      int this_process_column;

      bool mpi_process_is_active;
    };

    /*--------------------- Inline functions --------------------------------*/

#  ifndef DOXYGEN

    inline unsigned int
    ProcessGrid::get_process_grid_rows() const
    {
      return n_process_rows;
    }



    inline unsigned int
    ProcessGrid::get_process_grid_columns() const
    {
      return n_process_columns;
    }



    inline int
    ProcessGrid::get_this_process_row() const
    {
      return this_process_row;
    }



    inline int
    ProcessGrid::get_this_process_column() const
    {
      return this_process_column;
    }



    inline bool
    ProcessGrid::is_process_active() const
    {
      return mpi_process_is_active;
    }


#  endif // ifndef DOXYGEN

  } // end of namespace MPI

} // end of namespace Utilities


DEAL_II_NAMESPACE_CLOSE

#endif // DEAL_II_WITH_SCALAPACK

#endif