Program Listing for File mpi_comm_set.h

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// SPDX-FileCopyrightText: 2024 The OpenSn Authors <https://open-sn.github.io/opensn/>
// SPDX-License-Identifier: MIT

#pragma once

#include "framework/mesh/mesh.h"
#include "framework/runtime.h"
#include "mpicpp-lite/mpicpp-lite.h"

namespace mpi = mpicpp_lite;

namespace opensn
{

/**
 * Simple implementation a communicator set.
 * Definitions:
 * P = total amount of processors.
 * locI = process I in [0,P]
 */
class MPICommunicatorSet
{
private:
  /**
   * A list of communicators, size P, contains a communicator for only communicating with the
   * neighbors of locI.
   */
  std::vector<mpi::Communicator> communicators_;
  /**
   * A list of groupings, size P, allows mapping of the rank of locJ relative to the local
   * communicator.
   */
  std::vector<mpi::Group> location_groups_;
  /// Used to translate ranks.
  mpi::Group world_group_;

public:
  MPICommunicatorSet(std::vector<mpi::Communicator>& communicators,
                     std::vector<mpi::Group>& location_groups,
                     mpi::Group& world_group)
    : communicators_(communicators), location_groups_(location_groups), world_group_(world_group)
  {
  }

  const mpi::Communicator& LocICommunicator(int locI) const { return communicators_[locI]; }

  int MapIonJ(int locI, int locJ) const
  {
    return world_group_.translate_rank(locI, location_groups_[locJ]);
  }
};

} // namespace opensn