getCommunicator.cpp

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#include "getCommunicator.h"
 
#include <hdf5.h>
#include <math.h>
#include <mpi.h>
 
#include <cassert>
 
#include "BaseLib/Logging.h"
#include "BaseLib/MPI.h"
#include "MeshLib/IO/XDMF/fileIO.h"
 
namespace MeshLib::IO
{
int getGroupIndex(int const input_index, int const input_size,
                  int const new_group_size)
{
    // A grouping algorithm that determines the number of groups and return the
    // group idx of the specified input_index
    assert(input_size >= new_group_size);
    int const minimum_output_group_size =
        std::lround(input_size / new_group_size);
    int const maximum_output_group_size = (input_size % new_group_size)
                                              ? minimum_output_group_size + 1
                                              : minimum_output_group_size;
    return std::lround(input_index / maximum_output_group_size);
};
 
FileCommunicator getCommunicator(unsigned int const n_files)
{
    int num_procs;
    MPI_Comm_size(BaseLib::MPI::OGS_COMM_WORLD, &num_procs);
    int rank_id;
    MPI_Comm_rank(BaseLib::MPI::OGS_COMM_WORLD, &rank_id);
    int const file_group_id = getGroupIndex(rank_id, num_procs, n_files);
    MPI_Comm new_communicator;
    MPI_Comm_split(BaseLib::MPI::OGS_COMM_WORLD, file_group_id, rank_id,
                   &new_communicator);
    return FileCommunicator{std::move(new_communicator),
                            std::move(file_group_id), ""};
}
}  // namespace MeshLib::IO