mpi/partition.cpp

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#include "../partition.h"
 
#include <mpi.h>
 
#include <numeric>
 
#include "BaseLib/Algorithm.h"
#include "BaseLib/Logging.h"
#include "BaseLib/MPI.h"
#include "MeshLib/IO/XDMF/fileIO.h"
#include "getCommunicator.h"
 
namespace MeshLib::IO
{
bool isFileManager()
{
    int mpi_rank;
    MPI_Comm_rank(BaseLib::MPI::OGS_COMM_WORLD, &mpi_rank);
    return mpi_rank == 0;
}
 
PartitionInfo getPartitionInfo(std::size_t const size,
                               unsigned int const n_files)
{
    BaseLib::MPI::Mpi const mpi{getCommunicator(n_files).mpi_communicator};
 
    std::vector<std::size_t> const partition_sizes =
        BaseLib::MPI::allgather(size, mpi);
 
    // the first partition's offset is zero, offsets for subsequent
    // partitions are the accumulated sum of all preceding size.
    std::vector<std::size_t> const partition_offsets =
        BaseLib::sizesToOffsets(partition_sizes);
 
    // chunked
    std::size_t longest_partition =
        *max_element(partition_sizes.begin(), partition_sizes.end());
 
    // local_offset, local_length, longest_local_length, global_length
    return {partition_offsets[mpi.rank], size, longest_partition,
            partition_offsets.back()};
}
}  // namespace MeshLib::IO