partition.cpp

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#include "../partition.h"
 
#include <mpi.h>
 
#include <numeric>
 
#include "BaseLib/Logging.h"
#include "MeshLib/IO/XDMF/fileIO.h"
#include "getCommunicator.h"
 
namespace MeshLib::IO
{
bool isFileManager()
{
    int mpi_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &mpi_rank);
    return mpi_rank == 0;
}
 
PartitionInfo getPartitionInfo(std::size_t const size,
                               unsigned int const n_files)
{
    MPI_Comm const mpi_comm = getCommunicator(n_files).mpi_communicator;
    int mpi_size;
    int mpi_rank;
    MPI_Comm_size(mpi_comm, &mpi_size);
    MPI_Comm_rank(mpi_comm, &mpi_rank);
 
    std::vector<std::size_t> partition_sizes;
    partition_sizes.resize(mpi_size);
 
    MPI_Allgather(&size,
                  1,
                  MPI_UNSIGNED_LONG,
                  partition_sizes.data(),
                  1,
                  MPI_UNSIGNED_LONG,
                  mpi_comm);
 
    // the first partition's offset is zero, offsets for subsequent
    // partitions are the accumulated sum of all preceding size (excluding
    // own size)
    std::vector<std::size_t> partition_offsets(1, 0);
    std::partial_sum(partition_sizes.begin(),
                     partition_sizes.end(),
                     back_inserter(partition_offsets));
 
    // 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