mpi_utils.cpp

 
// Description: Utility functions for MPI distribution.
 
#include "mpi_utils.h"
#include "Utilities.h"
 
#include <iomanip>
#include <stdlib.h>
#include <sys/stat.h>
 
namespace CAROM {
 
int
split_dimension(const int dim, const MPI_Comm &comm)
{
    int mpi_init;
    MPI_Initialized(&mpi_init);
    CAROM_VERIFY(mpi_init != 0);
 
    int d_num_procs, d_rank;
    MPI_Comm_rank(comm, &d_rank);
    MPI_Comm_size(comm, &d_num_procs);
 
    int local_dim = dim / d_num_procs;
    if (dim % d_num_procs > d_rank)
        local_dim++;
 
    return local_dim;
}
 
int
get_global_offsets(const int local_dim, std::vector<int> &offsets,
                   const MPI_Comm &comm)
{
    int mpi_init;
    MPI_Initialized(&mpi_init);
    CAROM_VERIFY(mpi_init != 0);
 
    int d_num_procs, d_rank;
    MPI_Comm_rank(comm, &d_rank);
    MPI_Comm_size(comm, &d_num_procs);
 
    offsets.resize(d_num_procs + 1);
    offsets[d_rank] = local_dim;
    CAROM_VERIFY(MPI_Allgather(MPI_IN_PLACE, 1, MPI_INT,
                               &offsets[0], 1, MPI_INT,
                               comm) == MPI_SUCCESS);
 
    int dim = 0;
    for (int i = 0; i < d_num_procs; i++)
        dim += offsets[i];
    offsets[d_num_procs] = dim;
 
    for (int i = d_num_procs - 1; i >= 0; i--)
        offsets[i] = offsets[i + 1] - offsets[i];
 
    CAROM_VERIFY(offsets[0] == 0);
 
    return dim;
}
 
bool
is_same(int x, const MPI_Comm &comm) {
    int p[2] = {-x, x};
    MPI_Allreduce(MPI_IN_PLACE, p, 2, MPI_INT, MPI_MIN, comm);
    return (p[0] == -p[1]);
}
 
}