Intel® MPI Library Developer Guide for Linux* OS

ID 768728
Date 12/16/2022
Public

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thread_split_omp_task.c

#include <mpi.h>
#include <omp.h>
#define n 2
MPI_Comm split_comm[n];
int main()
{
    MPI_Info info;
    int i, provided;
    char s[16];
    MPI_Init_thread(NULL, NULL, MPI_THREAD_MULTIPLE, &provided);
    MPI_Info_create(&info);
    for (i = 0; i < n; i++) {
        MPI_Comm_dup(MPI_COMM_WORLD, &split_comm[i]);
        sprintf(s, "%d", i);
        MPI_Info_set(info, "thread_id", s);
        MPI_Comm_set_info(split_comm[i], info);
    }
#pragma omp parallel num_threads(n)
    {
#pragma omp task
        {
            int j = 1;
            MPI_Allreduce(MPI_IN_PLACE, &j, 1, MPI_INT, MPI_SUM, split_comm[1]);
            printf("OMP thread %d, logical thread %d: allreduce returned %d\n",
                   omp_get_thread_num(), 1, j);
        }
#pragma omp task
        {
            int j = 0;
            MPI_Allreduce(MPI_IN_PLACE, &j, 1, MPI_INT, MPI_SUM, split_comm[0]);
            printf("OMP thread %d, logical thread %d: allreduce returned %d\n",
                   omp_get_thread_num(), 0, j);
        }
    }
    MPI_Info_free(&info);
    MPI_Finalize();
}