communicator.c

#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
 
int
main(argc, argv)
 
int                     argc;
char                    *argv[];
 
{
        int             rank, size, data;
        MPI_Status      status;
        MPI_Comm        libcomm;
 
        MPI_Init(&argc, &argv);
        MPI_Comm_rank(MPI_COMM_WORLD, &rank);
        MPI_Comm_size(MPI_COMM_WORLD, &size);
 
        if (size != 2) {
                if ( ! rank) printf("communicator: must have two processes\n");
                MPI_Finalize();
                exit(0);
        }
 
        MPI_Comm_dup(MPI_COMM_WORLD, &libcomm);
 
        if (rank == 0) {
                data = 12345;
                MPI_Send(&data, 1, MPI_INT, 1, 5, MPI_COMM_WORLD);
                data = 6789;
                MPI_Send(&data, 1, MPI_INT, 1, 5, libcomm);
        } else {
                MPI_Recv(&data, 1, MPI_INT, 0, 5, libcomm, &status);
                printf("received libcomm data = %d\n", data);
                MPI_Recv(&data, 1, MPI_INT, 0, 5, MPI_COMM_WORLD, &status);
                printf("received data = %d\n", data);
        }
 
        MPI_Comm_free(&libcomm);
        MPI_Finalize();
        return(0);
}