#include <stdio.h>
#include <mpi.h>

int main(int argc, char* argv[])
{
    int msg;
    MPI_Comm parent, child;

    MPI_Init(NULL, NULL);
    MPI_Comm_get_parent(&parent);
    /* If we get COMM_NULL back, then we're the parent */
    if (MPI_COMM_NULL == parent) {
        printf("Parent about to spawn!\n");
        MPI_Comm_spawn(argv[0], MPI_ARGV_NULL, 1, MPI_INFO_NULL, 
                       0, MPI_COMM_WORLD, &child, MPI_ERRCODES_IGNORE);
        printf("Parent done with spawn\n");
        msg = 38;
        printf("Parent sending message to child\n");
        MPI_Send(&msg, 1, MPI_INT, 0, 1, child);
        MPI_Comm_disconnect(&child);
        printf("Parent disconnected\n");
    } 
    /* Otherwise, we're the child */
    else {
        printf("Hello from the child!\n");
        MPI_Recv(&msg, 1, MPI_INT, 0, 1, parent, MPI_STATUS_IGNORE);
        printf("Child received msg: %d\n", msg);
        MPI_Comm_disconnect(&parent);
        printf("Child disconnected\n");
    }

    MPI_Finalize();
    return 0;
}