/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */

/*

 *  (C) 2013 by Argonne National Laboratory.

 *      See COPYRIGHT in top-level directory.

 */

#include <stdio.h>

#include <mpi.h>

int main(int argc, char **argv)

{

    int i, rank, size, color;

    MPI_Group group;

    MPI_Comm primary[2], secondary[2], tmp;

    MPI_Request req[2];

    MPI_Init(&argc, &argv);

    MPI_Comm_rank(MPI_COMM_WORLD, &rank;;

    MPI_Comm_size(MPI_COMM_WORLD, &size);

    /* Each pair of processes creates a communicator */

    for (i = 0; i < size; i++) {

        if (rank == i)

            MPI_Comm_split(MPI_COMM_WORLD, 0, 0, &primary[0]);

        else if (rank == (i + 1) % size)

            MPI_Comm_split(MPI_COMM_WORLD, 0, 0, &secondary[0]);

        else {

            MPI_Comm_split(MPI_COMM_WORLD, 1, 0, &tmp);

            MPI_Comm_free(&tmp);

        }

        MPI_Barrier(MPI_COMM_WORLD);

    }

    /* Each pair dups the communicator such that the dups are

     * overlapping.  If this were done with MPI_Comm_dup, this should

     * deadlock. */

    MPI_Comm_idup(primary[0], &primary[1], &req[0]);

    MPI_Comm_idup(secondary[0], &secondary[1], &req[1]);

    MPI_Waitall(2, req, MPI_STATUSES_IGNORE);

    for (i = 0; i < 2; i++) {

        MPI_Comm_free(&primary[i]);

        MPI_Comm_free(&secondary[i]);

    }

    if (rank == 0)

        printf(" No Errors\n");

    MPI_Finalize();

    return 0;

}