#include <mpi.h>

#include <stdio.h>

#include "mpitest.h"

int main(int argc, char **argv)

{

    MPI_Group basegroup;

    MPI_Group g1, g2;

    MPI_Comm comm, newcomm, dupcomm;

    int errs = 0, mpi_errno, rank, size;

    int errclass, worldrank;

    MTest_Init(&argc, &argv);

    MPI_Comm_rank(MPI_COMM_WORLD, &worldrank);

    comm = MPI_COMM_WORLD;

    MPI_Comm_group(comm, &basegroup);

    MPI_Comm_rank(comm, &rank;;

    MPI_Comm_size(comm, &size);

    MPI_Errhandler_set(MPI_COMM_WORLD, MPI_ERRORS_RETURN);

    MPI_Comm_split(comm, 0, size - rank, &newcomm);

    MPI_Comm_group(newcomm, &g1;;

    MPI_Comm_dup(comm, &dupcomm);

    MPI_Comm_group(dupcomm, &g2;;

    /* checking group_union for NULL variable */

    mpi_errno = MPI_Group_union(g1, g2, NULL);

    MPI_Error_class(mpi_errno, &errclass);

    if (errclass != MPI_ERR_ARG)

        ++errs;

    MPI_Comm_free(&comm);

    MPI_Comm_free(&newcomm);

    MPI_Comm_free(&dupcomm);

    MPI_Group_free(&basegroup);

    MPI_Group_free(&g1;;

    MPI_Group_free(&g2;;

    MTest_Finalize(errs);

    return 0;

}