#include <mpi.h>

#include <stdio.h>

int

main(

    int					argc,

    char *				argv[])

{

    int					np;

    int					my_rank;

    MPI_Win				win;

    double				my_data;

    double				win_data;

    int					assert;

    MPI_Init(NULL, NULL);

    MPI_Comm_size(MPI_COMM_WORLD, &np);

    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    if (np < 2)

    {

	if ( my_rank == 0)

	{

	    printf("\nERROR: fence_acc_simple must be at least (2) "

		   "processes\n\n");

	}

	MPI_Finalize();

	return 1;

    }

    if (my_rank == 0)

    {

	MPI_Win_create(&my_data, sizeof(double), sizeof(double), MPI_INFO_NULL,

		       MPI_COMM_WORLD, &win);

	assert = MPI_MODE_NOPRECEDE;

	win_data = 0.0;

    }

    else

    {

	MPI_Win_create(0, 0, 0, MPI_INFO_NULL, MPI_COMM_WORLD, &win);

        assert = MPI_MODE_NOSTORE | MPI_MODE_NOPUT | MPI_MODE_NOPRECEDE;

    }

    MPI_Win_fence(assert, win);

    {

	my_data = 42.0;

	MPI_Accumulate(&my_data, 1, MPI_DOUBLE,

		       0, 0, 1, MPI_DOUBLE, MPI_SUM, win);

    }

    MPI_Win_fence(MPI_MODE_NOSTORE | MPI_MODE_NOSUCCEED, win);

    if (win_data == 42.0 * np)

    {

	printf("%d: data=%f\n", my_rank, win_data);

    }

    else

    {

	printf("%d: ERROR - data=%f NOT %f\n",

	       my_rank, win_data, np * 42.0);

    }

    MPI_Win_free(&win);

    MPI_Finalize();

    return 0;

}