#include <mpi.h>

#include <stdio.h>

int

main(

    int					argc,

    char *				argv[])

{

    int					np;

    int					rank;

    MPI_Win				win;

    int					data[2];

    MPI_Init(NULL, NULL);

    MPI_Comm_size(MPI_COMM_WORLD, &np);

    MPI_Comm_rank(MPI_COMM_WORLD, &rank;;

    neighbor_rank = (my_rank + 1) % np;

    if (np < 2)

    {

	if (rank == 0)

	{

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

		   "processes\n\n");

	}

	MPI_Finalize();

	return 1;

    }

    data[0] = 0;

    data[1] = 0;

    if (rank == 0)

    {

	int				count;

	MPI_Win_create(&data, sizeof(int), sizeof(int), MPI_INFO_NULL,

		       MPI_COMM_WORLD, &win);

	do

	{

	    MPI_Win_lock(MPI_LOCK_EXCLUSIVE, 0, 0, win);

	    {

		count = data[0];

	    }

	    MPI_Win_unlock(0, win);

	}

	while (count < np - 1);

	printf("\nPassively accumulated a value of %d from %d processes\n\n",

	       data[1], data[0]);

	MPI_Win_free(&win);

    }

    else

    {

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

	data[0] = 1;

	data[1] = rank;

	MPI_Win_lock(MPI_LOCK_SHARED, 0, 0, win);

	{

	    MPI_Accumulate(data, 2, MPI_INT,

		0, 0, 2, MPI_INT, MPI_SUM, win);

	}

	MPI_Win_unlock(0, win);

	MPI_Win_free(&win);

    }

    MPI_Finalize();

    return 0;

}