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

/*

 *  (C) 2005 by Argonne National Laboratory.

 *      See COPYRIGHT in top-level directory.

 */

/* A very simple program that performs only a send and a receive.  This

   program can be use with logging enabled (configure with

   --enable-g=dbg,log) and run with -mpich-dbg-class=routine to get

   a trace of the execution of the functions in MPICH */

#include <stdio.h>

#include "mpi.h"

#define SENDER_RANK 0

#define RECEIVER_RANK 1

int main(int argc, char *argv[])

{

    int rank, size, val;

    MPI_Status status;

    MPI_Init(&argc, &argv);

    MPI_Comm_size(MPI_COMM_WORLD, &size);

    MPI_Comm_rank(MPI_COMM_WORLD, &rank;;

    if (size < 2) {

        fprintf(stderr, "This program requires at least 2 processes\n");

        MPI_Abort(MPI_COMM_WORLD, 1);

    }

    if (rank == SENDER_RANK) {

        MPI_Send(&rank, 1, MPI_INT, RECEIVER_RANK, 0, MPI_COMM_WORLD);

    } else if (rank == RECEIVER_RANK) {

        /* This may or may not post the receive before the send arrives */

        MPI_Recv(&val, 1, MPI_INT, SENDER_RANK, 0, MPI_COMM_WORLD, &status);

    }

    /* Perform a second send/receive to allow the first pair to handle

     * any connection logic */

#if 1

    if (rank == SENDER_RANK) {

        MPI_Send(&rank, 1, MPI_INT, RECEIVER_RANK, 0, MPI_COMM_WORLD);

    } else if (rank == RECEIVER_RANK) {

        /* This may or may not post the receive before the send arrives */

        MPI_Recv(&val, 1, MPI_INT, SENDER_RANK, 0, MPI_COMM_WORLD, &status);

    }

#endif

    MPI_Finalize();

    return 0;

}