/* -*- 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;
}