Sample C code:

#include <stdio.h>

#include <mpi.h>
 

#define MAX_INTS  65536
#define TEST_RUNS 100

int blip [MAX_INTS];
 

void main (int argc, char **argv)
{
    int              rank, size;                 /* of MPI_COMM_WORLD */
    MPI_Status       status;                     /* For MPI_Recv      */
    int              i, j;                       /* loop variables    */
    double           start, end;                 /* for MPI_Wtime()   */
    double           tot_sec;                    /* for MPI_Wtime()   */
    int              num_ints;

    MPI_Init( &argc, &argv );
    MPI_Comm_rank( MPI_COMM_WORLD, &rank );
    MPI_Comm_size( MPI_COMM_WORLD, &size );

    fprintf (stderr, "[%2d] Init\n", rank);

    tot_sec = 0.0;

    for (j = 0; j < 3; j++)
    {
        if ((rank % 2) == 0)
        {
            fprintf (stderr, "[%2d] receiving/sending\n", rank);

            MPI_Recv (blip, MAX_INTS, MPI_INT, rank+1, 1,
                      MPI_COMM_WORLD, &status);
            fprintf (stderr, "[%2d] received/sending\n", rank);
            MPI_Send (blip, MAX_INTS, MPI_INT, rank+1, 1,
                      MPI_COMM_WORLD);

            fprintf (stderr, "[%2d] received/sent\n", rank);
        }
        else
        {
            fprintf (stderr, "[%2d] sending/receiving\n", rank);

            MPI_Send (blip, MAX_INTS, MPI_INT, rank-1, 1,
                      MPI_COMM_WORLD);
            fprintf (stderr, "[%2d] sent/receiving\n", rank);
            MPI_Recv (blip, MAX_INTS, MPI_INT, rank-1, 1,
                      MPI_COMM_WORLD, &status);

            fprintf (stderr, "[%2d] sent/received\n", rank);
        }
    }
    for (num_ints = 8; num_ints <= MAX_INTS; num_ints *= 2) {

        for (i = 0; i < num_ints; i++)
        {
            blip [i] = (((i * size) + rank) << 16) + (num_ints / 1024);
        }
        /*
         * get starting time
         */
        start = MPI_Wtime();
        for (j = 0; j < TEST_RUNS; j++)
        {
            if ((rank % 2) == 0)                 /* I receive first */
            {
                MPI_Recv (blip, num_ints, MPI_INT, rank+1, 1,
                          MPI_COMM_WORLD, &status);
                MPI_Send (blip, num_ints, MPI_INT, rank+1, 1,
                          MPI_COMM_WORLD);
            }
            else                                 /* I send first */
            {
                MPI_Send (blip, num_ints, MPI_INT, rank-1, 1,
                          MPI_COMM_WORLD);
                MPI_Recv (blip, num_ints, MPI_INT, rank-1, 1,
                          MPI_COMM_WORLD, &status);
            }
        }
        /*
         * get final time
         */
        end = MPI_Wtime();

        if ((rank % 2) == 1) {
        tot_sec = (end - start) / 2.0;
        printf ("[%2d] %10d %6.3f MB/sec\n", rank, num_ints * sizeof(int),
                (float) ((float) num_ints / (256.0 * 1024.0)) /
                ((float) tot_sec / (float) TEST_RUNS));
        fflush (stdout);
        }
    }

    MPI_Finalize();
    fprintf(stderr, "[%2d] done\n", rank );
}