/*
 * OSU MPI Latency test v2.2
 */
/*
 * Copyright (C) 2002-2007 the Network-Based Computing Laboratory
 * (NBCL), The Ohio State University. 
 *
 * Contact: Dr. D. K. Panda (panda@cse.ohio-state.edu)
 */

/*
This program is available under BSD licensing.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

(1) Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

(2) Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

(3) Neither the name of The Ohio State University nor the names of
their contributors may be used to endorse or promote products derived
from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#ifndef _WIN32_
#include <unistd.h>
#endif

#define MESSAGE_ALIGNMENT 64
#define MAX_MSG_SIZE (1<<22)
#define MYBUFSIZE (MAX_MSG_SIZE + MESSAGE_ALIGNMENT)

char s_buf_original[MYBUFSIZE];
char r_buf_original[MYBUFSIZE];

int skip = 1000;
int loop = 10000;
int skip_large = 10;
int loop_large = 100;
int large_message_size = 8192;

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

    int myid, numprocs, i;
    int size;
    MPI_Status reqstat;
    char *s_buf, *r_buf;
    int align_size;

    double t_start = 0.0, t_end = 0.0;

    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);

    align_size = MESSAGE_ALIGNMENT;

    s_buf =
        (char *) (((unsigned long) s_buf_original + (align_size - 1)) /
                  align_size * align_size);
    r_buf =
        (char *) (((unsigned long) r_buf_original + (align_size - 1)) /
                  align_size * align_size);

    if (myid == 0) {
        fprintf(stdout, "# OSU MPI Latency Test (Version 2.2)\n");
        fprintf(stdout, "# Size\t\tLatency (us) \n");
    }

    for (size = 0; size <= MAX_MSG_SIZE;
         size = (size ? size * 2 : size + 1)) {

        // touch the data
        for (i = 0; i < size; i++) {
            s_buf[i] = 'a';
            r_buf[i] = 'b';
        }

        if (size > large_message_size) {
            loop = loop_large;
            skip = skip_large;
        }

        MPI_Barrier(MPI_COMM_WORLD);

        if (myid == 0) {
            for (i = 0; i < loop + skip; i++) {
                if (i == skip)
                    t_start = MPI_Wtime();
                MPI_Send(s_buf, size, MPI_CHAR, 1, 1, MPI_COMM_WORLD);
                MPI_Recv(r_buf, size, MPI_CHAR, 1, 1, MPI_COMM_WORLD,
                         &reqstat);
            }
            t_end = MPI_Wtime();

        } else if (myid == 1) {
            for (i = 0; i < loop + skip; i++) {
                MPI_Recv(r_buf, size, MPI_CHAR, 0, 1, MPI_COMM_WORLD,
                         &reqstat);
                MPI_Send(s_buf, size, MPI_CHAR, 0, 1, MPI_COMM_WORLD);
            }
        }

        if (myid == 0) {
            double latency;
            latency = (t_end - t_start) * 1.0e6 / (2.0 * loop);
            fprintf(stdout, "%d\t\t%0.2f\n", size, latency);
        }

    }

    MPI_Finalize();
    return 0;

}