packperf_nc.c

#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <string.h>
#include "mpi.h"

double
getavg(double *a, int n) {
    int i;
    double sum = 0;
    for (i=0; i<n; ++i) {
        sum += a[i];
    }
    return sum/n;
}

int
main(int argc, char* argv[])
{
    MPI_Datatype dtbig, dtsmall;
    MPI_Init(&argc, &argv);
    int i;

/*
 *  Make dtbig as            [double, --------, double, --------, etc..]
 *  Make dtsmall as just one [double, --------]
 */
    int nelements = 200000; /* number of doubles */
    MPI_Type_vector(nelements, 1, 2, MPI_DOUBLE ,&dtbig);
    MPI_Type_commit(&dtbig);
    MPI_Type_create_resized(MPI_DOUBLE, 0, 2*sizeof(double), &dtsmall);
    MPI_Type_commit(&dtsmall);

    double *packedbuf = malloc(nelements * sizeof(double));
    double *unpackedbuf = malloc(nelements * 2 * sizeof(double));
    int position;

    /* set unpackedbuf[] to [(double)1, (double)-1, (double)2, (double)-1, ...] */
    for (i=0; i<nelements; ++i) {
        unpackedbuf[2*i+0] = i+1;
        unpackedbuf[2*i+1] = -1;
    }
#define CHECK_UBUF() \
    do { \
        for (i=0; i<nelements; ++i) { \
            double got = unpackedbuf[2*i+0]; \
            double exp =  i+1; \
            if (got != exp) { \
                printf("unpacked[%d] = %f, exp %f\n", 2*i, got, exp); \
                MPI_Abort(MPI_COMM_WORLD, MPI_ERR_OTHER); \
            } \
        } \
    } while (0)

    double t, tpack_big[5], tunpack_big[5], tpack_small[5], tunpack_small[5];

    for (i=0; i<5; ++i) {
        t = MPI_Wtime();
        position = 0;
        MPI_Pack(unpackedbuf, 1, dtbig,
             packedbuf, nelements*sizeof(double), &position, MPI_COMM_WORLD);
        tpack_big[i] = MPI_Wtime() - t;
    }

    for (i=0; i<5; ++i) {
        t = MPI_Wtime();
        position = 0;
        MPI_Unpack(packedbuf, nelements*sizeof(double), &position,
               unpackedbuf, 1, dtbig, MPI_COMM_WORLD);
        tunpack_big[i] = MPI_Wtime() - t;
    }
    CHECK_UBUF();

    for (i=0; i<5; ++i) {
        t = MPI_Wtime();
        position = 0;
        MPI_Pack(unpackedbuf, nelements, dtsmall,
             packedbuf, nelements*sizeof(double), &position, MPI_COMM_WORLD);
        tpack_small[i] = MPI_Wtime() - t;
    }

    for (i=0; i<5; ++i) {
        t = MPI_Wtime();
        position = 0;
        MPI_Unpack(packedbuf, nelements*sizeof(double), &position,
               unpackedbuf, nelements, dtsmall, MPI_COMM_WORLD);
        tunpack_small[i] = MPI_Wtime() - t;
    }
    CHECK_UBUF();

    printf("times:\n");
    printf("pack dtbig    : %6.0f %6.0f %6.0f %6.0f %6.0f  (avg %.0f)  usec\n",
        tpack_big[0] * 1000000,
        tpack_big[1] * 1000000,
        tpack_big[2] * 1000000,
        tpack_big[3] * 1000000,
        tpack_big[4] * 1000000,
        getavg(tpack_big, 5) * 1000000);
    printf("unpack dtbig  : %6.0f %6.0f %6.0f %6.0f %6.0f  (avg %.0f)  usec\n",
        tunpack_big[0] * 1000000,
        tunpack_big[1] * 1000000,
        tunpack_big[2] * 1000000,
        tunpack_big[3] * 1000000,
        tunpack_big[4] * 1000000,
        getavg(tunpack_big, 5) * 1000000);
    printf("pack dtsmall  : %6.0f %6.0f %6.0f %6.0f %6.0f  (avg %.0f)  usec\n",
        tpack_small[0] * 1000000,
        tpack_small[1] * 1000000,
        tpack_small[2] * 1000000,
        tpack_small[3] * 1000000,
        tpack_small[4] * 1000000,
        getavg(tpack_small, 5) * 1000000);
    printf("unpack dtsmall: %6.0f %6.0f %6.0f %6.0f %6.0f  (avg %.0f)  usec\n",
        tunpack_small[0] * 1000000,
        tunpack_small[1] * 1000000,
        tunpack_small[2] * 1000000,
        tunpack_small[3] * 1000000,
        tunpack_small[4] * 1000000,
        getavg(tunpack_small, 5) * 1000000);

    MPI_Type_free(&dtbig);
    MPI_Type_free(&dtsmall);
    MPI_Finalize();
    return 0;
}