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

/*

 *  (C) 2010 by Argonne National Laboratory.

 *      See COPYRIGHT in top-level directory.

 */

#include "mpi.h"

#include <stdio.h>

#include <stdlib.h>

#include "mpitest.h"

#include <math.h>       /* for fabs(3) */

/* Measure and compare the relative performance of MPI_Group_translate_ranks

 * with small and large group2 sizes but a constant number of ranks.  This

 * serves as a performance sanity check for the Scalasca use case where we

 * translate to MPI_COMM_WORLD ranks.  The performance should only depend on the

 * number of ranks passed, not the size of either group (especially group2).

 *

 * This test is probably only meaningful for large-ish process counts, so we may

 * not be able to run this test by default in the nightlies. */

/* number of iterations used for timing */

#define NUM_LOOPS (1000000)

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

{

    int errs = 0;

    int *ranks;

    int *ranksout;

    MPI_Group gworld, grev, gself;

    MPI_Comm comm;

    MPI_Comm commrev;

    int rank, size, i;

    double start, end, time1, time2;

    MTest_Init(&argc, &argv);

    comm = MPI_COMM_WORLD;

    MPI_Comm_size(comm, &size);

    MPI_Comm_rank(comm, &rank;;

    ranks = malloc(size * sizeof(int));

    ranksout = malloc(size * sizeof(int));

    if (!ranks || !ranksout) {

        fprintf(stderr, "out of memory\n");

        MPI_Abort(MPI_COMM_WORLD, 1);

    }

    /* generate a comm with the rank order reversed */

    MPI_Comm_split(comm, 0, (size - rank - 1), &commrev);

    MPI_Comm_group(commrev, &grev);

    MPI_Comm_group(MPI_COMM_SELF, &gself);

    MPI_Comm_group(comm, &gworld);

    /* sanity check correctness first */

    for (i = 0; i < size; i++) {

        ranks[i] = i;

        ranksout[i] = -1;

    }

    MPI_Group_translate_ranks(grev, size, ranks, gworld, ranksout);

    for (i = 0; i < size; i++) {

        if (ranksout[i] != (size - i - 1)) {

            if (rank == 0)

                printf("%d: (gworld) expected ranksout[%d]=%d, got %d\n", rank, i,

                       (size - rank - 1), ranksout[i]);

            ++errs;

        }

    }

    MPI_Group_translate_ranks(grev, size, ranks, gself, ranksout);

    for (i = 0; i < size; i++) {

        int expected = (i == (size - rank - 1) ? 0 : MPI_UNDEFINED);

        if (ranksout[i] != expected) {

            if (rank == 0)

                printf("%d: (gself) expected ranksout[%d]=%d, got %d\n", rank, i, expected,

                       ranksout[i]);

            ++errs;

        }

    }

    /* now compare relative performance */

    /* we needs lots of procs to get a group large enough to have meaningful

     * numbers.  On most testing machines this means that we're oversubscribing

     * cores in a big way, which might perturb the timing results.  So we make

     * sure everyone started up and then everyone but rank 0 goes to sleep to

     * let rank 0 do all the timings. */

    MPI_Barrier(comm);

    if (rank != 0) {

        MTestSleep(10);

    }

    else {      /* rank==0 */

        MTestSleep(1);  /* try to avoid timing while everyone else is making syscalls */

        MPI_Group_translate_ranks(grev, size, ranks, gworld, ranksout); /*throwaway iter */

        start = MPI_Wtime();

        for (i = 0; i < NUM_LOOPS; ++i) {

            MPI_Group_translate_ranks(grev, size, ranks, gworld, ranksout);

        }

        end = MPI_Wtime();

        time1 = end - start;

        MPI_Group_translate_ranks(grev, size, ranks, gself, ranksout);  /*throwaway iter */

        start = MPI_Wtime();

        for (i = 0; i < NUM_LOOPS; ++i) {

            MPI_Group_translate_ranks(grev, size, ranks, gself, ranksout);

        }

        end = MPI_Wtime();

        time2 = end - start;

        /* complain if the "gworld" time exceeds 2x the "gself" time */

        if (fabs(time1 - time2) > (2.00 * time2)) {

            printf("too much difference in MPI_Group_translate_ranks performance:\n");

            printf("time1=%f time2=%f\n", time1, time2);

            printf("(fabs(time1-time2)/time2)=%f\n", (fabs(time1 - time2) / time2));

            if (time1 < time2) {

                printf("also, (time1

            }

            ++errs;

        }

    }

    free(ranks);

    free(ranksout);

    MPI_Group_free(&grev);

    MPI_Group_free(&gself);

    MPI_Group_free(&gworld);

    MPI_Comm_free(&commrev);

    MTest_Finalize(errs);

    MPI_Finalize();

    return 0;

}