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

/*

 *  (C) 2009 by Argonne National Laboratory.

 *      See COPYRIGHT in top-level directory.

 */

#include "mpi.h"

#include <stdio.h>

#include <stdlib.h>

#include "mpitest.h"

#define MAX_LOG_WSIZE 31

#define MAX_LOOP 20

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

{

    MPI_Group gworld, g;

    MPI_Comm comm, newcomm[MAX_LOOP];

    int wsize, wrank, range[1][3], errs = 0;

    double t[MAX_LOG_WSIZE], tf;

    int maxi, i, k, ts, gsize[MAX_LOG_WSIZE];

    MTest_Init(&argc, &argv);

    MPI_Comm_size(MPI_COMM_WORLD, &wsize);

    MPI_Comm_rank(MPI_COMM_WORLD, &wrank);

    if (wrank == 0)

        MTestPrintfMsg(1, "size\ttime\n");

    MPI_Comm_group(MPI_COMM_WORLD, &gworld);

    ts = 1;

    comm = MPI_COMM_WORLD;

    for (i = 0; ts <= wsize; i++, ts = ts + ts) {

        /* Create some groups with at most ts members */

        range[0][0] = ts - 1;

        range[0][1] = 0;

        range[0][2] = -1;

        MPI_Group_range_incl(gworld, 1, range, &g);

        MPI_Barrier(MPI_COMM_WORLD);

        tf = MPI_Wtime();

        for (k = 0; k < MAX_LOOP; k++)

            MPI_Comm_create(comm, g, &newcomm[k]);

        tf = MPI_Wtime() - tf;

        MPI_Allreduce(&tf, &t[i], 1, MPI_DOUBLE, MPI_MAX, MPI_COMM_WORLD);

        t[i] = t[i] / MAX_LOOP;

        gsize[i] = ts;

        if (wrank == 0)

            MTestPrintfMsg(1, "%d\t%e\n", ts, t[i]);

        MPI_Group_free(&g);

        if (newcomm[0] != MPI_COMM_NULL)

            for (k = 0; k < MAX_LOOP; k++)

                MPI_Comm_free(&newcomm[k]);

    }

    MPI_Group_free(&gworld);

    maxi = i - 1;

    /* The cost should be linear or at worst ts*log(ts).

     * We can check this in a number of ways.

     */

    if (wrank == 0) {

        for (i = 4; i <= maxi; i++) {

            double rdiff;

            if (t[i] > 0) {

                rdiff = (t[i] - t[i - 1]) / t[i];

                if (rdiff >= 4) {

                    errs++;

                    fprintf(stderr,

                            "Relative difference between group of size %d and %d is %e exceeds 4\n",

                            gsize[i - 1], gsize[i], rdiff);

                }

            }

        }

    }

    MTest_Finalize(errs);

    MPI_Finalize();

    return 0;

}