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

/*

 *  (C) 2001 by Argonne National Laboratory.

 *      See COPYRIGHT in top-level directory.

 */

#include "mpi.h"

#include <stdio.h>

#include "mpitest.h"

#define MAX_PROCESSES 10

int main(int argc, char **argv)

{

    int rank, size, i, j;

    int table[MAX_PROCESSES][MAX_PROCESSES];

    int errors = 0;

    int participants;

    MTest_Init(&argc, &argv);

    MPI_Comm_rank(MPI_COMM_WORLD, &rank;;

    MPI_Comm_size(MPI_COMM_WORLD, &size);

    /* A maximum of MAX_PROCESSES processes can participate */

    if (size > MAX_PROCESSES)

        participants = MAX_PROCESSES;

    else

        participants = size;

    if (MAX_PROCESSES % participants) {

        fprintf(stderr, "Number of processors must divide %d\n", MAX_PROCESSES);

        MPI_Abort(MPI_COMM_WORLD, 1);

    }

    /* while (MAX_PROCESSES % participants) participants--; */

    if ((rank < participants)) {

        /* Determine what rows are my responsibility */

        int block_size = MAX_PROCESSES / participants;

        int begin_row = rank * block_size;

        int end_row = (rank + 1) * block_size;

        int send_count = block_size * MAX_PROCESSES;

        int recv_count = send_count;

        /* Paint my rows my color */

        for (i = begin_row; i < end_row; i++)

            for (j = 0; j < MAX_PROCESSES; j++)

                table[i][j] = rank + 10;

        /* Everybody gets the gathered table */

        MPI_Allgather(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL,

                      &table[0][0], recv_count, MPI_INT, MPI_COMM_WORLD);

        /* Everybody should have the same table now,  */

        /* This test does not in any way guarantee there are no errors */

        /* Print out a table or devise a smart test to make sure it's correct */

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

            if ((table[i][0] - table[i][MAX_PROCESSES - 1] != 0))

                errors++;

        }

    }

    MTest_Finalize(errors);

    return MTestReturnValue(errors);

}