/* -*- 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);
    MPI_Finalize();
    return MTestReturnValue(errors);
}
