/* -*- 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;
    int displs[MAX_PROCESSES];
    int recv_counts[MAX_PROCESSES];

    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;
    /* while (MAX_PROCESSES % participants) participants--; */
    if (MAX_PROCESSES % participants) {
        fprintf(stderr, "Number of processors must divide %d\n", MAX_PROCESSES);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }
    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;

        /* Fill in the displacements and recv_counts */
        for (i = 0; i < participants; i++) {
            displs[i] = i * block_size * MAX_PROCESSES;
            recv_counts[i] = 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;

        /* Gather everybody's result together - sort of like an */
        /* inefficient allgather */
        for (i = 0; i < participants; i++) {
            void *sendbuf = (i == rank ? MPI_IN_PLACE : &table[begin_row][0]);
            MPI_Gatherv(sendbuf, send_count, MPI_INT,
                        &table[0][0], recv_counts, displs, MPI_INT, i, MPI_COMM_WORLD);
        }


        /* Everybody should have the same table now.
         *
         * The entries are:
         * Table[i][j] = (i/block_size) + 10;
         */
        for (i = 0; i < MAX_PROCESSES; i++)
            if ((table[i][0] - table[i][MAX_PROCESSES - 1] != 0))
                errors++;
        for (i = 0; i < MAX_PROCESSES; i++) {
            for (j = 0; j < MAX_PROCESSES; j++) {
                if (table[i][j] != (i / block_size) + 10)
                    errors++;
            }
        }
        if (errors) {
            /* Print out table if there are any errors */
            for (i = 0; i < MAX_PROCESSES; i++) {
                printf("\n");
                for (j = 0; j < MAX_PROCESSES; j++)
                    printf("  %d", table[i][j]);
            }
            printf("\n");
        }
    }

    MTest_Finalize(errors);
    return MTestReturnValue(errors);
}