#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include <strings.h>
#include <assert.h>

#include <mpi.h>
#include "bigmpi.h"
#include "verify_buffer.h"

/* Yes, it is technically unsafe to cast MPI_Count to MPI_Aint or size_t without checking,
 * given that MPI_Count might be 128b and MPI_Aint and size_t might be 64b, but BigMPI
 * does not aspire to support communication of more than 8 EiB messages at a time. */

int main(int argc, char * argv[])
{
    const MPI_Count test_int_max = BigMPI_Get_max_int();

    MPI_Init(&argc, &argv);

    int rank, size;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    if (size<1) {
        printf("Use 1 or more processes. \n");
        MPI_Finalize();
        return 1;
    }

    int l = (argc > 1) ? atoi(argv[1]) : 2;
    int m = (argc > 2) ? atoi(argv[2]) : 17777;
    MPI_Count n = l * test_int_max + m;

    char * buf_send = NULL;
    char * buf_recv = NULL;

    MPI_Alloc_mem((MPI_Aint)n * size, MPI_INFO_NULL, &buf_send);
    assert(buf_send!=NULL);
    MPI_Alloc_mem((MPI_Aint)n,        MPI_INFO_NULL, &buf_recv);
    assert(buf_recv!=NULL);

    if (rank==0) {
        for (int i = 0; i < size; ++i) {
            for (MPI_Count j = 0; j < n; ++j) {
                buf_send[i*n+j] = (unsigned char)i;
            }
        }
    }
    memset(buf_recv, -1, (size_t)n);

    /* collective communication */
    MPIX_Scatter_x(buf_send, n, MPI_CHAR,
                   buf_recv, n, MPI_CHAR,
                   0 /* root */, MPI_COMM_WORLD);

    size_t errors = verify_buffer(buf_recv, n, rank);

    MPI_Free_mem(buf_send);
    MPI_Free_mem(buf_recv);

    if (rank==0 && errors==0) {
        printf("SUCCESS\n");
    }

    MPI_Finalize();

    return 0;
}
