/* -*- Mode: C; c-basic-offset:4 ; -*- */
/*
 *  (C) 2001 by Argonne National Laboratory.
 *      See COPYRIGHT in top-level directory.
 */
#include "mpi.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

/* writes a file of size 4 Gbytes and reads it back.
   should be run on one process only*/
/* The file name is taken as a command-line argument. */
/* Can be used only on file systems on which ROMIO supports large files,
   i.e., any file system created after 1999 */

#define SIZE 1048576*4  /* no. of long longs in each write/read */
#define NTIMES 128      /* no. of writes/reads */

static void handle_error(int errcode, const char *str)
{
    char msg[MPI_MAX_ERROR_STRING];
    int resultlen;
    MPI_Error_string(errcode, msg, &resultlen);
    fprintf(stderr, "%s: %s\n", str, msg);
    MPI_Abort(MPI_COMM_WORLD, 1);
}

#define MPI_CHECK(fn) { int errcode; errcode = (fn); if (errcode != MPI_SUCCESS) handle_error(errcode, #fn); }


int main(int argc, char **argv)
{
    MPI_File fh;
    MPI_Status status;
    MPI_Offset size;
    long long *buf, i;
    char *filename;
    int j, mynod, nprocs, len, flag, err;

    MPI_Init(&argc, &argv);

    MPI_Comm_rank(MPI_COMM_WORLD, &mynod);
    MPI_Comm_size(MPI_COMM_WORLD, &nprocs);

    if (nprocs != 1) {
        fprintf(stderr, "Run this program on one process only\n");
        MPI_Abort(MPI_COMM_WORLD, 1);
    }

    i = 1;
    while ((i < argc) && strcmp("-fname", *argv)) {
        i++;
        argv++;
    }
    if (i >= argc) {
        fprintf(stderr, "\n*#  Usage: large -fname filename\n\n");
        MPI_Abort(MPI_COMM_WORLD, 1);
    }
    argv++;
    len = strlen(*argv);
    filename = (char *) malloc(len + 1);
    strcpy(filename, *argv);
    fprintf(stderr,
            "This program creates an 4 Gbyte file. Don't run it if you don't have that much disk space!\n");

    buf = (long long *) malloc(SIZE * sizeof(long long));
    if (!buf) {
        fprintf(stderr, "not enough memory to allocate buffer\n");
        MPI_Abort(MPI_COMM_WORLD, 1);
    }

    MPI_CHECK(MPI_File_open(MPI_COMM_SELF, filename,
                            MPI_MODE_CREATE | MPI_MODE_RDWR, MPI_INFO_NULL, &fh));

    for (i = 0; i < NTIMES; i++) {
        for (j = 0; j < SIZE; j++)
            buf[j] = i * SIZE + j;

        err = MPI_File_write(fh, buf, SIZE, MPI_DOUBLE, &status);
        /* MPI_DOUBLE because not all MPI implementations define
         * MPI_LONG_LONG_INT, even though the C compiler supports long long. */
        if (err != MPI_SUCCESS) {
            fprintf(stderr, "MPI_File_write returned error\n");
            MPI_Abort(MPI_COMM_WORLD, 1);
        }
    }

    MPI_CHECK(MPI_File_get_size(fh, &size));
    fprintf(stderr, "file size = %@LL@ bytes\n", size);

    MPI_CHECK(MPI_File_seek(fh, 0, MPI_SEEK_SET));

    for (j = 0; j < SIZE; j++)
        buf[j] = -1;

    flag = 0;
    for (i = 0; i < NTIMES; i++) {
        err = MPI_File_read(fh, buf, SIZE, MPI_DOUBLE, &status);
        /* MPI_DOUBLE because not all MPI implementations define
         * MPI_LONG_LONG_INT, even though the C compiler supports long long. */
        if (err != MPI_SUCCESS) {
            fprintf(stderr, "MPI_File_write returned error\n");
            MPI_Abort(MPI_COMM_WORLD, 1);
        }
        for (j = 0; j < SIZE; j++)
            if (buf[j] != i * SIZE + j) {
                fprintf(stderr, "error: buf %d is %@LL@, should be %@LL@ \n", j, buf[j],
                        i * SIZE + j);
                flag = 1;
            }
    }

    if (!flag)
        fprintf(stderr, "Data read back is correct\n");
    MPI_CHECK(MPI_File_close(&fh));

    free(buf);
    free(filename);
    MPI_Finalize();
    return 0;
}