/* -*- 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 <string.h>
#include <stdlib.h>

#define SIZE (65536)

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);
}

/* Each process writes to separate files and reads them back.
   The file name is taken as a command-line argument, and the process rank
   is appended to it. */

int main(int argc, char **argv)
{
    int *buf, i, rank, nints, len;
    char *filename, *tmp;
    int errs = 0, toterrs, errcode;
    MPI_File fh;
    MPI_Status status;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

/* process 0 takes the file name as a command-line argument and
   broadcasts it to other processes */
    if (!rank) {
        i = 1;
        while ((i < argc) && strcmp("-fname", *argv)) {
            i++;
            argv++;
        }
        if (i >= argc) {
            fprintf(stderr, "\n*#  Usage: simple -fname filename\n\n");
            MPI_Abort(MPI_COMM_WORLD, 1);
        }
        argv++;
        len = strlen(*argv);
        filename = (char *) malloc(len + 10);
        strcpy(filename, *argv);
        MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);
        MPI_Bcast(filename, len + 10, MPI_CHAR, 0, MPI_COMM_WORLD);
    } else {
        MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);
        filename = (char *) malloc(len + 10);
        MPI_Bcast(filename, len + 10, MPI_CHAR, 0, MPI_COMM_WORLD);
    }


    buf = (int *) malloc(SIZE);
    nints = SIZE / sizeof(int);
    for (i = 0; i < nints; i++)
        buf[i] = rank * 100000 + i;

    /* each process opens a separate file called filename.'myrank' */
    tmp = (char *) malloc(len + 10);
    strcpy(tmp, filename);
    sprintf(filename, "%s.%d", tmp, rank);

    errcode = MPI_File_open(MPI_COMM_SELF, filename,
                            MPI_MODE_CREATE | MPI_MODE_RDWR, MPI_INFO_NULL, &fh);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_open(1)");

    errcode = MPI_File_write(fh, buf, nints, MPI_INT, &status);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_write");

    errcode = MPI_File_close(&fh);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_clode (1)");

    /* reopen the file and read the data back */

    for (i = 0; i < nints; i++)
        buf[i] = 0;
    errcode = MPI_File_open(MPI_COMM_SELF, filename,
                            MPI_MODE_CREATE | MPI_MODE_RDWR, MPI_INFO_NULL, &fh);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_open(2)");

    errcode = MPI_File_read(fh, buf, nints, MPI_INT, &status);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_read");

    errcode = MPI_File_close(&fh);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_close(2)");

    /* check if the data read is correct */
    for (i = 0; i < nints; i++) {
        if (buf[i] != (rank * 100000 + i)) {
            errs++;
            fprintf(stderr, "Process %d: error, read %d, should be %d\n",
                    rank, buf[i], rank * 100000 + i);
        }
    }

    MPI_Allreduce(&errs, &toterrs, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
    if (rank == 0) {
        if (toterrs > 0) {
            fprintf(stderr, "Found %d errors\n", toterrs);
        } else {
            fprintf(stdout, " No Errors\n");
        }
    }

    free(buf);
    free(filename);
    free(tmp);

    MPI_Finalize();
    return 0;
}