/* -*- 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;

}