/* -*- 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>

/* Writes a 4-Gbyte distributed array, reads it back, and then deletes the

   file. Uses collective I/O. */

/* The file name is taken as a command-line argument. */

/* Run it only on a machine with sufficient memory and a file system

   on which ROMIO supports large files, i.e., any file system created after

   1999 */

/* This program will work only if the MPI implementation defines MPI_Aint

   as a 64-bit integer. */

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_Datatype newtype;

    int i, ndims, array_of_gsizes[3], array_of_distribs[3];

    int order, nprocs, len, flag, err;

    int array_of_dargs[3], array_of_psizes[3];

    int *readbuf, *writebuf, mynod;

    MPI_Count bufcount;

    char filename[1024];

    MPI_File fh;

    MPI_Status status;

    MPI_Aint size_with_aint;

    MPI_Offset size_with_offset;

    MPI_Init(&argc, &argv);

    MPI_Comm_rank(MPI_COMM_WORLD, &mynod);

    MPI_Comm_size(MPI_COMM_WORLD, &nprocs);

/* process 0 takes the file name as a command-line argument and

   broadcasts it to other processes */

    if (!mynod) {

        i = 1;

        while ((i < argc) && strcmp("-fname", *argv)) {

            i++;

            argv++;

        }

        if (i >= argc) {

            fprintf(stderr, "\n*#  Usage: large_array -fname filename\n\n");

            MPI_Abort(MPI_COMM_WORLD, 1);

        }

        argv++;

        len = strlen(*argv);

        strcpy(filename, *argv);

        MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);

        MPI_Bcast(filename, len + 1, MPI_CHAR, 0, MPI_COMM_WORLD);

        fprintf(stderr,

                "This program creates a 4 Gbyte file. Don't run it if you don't have that much disk space!\n");

    } else {

        MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);

        MPI_Bcast(filename, len + 1, MPI_CHAR, 0, MPI_COMM_WORLD);

    }

/* create the distributed array filetype */

    ndims = 3;

    order = MPI_ORDER_C;

    array_of_gsizes[0] = 1024;

    array_of_gsizes[1] = 1024;

    array_of_gsizes[2] = 4 * 1024 / sizeof(int);

    array_of_distribs[0] = MPI_DISTRIBUTE_BLOCK;

    array_of_distribs[1] = MPI_DISTRIBUTE_BLOCK;

    array_of_distribs[2] = MPI_DISTRIBUTE_BLOCK;

    array_of_dargs[0] = MPI_DISTRIBUTE_DFLT_DARG;

    array_of_dargs[1] = MPI_DISTRIBUTE_DFLT_DARG;

    array_of_dargs[2] = MPI_DISTRIBUTE_DFLT_DARG;

    for (i = 0; i < ndims; i++)

        array_of_psizes[i] = 0;

    MPI_Dims_create(nprocs, ndims, array_of_psizes);

/* check if MPI_Aint is large enough for size of global array.

   if not, complain. */

    size_with_aint = sizeof(int);

    for (i = 0; i < ndims; i++)

        size_with_aint *= array_of_gsizes[i];

    size_with_offset = sizeof(int);

    for (i = 0; i < ndims; i++)

        size_with_offset *= array_of_gsizes[i];

    if (size_with_aint != size_with_offset) {

        fprintf(stderr,

                "Can't use an array of this size unless the MPI implementation defines a 64-bit MPI_Aint\n");

        MPI_Abort(MPI_COMM_WORLD, 1);

    }

    MPI_Type_create_darray(nprocs, mynod, ndims, array_of_gsizes,

                           array_of_distribs, array_of_dargs,

                           array_of_psizes, order, MPI_INT, &newtype);

    MPI_Type_commit(&newtype);

/* initialize writebuf */

    MPI_Type_size_x(newtype, &bufcount);

    bufcount = bufcount / sizeof(int);

    writebuf = (int *) malloc(bufcount * sizeof(int));

    if (!writebuf)

        fprintf(stderr, "Process %d, not enough memory for writebuf\n", mynod);

    for (i = 0; i < bufcount; i++)

        writebuf[i] = mynod * 1024 + i;

    /* write the array to the file */

    MPI_CHECK(MPI_File_open(MPI_COMM_WORLD, filename,

                            MPI_MODE_CREATE | MPI_MODE_RDWR, MPI_INFO_NULL, &fh));

    MPI_CHECK(MPI_File_set_view(fh, 0, MPI_INT, newtype, "native", MPI_INFO_NULL));

    MPI_CHECK(MPI_File_write_all(fh, writebuf, bufcount, MPI_INT, &status));

    MPI_CHECK(MPI_File_close(&fh));

    free(writebuf);

    /* now read it back */

    readbuf = (int *) calloc(bufcount, sizeof(int));

    if (!readbuf)

        fprintf(stderr, "Process %d, not enough memory for readbuf\n", mynod);

    MPI_CHECK(MPI_File_open(MPI_COMM_WORLD, filename,

                            MPI_MODE_CREATE | MPI_MODE_RDWR, MPI_INFO_NULL, &fh));

    MPI_CHECK(MPI_File_set_view(fh, 0, MPI_INT, newtype, "native", MPI_INFO_NULL));

    MPI_CHECK(MPI_File_read_all(fh, readbuf, bufcount, MPI_INT, &status));

    MPI_CHECK(MPI_File_close(&fh));

    /* check the data read */

    flag = 0;

    for (i = 0; i < bufcount; i++)

        if (readbuf[i] != mynod * 1024 + i) {

            fprintf(stderr, "Process %d, readbuf=%d, writebuf=%d\n", mynod, readbuf[i],

                    mynod * 1024 + i);

            flag = 1;

        }

    if (!flag)

        fprintf(stderr, "Process %d: data read back is correct\n", mynod);

    MPI_Type_free(&newtype);

    free(readbuf);

    MPI_Barrier(MPI_COMM_WORLD);

    if (!mynod) {

        err = MPI_File_delete(filename, MPI_INFO_NULL);

        if (err == MPI_SUCCESS)

            fprintf(stderr, "file deleted\n");

    }

    MPI_Finalize();

    return 0;

}