/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
 *  (C) 2014 by Argonne National Laboratory.
 *      See COPYRIGHT in top-level directory.
 */

#include "mpi.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

/* A 32^3 array. For other array sizes, change array_of_gsizes below. */

/* Uses nonblocking collective I/O. Writes a 3D block-distributed array to
   a file corresponding to the global array in row-major (C) order, reads it
   back, and checks that the data read is correct. */

/* Note that the file access pattern is noncontiguous. */

void handle_error(int errcode, const char *str);

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);
}

int main(int argc, char **argv)
{
    MPI_Datatype newtype;
    int i, ndims, array_of_gsizes[3], array_of_distribs[3];
    int order, nprocs, j, len;
    int array_of_dargs[3], array_of_psizes[3];
    int *readbuf, *writebuf, mynod, *tmpbuf, array_size;
    MPI_Count bufcount;
    char *filename;
    int errs = 0, toterrs;
    MPI_File fh;
    MPI_Status status;
    MPI_Request request;
    MPI_Info info = MPI_INFO_NULL;
    int errcode;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &mynod);
    MPI_Comm_size(MPI_COMM_WORLD, &nprocs);

    /* process 0 broadcasts the file name to other processes */
    if (!mynod) {
        filename = "testfile";
        len = strlen(filename);
        MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);
        MPI_Bcast(filename, len + 1, MPI_CHAR, 0, MPI_COMM_WORLD);
    }
    else {
        MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);
        filename = (char *) malloc(len + 1);
        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] = 32;
    array_of_gsizes[1] = 32;
    array_of_gsizes[2] = 32;

    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);

    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));
    for (i = 0; i < bufcount; i++)
        writebuf[i] = 1;

    array_size = array_of_gsizes[0] * array_of_gsizes[1] * array_of_gsizes[2];
    tmpbuf = (int *) calloc(array_size, sizeof(int));
    MPI_Irecv(tmpbuf, 1, newtype, mynod, 10, MPI_COMM_WORLD, &request);
    MPI_Send(writebuf, bufcount, MPI_INT, mynod, 10, MPI_COMM_WORLD);
    MPI_Wait(&request, &status);

    j = 0;
    for (i = 0; i < array_size; i++)
        if (tmpbuf[i]) {
            writebuf[j] = i;
            j++;
        }
    free(tmpbuf);

    if (j != bufcount) {
        fprintf(stderr, "Error in initializing writebuf on process %d\n", mynod);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }
    /* end of initialization */

    /* write the array to the file */
    errcode = MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE | MPI_MODE_RDWR, info, &fh);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_open");

    errcode = MPI_File_set_view(fh, 0, MPI_INT, newtype, "native", info);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_set_view");

    errcode = MPI_File_iwrite_all(fh, writebuf, bufcount, MPI_INT, &request);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_iwrite_all");
    MPI_Wait(&request, &status);

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

    if (!mynod) {
        /* wkl suggests potential for false " No Errors" if both read
         * and write use the same file view */
        /* solution: rank 0 reads entire file and checks write values */
        errcode = MPI_File_open(MPI_COMM_SELF, filename, MPI_MODE_RDONLY, info, &fh);
        if (errcode != MPI_SUCCESS)
            handle_error(errcode, "MPI_File_open");

        readbuf = (int *) malloc(array_size * sizeof(int));
        errcode = MPI_File_read(fh, readbuf, array_size, 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");

        for (i = 0; i < array_size; i++)
            if (readbuf[i] != i) {
                errs++;
                fprintf(stderr, "Error: write integer %d but read %d\n", i, readbuf[i]);
                break;
            }
        free(readbuf);
    }
    MPI_Barrier(MPI_COMM_WORLD);

    /* now read it back */
    readbuf = (int *) malloc(bufcount * sizeof(int));
    errcode = MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE | MPI_MODE_RDWR, info, &fh);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_open");

    errcode = MPI_File_set_view(fh, 0, MPI_INT, newtype, "native", info);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_set_view");
    errcode = MPI_File_iread_all(fh, readbuf, bufcount, MPI_INT, &request);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_iread_all");
    MPI_Wait(&request, &status);
    errcode = MPI_File_close(&fh);
    if (errcode != MPI_SUCCESS)
        handle_error(errcode, "MPI_File_close");

    /* check the data read */
    for (i = 0; i < bufcount; i++) {
        if (readbuf[i] != writebuf[i]) {
            errs++;
            fprintf(stderr, "Process %d, readbuf %d, writebuf %d, i %d\n",
                    mynod, readbuf[i], writebuf[i], i);
        }
    }

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

    MPI_Type_free(&newtype);
    free(readbuf);
    free(writebuf);
    if (mynod)
        free(filename);

    MPI_Finalize();
    return 0;
}