/* -*- 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>

/* A simple performance test. The file name is taken as a
   command-line argument. */

#define SIZE (1048576*4)        /* read/write size per node in bytes */

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)
{
    int *buf, i, j, mynod, nprocs, ntimes = 5, len, err, flag;
    double stim, read_tim, write_tim, new_read_tim, new_write_tim;
    double min_read_tim = 10000000.0, min_write_tim = 10000000.0, read_bw, write_bw;
    MPI_File fh;
    MPI_Status status;
    char *filename;

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

/* 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: perf -fname filename\n\n");
            MPI_Abort(MPI_COMM_WORLD, 1);
        }
        argv++;
        len = strlen(*argv);
        filename = (char *) malloc(len + 1);
        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, "Access size per process = %d bytes, ntimes = %d\n", SIZE, ntimes);
    } 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);
    }


    buf = (int *) malloc(SIZE);

    for (j = 0; j < ntimes; j++) {
        MPI_CHECK(MPI_File_open(MPI_COMM_WORLD, filename,
                                MPI_MODE_CREATE | MPI_MODE_RDWR, MPI_INFO_NULL, &fh));
        MPI_CHECK(MPI_File_seek(fh, mynod * SIZE, MPI_SEEK_SET));

        MPI_Barrier(MPI_COMM_WORLD);
        stim = MPI_Wtime();
        MPI_CHECK(MPI_File_write(fh, buf, SIZE, MPI_BYTE, &status));
        write_tim = MPI_Wtime() - stim;

        MPI_CHECK(MPI_File_close(&fh));

        MPI_Barrier(MPI_COMM_WORLD);

        MPI_CHECK(MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE |
                                MPI_MODE_RDWR, MPI_INFO_NULL, &fh));
        MPI_CHECK(MPI_File_seek(fh, mynod * SIZE, MPI_SEEK_SET));

        MPI_Barrier(MPI_COMM_WORLD);
        stim = MPI_Wtime();
        MPI_CHECK(MPI_File_read(fh, buf, SIZE, MPI_BYTE, &status));
        read_tim = MPI_Wtime() - stim;

        MPI_CHECK(MPI_File_close(&fh));

        MPI_Allreduce(&write_tim, &new_write_tim, 1, MPI_DOUBLE, MPI_MAX, MPI_COMM_WORLD);
        MPI_Allreduce(&read_tim, &new_read_tim, 1, MPI_DOUBLE, MPI_MAX, MPI_COMM_WORLD);

        min_read_tim = (new_read_tim < min_read_tim) ? new_read_tim : min_read_tim;
        min_write_tim = (new_write_tim < min_write_tim) ? new_write_tim : min_write_tim;
    }

    if (mynod == 0) {
        read_bw = (SIZE * nprocs) / (min_read_tim * 1024.0 * 1024.0);
        write_bw = (SIZE * nprocs) / (min_write_tim * 1024.0 * 1024.0);
        fprintf(stderr, "Write bandwidth without file sync = %f Mbytes/sec\n", write_bw);
        fprintf(stderr, "Read bandwidth without prior file sync = %f Mbytes/sec\n", read_bw);
    }

    min_write_tim = 10000000.0;
    min_read_tim = 10000000.0;

    flag = 0;
    for (j = 0; j < ntimes; j++) {
        MPI_CHECK(MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE |
                                MPI_MODE_RDWR, MPI_INFO_NULL, &fh));
        MPI_CHECK(MPI_File_seek(fh, mynod * SIZE, MPI_SEEK_SET));

        MPI_Barrier(MPI_COMM_WORLD);
        stim = MPI_Wtime();
        MPI_CHECK(MPI_File_write(fh, buf, SIZE, MPI_BYTE, &status));
        err = MPI_File_sync(fh);
        write_tim = MPI_Wtime() - stim;
        if (err == MPI_ERR_UNKNOWN) {
            flag = 1;
            break;
        }

        MPI_CHECK(MPI_File_close(&fh));

        MPI_Barrier(MPI_COMM_WORLD);

        MPI_CHECK(MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE |
                                MPI_MODE_RDWR, MPI_INFO_NULL, &fh));
        MPI_CHECK(MPI_File_seek(fh, mynod * SIZE, MPI_SEEK_SET));

        MPI_Barrier(MPI_COMM_WORLD);
        stim = MPI_Wtime();
        MPI_CHECK(MPI_File_read(fh, buf, SIZE, MPI_BYTE, &status));
        read_tim = MPI_Wtime() - stim;

        MPI_CHECK(MPI_File_close(&fh));

        MPI_Allreduce(&write_tim, &new_write_tim, 1, MPI_DOUBLE, MPI_MAX, MPI_COMM_WORLD);
        MPI_Allreduce(&read_tim, &new_read_tim, 1, MPI_DOUBLE, MPI_MAX, MPI_COMM_WORLD);

        min_read_tim = (new_read_tim < min_read_tim) ? new_read_tim : min_read_tim;
        min_write_tim = (new_write_tim < min_write_tim) ? new_write_tim : min_write_tim;
    }

    if (mynod == 0) {
        if (flag)
            fprintf(stderr, "MPI_File_sync returns error.\n");
        else {
            read_bw = (SIZE * nprocs) / (min_read_tim * 1024.0 * 1024.0);
            write_bw = (SIZE * nprocs) / (min_write_tim * 1024.0 * 1024.0);
            fprintf(stderr, "Write bandwidth including file sync = %f Mbytes/sec\n", write_bw);
            fprintf(stderr, "Read bandwidth after file sync = %f Mbytes/sec\n", read_bw);
        }
    }

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