ad_testfs_seek.c

mpi并行计算的c++代码 可用vc或gcc编译通过 可以用来搭建并行计算试验环境

/* -*- Mode: C; c-basic-offset:4 ; -*- */
/* 
 *
 *   Copyright (C) 2001 University of Chicago. 
 *   See COPYRIGHT notice in top-level directory.
 */

#include "ad_testfs.h"
#include "adioi.h"
#include "adio_extern.h"

/* ADIOI_TESTFS_SeekIndividual()
 *
 * Implements SEEK_SET only (and doesn't test for whence type); all
 * other types of whence must be converted before calling this.
 *
 * Returns an absolute offset in bytes.  The offset passed into the call is in
 * terms of the etype relative to the filetype, so some calculations are
 * necessary.  
 */
ADIO_Offset ADIOI_TESTFS_SeekIndividual(ADIO_File fd, ADIO_Offset offset, 
					int whence, int *error_code)
{
    int myrank, nprocs;

    ADIO_Offset off;
    ADIOI_Flatlist_node *flat_file;
    int i, n_etypes_in_filetype, n_filetypes, etype_in_filetype;
    ADIO_Offset abs_off_in_filetype=0;
    int size_in_filetype, sum;
    int filetype_size, etype_size, filetype_is_contig;
    MPI_Aint filetype_extent;

    *error_code = MPI_SUCCESS;

    MPI_Comm_size(fd->comm, &nprocs);
    MPI_Comm_rank(fd->comm, &myrank);
    FPRINTF(stdout, "[%d/%d] ADIOI_TESTFS_SeekIndividual called on %s\n", 
	    myrank, nprocs, fd->filename);

    ADIOI_Datatype_iscontig(fd->filetype, &filetype_is_contig);
    etype_size = fd->etype_size;

    if (filetype_is_contig) off = fd->disp + etype_size * offset;
    else {
        flat_file = ADIOI_Flatlist;
        while (flat_file->type != fd->filetype) flat_file = flat_file->next;

	MPI_Type_extent(fd->filetype, &filetype_extent);
	MPI_Type_size(fd->filetype, &filetype_size);
	if ( ! filetype_size ) {
	    *error_code = MPI_SUCCESS; 
	    return 0;
	}

	n_etypes_in_filetype = filetype_size/etype_size;
	n_filetypes = (int) (offset / n_etypes_in_filetype);
	etype_in_filetype = (int) (offset % n_etypes_in_filetype);
	size_in_filetype = etype_in_filetype * etype_size;
 
	sum = 0;
	for (i=0; i<flat_file->count; i++) {
	    sum += flat_file->blocklens[i];

	    if (sum > size_in_filetype) {
		abs_off_in_filetype = flat_file->indices[i] +
		    size_in_filetype - (sum - flat_file->blocklens[i]);
		break;
	    }
	}

	/* abs. offset in bytes in the file */
	off = fd->disp + (ADIO_Offset) n_filetypes * filetype_extent +
                abs_off_in_filetype;
    }

    fd->fp_ind = off;

    return off;
}