DeinoMPI

The Great and Terrible implementation of MPI-2

MPI_File_get_info

Returns the hints for a file that are actually being used by MPI

int MPI_File_get_info(
  MPI_File mpi_fh,
  MPI_Info *info_used
);

Parameters

mpi_fh: [in] file handle (handle)
info_used: [out] info object (handle)

Remarks

MPI_FILE_GET_INFO returns a new info object containing the hints of the file associated with fh. The current setting of all hints actually used by the system related to this open file is returned in info_used. The user is responsible for freeing info_used via MPI_INFO_FREE.

Advice to users.

The info object returned in info_used will contain all hints currently active for this file. This set of hints may be greater or smaller than the set of hints passed in to MPI_FILE_OPEN, MPI_FILE_SET_VIEW, and MPI_FILE_SET_INFO, as the system may not recognize some hints set by the user, and may recognize other hints that the user has not set.

Example Code

The following sample code illustrates MPI_File_get_info.

#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/*
* access style is explicitly described as modifiable. values include
* read_once, read_mostly, write_once, write_mostlye, random
*/
int main( int argc, char *argv[] )
{
    int errs = 0, err;
    int buf[10];
    int rank;
    MPI_Comm comm;
    MPI_Status status;
    MPI_File fh;
    MPI_Info infoin, infoout;
    char value[1024];
    int flag, count;

    MPI_Init( &argc, &argv );
    comm = MPI_COMM_WORLD;
    MPI_Comm_rank( comm, &rank );
    MPI_Info_create( &infoin );
    MPI_Info_set( infoin, "access_style", "write_once,random" );

    err = MPI_File_open( comm, "testfile", MPI_MODE_RDWR | MPI_MODE_CREATE, infoin, &fh );
    if (err) {
        errs ++;
        MPI_Abort( MPI_COMM_WORLD, 911 );
    }

    buf[0] = rank;
    err = MPI_File_write_ordered( fh, buf, 1, MPI_INT, &status );
    if (err) { errs ++; }

    MPI_Info_set( infoin, "access_style", "read_once" );
    err = MPI_File_seek_shared( fh, 0, MPI_SEEK_SET );
    if (err) { errs ++; }

    err = MPI_File_set_info( fh, infoin );
    if (err) { errs ++; }
    MPI_Info_free( &infoin );
    buf[0] = -1;

    err = MPI_File_read_ordered( fh, buf, 1, MPI_INT, &status );
    if (err) { errs ++; }
    MPI_Get_count( &status, MPI_INT, &count );
    if (count != 1) {
        errs++;
        printf( "Expected to read one int, read %d\n", count );fflush(stdout);
    }
    if (buf[0] != rank) {
        errs++;
        printf( "Did not read expected value (%d)\n", buf[0] );fflush(stdout);
    }
    err = MPI_File_get_info( fh, &infoout );
    if (err) { errs ++; }
    MPI_Info_get( infoout, "access_style", 1024, value, &flag );
    /* Note that an implementation is allowed to ignore the set_info, so we'll accept either the original or the updated version */
    if (!flag) {
    }
    else {
        if (strcmp( value, "read_once" ) != 0 && strcmp( value, "write_once,random" ) != 0) {
            errs++;
            printf( "value for access_style unexpected; is %s\n", value );fflush(stdout);
        }
    }
    MPI_Info_free( &infoout );

    err = MPI_File_close( &fh );
    if (err) { errs ++; }

    MPI_Barrier( comm );

    if (rank == 0) {
        err = MPI_File_delete( "testfile", MPI_INFO_NULL );
        if (err) { errs ++; }
    }
    MPI_Finalize( );
    return errs;
}

DOWNLOAD

Win32 DeinoMPI.2.0.1.msi
Win64 DeinoMPI.x64.2.0.1.msi