function index

MPI_Win_get_attr

Get attribute cached on an MPI window object

int MPI_Win_get_attr(
  MPI_Win win,
  int win_keyval,
  void *attribute_val,
  int *flag
);

Parameters

win

[in] window to which the attribute is attached (handle)

win_keyval

[in] key value (integer)

attribute_val

[out] attribute value, unless flag is false

flag

[out] false if no attribute is associated with the key (logical)

Remarks

The following attributes are predefined for all MPI Window objects:

MPI_WIN_BASE

window base address.

MPI_WIN_SIZE

window size, in bytes.

MPI_WIN_DISP_UNIT

displacement unit associated with the window.

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.

Errors

All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS

No error; MPI routine completed successfully.

MPI_ERR_WIN

Invalid MPI window object

MPI_ERR_KEYVAL

Invalid keyval

MPI_ERR_OTHER

Other error; use MPI_Error_string to get more information about this error code.

Example Code

The following sample code illustrates MPI_Win_get_attr.

#include "mpi.h"
#include <stdio.h>

/* Test creating and inserting attributes in different orders */

int checkAttrs( MPI_Win win, int n, int key[], int attrval[] );
int checkNoAttrs( MPI_Win win, int n, int key[] );

int main( int argc, char *argv[] )
{
    int errs = 0;
    int key[3], attrval[3];
    int i;
    int buf[1];
    MPI_Comm comm;
    MPI_Win  win;

    MPI_Init( &argc, &argv );

    comm = MPI_COMM_WORLD;
    MPI_Win_create( buf, sizeof(int), sizeof(int), MPI_INFO_NULL, comm, &win );

    /* Create key values */
    for (i=0; i<3; i++) {
        MPI_Win_create_keyval( MPI_NULL_COPY_FN, MPI_NULL_DELETE_FN, &key[i], (void *)0 );
        attrval[i] = 1024 * i;
    }

    /* Insert attribute in several orders.  Test after put with get, then delete, then confirm delete with get. */

    MPI_Win_set_attr( win, key[2], &attrval[2] );
    MPI_Win_set_attr( win, key[1], &attrval[1] );
    MPI_Win_set_attr( win, key[0], &attrval[0] );
    errs += checkAttrs( win, 3, key, attrval );

    MPI_Win_delete_attr( win, key[0] );
    MPI_Win_delete_attr( win, key[1] );
    MPI_Win_delete_attr( win, key[2] );
    errs += checkNoAttrs( win, 3, key );

    MPI_Win_set_attr( win, key[1], &attrval[1] );
    MPI_Win_set_attr( win, key[2], &attrval[2] );
    MPI_Win_set_attr( win, key[0], &attrval[0] );
    errs += checkAttrs( win, 3, key, attrval );

    MPI_Win_delete_attr( win, key[2] );
    MPI_Win_delete_attr( win, key[1] );
    MPI_Win_delete_attr( win, key[0] );
    errs += checkNoAttrs( win, 3, key );

    MPI_Win_set_attr( win, key[0], &attrval[0] );
    MPI_Win_set_attr( win, key[1], &attrval[1] );
    MPI_Win_set_attr( win, key[2], &attrval[2] );
    errs += checkAttrs( win, 3, key, attrval );

    MPI_Win_delete_attr( win, key[1] );
    MPI_Win_delete_attr( win, key[2] );
    MPI_Win_delete_attr( win, key[0] );
    errs += checkNoAttrs( win, 3, key );

    for (i=0; i<3; i++) {
        MPI_Win_free_keyval( &key[i] );
    }
    MPI_Win_free( &win );

    MPI_Finalize();
    return errs;
}

int checkAttrs( MPI_Win win, int n, int key[], int attrval[] )
{
    int errs = 0;
    int i, flag, *val_p;

    for (i=0; i<n; i++) {
        MPI_Win_get_attr( win, key[i], &val_p, &flag );
        if (!flag) {
            errs++;
            fprintf( stderr, "Attribute for key %d not set\n", i );fflush(stderr);
        }
        else if (val_p != &attrval[i]) {
            errs++;
            fprintf( stderr, "Atribute value for key %d not correct\n", i );fflush(stderr);
        }
    }

    return errs;
}

int checkNoAttrs( MPI_Win win, int n, int key[] )
{
    int errs = 0;
    int i, flag, *val_p;

    for (i=0; i<n; i++) {
        MPI_Win_get_attr( win, key[i], &val_p, &flag );
        if (flag) {
            errs++;
            fprintf( stderr, "Attribute for key %d set but should be deleted\n", i );fflush(stderr);
        }
    }

    return errs;
}