int MPI_Attr_put(
  MPI_Comm comm,
  int keyval,
  void *attr_value
);

Parameters

comm

[in] communicator to which attribute will be attached (handle)

keyval

[in] key value, as returned by MPI_KEYVAL_CREATE (integer)

attribute_val

[in] attribute value

Remarks

This function stores the stipulated attribute value attribute_val for subsequent retrieval by MPI_ATTR_GET. If the value is already present, then the outcome is as if MPI_ATTR_DELETEwas first called to delete the previous value (and the callback function delete_fn was executed), and a new value was next stored. The call is erroneous if there is no key with value keyval; in particular MPI_KEYVAL_INVALID is an erroneous key value. The call will fail if the delete_fn function returned an error code other than MPI_SUCCESS.

The type of the attribute value depends on whether C, C++, or Fortran is being used. In C and C++, an attribute value is a pointer (void *); in Fortran, it is a single integer (not a pointer, since Fortran has no pointers and there are systems for which a pointer does not fit in an integer (e.g., any > 32 bit address system that uses 64 bits for Fortran DOUBLE PRECISION).

If an attribute is already present, the delete function (specified when the corresponding keyval was created) will be called.

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.

Deprecated Function

Notes for Fortran

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_COMM

Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank).

MPI_ERR_KEYVAL

Invalid keyval

MPI_ERR_ARG

This error class is associated with an error code that indicates that an attempt was made to free one of the permanent keys.

See Also

Example Code

The following sample code illustrates MPI_Attr_put.

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

int checkAttrs( MPI_Comm comm, int n, int key[], int attrval[] );
int checkNoAttrs( MPI_Comm comm, int n, int key[] );

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

    MPI_Init(&argc, &argv);
    comm = MPI_COMM_WORLD;
    /* Create key values */
    for (i=0; i<3; i++) {
        MPI_Keyval_create( 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_Attr_put( comm, key[2], &attrval[2] );
    MPI_Attr_put( comm, key[1], &attrval[1] );
    MPI_Attr_put( comm, key[0], &attrval[0] );

    errs += checkAttrs( comm, 3, key, attrval );

    MPI_Attr_delete( comm, key[0] );
    MPI_Attr_delete( comm, key[1] );
    MPI_Attr_delete( comm, key[2] );

    errs += checkNoAttrs( comm, 3, key );

    MPI_Attr_put( comm, key[1], &attrval[1] );
    MPI_Attr_put( comm, key[2], &attrval[2] );
    MPI_Attr_put( comm, key[0], &attrval[0] );

    errs += checkAttrs( comm, 3, key, attrval );

    MPI_Attr_delete( comm, key[2] );
    MPI_Attr_delete( comm, key[1] );
    MPI_Attr_delete( comm, key[0] );

    errs += checkNoAttrs( comm, 3, key );

    MPI_Attr_put( comm, key[0], &attrval[0] );
    MPI_Attr_put( comm, key[1], &attrval[1] );
    MPI_Attr_put( comm, key[2], &attrval[2] );

    errs += checkAttrs( comm, 3, key, attrval );

    MPI_Attr_delete( comm, key[1] );
    MPI_Attr_delete( comm, key[2] );
    MPI_Attr_delete( comm, key[0] );

    errs += checkNoAttrs( comm, 3, key );

    for (i=0; i<3; i++) {
        MPI_Keyval_free( &key[i] );
    }
    MPI_Finalize();
    return 0;
}

int checkAttrs( MPI_Comm comm, int n, int key[], int attrval[] )
{
    int errs = 0;
    int i, flag, *val_p;
    for (i=0; i<n; i++) {
        MPI_Attr_get( comm, 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_Comm comm, int n, int key[] )
{
    int errs = 0;
    int i, flag, *val_p;
    for (i=0; i<n; i++) {
        MPI_Attr_get( comm, 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;
}