int MPI_Op_free(
  MPI_Op *op
);

Parameters

op

[in] operation (handle)

Remarks

Null Handles The MPI 1.1 specification, in the section on opaque objects, explicitly disallows freeing a null MPI_Op. The text from the standard is:

 A null handle argument is an erroneous IN argument in MPI calls, unless an
 exception is explicitly stated in the text that defines the function. Such
 exception is allowed for handles to request objects in Wait and Test calls
 (sections Communication Completion and Multiple Completions ). Otherwise, a
 null handle can only be passed to a function that allocates a new object and
 returns a reference to it in the handle.

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 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_ARG

Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).

MPI_ERR_ARG

Invalid argument; the error code associated with this error indicates an attempt to free an MPI permanent operation (e.g., MPI_SUM).

See Also

Example Code

The following sample code illustrates MPI_Op_free.

#include "mpi.h"
#include <stdio.h>
 
void addem ( int *, int *, int *, MPI_Datatype * );
 
void addem(int *invec, int *inoutvec, int *len, MPI_Datatype *dtype)
{
    int i;
    for ( i=0; i<*len; i++ )
        inoutvec[i] += invec[i];
}
 
int main( int argc, char **argv )
{
    int rank, size, i;
    int data;
    int errors=0;
    int result = -100;
    int correct_result;
    MPI_Op op;
 
    MPI_Init( &argc, &argv );
    MPI_Comm_rank( MPI_COMM_WORLD, &rank );
    MPI_Comm_size( MPI_COMM_WORLD, &size );
 
    data = rank;
    MPI_Op_create( (MPI_User_function *)addem, 1, &op );
    MPI_Reduce ( &data, &result, 1, MPI_INT, op, 0, MPI_COMM_WORLD );
    MPI_Bcast ( &result, 1, MPI_INT, 0, MPI_COMM_WORLD );
    MPI_Op_free( &op );
    correct_result = 0;
    for(i=0;i<size;i++)
        correct_result += i;
    if (result != correct_result) errors++;
 
    MPI_Finalize();
    return errors;
}