int MPI_Request_free(MPI_Request *request)
This routine is normally used to free inactive persistent requests created with either MPI_Recv_init or MPI_Send_init and friends. It is also permissible to free an active request. However, once freed, the request can no longer be used in a wait or test routine (e.g., MPI_Wait) to determine completion.
This routine may also be used to free a non-persistent requests such as those created with MPI_Irecv or MPI_Isend and friends. Like active persistent requests, once freed, the request can no longer be used with test/wait routines to determine completion.
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.
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.
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.