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MPI_Grequest_start(3) MPI MPI_Grequest_start(3)
MPI_Grequest_start - Create and return a user-defined request
int MPI_Grequest_start( MPI_Grequest_query_function *query_fn,
void *extra_state, MPI_Request *request )
- callback function invoked when request status is queried
- callback function invoked when request is freed (function)
- callback function invoked when request is cancelled (function)
- Extra state passed to the above functions.
- Generalized request (handle)
NOTES ON THE CALLBACK FUNCTIONS
The return values from the callback functions must be a valid MPI error
code or class. This value may either be the return value from any MPI
routine (with one exception noted below) or any of the MPI error
classes. For portable programs, MPI_ERR_OTHER may be used; to provide
more specific information, create a new MPI error class or code with
MPI_Add_error_class or MPI_Add_error_code and return that value.
The MPI standard is not clear on the return values from the callback
routines. However, there are notes in the standard that imply that
these are MPI error codes. For example, pages 169 line 46 through page
170, line 1 require that the free_fn return an MPI error code that may
be used in the MPI completion functions when they return
The one special case is the error value returned by MPI_Comm_dup when
the attribute callback routine returns a failure. The MPI standard is
not clear on what values may be used to indicate an error return.
Further, the Intel MPI test suite made use of non-zero values to
indicate failure, and expected these values to be returned by the
MPI_Comm_dup when the attribute routines encountered an error. Such
error values may not be valid MPI error codes or classes. Because of
this, it is the user's responsibility to either use valid MPI error
codes in return from the attribute callbacks, if those error codes are
to be returned by a generalized request callback, or to detect and
convert those error codes to valid MPI error codes (recall that MPI
error classes are valid error codes).
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-
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
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.
- No error; MPI routine completed successfully.
- Invalid argument. Some argument is invalid and is not
identified by a specific error class (e.g., MPI_ERR_RANK ).