NAME¶
MPI_Grequest_start - Create and return a user-defined request
SYNOPSIS¶
int MPI_Grequest_start( MPI_Grequest_query_function *query_fn,
MPI_Grequest_free_function *free_fn,
MPI_Grequest_cancel_function *cancel_fn,
void *extra_state, MPI_Request *request )
- query_fn
- - callback function invoked when request status is queried
(function)
- free_fn
- - callback function invoked when request is freed
(function)
- cancel_fn
- - callback function invoked when request is cancelled
(function)
- extra_state
- - Extra state passed to the above functions.
OUTPUT PARAMETER¶
- request
- - 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
MPI_ERR_IN_STATUS .
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-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_ARG
- - Invalid argument. Some argument is invalid and is not
identified by a specific error class (e.g., MPI_ERR_RANK ).
LOCATION¶
greq_start.c