NAME¶
MPI_Waitsome - Waits for some given MPI Requests to complete
SYNOPSIS¶
int MPI_Waitsome(int incount, MPI_Request array_of_requests[],
int *outcount, int array_of_indices[],
MPI_Status array_of_statuses[])
- incount
- - length of array_of_requests (integer)
- array_of_requests
- - array of requests (array of handles)
OUTPUT PARAMETERS¶
- outcount
- - number of completed requests (integer)
- array_of_indices
- - array of indices of operations that completed (array of integers)
- array_of_statuses
- - array of status objects for operations that completed (array of Status).
May be MPI_STATUSES_IGNORE .
NOTES¶
The array of indicies are in the range
0 to
incount - 1 for C and
in the range
1 to
incount for Fortran.
Null requests are ignored; if all requests are null, then the routine returns
with
outcount set to
MPI_UNDEFINED .
While it is possible to list a request handle more than once in the
array_of_requests, such an action is considered erroneous and may cause the
program to unexecpectedly terminate or produce incorrect results.
MPI_Waitsome provides an interface much like the Unix
select or
poll calls and, in a high qualilty implementation, indicates all of the
requests that have completed when
MPI_Waitsome is called. However,
MPI_Waitsome only guarantees that at least one request has completed;
there is no guarantee that
all completed requests will be returned, or
that the entries in
array_of_indices will be in increasing order. Also,
requests that are completed while
MPI_Waitsome is executing may or may
not be returned, depending on the timing of the completion of the message.
NOTES ON THE MPI_STATUS ARGUMENT¶
The
MPI_ERROR field of the status return is only set if the return from
the MPI routine is
MPI_ERR_IN_STATUS . That error class is only
returned by the routines that take an array of status arguments (
MPI_Testall ,
MPI_Testsome ,
MPI_Waitall , and
MPI_Waitsome ). In all other cases, the value of the
MPI_ERROR
field in the status is unchanged. See section 3.2.5 in the MPI-1.1
specification for the exact text.
For send operations, the only use of status is for
MPI_Test_cancelled or
in the case that there is an error in one of the four routines that may return
the error class
MPI_ERR_IN_STATUS , in which case the
MPI_ERROR
field of status will be set. In that case, the value will be set to
MPI_SUCCESS for any send or receive operation that completed
successfully, or
MPI_ERR_PENDING for any operation which has neither
failed nor completed.
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_REQUEST
- - Invalid MPI_Request . Either null or, in the case of a
MPI_Start or MPI_Startall , not a persistent request.
- 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_IN_STATUS
- - The actual error value is in the MPI_Status argument. This error
class is returned only from the multiple-completion routines (
MPI_Testall , MPI_Testany , MPI_Testsome ,
MPI_Waitall , MPI_Waitany , and MPI_Waitsome ). The
field MPI_ERROR in the status argument contains the error value or
MPI_SUCCESS (no error and complete) or MPI_ERR_PENDING to
indicate that the request has not completed. The MPI Standard does not
specify what the result of the multiple completion routines is when an
error occurs. For example, in an MPI_WAITALL , does the routine
wait for all requests to either fail or complete, or does it return
immediately (with the MPI definition of immediately, which means
independent of actions of other MPI processes)? MPICH has chosen to make
the return immediate (alternately, local in MPI terms), and to use the
error class MPI_ERR_PENDING (introduced in MPI 1.1) to indicate
which requests have not completed. In most cases, only one request with an
error will be detected in each call to an MPI routine that tests multiple
requests. The requests that have not been processed (because an error
occured in one of the requests) will have their MPI_ERROR field
marked with MPI_ERR_PENDING .
LOCATION¶
/tmp/gyCYfBi4J6/mpich-3.1/src/mpi/pt2pt/waitsome.c