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MPI_Waitany - Waits for any specified send or receive to complete.
#include <mpi.h>
int MPI_Waitany(int count, MPI_Request array_of_requests[],
int *index, MPI_Status *status)
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_WAITANY(COUNT, ARRAY_OF_REQUESTS, INDEX, STATUS, IERROR)
INTEGER COUNT, ARRAY_OF_REQUESTS(*), INDEX
INTEGER STATUS(MPI_STATUS_SIZE), IERROR
USE mpi_f08
MPI_Waitany(count, array_of_requests, index, status, ierror)
INTEGER, INTENT(IN) :: count
TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(count)
INTEGER, INTENT(OUT) :: index
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- count
- List length (integer).
- array_of_requests
- Array of
requests (array of handles).
- index
- Index of handle for
operation that completed (integer). In the range 0 to count-1. In Fortran,
the range is 1 to count.
- status
- Status object (status).
- IERROR
- Fortran only:
Error status (integer).
A call to MPI_Waitany can be used to
wait for the completion of one out of several requests.
The array_of_requests
list may contain null or inactive handles. If the list contains no active
handles (list has length zero or all entries are null or inactive), then
the call returns immediately with index = MPI_UNDEFINED, and an empty status.
The execution of MPI_Waitany(count, array_of_requests, index, status) has
the same effect as the execution of MPI_Wait(&array_of_requests[i], status),
where i is the value returned by index (unless the value of index is MPI_UNDEFINED).
MPI_Waitany with an array containing one active entry is equivalent to
MPI_Wait.
If your application does not need to examine the status field,
you can save resources by using the predefined constant MPI_STATUS_IGNORE
as a special value for the status argument.
Example: Client-server code (starvation
can occur).
CALL MPI_COMM_SIZE(comm, size, ierr)
CALL MPI_COMM_RANK(comm, rank, ierr)
IF(rank .GT 0) THEN ! client code
DO WHILE(.TRUE.)
CALL MPI_ISEND(a, n, MPI_REAL, 0, tag, comm, request, ierr)
CALL MPI_WAIT(request, status, ierr)
END DO
ELSE ! rank=0 -- server code
DO i=1, size-1
CALL MPI_IRECV(a(1,i), n, MPI_REAL, i tag,
comm, request_list(i), ierr)
END DO
DO WHILE(.TRUE.)
CALL MPI_WAITANY(size-1, request_list, index, status, ierr)
CALL DO_SERVICE(a(1,index)) ! handle one message
CALL MPI_IRECV(a(1, index), n, MPI_REAL, index, tag,
comm, request_list(index), ierr)
END DO
END IF
Almost all MPI routines return an error value; C routines as the
value of the function and Fortran routines in the last argument. C++ functions
do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS,
then on error the C++ exception mechanism will be used to throw an MPI::Exception
object.
Before the error value is returned, the current MPI error handler
is called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler,
MPI_File_set_errhandler, or MPI_Win_set_errhandler (depending on the type
of MPI handle that generated the request); the predefined error handler
MPI_ERRORS_RETURN may be used to cause error values to be returned. Note
that MPI does not guarantee that an MPI program can continue past an error.
Note that per MPI-1 section 3.2.5, MPI exceptions on requests passed to MPI_WAITANY
do not set the status.MPI_ERROR field in the returned status. The error
code is passed to the back-end error handler and may be passed back to the
caller through the return value of MPI_WAITANY if the back-end error handler
returns it. The pre-defined MPI error handler MPI_ERRORS_RETURN exhibits
this behavior, for example.
MPI_Comm_set_errhandler
MPI_File_set_errhandler
MPI_Test
MPI_Testall
MPI_Testany
MPI_Testsome
MPI_Wait
MPI_Waitall
MPI_Waitsome
MPI_Win_set_errhandler
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