MPI_Waitsome(3)                    Open MPI                    MPI_Waitsome(3)



NAME
       MPI_Waitsome - Waits for some given communications to complete.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Waitsome(int incount, MPI_Request *array_of_requests,
            int *outcount, int *array_of_indices,
            MPI_Status *array_of_statuses)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_WAITSOME(INCOUNT, ARRAY_OF_REQUESTS, OUTCOUNT,
                 ARRAY_OF_INDICES, ARRAY_OF_STATUSES, IERROR)
            INTEGER   INCOUNT, ARRAY_OF_REQUESTS(*), OUTCOUNT
            INTEGER   ARRAY_OF_INDICES(*)
            INTEGER   ARRAY_OF_STATUSES(MPI_STATUS_SIZE*)
            INTEGER   IERROR


C++ Syntax
       #include <mpi.h>
       static int Request::Waitsome(int incount, Request
            array_of_requests[], int array_of_indices[], Status array_of_statuses[])

       static int Request::Waitsome(int incount, Request
            array_of_requests[], int array_of_indices[])


INPUT PARAMETERS
       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).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       Waits until at least one of the operations associated with active
       handles in the list have completed. Returns in outcount the number of
       requests from the list array_of_requests that have completed. Returns
       in the first outcount locations of the array array_of_indices the
       indices of these operations (index within the array array_of_requests;
       the array is indexed from 0 in C and from 1 in Fortran). Returns in the
       first outcount locations of the array array_of_status the status for
       these completed operations. If a request that completed was allocated
       by a nonblocking communication call, then it is deallocated, and the
       associated handle is set to MPI_REQUEST_NULL.

       If the list contains no active handles, then the call returns
       immediately with outcount = MPI_UNDEFINED.

       When one or more of the communications completed by MPI_Waitsome fails,
       then it is desirable to return specific information on each
       communication. The arguments outcount, array_of_indices, and
       array_of_statuses will be adjusted to indicate completion of all
       communications that have succeeded or failed. The call will return the
       error code MPI_ERR_IN_STATUS and the error field of each status
       returned will be set to indicate success or to indicate the specific
       error that occurred. The call will return MPI_SUCCESS if no request
       resulted in an error, and will return another error code if it failed
       for other reasons (such as invalid arguments). In such cases, it will
       not update the error fields of the statuses.

       If your application does not need to examine the array_of_statuses
       field, you can save resources by using the predefined constant
       MPI_STATUSES_IGNORE can be used as a special value for the
       array_of_statuses argument.

       Example: Same code as the example in the MPI_Waitany man page, but
       using MPI_Waitsome.

           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, requests(i), ierr)
               END DO
               DO WHILE(.TRUE.)
                  CALL MPI_WAITSOME(size, request_list, numdone,
                                   indices, statuses, ierr)
                  DO i=1, numdone
                     CALL DO_SERVICE(a(1, indices(i)))
                     CALL MPI_IRECV(a(1, indices(i)), n, MPI_REAL, 0, tag,
                                  comm, requests(indices(i)), ierr)
                  END DO
               END DO
           END IF


NOTES
       The array of indices are in the range 0 to incount-1 for C and in the
       range 1 to incount for Fortran.


ERRORS
       For each invocation of MPI_Waitsome, if one or more requests generate
       an MPI exception, only the first MPI request that caused an exception
       will be passed to its corresponding error handler.  No other error
       handlers will be invoked (even if multiple requests generated
       exceptions).  However, all requests that generate an exception will
       have a relevant error code set in the corresponding status.MPI_ERROR
       field (unless MPI_IGNORE_STATUSES was used).

       The default 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 MPI 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.

       If the invoked error handler allows MPI_Waitsome to return to the
       caller, the value MPI_ERR_IN_STATUS will be returned in the C and
       Fortran bindings.  In C++, if the predefined error handler
       MPI::ERRORS_THROW_EXCEPTIONS is used, the value MPI::ERR_IN_STATUS will
       be contained in the MPI::Exception object.  The MPI_ERROR field can
       then be examined in the array of returned statuses to determine exactly
       which request(s) generated an exception.


SEE ALSO
       MPI_Comm_set_errhandler
       MPI_File_set_errhandler
       MPI_Test
       MPI_Testall
       MPI_Testany
       MPI_Testsome
       MPI_Wait
       MPI_Waitall
       MPI_Waitany
       MPI_Win_set_errhandler




1.4.1                            Jan 14, 2010                  MPI_Waitsome(3)
