MPI_Testsome(3)                    Open MPI                    MPI_Testsome(3)



NAME
       MPI_Testsome - Tests for completion of one or more previously initiated
       communications in a list.


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


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


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

       static int Request::Testsome(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
       Behaves like MPI_Waitsome, except that it returns immediately. If no
       operation has completed it returns outcount = 0. If there is no active
       handle in the list, it returns outcount = MPI_UNDEFINED.

       MPI_Testsome is a local operation, which returns immediately, whereas
       MPI_Waitsome blocks until a communication completes, if it was passed a
       list that contains at least one active handle. Both calls fulfill a
       fairness requirement: If a request for a receive repeatedly appears in
       a list of requests passed to MPI_Waitsome or MPI_Testsome, and a
       matching send has been posted, then the receive will eventually succeed
       unless the send is satisfied by another receive; send requests also
       fulfill this fairness requirement.

       Errors that occur during the execution of MPI_Testsome are handled as
       for MPI_Waitsome.

       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.


NOTES
       The use of MPI_Testsome is likely to be more efficient than the use of
       MPI_Testany. The former returns information on all completed
       communications; with the latter, a new call is required for each
       communication that completes.

       A server with multiple clients can use MPI_Waitsome so as not to starve
       any client. Clients send messages to the server with service requests.
       The server calls MPI_Waitsome with one receive request for each client,
       then handles all receives that have completed. If a call to MPI_Waitany
       is used instead, then one client could starve while requests from
       another client always sneak in first.


ERRORS
       For each invocation of MPI_Testsome, 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_Testsome 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_Wait
       MPI_Waitall
       MPI_Waitany
       MPI_Waitsome
       MPI_Win_set_errhandler




1.4.1                            Jan 14, 2010                  MPI_Testsome(3)
