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

Provided by: openmpi-doc_4.1.6-7ubuntu2_all

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

       USE MPI
       ! or the older form: 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

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Testsome(incount, array_of_requests, outcount, array_of_indices,
                 array_of_statuses, ierror)
            INTEGER, INTENT(IN) :: incount
            TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(incount)
            INTEGER, INTENT(OUT) :: outcount, array_of_indices(*)
            TYPE(MPI_Status) :: array_of_statuses(*)
            INTEGER, OPTIONAL, INTENT(OUT) :: 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.

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 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_STATUSES_IGNORE 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.