trusty (3) MPI_Testsome.openmpi.3.gz

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_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.

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