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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



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