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

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

       Almost all MPI routines return an error value; C routines as  the  return  result  of  the  function  and
       Fortran routines in the last argument.

       Before  the  error  value  is  returned,  the current MPI error handler associated with the communication
       object (e.g., communicator, window, file) is called.  If no communication object is associated  with  the
       MPI  call,  then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error
       handler.  When  MPI_COMM_SELF  is  not  initialized   (i.e.,   before   MPI_Init/MPI_Init_thread,   after
       MPI_Finalize,  or  when using the Sessions Model exclusively) the error raises the initial error handler.
       The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF  when  using
       the  World  model,  or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.  If no other appropriate error handler has been set, then the  MPI_ERRORS_RETURN
       error  handler  is  called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called on a communicator, it acts as if MPI_Abort was called on  that  communicator.  If  called  on  a
         window  or file, acts as if MPI_Abort was called on a communicator containing the group of processes in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

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

       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.

       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

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                                   MPI_TESTSOME(3)