plucky (3) MPI_Test.openmpi.3.gz

SYNTAX

   C Syntax
          #include <mpi.h>

          int MPI_Test(MPI_Request *request, int *flag, MPI_Status *status)

   Fortran Syntax
          USE MPI
          ! or the older form: INCLUDE 'mpif.h'
          MPI_TEST(REQUEST, FLAG, STATUS, IERROR)
               LOGICAL FLAG
               INTEGER REQUEST, STATUS(MPI_STATUS_SIZE), IERROR

   Fortran 2008 Syntax
          USE mpi_f08
          MPI_Test(request, flag, status, ierror)
               TYPE(MPI_Request), INTENT(INOUT) :: request
               LOGICAL, INTENT(OUT) :: flag
               TYPE(MPI_Status) :: status
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETER

       • request: Communication request (handle).

OUTPUT PARAMETERS

       • flag: True if operation completed (logical).

       • status: Status object (status).

       • ierror: Fortran only: Error status (integer).

DESCRIPTION

       A  call  to  MPI_Test  returns  flag = true if the operation identified by request is complete. In such a
       case, the status object is set to contain information on the completed operation;  if  the  communication
       object was created by a nonblocking send or receive, then it is deallocated and the request handle is set
       to MPI_REQUEST_NULL. The call returns flag = false, otherwise. In this case,  the  value  of  the  status
       object is undefined. MPI_Test is a local operation.

       The return status object for a receive operation carries information that can be accessed as described in
       the “Return Status” subsection of the “Point-to-Point Communication” chapter in  the  MPI  Standard.  The
       status   object   for  a  send  operation  carries  information  that  can  be  accessed  by  a  call  to
       MPI_Test_cancelled (see the “Probe and Cancel” section of the MPI Standard).

       If your application does not need to examine the status field,  you  can  save  resources  by  using  the
       predefined constant MPI_STATUS_IGNORE as a special value for the status argument.

       One  is  allowed  to call MPI_Test with a null or inactive request argument. In such a case the operation
       returns with flag = true and empty status.

       The functions MPI_Wait and MPI_Test can be used to complete both sends and receives.

NOTES

       The use of the nonblocking MPI_Test call allows the user to  schedule  alternative  activities  within  a
       single  thread  of  execution.  An  event-driven  thread scheduler can be emulated with periodic calls to
       MPI_Test.

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.

       Note  that  per  the  “Return  Status”  section  in the “Point-to-Point Communication” chapter in the MPI
       Standard, MPI errors on requests passed to MPI_Test do not set the status.MPI_ERROR field in the returned
       status.   The  error  code  is  always passed to the back-end error handler and may be passed back to the
       caller through the return value of MPI_Test if the back-end error handler returns  it.   The  pre-defined
       MPI error handler MPI_ERRORS_RETURN exhibits this behavior, for example.

       SEE ALSO:

          • MPI_Comm_set_errhandler

          • MPI_File_set_errhandler

          • MPI_Testall

          • MPI_Testany

          • MPI_Testsome

          • MPI_Wait

          • MPI_Waitall

          • MPI_Waitany

          • MPI_Waitsome

          • MPI_Win_set_errhandler

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                                       MPI_TEST(3)