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       MPI_Win_fence -  Perform an MPI fence synchronization on a MPI window


       int MPI_Win_fence(int assert, MPI_Win win)


       assert - program assertion (integer)
       win    - window object (handle)


       The  assert  argument  is  used  to  indicate  special  conditions  for  the fence that an
       implementation may use to optimize the MPI_Win_fence operation.  The value zero is  always
       correct.   Other  assertion  values  may be or'ed together.  Assertions that are valid for
       MPI_Win_fence are:

              - the local window was not updated by local stores (or local get or receive  calls)
              since last synchronization.
              -  the  local window will not be updated by put or accumulate calls after the fence
              call, until the ensuing (fence) synchronization.
              - the fence does not complete any sequence of locally issued  RMA  calls.  If  this
              assertion is given by any process in the window group, then it must be given by all
              processes in the group.
              - the fence does not start any  sequence  of  locally  issued  RMA  calls.  If  the
              assertion is given by any process in the window group, then it must be given by all
              processes in the group.


       This routine is thread-safe.  This means that this routine may be safely used by  multiple
       threads  without the need for any user-provided thread locks.  However, the routine is not
       interrupt safe.  Typically, this is due to the use of memory allocation routines  such  as
       malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.


       All  MPI  routines  in  Fortran  (except  for MPI_WTIME and MPI_WTICK ) have an additional
       argument ierr at the end of the argument list.  ierr  is  an  integer  and  has  the  same
       meaning  as  the  return  value  of  the  routine  in  C.   In  Fortran,  MPI routines are
       subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.


       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value;  C  routines  as
       the  value of the function and Fortran routines in the last argument.  Before the value is
       returned, the current MPI error handler is called.  By default, this error handler  aborts
       the  MPI  job.   The  error  handler  may  be  changed  with  MPI_Comm_set_errhandler (for
       communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler  (for  RMA
       windows).   The  MPI-1  routine  MPI_Errhandler_set may be used but its use is deprecated.
       The predefined error handler MPI_ERRORS_RETURN may be used to cause  error  values  to  be
       returned.   Note  that  MPI  does  not  guarentee that an MPI program can continue past an
       error; however, MPI implementations will attempt to continue whenever possible.

              - No error; MPI routine completed successfully.
              - Other error; use MPI_Error_string to get more information about this error code.
              - Invalid MPI window object

                                            11/21/2018                           MPI_Win_fence(3)