MPI_Win_fence(3OpenMPI) 												   MPI_Win_fence(3OpenMPI)

NAME

       MPI_Win_fence - Synchronizes RMA calls on a window.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Win_fence(int assert, MPI_Win win)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_WIN_FENCE(ASSERT, WIN, IERROR)
	    INTEGER ASSERT, WIN, IERROR

C++ Syntax
       #include <mpi.h>
       void MPI::Win::Fence(int assert) const

INPUT PARAMETERS

       assert	 Program assertion (integer).

       win	 Window object (handle).

OUTPUT PARAMETER

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       MPI_Win_fence  synchronizes  RMA calls on win. The call is collective on the group of win. All RMA operations on win originating at a given
       process and started before the fence call will complete at that process before the fence call returns. They will be completed at their tar-
       get  before the fence call returns at the target. RMA operations on win started by a process after the fence call returns will access their
       target window only after MPI_Win_fence has been called by the target process.

       The call completes an RMA access epoch if it was preceded by another fence call and the local process issued RMA communication calls on win
       between	these  two  calls.  The call completes an RMA exposure epoch if it was preceded by another fence call and the local window was the
       target of RMA accesses between these two calls. The call starts an RMA access epoch if it is followed by another fence call and by RMA com-
       munication  calls  issued  between these two fence calls. The call starts an exposure epoch if it is followed by another fence call and the
       local window is the target of RMA accesses between these two fence calls. Thus, the fence call is equivalent to calls to a subset of  post,
       start, complete, wait.

       A  fence  call usually entails a barrier synchronization: a process completes a call to MPI_Win_fence only after all other processes in the
       group have entered their matching call. However, a call to MPI_Win_fence that is known not to end any epoch (in	particular,  a	call  with
       assert = MPI_MODE_NOPRECEDE) does not necessarily act as a barrier.

NOTE

       Calls to MPI_Win_fence should both precede and follow calls to put, get or accumulate that are synchronized with fence calls.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
       tions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception  mechanism
       will be used to throw an MPI:Exception object.

       Before  the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for
       I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; 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.

SEE ALSO

       MPI_Win_create MPI_Win_start MPI_Win_post MPI_Win_complete MPI_Win_wait

Open MPI 1.2							    March 2007						   MPI_Win_fence(3OpenMPI)