MPI_Win_fence - Synchronizes RMA calls on a window.
17.2.437.1.1. C Syntax
#include <mpi.h> int MPI_Win_fence(int assert, MPI_Win win)
17.2.437.1.2. Fortran Syntax
USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_WIN_FENCE(ASSERT, WIN, IERROR) INTEGER ASSERT, WIN, IERROR
17.2.437.1.3. Fortran 2008 Syntax
USE mpi_f08 MPI_Win_fence(assert, win, ierror) INTEGER, INTENT(IN) :: assert TYPE(MPI_Win), INTENT(IN) :: win INTEGER, OPTIONAL, INTENT(OUT) :: ierror
17.2.437.2. INPUT PARAMETERS
assert: Program assertion (integer).
win: Window object (handle).
17.2.437.3. OUTPUT PARAMETER
IERROR: Fortran only: Error status (integer).
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 target 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 communication 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.
The assert argument is used to provide assertions on the context of
the call that may be used for various optimizations. A value of assert ^ 0 is always valid. The following assertion value is supported:
No local RMA calls have been issued before this fence. This assertion must be provided by all or no members of the group of the window. It may enable faster fence call by avoiding unnecessary synchronization.
Informs that the local window was not updated by local stores or get calls in the preceding epoch.
Informs that the local window will not be updated by any put or accummulate calls in the ensuing epoch (until next fence call).
No local RMA calls will be issued after this fence. This assertion must be provided by all or no members of the group of the window. It may enable faster fence call by avoiding unnecessary synchronization.
Calls to MPI_Win_fence should both precede and follow calls to put, get or accumulate that are synchronized with fence calls.
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.
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.