| MPI_WIN_FENCE(assert, win) | |
| IN assert | program assertion (integer) |
| IN win | window object (handle) |
int MPI_Win_fence(int assert, MPI_Win win)
MPI_WIN_FENCE(ASSERT, WIN, IERROR)
INTEGER ASSERT, WIN, IERROR
{ void MPI::Win::Fence(int assert) const (binding deprecated, see Section Deprecated since MPI-2.2
) }
The MPI call MPI_WIN_FENCE(assert, win) 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.
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 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.
The assert argument is used to provide assertions on the
context of the call that may be used for various optimizations. This
is described in
Section Assertions
. A value of assert = 0 is
always valid.
Calls to MPI_WIN_FENCE should both precede and follow calls to
put, get or accumulate that are synchronized with fence calls.
( End of advice to users.)
Advice to users.
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