[mpiwg-rma] Inconsistency of MPI_WIN_FENCE semantic

[Rajeev Thakur]

> (1) On P440-P441 it say that "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". This requires MPI_WIN_FENCE that starts an epoch to act as an barrier.

It only says "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".   NOT   "This requires MPI_WIN_FENCE that starts an epoch to act as an barrier."

Why does the fence have to act as a barrier. The handshake could be done when first RMA operation is called after the fence.

Rajeev


On Feb 25, 2014, at 8:41 PM, "Zhao, Xin" <xinzhao3 at illinois.edu> wrote:

> Hi all,
> 
> There is an inconsistency of MPI_WIN_FENCE semantic in MPI 3.0 Standard that makes me confused:
> 
> (1) On P440-P441 it say that "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". This requires MPI_WIN_FENCE that starts an epoch to act as an barrier.
> 
> (2) However, (1) contradict with the word at end of P441: "a call to MPI_WIN_FENCE that is known not to end any epoch (in particular a call with assert equal to MPI_MODE_NOPRECEDE) does not necessarily act as a barrier".
> 
> Should the word of (1) add: "when MPI_MODE_NOPRECEDE is not given"?
> 
> Thanks,
> 
> Xin
> 
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