[mpiwg-rma] [EXTERNAL] Re: Synchronization on shared memory windows

Balaji, Pavan balaji at anl.gov
Tue Feb 4 12:05:15 CST 2014

On Feb 4, 2014, at 12:01 PM, Rolf Rabenseifner <rabenseifner at hlrs.de> wrote:
> The MPI_WIN_SYNC (not the Fortran MPI_F_SYNC_REG)
> has no meaning in the unified memory model if all accesses 
> are done without RMA routines.

No.  On shared memory windows, if you are using load/store, you still need WIN_SYNC.

> It has only a meaning if different public and privat copy is 
> there (MPI-3.0 p450:46-p451:2).
> MPI-3.0 p456:3 - p457:7 define the rules for the unified memory model
> but there is no need to use MPI_WIN_SYNC.

There probably needs to be some tweaks to the wording, but the intention was that the accesses will become visible “eventually”, not “immediately”.  If you want them to become visible immediately, you need to do a WIN_SYNC.

  — Pavan

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