[mpiwg-rma] FW: [Mpi3-rma] [EXTERNAL] Re: MPI-3 UNIFIED model updates

Pavan Balaji balaji at mcs.anl.gov
Tue Aug 27 08:52:42 CDT 2013

On 08/27/2013 07:15 AM, Underwood, Keith D wrote:
>>> I prefer option #1 -- that a window synchronization (e.g. Win_sync)
>>> can be used to order load/store operations with respect to actions
>>> performed by other processes in the target's window.  If no ordering
>>> is enforced, the MPI standard does not define what is seen by load
>>> operations at the target process.  As a rationale, the local process'
>>> view of the window may not be consistent with the window because of
>>> performance optimizations or the consistency model of the underlying
>>> architecture.  This would allow e.g. SHMEM implementations to still
>>> use MPI-3 RMA, but they would have to rely on a behavior that is
>>> defined by the architecture/implementation, as they currently do.
> My statement:  this seems to be what SHMEM does - except they don't
> provide the equivalent of Win_sync.  If we are going to hack on the
> text, I would prefer that we be *very* careful in our wording.
> Specifically, we need to make it very clear that the SHMEM approach
> is *legal*, but the burden is on the user to do potentially
> implementation specific things to make it work right.

Hmm.  OK.  Just so there's no confusion, by "SHMEM approach", you are 
saying that the application can use its own platform-specific memory 
consistency calls and avoid using WIN_SYNC, correct?

Pavan Balaji

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