Hubert, Thanks for your comment -- in general, the RMA group is thinking about the vector systems. Is there a desire from users to have shared memory windows defined for this platform? Keeping in mind that the synchronization required will be harder to reason about than get/put? ~Jim. On 12/3/12 10:24 AM, Hubert Ritzdorf wrote:

NEC SX (including the Earth Simulator) memory is not cache coherent and MPI-2 RMA is working since many years on these systems.

Hubert ________________________________________ From: [email protected] [[email protected]] on behalf of Jim Dinan [[email protected]] Sent: Monday, December 03, 2012 4:39 PM To: [email protected] Subject: Re: [Mpi3-rma] MPI-3.1 consideration slides

On 12/2/12 7:44 AM, Jeff Hammond wrote:

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(1) Define semantics of shared memory windows in separate model.

In Section 11.2.3 it says "MPI does not define semantics for accessing shared memory windows in the separate memory model."

I would like to try to define these semantics in MPI 3.1. Shouldn't it at least be possible to use MPI_WIN_(UN)LOCK with MPI_LOCK_EXCLUSIVE here?

I believe that supporting RMA for weakly- or non- coherent memory architectures is vital for future systems. I agree. We had this discussion and decided to postpone it because we had other more pressing issues. Now may be the time. A discussion would be good.

Yes, there was no urgency. I'm glad the standard left this issue wide open instead of defining something restrictive.

IMHO, defining shared memory windows in the separate model is not a worthy use of the Forum's time. This will be hard to get right, and AFAIK no (reasonable) system requires it. As we've currently left it, if this functionality is needed, one can define the semantics as an MPI extension. I think this is a better option that defining a new model in the absence of a platform that uses it.

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