[Mpi3-rma] Alternative Proposal for Shared Memory Support

Rajeev Thakur thakur at mcs.anl.gov
Tue Mar 15 21:22:49 CDT 2011

All can be used, but none are needed, right?

Currently, in the unified model you can do:

barrier          barrier
                      x = A

With shared memory, you could do

barrier         barrier
                     x = A


If the above is true, it might be a bit confusing to users that in the RMA chapter you use put, get, and synchronization functions for some things and can directly read/write memory for some other things.


On Mar 15, 2011, at 9:17 PM, Torsten Hoefler wrote:

> On Tue, Mar 15, 2011 at 09:03:40PM -0500, Rajeev Thakur wrote:
>> Since processes sharing memory can/will access it directly using
>> memory references (not put/get), and this proposal is for the unified
>> memory model, we need to say whether any of the synchronization
>> functions in the RMA chapter are needed at all for such usage.
> Well, put/get to local windows are also allowed, so this would not be an
> exception. It's even nicely defined because the chapter defines the
> behavior for overlapping windows, and a shared window could be treated
> semantically like multiple overlapping windows. I am not sure if all are
> needed but I would say that all can be used. 
> Yes, load/store accesses would probably be the most common use (plus
> maybe the new (portable) atomics!).
> Best,
>  Torsten
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