[Mpi3-rma] Alternative Proposal for Shared Memory Support

James Dinan dinan at mcs.anl.gov
Wed Mar 16 08:22:05 CDT 2011

Hi Rajeev,

Why not use lock/unlock?  Lock_all seems like a good fit here.


On 3/16/11 8:09 AM, Rajeev Thakur wrote:
> Right. Some things that need to be touched up are that flush can only be called within lock-unlock currently. Also flush takes a target rank, which is the rank passed to the put/get. Flush_all has the notion of all ranks used in preceding puts/gets. Such things would need to be addressed.
> Rajeev
> On Mar 15, 2011, at 11:22 PM, Torsten Hoefler wrote:
>> On Tue, Mar 15, 2011 at 09:39:24PM -0500, Rajeev Thakur wrote:
>>> That's what I meant in my first mail. We need to say whether this example will work or not.
>>> A=10
>>> barrier         barrier
>>>                     x = A
>>> If not, which synchronization functions need to be used and how? The
>>> current text does not automatically cover this example.
>> Right, I never claimed that the proposal is complete :-). It's basically
>> a quick poll to see if there are major flaws and I should retract or if
>> it is worth discussing at the Forum (to flesh out such things like you
>> mentioned).
>> To answer your question: I think this should either be:
>> A=10
>> MPI_Win_flush
>> barrier           barrier
>>                   x=A
>> This would basically insert a membar in MPI_Win_flush which makes
>> sure that A is committed before the barrier completes (a barrier flag is
>> set and read).
>> This fits our current semantics where we suggest that win_flush can be
>> used for ordering. Keep in mind that it's still the unified model, i.e.,
>> the value would commit eventually, the flush is just needed to enforce
>> ordering with regards to the barrier.
>> Thanks&  Best,
>>   Torsten
>> --
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