[Mpi3-rma] Unified model discussion

[William Gropp]

That's a good idea.
Bill

On Apr 2, 2011, at 12:37 PM, Pavan Balaji wrote:

>
> In the case of SEPARATE, Win_sync will be required to do two things:  
> (1)
> order load/stores, and (2) synchronize public/private windows.
>
> We can as well use Win_sync for unified too, and just get it to do the
> first part.
>
>  -- Pavan
>
> On 04/02/2011 12:35 PM, William Gropp wrote:
>> Would that call also complete/order local memory operations (e.g., we
>> could use the same routine)?
>>
>> Bill
>>
>> On Apr 2, 2011, at 11:50 AM, Underwood, Keith D wrote:
>>
>>> That is an important point.  What if we allow unified to work for
>>> this use case without additional calls, but add a call to force
>>> synchronization when the local and remote accesses would conflict?
>>>
>>> Keith
>>>
>>>> -----Original Message-----
>>>> From: mpi3-rma-bounces at lists.mpi-forum.org [mailto:mpi3-rma-
>>>> bounces at lists.mpi-forum.org] On Behalf Of Pavan Balaji
>>>> Sent: Thursday, March 31, 2011 3:52 PM
>>>> To: mpi3-rma at lists.mpi-forum.org
>>>> Subject: [Mpi3-rma] Unified model discussion
>>>>
>>>>
>>>> When we were having the discussion on the unified model during the
>>>> last
>>>> working group meeting, I forgot to point out one important use  
>>>> case:
>>>>
>>>> Process 0
>>>> ----------
>>>> Win_lock(shared, P0)
>>>> load(A)
>>>> store(B)
>>>> Win_unlock
>>>>
>>>> Process 1
>>>> ---------
>>>> Win_lock(shared, P0)
>>>> Put(C)
>>>> Get(D)
>>>> Win_unlock
>>>>
>>>> That is, two processes are reading/writing to different parts of  
>>>> the
>>>> window. This is an important model and can only be supported in
>>>> unified,
>>>> not separate (because of potential cache-line false sharing).
>>>>
>>>> So, basically, no we cannot remove the unified model in spite of  
>>>> all
>>>> its
>>>> nonsense with load/store ordering.
>>>>
>>>>  -- Pavan
>>>>
>>>> --
>>>> Pavan Balaji
>>>> http://www.mcs.anl.gov/~balaji
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>>>
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>>
>> William Gropp
>> Deputy Director for Research
>> Institute for Advanced Computing Applications and Technologies
>> Paul and Cynthia Saylor Professor of Computer Science
>> University of Illinois Urbana-Champaign
>>
>>
>>
>>
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>
> -- 
> Pavan Balaji
> http://www.mcs.anl.gov/~balaji

William Gropp
Deputy Director for Research
Institute for Advanced Computing Applications and Technologies
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign