[Mpi3-rma] Unified model discussion

[Rajeev Thakur]

Pavan is referring to this rule for the separate model on pg 46, which also exists in MPI 2.2. It means one cannot use shared locks and mix local stores with remote puts even to different parts of the window.


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On Mar 31, 2011, at 4:51 PM, Pavan Balaji wrote:

> 
> 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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