[Mpi3-rma] [EXTERNAL] Re: MPI-3 UNIFIED model clarification

Pavan Balaji balaji at mcs.anl.gov
Sun Aug 4 18:38:54 CDT 2013

On 08/04/2013 06:31 PM, Jed Brown wrote:
> Pavan Balaji <balaji at mcs.anl.gov> writes:
>> This is not an ordering issue if I'm talking about nonoverlapping
>> memory.  If P0 is doing PUTs to P1s memory, and P1 is reading some other
>> nonoverlapping region of it's own memory, P0 and P1 need to synchronize
>> in some way if they use the SEPARATE model (e.g., by using EXCLUSIVE
>> locks).  If they used the UNIFIED model, they can do these accesses
>> concurrently without any synchronization.
> At some point, P1 (or other ranks) must learn that it can now access the
> memory that P0 was PUTing into.  How would you do that?

Jed: there is still a WIN_SYNC required when you want to use that data. 
  I'm not arguing about that.  My point was merely to say that there are 
cases where some accesses require additional synchronization in the 
SEPARATE model compared to UNIFIED or KIND_OF_UNIFIED (if we ever create 
such a model).

Pavan Balaji

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