[Mpi3-rma] Conflicting PUT/GET accesses clarification

James Dinan dinan at mcs.anl.gov
Wed Apr 27 17:12:24 CDT 2011


Logically, I would think of this as two concurrent (conflicting) updates 
to the same location.  The MPI implementation could detect and avoid a 
problem.  The same goes for two conflicting puts; the MPI implementation 
can also detect and avoid the problem but we define it to be erroneous.

How is this defined for send/recv?  I think I looked it up once and 
found that it was an error in that case.

  ~Jim.

On 04/27/2011 05:07 PM, Pavan Balaji wrote:
>
> It's not two concurrent accesses -- it's a single (overlapping) access.
>
> -- Pavan
>
> On 04/27/2011 04:58 PM, James Dinan wrote:
>> On 04/27/2011 03:51 PM, Pavan Balaji wrote:
>>>
>>> Page 339 lines 21-24 of MPI-2.2 states the following:
>>>
>>> "It is erroneous to have concurrent confl icting accesses to the same
>>> memory location in a window; if a location is updated by a put or
>>> accumulate operation, then this location cannot be accessed by a load or
>>> another RMA operation until the updating operation has completed at the
>>> target."
>>>
>>> What does this mean when I do PUT with a datatype with overlapping
>>> buffers? Is that valid or erroneous?
>>
>> My interpretation is that this is also erroneous.
>>
>> ~Jim.
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>




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