[Mpi3-rma] MPI-3.1 consideration slides

[Pavan Balaji]

Attached is a slightly updated version of the slides.  I had forgotten
to include one additional item (in the last slide of the attached slide
deck).

 -- Pavan

On 12/02/2012 09:30 AM US Central Time, Pavan Balaji wrote:
> 
> On 12/02/2012 05:27 AM US Central Time, Torsten Hoefler wrote:
>> The only thing I disagree to is slide 6. Win_sync really does nothing
>> in the separate case. Your example would work on shared memory if
>> flush issues a memory barrier *and* MPI_Barrier() is an optimization
>> barrier (which is is in C and needs to be ensured in Fortran anyway).
>> But we can discuss next week.
> 
> The problem here is that MPI_BARRIER is a process barrier, not a memory
> barrier.  FWIW, with current compilers, which do not reorder
> instructions across functions, this should work correctly.  But this is
> a correctness concern when compilers do more than that, e.g., IPC
> optimizations.
> 
> An alternative would be to leave it as-is, and add a note that we assume
> the compiler will not reorder instructions here because it's a function
> call, though I don't prefer this alternative.
> 
>  -- Pavan
> 

-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji
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