[Mpi3-rma] [EXTERNAL] Re: Disp_unit in allocate_shared should be returned by win_shared_query?

[Torsten Hoefler]

On Thu, Jul 26, 2012 at 11:18:05AM -0500, James Dinan wrote:
> I do have a concern that different disp_units can occur unexpectedly  
> because of heterogeneous hardware or software -- e.g. MPMD launch with  
> different executables or language incompatibility where both C and  
> Fortran code are involved in creating the window.
>
> Rather than ruling these cases out (option #1), how about including the  
> following advice to users:
>
> Advice to users.  If disp_unit values differ across processes in a  
> shared memory window, the programmer may need to use the target's  
> disp_unit value in address calculations and use different load/store  
> operations depending on the target's disp_unit value. (End of advice to  
> users.)
>
> If we included this, I think I would be ok with option #2.
I don't object, however, we're supposed to freeze the document by today.
I guess we can add this advice nevertheless. I think this would also
cover Rolf's comment.

> An orthogonal observation -- it would have given us a lot more  
> flexibility to define MPI_Win_shared_query as:
>
> int MPI_Win_shared_get_attr(MPI_Win win, int target_rank, int  
> win_keyval, void *attribute_val, int *flag)
Of course. I still like the MPI_Func(...) idea :-). 

But I agree, this would also fit the current design with attributes
better. Hmm, is probably too late for such a syntactic sugar change. Any
opinions?

All the Best,
  Torsten

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Torsten Hoefler         | Performance Modeling and Simulation Lead
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