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

Jim Dinan dinan at mcs.anl.gov
Wed Jul 18 13:18:53 CDT 2012

On 7/18/12 1:06 PM, Torsten Hoefler wrote:
> On Wed, Jul 18, 2012 at 01:08:43PM -0500, Pavan Balaji wrote:
>> On 07/18/2012 01:02 PM, Torsten Hoefler wrote:
>>> Jim,
>>>> Is one process' disp_unit meaningful at another process?  I thought that
>>>> this is not the case.  MPI provides no other routines to query another
>>>> process' disp_unit.
>>> It is something that the user is passing in. I don't know of a
>>> particular use-case but we can query all other arguments that each
>>> process passed. One more integer seemed safe to me.
>>>> Also, what meaning does a disp_unit have in the context of load/store
>>>> operations that will result from win_shared_query?
>>> Nothing.
>>>> Maybe I'm missing something, but this doesn't seem necessary.
>>> Well, it's better to have it than to introduce it with a different name
>>> later. That was my main motivation. One could also use it in a library
>>> context to query. But that's weak, I know.
>> This doesn't seem critical, and can always be added in MPI-3.1 if we
>> find it necessary.  No reason to rush it.
> It cannot be added without a new function name. That was the concern
> here. Adding it seems less risk than not adding it. In addition, it is
> already added ;-).

I am concerned that this is a harmful change.  The disp_unit from one 
process has no meaningful use at another process.  If the user wants to 
know it for some reason, they can use a separate communication operation.


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