[Mpi3-hybridpm] First cut at slides
balaji at mcs.anl.gov
Sat Jun 22 08:30:55 CDT 2013
On 06/22/2013 08:27 AM, Jeff Squyres (jsquyres) wrote:
> On Jun 22, 2013, at 9:03 AM, Pavan Balaji <balaji at mcs.anl.gov> wrote:
>> Thanks. The slides seem to be confusing collective vs. synchronizing. I think you mean to say that INIT/FINALIZE are always collective, and they *might* be synchronizing (though we expect most implementations to not be synchronizing when they are not actually initializing or finalizing).
> How so? I thought slide 13 was fairly explicit about that:
> - INIT and FINALIZE still collective
> - Continue to not specify if they synchronize or not
Ok, thanks. I might have missed that.
>> I agree with JeffH that CONNECT/DISCONNECT is not a problem. MPI
>> cannot actually finalize in the first call to MPI_FINALIZE in your
>> example, since the ref-count didn't reach zero.
> I guess my point is that process A must wait for the *actual*
> finalization in process B (which is the 2nd one), and if Finalize
> synchronizes (which most.. but not all.. MPI implementations do),
> then A will block until B calls the 2nd Finalize.
Eh? My reading was that they *might* synchronize on every FINALIZE
call, but will *finalize* only when ref-count is zero.
> But I think I'm coming to the conclusion that if you want to not be
> affected by Finalize-possibly-blocking semantics, then you should
> just call MPI_COMM_DISCONNECT first.
I don't think so.
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