[Mpi3-hybridpm] First cut at slides

Steve Oyanagi sko at cray.com
Thu Jun 20 17:20:42 CDT 2013


My apologies for some potentially dumb comments here, but I am missing
some context:

1. Can slides be expanded or can some one explain why the items in
    question are desirable?  (i.e. use cases)  One case is libraries,
    but I suspect there are others.

2. What does it mean if the first thread calls MPI_Init_thread with
    required=MPI_THREAD_FUNNELD, then a later thread calls MPI_Init_thread
    (MPI already initialized, now in "epoch" in slide-speak) with
    required=MPI_THREAD_MULTIPLE?  Does the second call see an error?
    What does second call return for provided?

    I suspect the second call succeeds and provided=MPI_THREAD_FUNNED
    but I won't be surprised if that's wrong.

3. Slide 13 seems to imply that the implementation doesn't need to
    actually implement an intermediate finalize/initialization, just
    allow the calls.  Is that correct?  Does that satisfy the use

       - Steve

On 06/18/2013 07:47 AM, Jeff Squyres (jsquyres) wrote:
> For comment...
> Here's a first cut at slides that we discussed yesterday.  It's meant to be a rollup of all the issues surrounding:
> - thread safe INIT / FINALIZE
> - reference-counting INIT / FINALIZE
> - nesting of INIT / FINALIZE
> I discovered a new issue when making up these slides: with ref-counting INIT/FINALIZE, since INIT/FINALIZE are collective, we have the same ref counts in all procs in MPI_COMM_WORLD.  But the ref counts may be different in non-COMM_WORLD connected processes.  What happens when they try to finalize over all connected processes?  See slide 12 for an example.  I'm not sure what the right answer is yet.
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