[Mpi3-hybridpm] Reminder for the hybrid telecon tomorrow

[Jeff Squyres (jsquyres)]

Points to think about for the Monday teleconf...

With regards to ref-counted MPI_INIT / MPI_FINALIZE (https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/302):

PROBLEMS IT SOLVES:
- multiple, separate libraries in a single process needing access to MPI
  ==> works best when all entities call MPI_INIT* at the beginning of time, work for a "long" period of time, and then call MPI_FINALIZE at the end of time (i.e., there's no race condition -- see below)

PROBLEMS IT DOES NOT SOLVE:
- Implementation not providing MPI_THREAD_MULTIPLE support (e.g., if the separate libraries are in different threads and someone already initialized MPI with THREAD_SINGLE, other threads can't know if it's safe to call MPI_INIT* or not)
- The "finalize" problem (i.e., can't guarantee to know if MPI has been finalized or not -- there's a race between calling MPI_FINALIZED, seeing that MPI is not finalized, and then calling MPI_INIT)

PROBLEMS IT CREATES:
- Will need to change the definition of "main thread"
- Possibly also need to change the definitions of MPI_THREAD_SERIALIZED and MPI_THREAD_FUNNELED

OPEN QUESTIONS:
- Do we still need to keep the restriction that the thread that initializes MPI is the same thread that finalizes MPI?
- Should we allow re-initialization?  This effectively solves some (but not all) of the problems that have been discussed, but probably opens a new can of worms...



On Apr 12, 2013, at 8:27 AM, Pavan Balaji <balaji at mcs.anl.gov> wrote:

> All,
> 
> Jim and I will be late for the April 22nd meeting.  So we decided to
> move the endpoints discussion to the telecon after this one.
> 
> I chatted with Jeff Squyres yesterday.  He'll be driving the April 22nd
> telecon to discuss more details on the ref-counted init/finalize issue.
> He'll be sending out some notes before the call for discussion.
> 
> Thanks,
> 
> -- Pavan
> 
> On 04/08/2013 11:47 AM US Central Time, Pavan Balaji wrote:
>> 
>> The next call will be on April 22nd, 11am central.  Same telecon number.
>> 
>> -- Pavan
>> 
>> On 04/08/2013 11:42 AM US Central Time, Jim Dinan wrote:
>>> Meeting notes are on the wiki:
>>> 
>>> https://svn.mpi-forum.org/trac/mpi-forum-web/wiki/MPI3Hybrid/notes-2013-04-08
>>> 
>>> 
>>> ~Jim.
>>> 
>>> On 4/7/13 12:45 PM, Pavan Balaji wrote:
>>>> All,
>>>> 
>>>> This is a reminder that we'll have our hybrid telecon tomorrow at 11am.
>>>>  Here's the telecon information:
>>>> 
>>>> International dial-in number: 1-719-234-7800
>>>> Domestic dial-in number: 1-888-850-4523
>>>> Participant Passcode: 314159
>>>> 
>>>> The main item we'll be discussing is Jeff Squyres' ref-count proposal.
>>>> 
>>>> https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/302
>>>> 
>>>>  -- Pavan
>>>> 
>>> _______________________________________________
>>> Mpi3-hybridpm mailing list
>>> Mpi3-hybridpm at lists.mpi-forum.org
>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-hybridpm
>> 
> 
> -- 
> Pavan Balaji
> http://www.mcs.anl.gov/~balaji


-- 
Jeff Squyres
jsquyres at cisco.com
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