[Mpi-22] Higher-level languages proposal

[Jeff Squyres]

On Oct 14, 2008, at 7:07 AM, Supalov, Alexander wrote:

> Thanks. I'd rather say that if the purpose of the extension is  
> indeed to
> serialize the Probe/Recv pair, the better way to solve this and many
> other problems would be to make threads directly addressable, as if  
> they
> were MPI processes.
>
> One way to do this might be, say, to create a call like
> MPI_Comm_thread_enroll that creates an intra-communicator out of all
> threads that call this function in a loosely synchronous fashion,
> collectively over one or several MPI processes they constitute.

I'm still not sure I follow.  Can you provide more details, perhaps  
with function prototypes and specific rules?  (i.e., an alternate  
proposal)?

> If paired with the appropriately extended MPI_Comm_free, this would
> allow, for example, all threads in an OpenMP parallel section to be
> addressed as if they were fully fledged MPI processes. Note that this
> would allow more than one parallel section during the program run.
>
> Other threading models would profit from this "opt-in/opt-out" method,
> too. This may be a more flexible way of dealing with threads than the
> one-time MPI_Init variety mentioned by George Bosilica in his
> EuroPVM/MPI keynote, by the way.
>
> Best regards.
>
> Alexander
>
> -----Original Message-----
> From: mpi-22-bounces_at_[hidden]
> [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Terry Dontje
> Sent: Tuesday, October 14, 2008 12:45 PM
> To: MPI 2.2
> Subject: Re: [Mpi-22] Higher-level languages proposal
>
> Supalov, Alexander wrote:
>> Dear Jeff,
>>
>> Unfortunately, I won't be in Chicago, so we should rather discuss  
>> this
>> here. I talked to Torsten last time about this extension. As far as I
>> can remember, the main purpose of this extension is to make sure that
>> the thread that called the MPI_Probe also calls the MPI_Recv and gets
>> the message matched by the aforementioned MPI_Probe.
>>
>> If so, the main problem here is not the matching. The main problem is
>> that one cannot address threads in MPI. If we fix that, the proposed
>> extension with the message handle and such will become superfluous.
>>
>> See what I mean?
>>
>>
> Interesting, so you are basically redefining the MPI_Probe/Recv pair  
> to
> guarrantee a message to go to a specific thread.  Or in other words
> lowering the proposal's MPI_Mprobe/recv to be in the implementation of
> MPI_Probe/Recv.  This seems reasonable to me since MPI_Probe/Recv  
> itself
>
> is basically useless unless the programmer assures serialization when
> that combination is used.
>
> --td
>> Best regards.
>>
>> Alexander
>>
>> -----Original Message-----
>> From: mpi-22-bounces_at_[hidden]
>> [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Jeff Squyres
>> Sent: Monday, October 13, 2008 11:48 PM
>> To: MPI 2.2
>> Subject: Re: [Mpi-22] Higher-level languages proposal
>>
>> On Oct 13, 2008, at 10:46 AM, Supalov, Alexander wrote:
>>
>>
>>> Thanks. The 2.1.1, which was presented last time, in my opinion does
>
>>> not
>>> seem to solve the right problem. Instead of defining a way for
>>> unambiguous addressing of the threads in MPI, which would eliminate
>>> the
>>> MPI_Probe/Recv ambiguity and many other issues, it attempts to add
> yet
>>> another concept (this time, a message id) in the current situation
>>> where
>>> any thread can do what they please.
>>>
>>
>> I'm not quite sure I understand your proposal.
>>
>> <... after typing out a lengthy/rambling discourse that made very
>> little sense and was fraught with questions and ambiguities :-) ...>
>>
>> Let's discuss this in Chicago; Rich has allocated 5-7pm on Monday for
>
>> discussion of this proposal.  These are exactly the kinds of larger
>> issues that we want to raise via this proposal.
>>
>>
>
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-- 
Jeff Squyres
Cisco Systems