[Mpi-forum] MPI "Allocate receive" proposal

[Jeff Squyres (jsquyres)]

FWIW, I'm not really sure I see how the failure for MPI_ARECV to get a buffer (via malloc or whatever mechanism it wants) is substantially different than failing to get a buffer for any incoming message.

Indeed, for ARECV, an implementation may well try to use a freelist to allocate a buffer, or fully-lazily allocate a buffer (because it won't know the size until the message is received).  Meaning that the allocation will (potentially) occur on the same/similar path as all receive messages.

Put that together with the fact that normal receives can also fail to get an eager or unexpected buffer when a new message arrives, for example.  

Therefore the error handling could well be the same between the ARECV and "regular" receive cases.


On Aug 26, 2013, at 11:27 AM, Pavan Balaji <balaji at mcs.anl.gov> wrote:

> 
> Can you clarify a bit more?
> 
> Is that a fatal failure at that point?  Or is it more like MPI_Alloc_mem failing where I can retry later or just do a regular malloc (in this case, a regular MPI_RECV).
> 
> -- Pavan
> 
> On 08/26/2013 10:19 AM, David Goodell (dgoodell) wrote:
>> I'd say that's implementation defined behavior, no different than hitting any other system resource limitation right now.
>> 
>> -Dave
>> 
>> On Aug 26, 2013, at 10:14 AM, Pavan Balaji <balaji at mcs.anl.gov> wrote:
>> 
>>> Jeff,
>>> 
>>> This should probably be moved to the point-to-point WG, but I'll comment on this thread for now.
>>> 
>>> Such a proposal was brought up at the very early stage of the MPI-2.1 process (I don't remember by whom).  The main concern at that point was what happens when the memory allocation fails.  Will the receive fail? What happens to the sent message?
>>> 
>>> Can you work these details into your slides?
>>> 
>>> -- Pavan
>>> 
>>> On 08/26/2013 10:10 AM, Jeff Squyres (jsquyres) wrote:
>>>> Dave Goodell and I have a proposal that we've socialized a bit around with other Forum members, and would now like larger Forum feedback.  I'll be presenting the attached slides on the concept of an "allocate receive" in Madrid (3:30-4pm on Thursday).
>>>> 
>>>> There's no text or ticket yet; this is an idea that we want to get feedback on before working up a full proposal.
>>>> 
>>>> 
>>>> 
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>>> 
>>> --
>>> Pavan Balaji
>>> http://www.mcs.anl.gov/~balaji
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>> 
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> 
> -- 
> Pavan Balaji
> http://www.mcs.anl.gov/~balaji
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-- 
Jeff Squyres
jsquyres at cisco.com
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