[Mpi-forum] [EXTERNAL] Re: MPI "Allocate receive" proposal

[Barrett, Brian W]

On 8/26/13 10:31 AM, "Dries Kimpe" <dkimpe at mcs.anl.gov> wrote:

>* Barrett, Brian W <bwbarre at sandia.gov> [2013-08-26 16:06:00]:
>
>[...]
>
>> That being said, I don't think resource exhaustion corner cases are a
>>deal
>> breaker for me.  I think some implementation-dependent phrasing might be
>> acceptable.  It might be useful to define the message
>> transmission/matching semantics for these corner cases.  For example, if
>> MPI_Arecv returns an error because of resource exhaustion, is the
>>message
>> lost (my preference) or left in the receive queue?  If the message is
>> lost, what happens to the sender if the send was a synchronous send?
>
>I think allowing the message to be 'lost' should be last resort and not
>taken lightly, since as far as I know, a message cannot be lost using the
>existing MPI functions (ignoring fault tolerance/resilience here) and, as
>you pointout in your example, might cause many complexities at other
>places.

Sure they can.  The standard is totally silent on what happens when
MPI_RECV returns an error.  You're firmly in the realm of undefined
behavior.

Brian

--
  Brian W. Barrett
  Scalable System Software Group
  Sandia National Laboratories



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