[Mpi3-tools] Meaning of meaning of unique_id inmqs_communicator?

[John DelSignore]

Sure, if I ever find the time to actually work on it.

Cheers, John D.


Jeff Squyres wrote:
> John --
> 
> Can this be part of the text that you write up for standardizing the
> message queues stuff?
> 
> 
> On May 11, 2009, at 3:21 PM, Geoffrey R. Paulsen wrote:
> 
>>
>>
>> Regarding Ashley Pittman's message:
>> >
>> > >  I'm not sure I understand the difference between (b) and (c).
>> >
>> > The difference between (b) and (c) is best explained with reference to
>> > MPI_COMM_SELF, in (b) it can have the same id in every process, in (c)
>> > it has to have different values everywhere.  This has a practical
>> > implication, in (c) you can say "Communicator X in this job is...",
>> with
>> > (b) to be able to describe the communicator you have to also include
>> > some information about the communicator members, for example the global
>> > rank of local rank zero.
>> >
>> > In my opinion (c) would make the most logical sense and be easiest for
>> > tools to work with however I know from my time working with MPI
>> > libraries that (b) is a much more sensible option in reality.
>> >
>> > Ashley Pittman.
>>
>> Thank you for that description.  I've been able to verify that HP-MPI
>> indeed only supports the (b) and not (c).
>>
>> I agree that from a tools standpoint, (c) would be much more useful,
>> but that from an MPI point of view, it might require some semimajor
>> changes to the way that we create communicators.
>>
>> Currently MPI_Comm_Create() does not block for an entire job, just
>> for the ranks involved, which would make it tricky to ensure uniqueness
>> across an entire job of the communicator id.
>>
>> I don't think this would be impossible, but should be well thought
>> out.
>>
>>   Geoff Paulsen
>>
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>>
> 
> 
> --Jeff Squyres
> Cisco Systems
> 
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