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

[Jeff Squyres]

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