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From: Ralph H Castain (rhc_at_[hidden])
Date: 2007-04-03 14:33:05


On 4/3/07 9:32 AM, "Li-Ta Lo" <ollie_at_[hidden]> wrote:

> On Sun, 2007-04-01 at 13:12 -0600, Ralph Castain wrote:
>
>>
>> 2. I'm not sure what you mean by mapping MPI processes to "physical"
>> processes, but I assume you mean how do we assign MPI ranks to processes on
>> specific nodes. You will find that done in the orte/mca/rmaps framework. We
>> currently only have one component in that framework - the round-robin
>> implementation - that maps either by slot or by node, as indicated by the
>> user. That code is fairly heavily commented, so you hopefully can understand
>> what it is doing.
>>
>
> How does this work in a multi-core environment? the optimal way may be
> putting processes on every other "slot" on a two cores system?

Well, that's a good question. At the moment, the only environments where we
encounter multiple cores treat each core as a separate "slot" when they
assign resources. We don't currently provide an option that says "map by
two", so the only way to do what you describe would be to manually specify
the mapping, slot by slot.

Not very pretty.

If someone cares to suggest some alternative notation/option for requesting
that kind of mapping flexibility, I'm certainly willing to implement it (it
would be rather trivial to do "map by N", but might be more complicated if
you want other things).

Ralph

>
> Ollie
>
>
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