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Subject: Re: [hwloc-devel] towards PLPA-like API in 1.0
From: Samuel Thibault (samuel.thibault_at_[hidden])
Date: 2009-12-10 17:22:54

Jeff Squyres, le Thu 10 Dec 2009 16:57:56 -0500, a écrit :
> Are you saying that the API will be all OS/physical, with conversion functions from #3 to convert to/from logical?

No, it should stay logical, conversion would be just to translate into OS/physical.

> Additionally, what exactly is the logical ordering defined to be?

See topology.c, it's always topologically ordered, and then ordered
by OS cpu numbers. So for instance if the topology is flat, the OS
CPU numbers would get used. Then the topology distorts the OS CPU
numbering. So logical ordering is as close as OS CPU numbering as
possible, constrained by topology.

> We need to guarantee that it is the same across every run,

It is, unless the BIOS changes the CPU numbers.

> I see that topology-linux.c uses diropen()

No need to read the OS backends code, the whole sort is achieved in the
generic topology.c code.

> My point: if we're going to have a logical ordering, we should be able to provide at least some level of guarantee of stability about that logical ordering.
> Make sense?

For sure since that was precisely what I had in my when I put the
sorting code in the generic part.