[HEADSUP] Atlas changed libraries

[Susi Lehtola]

On Mon, 23 Sep 2013 14:34:50 +0200
Kevin Kofler <kevin.kofler at chello.at> wrote:
> Matthew Miller wrote:
> > Actually, what ATLAS upstream intends is for the program to be
> > recompiled on every installation (or boot, even). I think we used
> > to have packages that did that; this is a compromise.
> 
> Yes, ATLAS upstream has always been smoking deep crack. It looks like 
> OpenBLAS is the much better option, now that it is available. (ATLAS
> used to be the best available as Free Software back when GotoBLAS was
> still proprietary, but now that the Goto code has been freed, ATLAS
> is not looking so great anymore.)

Well, it's not too hard to understand why ATLAS does things the way it
does. It's already in the acronym: Automatically Tuned Linear Algebra
Software. You generate a library that is optimal for your processor. In
comparison, GotoBLAS (OpenBLAS) has been hand-tuned in assembly for
every supported CPU.

On the other hand, I'm not sure why they don't just take their tool and
pregenerate lists of optimal parameters for every available CPU. That
way you could compile everything in the same package and do runtime CPU
detection. Currently binary distributions have to do some hackaround to
generate a reasonably efficient one-size-fits-all library.
-- 
Susi Lehtola
Fedora Project Contributor
jussilehtola at fedoraproject.org