> We may be getting a P4 hyperthreaded system to play with, but under
> different rules, where I get to do a bit of tuning first.  I have
> already built the core system on another machine using gcc-3.2.3,
> "-march=pentium4 -O3 -pipe -fomit-frame-pointer"  I note that the
> pentium4 warning still appears in make.conf, though I believe it no
> longer applies to this gcc.
>
> A while ago I emailed this list and asked for information on tests and
> settings for HT P4's, without a reply.  So again, has anyone done any
> tests on a HT P4 and is willing to support the flags they chose as being
> "the best"?  In particular, does -ffast-math give a measurable gain?
> Most of my machines have been built as scientific stations, so accuracy
> is more important than ultimate speed, so this is one I have never
> tested.  I am not interested in the -O9 -max-everything kiddies who have
> been so vocal, but reasoned choices.
>
> If you want to flame, go ahead - but support your statements!

Well all packages that cannot handle -march=pentium4 should filter it out. 
This filtering is imprefect so adding -mcpu=pentium4 should ensure correct 
scheduling of all packages. One thing, do not use -ffast-math, as can be seen 
in the manual this can actually produce mathematic errors. Normally one does 
not want this in most packages, so leave it alone. It could be used in things 
like games, wher the precision does not matter that much, but it is not safe 
as a default.

Paul

-- 
Paul de Vrieze
Gentoo Developer
Mail: pauldv@gentoo.org
Homepage: http://www.devrieze.net