-O3 vs. -O2 (was Re: [ale] sharing an experience....debian....)
hbbs at comcast.net
Wed Feb 11 22:38:05 EST 2004
Can someone explain to me why the -O3 optimization would make programs
run *slower*? In asking, I'm not trying to cast aspersions or challenge
the assertion, I'm really only just trying to ask how this is so.
On Wed, 2004-02-11 at 19:23, James Sumners wrote:
> Stupid exmh didn't send this with the correct From: address earlier today.
> >From the November 04, 2003 Debian news
> --- Begin Quote ---
> Debian faster than Gentoo? Matt Garman wondered why his C++
> program ran dramatically slower when compiled on a Gentoo machine than
> when compiled with Debian Sid. He later reported that recompiling
> the Gentoo C++ libraries with less aggressive optimization flags (-O2
> instead of -O3) eliminated the speed difference. Matt also added
> that Debian and other distributions are conservative, but set up by
> very experienced people.
> 2. http://article.gmane.org/gmane.linux.gentoo.user/50924
> 3. http://article.gmane.org/gmane.linux.gentoo.user/50973
> 4. http://article.gmane.org/gmane.linux.gentoo.user/50953
> --- End Quote ---
> Basically, Red Hat (Fedora) packages are typically compiled in a haphazard
> fashion in relation to the other packages in the distribution. The packages in
> Debian go through an arduous testing process and are built according to rather
> strict rules.
> James Sumners
> On Wed, 11 Feb 2004 13:12:30 -0500
> Keith Morris - IQ <keith at iqtv.com> wrote:
> > Hi all, just wanted to share a quick experience and get your opinions if
> > you are willing.
> > I have been using linux off and on since Redhat 5.1 and exclusively for
> > the last 3 years at home. I have pretty much been a redhat man with no
> > complaints. I use Fedora Core 1 on my 2 main machines at home (both
> > 1.6GHz). Well, recently I got a PIII 866 to play with and installed FC1
> > on it and the speed was really quite sluggish. Played with a few more
> > distros which I wasn't really happy with. Well, I've always been afraid
> > of Debian with it's infamous hell-installer, but with it's new Beta
> > installer, I decided to try it.
> > After a pretty painless net-install, I was totally shocked with the
> > speed of Debian. Easily twice as fast as Fedora on the 866 using the
> > *SAME* software (Gnome 2.4, KDE 3.1.5, OpenOffice, Evolution, XFT
> > support, antialiasing, etc.) I still have not gotten the sound working,
> > but believe that I will be able to (with a few posts to the ALE list :))
> > The only main difference is that I formatted / with reiserfs instead of
> > ext3 with FC1.
> > I was wondering if anyone could guess why debian would be sooooo much
> > faster with basically the same "Desktop" type of configuration? Do many
> > of you use Debian?
> > I will probably stick with Debian on this machine to learn about the
> > different ins-and-outs. I absolutely *love* apt-get for debian. I have
> > used it with rpms on redhat, but it seems better with debs...dunno...
> > Anyway, thanks for letting me share.
> > Keith Morris
> > Creative Director
> > Design / Effects
> > IQ television group
> > http://www.iqtv.com
> > _______________________________________________
> > Ale mailing list
> > Ale at ale.org
> > http://www.ale.org/mailman/listinfo/ale
Jeff Hubbs <hbbs at comcast.net>
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