Re: Optimizations (was Re: [gentoo-amd64] First Impressions)

[Boyd Stephen Smith Jr.]

On Thursday 28 September 2006 16:17, Barry.SCHWARTZ@×××××××××××××.org wrote 
about 'Optimizations (was Re: [gentoo-amd64] First Impressions)':
> "Boyd Stephen Smith Jr." <bss03@××××××××××.net> skribis:
> > Now, I have to problem with developers closing some bug opened by a
> > ricer out there that's added -ffast-math to their CFLAGS as
> > WONTFIX/INVALID since it's not really a problem.  All the parts
> > provided by Gentoo (ebuild, source, compiler, portage, etc.) all
> > behaving properly.  It's just that, just like the warning says,
> > programs WILL break
> > under -ffast-math.
>
> I have to disagree with this strongly, because -ffast-math means you
> want code that violates the IEEE floating point standard.

Sorry, I mistyped "no" as "to" in the first sentence which completely 
changed my meaning.  I agree that -ffast-math ricers could have their bugs 
closed with prejudice.  -ffast-math is basically something that should 
only be allowed on a per-package basis, after consulting with upstream.

> > > Indeed, there aren’t many fields of ‘production’ in which end users
> > > ought to be encouraged to try things that expose flaws in design or
> > > manufacture.
> > I disagree.  I want to know about those flaws, and I want the
> > manufactures to fix them -- which is why I like Consumer Reports so
> > much. :)
> It’s one thing to read Consumer Reports and have it say your SUV rolls
> over easily, and another to drive in a manner likely to roll your SUV
> over. It’s even worse to sort of hold SUV drivers hostage by
> encouraging them to roll over their SUVs unless and until the
> manufacturer fixes the SUV. People should be encouraged to drive their
> dangerous vehicles safely, and so should users be encouraged to set
> their CFLAGS safely.

I encourage users to try to roll their SUVs safely. :)

If you are running a nuclear power plant off of Gentoo, then I hope you are 
going quite a bit further than just not using -O3.

However, using -O3 is usually dangerous to only the user themselves (at 
most) so I see no problem encouraging it.

That said, once somebody figures out (and publishes) that when you do X, Y, 
and Z to brand A SUV it rolls over.  I'd discourage doing X, Y, and Z to 
brand A SUVs (it'll cost you an SUV and really doesn't provide much 
benefit).  I'd encourage to X, Y, and Z to brand B, C, and D SUVs 
(*safely*) so that we can determine if the manufacturing flaw affects them 
as well.

-- 
"If there's one thing we've established over the years,
it's that the vast majority of our users don't have the slightest
clue what's best for them in terms of package stability."
-- Gentoo Developer Ciaran McCreesh