Justifying Optimization

MICHAEL DILLON <mike.dillon@lmco.com>
17 Jan 2003 23:07:09 -0500

          From comp.compilers

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Justifying Optimization mike.dillon@lmco.com (MICHAEL DILLON) (2003-01-17)
Re: Justifying Optimization joachim_d@gmx.de (Joachim Durchholz) (2003-01-20)
Re: Justifying Optimization srikanth@cup.hp.com (srikanth) (2003-01-21)
Re: Justifying Optimization christian.bau@cbau.freeserve.co.uk (Christian Bau) (2003-01-21)
Re: Justifying Optimization vbdis@aol.com (2003-01-21)
Re: Justifying Optimization jgd@cix.co.uk (2003-01-21)
Re: Justifying Optimization touati@prism.uvsq.fr (Sid TOUATI) (2003-01-25)
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From: MICHAEL DILLON <mike.dillon@lmco.com>
Newsgroups: comp.compilers
Date: 17 Jan 2003 23:07:09 -0500
Organization: Lockheed Martin
Keywords: optimize, question, practice
Posted-Date: 17 Jan 2003 23:07:09 EST

I'm looking for advice regarding compiler optimization of production
software. I admit I've not used this newsgroup before so I apologize
if this is off-target.

I've been developing for twenty years, and ever since I've been
allowed to have an opinion I've insisted that code ready for final
testing and deployment be optimized. I'm currently responsible for my
program's development strategy, and was recently blindsided by
resistance to this approach. Developers are stating that optimized
code produces errors and makes debugging more difficult.

While true that debugging is made more complicated when optimization
is used, I'm not considering that enough justification to avoid

The other argument, that optimization produces errors, is the one that
is new to me. While I've not had any personal indication of this, I
don't have any hard facts.

So with that as a long intro, I'd love to get some opinions on this?
Is there any substantiated data that says optimized code is more prone
to errors? Is there a generally accepted guideline in the community
that says when you should/should-not optimize? Is there a general
level of compiler technology so that I can say that I'd gain ~x% by

I really consider this a general question, but in case it helps, our
development will be with both Windows 2000, using .NET, and Sun
Solaris using Forte. Both predominantly C++.

Thanks, Al
[I didn't know that anyone was still having this argument. While it's
true that optimizers sometimes have bugs, it's far more common that
they reveal bugs in application code that does stuff that the language
spec forbids, e.g., depending on the relative order of evaluation of
subexpressions in the same expression. If you care whether your code
works, build test suites and test the optimized application before you
ship it. -John]

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