[Haskell-cafe] Re: speed: ghc vs gcc

[Louis Wasserman]

I said nothing about fairness, and *never at any point said I thought Don's
results were more useful or fair.*  What makes you think that's what I meant
to imply?

You have not responded to my separate concern that
> For code that actively requires computation at runtime, I have seen
> no examples of an instance where well-optimized GHC is actually
> dozens or hundreds of times slower than GCC output.

Rather than accusing me of taking sides, if you'd take an actual
apples-to-apples comparison, citing the best Haskell results and best GCC
results -- without using examples from either language which performed
computation at compile-time that would not be possible in everyday programs
-- my original claims were true: that GHC code is frequently within 3x the
speed of GCC code, and hacked-up GHC code can reach and match GCC
performance -- though I agree those hacks require an impractical blowup in
code size.  (Depending on your individual interpretation of what an average
Haskell program looks like, I concede that 3x might be off by a factor of 2
or so -- but not the factor of 50 you claimed.)

Don's "-D64" results, while *not* a useful gcc-vs-ghc comparison, are
relevant if really determined Haskellers are interested in learning how to
obtain the absolute optimal perfection from their code.  Don's results *are*
useful, but not in the way you say we're claiming.

Louis Wasserman
wasserman.louis at gmail.com


On Sat, Feb 21, 2009 at 5:35 PM, Bulat Ziganshin
<bulat.ziganshin at gmail.com>wrote:

> Hello Louis,
>
> Sunday, February 22, 2009, 2:30:23 AM, you wrote:
>
> yes, you are right. Don also compared results of 64x-reduced
> computation with full one. are you think that these results are more
> fair?
>
> > Observation:
>
> > The best gcc result shown in the thread, if I recall, precomputed
> > the result of the full computation at compiletime and simply
> > outputted it, when we looked at the assembly.
>
> > While I will accept that this could be seen as an optimization GHC
> > should have made, I do not accept that this will be the case with
> > most everyday code a programmer writes, as most code is not used to
> > simply compute arithmetic constants.
> >
> > For code that actively requires computation at runtime, I have seen
> > no examples of an instance where well-optimized GHC is actually
> > dozens or hundreds of times slower than GCC output.
>
> > Louis Wasserman
> >  wasserman.louis at gmail.com
> >
>
>
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