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

Louis Wasserman wasserman.louis at gmail.com
Sat Feb 21 18:30:23 EST 2009


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

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

> Hello Louis,
> Saturday, February 21, 2009, 4:16:10 AM, you wrote:
> > In the meantime, a brief summary:
> a minor correction: the best gcc result shown in the thread was 50x
> faster than Don's one, so you need to miltiple all ratios by a factor
> of 50
> > Straightforward and simple Haskell code, written by an individual
> > aware of issues with tail recursion and stream fusion, is frequently
> > within 3x the speed of GCC code when compiled with appropriate
> > optimizations in GHC.
> yes, within 150x margin
> > When performance is an absolute necessity,
> > Haskell code can sometimes be manually modified (e.g. with manual
> > loop unrolls) to equal GCC in performance.
> yes, to make it only 50x slower while being only 7 times larger (i
> mean source lines)
> > Can we move on?
> yes, we can! :)
> --
> Best regards,
>  Bulat                            mailto:Bulat.Ziganshin at gmail.com
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