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

Bulat Ziganshin bulat.ziganshin at gmail.com
Sat Feb 21 19:10:31 EST 2009

Hello Sebastian,

Sunday, February 22, 2009, 2:55:38 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?

> Yes. Clearly so.
> It still computes the result from scratch - it just uses a trick
> which generates better code. This is clearly a useful and worthwhile
> exercise as it shows A) A neat trick with TH, B) A reasonably
> practical way to produce fast code for the critical parts of a
> Haskell app, C) a motivating example for implementing a compiler
> optimization to do it automatically.

yes, but does you know why his last program is 64x faster than simple
code? it's because *gcc* optimize it this way. the first program i
published there does it by mistake, then i fixed it by using 'xor'
instead of (+) and published here that i've considered most fair

OTOH Don used this gcc optimization to generate faster code for
haskell. he doesn't used this trick for C++ and doesn't omitted
unoptimized gcc results from the chart. as a result people who don't
analyzed details made conclusion that ghc outperformed gcc here

so i have made experiment with cheating the same way, but in more
obvious manner. and i got 3 angry answers in 5 minutes. so what are
the difference? you don't catched details of Don comparison or you
bothered only by gcc-related cheating?

Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com

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