federico.squartini:
>
> Of course I know that the list version is very unfair, but I
> wanted to see what was the trade off between elegance and
> speed.
> Regarding whether low level programming makes sense or not,
> I was just curious to see what are the limits of Haskell.
> Moreover there is not much literature on high performance
> Haskell programming (tricks like unsafeWrite), at least
> organized in a systematic and concise way.
> My original problem was writing a fast library for simple
> matrix computations (i.e. multiplication and inversion for
> small dense matrices). I have not been able to make
> GSLHaskell work with Lapack so far. :(
> Anyway here are the new versions and timings, I increased
> the number of times the vector is reversed, I also compiled
> everything with -O2.
Probably a good idea to use techniques from Data.ByteString (ie. use
strict Ptr loops, and Foreign arrays), or techniques from the shootout,
if you're chasing C speed. Good examples are:
http://shootout.alioth.debian.org/gp4/benchmark.php?test=nsievebits&lang=ghc&id=4
(mutable bit arrays)
http://shootout.alioth.debian.org/gp4/benchmark.php?test=nsieve&lang=ghc&id=0
(mutable byte (foreign) arrays)
http://shootout.alioth.debian.org/gp4/benchmark.php?test=spectralnorm&lang=ghc&id=4
(more mutable arrays)
When I really really care about speed, I use
Foreign.Marshal.Array
Data.ByteString
and apply ! patterns liberally, checking the Core output for inner
loops. -O2 -optc-O2 -optc-march=pentium4 often helps.
1-4x C is around what you can best hope for. 10x says "still room for
improvement" in my experience.
-- Don
_______________________________________________
Haskell mailing list
Haskell@haskell.org
http://www.haskell.org/mailman/listinfo/haskell
