[Haskell-cafe] Toy compression algorithms [was: A very
andrewcoppin at btinternet.com
Sun Jul 8 11:12:38 EDT 2007
Stefan O'Rear wrote:
> On Sun, Jul 08, 2007 at 12:10:04PM +0100, Andrew Coppin wrote:
>> (Realistically though. My program takes a [Word8] and turns it into a
>> [Bool] before running a parser over it. The GHC optimiser doesn't really
>> stand a hope in hell of optimising that into a program that reads a machine
>> word into a CPU register and starts playing with bit flips on it...)
> Actually, if you're very lucky (fusion is just as hard in Haskell as it
> is in real life), it *does*. It seems to fit nicely into the
> stream-fusion framework.
Ooo... really? That's pretty impressive...(!)
Is there a way I can check? ;-) More usefully, can I do stuff to my code
to make myself more "lucky"?
(Love the comment about RL BTW!)
>> PS. Are those zlib libraries actually written in Haskell? Or are they a
>> thin layer on top of a C library?
> Yup, they wrap C's zlib.
Thought so. Comparing native Haskell to a heavily optimised C library
would surely be just like comparing native Haskell to a compiled C binary...
>> PPS. Does GHC make use of MMX, SSE, et al?
> No (in spirit - the native code generator uses 1-element SSE operations
> for floating point because it's easier to optimize than "FPU" code).
Does GHC actually do anything that could usefully use these primitives?
(I'm guessing "no"...)
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