[Haskell-cafe] Optimizing a hash function

[Ivan Tomac]

Hi,

Yesterday evening I had a go at porting Bob Jenkins' hash function  
(http://www.burtleburtle.net/bob/c/lookup3.c) to Haskell.

The first version I came up with ran 20 times slower than C.
Thanks to Don Stewart's suggestions on IRC, I managed to improve the  
performance by replacing tuples with a strict type so the current  
version is about 10 times slower than C code.
Is there any way this can be further optimized?

To keep things fair I've simplified the C function so it works on one  
byte at a time as opposed to an int at a time.
The code was compiled with GHC-6.6 on a G5 iMac running OS X 10.4.

Options used to compile the version using the hash function written  
in Haskell:
ghc -O -funbox-strict-fields -fglasgow-exts -fbang-patterns -cpp -o  
test hashByteString.hs test.hs

Options used to compile the version using the hash function in C:
ghc -O -fglasgow-exts -ffi -fbang-patterns -cpp -DCHASH -o ctest  
ctest.c test.hs


Ivan Tomac

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