[Haskell-cafe] Are there performant mutable Arrays in Haskell?
Brettschneider at hs-albsig.de
Thu Mar 19 07:16:30 EDT 2009
I am trying to write a hash-algorithm that in fact is working, but as you might have guessed the problem is the performance :) At the moment I am 40 times worse than the same implementation in C.
My problem is, I need mutable arrays which are the heart of that hash.
The algorithm is round-based and within each round I need the value of certain positions in that array.
At the moment I work with an unboxed ST-Array at the crucial part
--- snip ---
test list = runSTUArray $ do
a_arr <- newListArray (0, 1752) list
let round i = do
ain <- readArray a_arr (i-n)
at0 <- readArray a_arr (i-t0)
at1 <- readArray a_arr (i-t1)
at2 <- readArray a_arr (i-t2)
at3 <- readArray a_arr (i-t3)
at4 <- readArray a_arr (i-t4)
let li = ls $ (i - n) mod 16
ri = rs $ (i - n) mod 16
writeArray a_arr i $ (step4 li)
. (step3 ri)
. (step2 at1 at2 at3 at4)
$ (step1 ain at0 i)
mapM_ round [n..(n+t-1)]
--- snap ---
I also played around with peekElemOff and pokeElemOff, but this isn't much faster.
It took ~30sec with my Haskell-Code while the C-implementation need only ~1sec.
Is there someone who may have some hints for me, what I can do better, or just
lead me in the right direction? :)
Thanks a lot in advance
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