2006/1/3, Chris Kuklewicz
And finially, the haskel entry for http://shootout.alioth.debian.org/benchmark.php?test=fannkuch&lang=all is currently the *slowest* entry out of 28 languages. It is 813x slower than the c-code, 500x slower than OCaml. Should be easy to make it faster...
In this particular case the flop function is very slow. flop :: Int8 -> [Int8] -> Int8 flop acc (1:xs) = acc flop acc list@(x:xs) = flop (acc+1) mangle where mangle = (reverse front) ++ back (front,back) = splitAt (fromIntegral x) list It can be optimized using a new mangle function: mangle :: Int -> [a] -> [a] mangle m xs = xs' where (rs,xs') = splitAt m xs rs splitAt :: Int -> [a] -> [a] -> ([a], [a]) splitAt 0 xs ys = (xs,ys) splitAt _ [] ys = ([],ys) splitAt m (x:xs) ys = splitAt (m - 1) xs (x:ys) The mangle function transforms the list in one step while the original implementation is using reverse, (++) and splitAt. With this function the new flop is: flop :: Int8 -> [Int8] -> Int8 flop acc (1:xs) = acc flop acc list@(x:xs) = flop (acc+1) (mangle (fromIntegral x) list)