On Fri, Mar 26, 2010 at 10:46 AM, Rafael Cunha de Almeida < almeidaraf@gmail.com> wrote:
Hello,
During a talk with a friend I came up with two programs, one written in C and another in haskell.
Haskell main :: IO () main = print $ rangeI 0 0
rangeK :: Int -> Int -> Int -> Int -> Int rangeK i j k acc | k < 1000 = if i * i + j * j + k * k `mod` 7 == 0 then rangeK i j (k+1) (acc+1) else rangeK i j (k+1) acc | otherwise = acc
rangeJ :: Int -> Int -> Int -> Int rangeJ i j acc | j < 1000 = rangeJ i (j+1) (acc + rangeK i j 0 0) | otherwise = acc
rangeI :: Int -> Int -> Int rangeI i acc | i < 1000 = rangeI (i+1) (acc + (rangeJ i 0 0)) | otherwise = acc
You might try using bang patterns. It's possible that GHC didn't detect the strictness. Only way I know to check is to look at the core. Use something like ghc-core from Hackage to view it. Ideally the core is using Int# instead of Int and avoiding lots of boxing.
I compiled the haskell code with ghc -O3 and I compiled the C code with gcc -O3. The execution time of the programs were dramatically different. You can test it yourselves, but here is the time I've got in my system:
You might try -Odph . See http://book.realworldhaskell.org/read/profiling-and-optimization.htmlfor more ideas. Jason