[Haskell-cafe] benchmarking c/c++ and haskell

Hi, I would like to benchmark C/C++ and Haskell code. The goal is to improve the Haskell port[0] of smallpt[1]. To make sure my approach was reliable, I got the code of two programs (one in C, the other in Haskell) from a post[2] by Don. The code is reproduced below. When timing the execution of both program, I have a

4x difference. It is said on the blog the programs should have similar performance.

I simply don't get the reason of such a difference. I've tried the code on my Atom netbook and also on an older centrino machine. The timing are similar (i.e. the C and Haskell program show >4x difference). Both machines have GHC 6.12.1 on Linux. Would you have an idea? [0] http://hackage.haskell.org/package/smallpt-hs [1] http://www.kevinbeason.com/smallpt/ [2] http://donsbot.wordpress.com/2008/06/04/haskell-as-fast-as-c-working-at-a-hi... $ gcc -O2 mean.c -omean-c $ ghc --make -O2 mean.hs -o mean-hs $ time ./mean-c 1e8 50000000.500000 real 0m1.575s user 0m1.513s sys 0m0.000s $ time ./mean-hs 1e8 50000000.5 real 0m6.997s user 0m6.856s sys 0m0.013s -- file mean.hs module Main where import System.Environment import Text.Printf mean :: Double -> Double -> Double mean n m = go 0 0 n where go :: Double -> Int -> Double -> Double go s l x | x > m = s / fromIntegral l | otherwise = go (s+x) (l+1) (x+1) main = do [d] <- map read `fmap` getArgs printf "%f\n" (mean 1 d) /* file mean.c */ #include #include int main (int argc, char **argv) { double d = atof(argv[1]); double n; long a; double b; for (n = 1, a = 0, b = 0; n <= d; b+=n, n++, a++) ; printf("%f\n", b / a); return 0; }