hughperkins:
Sebastian, Why would I write a slow, complicated algorithm in C#? I'm not making these comparisons for some academic paper, I'm trying to get a feel for how the languages run in practice. And really in practice, I'm never going to write a prime algorithm using merge and so on, I'd just use the original naive Haskell algorithm, that runs 500 times slower (at least) than my naive C# algo. I'm just allowing you guys to optimize to see how close you can get. Note that the C# algo is not something created by C# experts, it's just something I hacked together in like 2 minutes.
For fast, mutable prime sieves, see the shootout: http://shootout.alioth.debian.org/gp4/benchmark.php?test=nsievebits&lang=ghc&id=4 (a bit sieve) is pretty fast, 1.8x highly optimised C, and also readable, for what it does: import Data.Array.IO import Data.Array.Base import System import Text.Printf main = do n <- getArgs >>= readIO . head :: IO Int mapM_ (sieve . (10000 *) . (2 ^)) [n, n-1, n-2] sieve n = do a <- newArray (2,n) True :: IO (IOUArray Int Bool) -- an array of Bool r <- go a n 2 0 printf "Primes up to %8d %8d\n" (n::Int) (r::Int) :: IO () go !a !m !n !c | n == m = return c | otherwise = do e <- unsafeRead a n if e then let loop !j | j <= m = unsafeWrite a j False >> loop (j+n) | otherwise = go a m (n+1) (c+1) in loop (n+n) else go a m (n+1) c So perhaps just code up a mutable array version the same as for C# ? -- Don