[Haskell-cafe] Memory leak or wrong use of Array ?

L.Guo leaveye.guo at gmail.com
Thu Sep 13 12:19:34 EDT 2007

Hi MailList Haskell-Cafe:

I am tring to solve Project Euler problem 70.
And write some code. (will at the end of this mail)
And, I run the code in GHCi.

The problem is that, when the input is 1,000,000, it works 
fine, when the input is up to 10,000,000, the memory GHCi 
used increase very fast and did not stop.

Is this a memory leak ? or, is there some mis-understand 
about array ?
-- Mudules :
import Data.Array.IO
import Foreign ( unsafePerformIO )
-- Codes :
p070_solve = putStrLn . show $ solutionOf 10000000
    isPerm a b = sort (show a) == sort (show b)
    phis n = unsafePerformIO $ do
        arr <- newArray (2,n) (False,1/1) :: Fractional t => IO (IOArray Int (Bool,t))
        mapM_ (sieve arr n) [2..n]
        factors <- getElems arr
        return . map (\(n,(b,f)) -> (n,floor $ toRational n*f)) $ zip [2..n] factors
        sieve arr ubound p = do
            (b,o) <- readArray arr p
            if b then return () else
              mapM_ (update arr (toRational p)) . takeWhile (<=ubound) $ iterate (+p) p
        update arr p i = do
            (_,o) <- readArray arr i
            writeArray arr i (True,o*(p-1)/p)
    solutionOf = snd . minimum
               . map (\(n,phi)->(toRational n / toRational phi,n))
               . filter (uncurry isPerm) . phis

More information about the Haskell-Cafe mailing list