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

13 Sep 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 ?

    Regards
--------------
-- Mudules :
import Data.Array.IO
import Foreign ( unsafePerformIO )
-- Codes :
p070_solve = putStrLn . show $ solutionOf 10000000
  where
    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
      where
        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
--------------
L.Guo
2007-09-14