[Haskell-cafe] Why does this program eat RAM?
lennart at augustsson.net
Mon Sep 4 23:39:02 EDT 2006
The x+1 looks suspicious.
On Sep 4, 2006, at 23:03 , John Goerzen wrote:
> I have the below program, and I'm trying to run it on an input of
> 90MB. It eats RAM like crazy, and I can't figure out why.
> I do know that the problem is not my custwords function (as you can
> I replaced the call to it with a call to the standard words
> function on
> the last line). It seems to be wordfreq, but I don't know why.
> For information about the problem, see
> Here's the code:
> import System.Environment
> import Data.List
> import Data.Char
> import qualified Data.Map as Map
> custwords = filter (/= "") . lines . map (conv . toLower)
> where iswordchar x = isAlphaNum x && isAscii x
> conv x = if iswordchar x then x else '\n'
> wordfreq inp = Map.toList $ foldl' updatemap (Map.empty::Map.Map
> String Int) inp
> where updatemap nm word = Map.insertWith updatefunc word 1 nm
> updatefunc _ x = x + 1
> freqsort (w1, c1) (w2, c2) = if c1 == c2
> then compare w1 w2
> else compare c2 c1
> showit (word, count) = show count ++ " " ++ word
> main = do args <- getArgs
> interact $ unlines . map showit . take (read . head $
> args) .
> sortBy freqsort . wordfreq . words
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