2008/12/7 S. Günther

Hi,

I have a small problem with System.Random.randoms. I need a rather large number of random numbers but the following program consumes a huge amount of memory. I terminated it when it used up more than 2 Gb:

module Main where

import System.Random

n :: Int n = maxBound

main = do g <- getStdGen print $ length $ take n $ ((randoms g)::[Int])

I think the problem is that the list spine is being forced, but not the elements, so the generator is becoming a rather massive thunk. This is peculiar to your benchmark, and would probably not occur in practice when you are actually using the random numbers. Try: strictTake 0 _ = [] strictTake n [] = [] strictTake n (x:xs) = x `seq` (x : strictTake (n-1) xs) And use that instead of take. Again, this strictTake is probably not necessary in your actual application, it's just to fix your benchmark. Luke

On the other hand using take n $ [1..] it runs in constant space. Am I doing something wrong? Or should I just abandon randoms and use the more primitive functions in System.Random?

Thanks in advance S. Günther

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