Someone else already replied with much information. I figured I'd try to add a small amount.
Basically, to clarify, the problem is that at every character you read, you do something like 'arr // list'. (//) is *not* an O(1) operation as you might expect. In fact, it *copies* the entire array. Why? Because if you later reference the old one, it needs to have a "backup" version. The solution, if you want to use arrays, is basically to use a mutable state array, like IO(U)Array or ST(U)Array. However, you might be better off using a different data structure. An easy solution would be to use a finite map from Data.FiniteMap. You'll incur a little overhead, but then again, the distribution of letters in natural language text is anything but flat; some you will likely never see and you're wasting space in your array for these. Of course, you could use a more informed coding tree based on letter distributions, but this is probably overkill. -- Hal Daume III | [EMAIL PROTECTED] "Arrest this man, he talks in maths." | www.isi.edu/~hdaume > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of mies > Sent: Thursday, June 19, 2003 2:11 AM > To: [EMAIL PROTECTED] > Subject: Array + memory usage > > > Hello, i'm a haskell newbie, and i'm trying to use arrays for > counting > letters. But when I input a textfile of lets say 100KB the > program uses > 75 M of memory, and I really don;t have a clue where the > problem could > be. I have searched many topics here but I didn't find a solution. I > have made an axample of how i am using the array. > > module Main where > > import Array > import IO > > main = do let fr = testUpdater f 100000 > writeFile "test.txt" (show (fr!155)) > > f :: Array Int Int > f = (array (0,255) [(i, 0) | i <- [0..255]]) > > testUpdater :: Array Int Int -> Int -> Array Int Int > testUpdater fr 0 = fr testUpdater fr x = testUpdater > ((fr//[(155, fr!(155) + 1)])) (x - 1) > > updateF :: Array Int Int -> Array Int Int > updateF x = (x//[(155, x!(155) + 1)]) > > Regards, Richard Nieuwenhuis > [EMAIL PROTECTED] > > _______________________________________________ > Haskell mailing list > [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell > _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
