Re: [Haskell-cafe] Differences in optimisiation with interactive and compiled mo

From: Cale Gibbard To: Branimir Maksimovic CC: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Differences in optimisiation with interactive and compiled mode Date: Thu, 8 Dec 2005 09:26:11 -0500

GHCi does things with optimisations off. Note the line on startup which says: Compiling Main ( search.hs, interpreted ) You'll have better luck if you compile the code with optimisations and keep the .o files around when running the program in ghci -- it will notice the compiled copies and load those instead. You'll see something like: Skipping Main ( search.hs, search.o )

This is good thing, thanks for noticing me about it. But something else bothers me. Perhaps I've missed some flag for ghci, but for stand alone executable I get low memory consumption (about 2mb), no matter optimised or not, except that non optimised version runs about three times slower. When running from ghci and invoking main function interactivelly, I get more then 400mb of ram used with optimisations and just 20mb without. So there must be something different in run time system as standalone executable use just 2mb of ram which is excellent performance, but in ghci non optimised version performs better and actually consume much less memory then optimised one.

Also note that your 'infinite' function is in the prelude. It's called 'cycle'.

Thanks. I will use it from now on. Greetings, Bane.

- Cale

On 08/12/05, Branimir Maksimovic wrote:

...

It seems that compiled programs run better then interactive ones. Following program with GHC works with pretty good performance in comparison to C++ one with similar but non recursive algorithm and beats it in memory consumtion. It only takes about 2mb of ram somehow when running compiled. I'm really amased. But in interactive mode both GHC and Hugs fail due heap exhaustion and running takes ages.Please can someone explain why? I intent to use only compiled Haskell anyway so GHC satisfies.

Greetings, Bane.

program performs search replace on a String

module Main where import IO main = do hSetBuffering stdout LineBuffering let sr = "search" rp = "replace" str= " able search sea baker search charlie \"" out = searchr sr rp (take (1000000*(length str)) $ infinite str) out1 = searchr sr rp (take (1000001*(length str)) $ infinite str) putStrLn $ "Working:" ++ sr ++ " " ++ rp ++ " " ++ str putStrLn $ (show (out == out1)) ++ "\n" ++ "\nDone\n" {- search replace " able search baker search charlie " -}

-------------------------------------------------------------------------------

...

infinite xs = xs ++ infinite xs

searchr :: String->String->String -> String searchr [] _ xs = xs searchr _ [] xs = xs searchr _ _ [] = [] searchr sr rp xs | fst fnd = rp ++ searchr sr rp (snd $ snd fnd) | otherwise = (reverse $ fst $ snd fnd) ++ searchr sr rp (snd $ snd fnd) where fnd = searchr' sr xs ""

searchr' :: String->String->String -> (Bool,(String,String)) searchr' (sr:srs) xs fndSoFar = searchr'' (sr:srs) xs fndSoFar sr

searchr'' :: String->String->String->Char -> (Bool,(String,String)) searchr'' [] xs fnd _ = (True,(fnd,xs)) searchr'' _ [] fnd _ = (False,(fnd,[])) searchr'' (sr:srs) (x:xs) fndSoFar s | sr == x = searchr'' srs xs xxs s | otherwise = (False,searchr''' s xs xxs) -- (False,(xxs,xs)) where xxs = x:fndSoFar

searchr''' :: Char->String->String -> (String,String) searchr''' sr [] fndSoFar = (fndSoFar,[]) searchr''' sr (x:xs) fndSoFar | sr /= x = searchr''' sr xs (x:fndSoFar) | otherwise = (fndSoFar,x:xs)

-------------------------------------------------------------------------------

...

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