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

[Branimir Maksimovic]

>From: Cale Gibbard <cgibbard at gmail.com>
>To: Branimir Maksimovic <bmaxa at hotmail.com>
>CC: haskell-cafe at 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 <bmaxa at hotmail.com> 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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