#3039: strange space usage
---------------------------------------+------------------------------------
Reporter: igloo | Owner:
Type: run-time performance bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.10.1
Severity: normal | Keywords:
Difficulty: Unknown | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
---------------------------------------+------------------------------------
This program:
{{{
module Main (main) where
import System.IO.Unsafe
main :: IO ()
main = do writeFile "wibbleflibble" (replicate 100 'z')
bs <- getCs $ g $ replicate 1000000 "flibble"
print $ last bs
getCs :: [FilePath] -> IO String
getCs [] = return ""
getCs (c : cs) = do x <- readFile c
xs <- unsafeInterleaveIO $ getCs cs
return (x ++ xs)
g :: [FilePath] -> [FilePath]
g is = map f is
f :: FilePath -> FilePath
f fn = "wibble" ++ fn
}}}
when run:
{{{
$ ghc -fforce-recomp -Wall --make -O2 -prof -auto-all z.hs -o z
$ ./z +RTS -h -p
}}}
shows that around 100k is used by `f` (`h.png`). Running with
{{{
$ ./z +RTS -hcf -hy -p
}}}
shows that it is all of type `[]` (`hcf_hy.png`). That seems like a large
amount of space for a 13 character filename, so it smells to me like
something is wrong somewhere.
If we inline `g`:
{{{
module Main (main) where
import System.IO.Unsafe
main :: IO ()
main = do writeFile "wibbleflibble" (replicate 100 'z')
bs <- getCs $ map f $ replicate 1000000 "flibble"
print $ last bs
getCs :: [FilePath] -> IO String
getCs [] = return ""
getCs (c : cs) = do x <- readFile c
xs <- unsafeInterleaveIO $ getCs cs
return (x ++ xs)
f :: FilePath -> FilePath
f fn = "wibble" ++ fn
}}}
then it all disappears (`h2.png`).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3039>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
