November 2009 - Haskell-Cafe

poor perfomance of indexU in uvector package
by Alexey Khudyakov 16 Nov '09

16 Nov '09

Hello This post meant to be literate haskell. I found that perfomace of indexU is very poor and it is not fast O(1) operation which is very surprising. Here is some benchmarcking I've done. Everything compiled with -O2 Code below converts square 2D array to list of 1D arrays. Summation of array contents is done in force evaluation > import Control.Monad > import Control.Monad.ST > import Data.Array.Vector > import System > > arr :: Int -> UArr Double > arr n = toU $ map fromIntegral [1 .. n*n] > This is fastest function. It slice arrays along another direction and used mainly as upper bound of speed > sliceY :: Int -> UArr Double -> [UArr Double] > sliceY n a = map (\i -> sliceU a (i*n) n) [0 .. n-1] > Naive implementation using lists and index lookup. 2.15 second for 200*200 array > sliceXlist :: Int -> UArr Double -> [UArr Double] > sliceXlist n a = map mkSlice [0 .. n-1] > where > mkSlice x = toU $ map (\y -> indexU a (x + y*n)) [0 .. n-1] Similar implementation in ST monad and it uses indexU too. 2.14 seconds for 200*200 array > sliceXst :: Int -> UArr Double -> [UArr Double] > sliceXst n a = map mkSlice [0 .. n-1] > where > mkSlice x = runST $ do arr <- newMU n > forM_ [0 .. n-1] $ \y -> writeMU arr y (indexU a (y*n + x)) > unsafeFreezeAllMU arr This implementation avoids use of indexU by copying entire 2D array into mutable array and using it for lookup. Surprisingly it outperform previsious implementations for sufficiently big n 1.19 seconds for 200*200 array > sliceXcopy :: Int -> UArr Double -> [UArr Double] > sliceXcopy n a = map mkSlice [0 .. n-1] > where > mkSlice x = runST $ do arr <- newMU n > cp <- newMU (n*n) > copyMU cp 0 a > forM_ [0 .. n-1] $ \y -> writeMU arr y =<< readMU cp (y*n + x) > unsafeFreezeAllMU arr This is another implementation with lists which convert whole array to list and picks appropriate element it. It is fastest implementation so far. 0.039 seconds for 200*200 array > sliceXlistfast :: Int -> UArr Double -> [UArr Double] > sliceXlistfast n a = map mkSlice [0 .. n-1] > where > takeEvery n [] = [] > takeEvery n (x:xs) = x : takeEvery n (drop (n-1) xs) > mkSlice x = toU $ takeEvery n . drop x $ fromU a > > > ---------------------------------------------------------------- > main :: IO () > main = do > [str,a] <- getArgs > let n = read str > case a of > "y" -> print $ sum $ map sumU (sliceY n (arr n)) > "list" -> print $ sum $ map sumU (sliceXlist n (arr n)) > "lf" -> print $ sum $ map sumU (sliceXlistfast n (arr n)) > "st" -> print $ sum $ map sumU (sliceXst n (arr n)) > "copy" -> print $ sum $ map sumU (sliceXcopy n (arr n))

6 8

Opinion about JHC
by Philippos Apolinarius 16 Nov '09

16 Nov '09

I discovered a Haskell compiler that generates very small and fast code. In fact, it beats Clean. It has the following properties: 1 --- One can cross-compile programs easily. For instance, here is how I generated code for Windows: jhc --cross -mwin32 genetic.hs -o genetic 2 -- It seems to be quite complete. 3 -- However, it often compiles a file, but the program fails to run. I have the following questions about it: 1 -- How active is the team who is writing the JHC compiler? 2 -- Is it complete Haskell? The author claims that it is; it compiled all programs that I wrote, but that does not mean much, because my programs are quite simple. 3 -- Why the Haskell community almost never talks about JHC? __________________________________________________________________ The new Internet Explorer® 8 - Faster, safer, easier. Optimized for Yahoo! Get it Now for Free! at http://downloads.yahoo.com/ca/internetexplorer/

14 32

About xmonad
by zaxis 16 Nov '09

16 Nov '09

%uname -a Linux myarch 2.6.31-ARCH #1 SMP PREEMPT Tue Nov 10 19:48:17 CET 2009 i686 AMD Athlon(tm) 64 X2 Dual Core Processor 3600+ AuthenticAMD GNU/Linux %xmonad --version xmonad 0.9 In firefox, the `save as` dialog doesnot appear when i want to choose picture to save by right clicking the mouse. %cat ~/.xmonad/xmonad.hs import XMonad import XMonad.Hooks.ManageDocks import XMonad.Hooks.EwmhDesktops import XMonad.Hooks.DynamicLog import XMonad.Hooks.ManageHelpers import XMonad.Util.Run(spawnPipe) import XMonad.Layout.TwoPane import XMonad.Layout.WindowNavigation import qualified XMonad.StackSet as W import qualified Data.Map as M main = do xmonad $ defaultConfig { borderWidth = 1 , focusedBorderColor = "#ff6666" , normalBorderColor = "#2222aa" , manageHook = manageHook defaultConfig <+> myManageHook , workspaces = map show [1 .. 10 :: Int] , terminal = "roxterm" , modMask = mod4Mask , focusFollowsMouse = True , startupHook = myStartupHook , logHook = myLogHook , layoutHook = windowNavigation $ avoidStruts $ (Mirror tall ||| tall ||| Full) --, layoutHook = ewmhDesktopsLayout $ windowNavigation $ avoidStruts $ (Mirror tall ||| tall ||| Full) , keys = \c -> myKeys c `M.union` keys defaultConfig c --, mouseBindings = \c -> myMouse c `M.union` mouseBindings defaultConfig c } where tall = Tall 1 (3/100) (1/2) myStartupHook :: X () myStartupHook = do { spawn "fcitx"; spawn "roxterm"; spawn "lxpanel"; spawn "/home/sw2wolf/bin/kvm.sh"; } myLogHook :: X () myLogHook = ewmhDesktopsLogHook myManageHook :: ManageHook myManageHook = composeAll . concat $ [ [ className =? c --> doFloat | c <- myCFloats] ,[ resource =? r --> doFloat | r <- myRFloats] ,[ title =? t --> doFloat | t <- myTFloats] ,[ className =? c --> doIgnore | c <- ignores] ,[ className =? "Audacious" --> doShift "3" ] ,[ className =? "Firefox" --> doF W.swapDown] ,[(role =? "gimp-toolbox" <||> role =? "gimp-image-window") --> (ask >>= doF . W.sink)]] where myCFloats = ["Thunderbird-bin", "GQview", "MPlayer", "Gimp","Vncviewer","Xmessage"] myRFloats = ["Dialog", "Download", "Places"] myTFloats = ["Firefox Preferences", "Element Properties"] ignores = ["trayer"] role = stringProperty "WM_WINDOW_ROLE" myKeys (XConfig {modMask = modm}) = M.fromList $ -- Apps and tools [ ((modm, xK_F2), spawn "gmrun") , ((modm, xK_f), spawn "/home/firefox/firefox") , ((modm, xK_t), spawn "thunderbird") --, ((modm, xK_p), spawn "exe=`dmenu_path | dmenu -b` && eval \"exec $exe\"") , ((modm, xK_F11), spawn "sudo shutdown -r now") , ((modm, xK_F12), spawn "sudo shutdown -h now") , ((modm .|. controlMask, xK_Print), spawn "sleep 0.2; scrot -s") , ((modm, xK_Print), spawn "scrot '/tmp/%Y-%m-%d_%H:%M:%S_$wx$h_scrot.png' -e 'mv $f ~'") , ((modm, xK_c), kill) -- Window Navigation , ((modm, xK_Right), sendMessage $ Go R) , ((modm, xK_Left ), sendMessage $ Go L) , ((modm, xK_Up ), sendMessage $ Go U) , ((modm, xK_Down ), sendMessage $ Go D) -- swap... , ((modm .|. controlMask, xK_Right), sendMessage $ Swap R) , ((modm .|. controlMask, xK_Left ), sendMessage $ Swap L) , ((modm .|. controlMask, xK_Up ), sendMessage $ Swap U) , ((modm .|. controlMask, xK_Down ), sendMessage $ Swap D) ] ----- fac n = foldr (*) 1 [1..n] -- View this message in context: http://old.nabble.com/About-xmonad-tp26367498p26367498.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

2 2

Strange parallel behaviour with Ubuntu Karmic / GHC 6.10.4
by Michael Lesniak 16 Nov '09

16 Nov '09

Hello, I'm currently developing some applications with explicit threading using forkIO and have strange behaviour on my freshly installed Ubuntu Karmic 9.10 (Kernel 2.6.31-14 SMP). Setup: Machine A: Quadcore, Ubuntu 9.04, Kernel 2.6.28-13 SMP Machine B: AMD Opteron 875, 8 cores, 2.6.18-164 SMP- (some redhat) Machine C: Dual-Core, Ubuntu 9.10, Kernel 2.6.31-14 SMP Compiler on all machines: ghc 6.10.4 (downloaded from GHCs official website) Program, Compilation, Execution A simple taskqueue with independent tasks and explicit parallelization (hence should deliver more or less perfect speedup). For one core wall-times around 16 are ok, for 2 a bit more than 8 seconds. Since I used the same sources and Makefiles on all machines all files were compiled with -threaded and started with +RTS -N2 -RTS. Testing: Machine A: Ok (meaning works and delivers the expected speedup) Machine B: Ok Machine C: Not ok (with -N2 wall times around 14-15 seconds) Looking at the core usage, for example with htop, I see that the second core is not really used on C. Executing OpenMP programs shows the expected speedup and usage of both cores, hence I do not think its a kind of general linux configuration problem. So, after all the testing I think its either the Linux Kernel or some other component of Ubuntu 9.10. But: Ubuntu is often used and I did not found any information regarding this problem. The simple solution of installing the old version of Ubuntu would probably help but should not be the way to go, should it? I'd be glad for any hints or comments, Michael -- Dipl.-Inf. Michael C. Lesniak University of Kassel Programming Languages / Methodologies Research Group Department of Computer Science and Electrical Engineering Wilhelmshöher Allee 73 34121 Kassel Phone: +49-(0)561-804-6269

2 5

How to update SSH key in code.haskell.org
by Andy Stewart 16 Nov '09

16 Nov '09

Hi all. I'm a developer of gtk2hs project at code.haskell.org But i found i lost my SSH key when i update new system, and i can't push patch to gtk2hs. I have send mail to support(a)community.haskell.org for this problem, but i'm not sure that's the right place. So how to update SSH key with my account (AndyStewart) ? Thanks, -- Andy

1 0

Logistic regression
by Colin Paul Adams 16 Nov '09

16 Nov '09

Is there any free code anywhere for performing logistic regression? I can't see anything on hackage. -- Colin Adams Preston Lancashire

1 0

What does the `forall` mean ?
by zaxis 16 Nov '09

16 Nov '09

import Text.ParserCombinators.Parsec data PermParser tok st a = Perm (Maybe a) [Branch tok st a] data Branch tok st a = forall b. Branch (PermParser tok st (b -> a)) (GenParser tok st b) I have hoogled the `forall` but i cannot find any appropriate answer! thanks! ----- fac n = foldr (*) 1 [1..n] -- View this message in context: http://old.nabble.com/What-does-the-%60forall%60-mean---tp26311291p26311291… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

14 20

Why can `env` be assigned value two times ?
by zaxis 16 Nov '09

16 Nov '09

defineVar :: Env -> (Id, Val) -> IOThrowsError Val defineVar envRef (id, val) = do { env <- liftIO $ readIORef envRef; env <- return $ filter (\(_id, _) -> _id/=id) env; -- clear the current scope valRef <- liftIO $ newIORef val; liftIO $ writeIORef envRef $ ((id, valRef):env); return val; } In haskell, the variable canot change its value , right? If so, why can the `env` be assigned value twice? Sincerely! ----- fac n = foldr (*) 1 [1..n] -- View this message in context: http://old.nabble.com/Why-can-%60env%60-be-assigned-value-two-times---tp263… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

3 3

attoparsec and parsec
by Manlio Perillo 16 Nov '09

16 Nov '09

Hi. I'm writing a generic log parsing package, and I'm serching a parser combinators library. Parsing log files is a simple task, so I would like to use the more efficient solution. I have looked at attoparsec source code, and it seems very specialized for lazy bytestrings parsing, so I assume it is very efficient. How stable is the attoparsec package? How much more efficient is attoparsec than standard packages like parsec? By the way: there seem to be problems with generated documentation in http://hackage.haskell.org/package/attoparsec. Moreover, there is a similar package: http://hackage.haskell.org/package/bytestringparser what is the status of this package? It has the same API of attoparsec, but its older. However there is no indication that this package is deprecated in favor of attoparsec. Thanks Manlio Perillo

2 3

slightly off-topic
by Günther Schmidt 15 Nov '09

15 Nov '09

1 0