- Haskell-Cafe - Haskell.org

RE: [Haskell-cafe] Re: Bring down the house (was Re: GHC cannot compilemy code)
by Simon Peyton-Jones 16 Nov '05

16 Nov '05

I've fixed the HEAD so that it behaves decently on this now. Thanks for reporting it. It's in the test suite! S | -----Original Message----- | From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Joel | Reymont | Sent: 09 November 2005 19:27 | To: Haskell Cafe | Subject: [Haskell-cafe] Re: Bring down the house (was Re: GHC cannot compilemy code) | | Shae (#haskell) figured out that this is called for and that GHC has | trouble deriving for large tuples. I have no idea what type of a | performance hit this is gonna be but I hope it's resolved at compile- | time and there's no impact afterwards. | | type TableInfo = TableInfo1 :*: TableInfo2 | | type TableInfo1 = | AvgPot :*: | NumPlayers :*: | Waiting :*: | PlayersFlop :*: | TableName :*: | TableID :*: | GameType :*: | InfoMaxPlayers :*: | RealMoneyTable :*: | LowBet :*: | HighBet :*: | HNil | | type TableInfo2 = | MinStartMoney :*: | MaxStartMoney :*: | GamesPerHour :*: | TourType :*: | TourID :*: | BetType :*: | CantReturnLess :*: | AffiliateID :*: | NIsResurrecting :*: | MinutesForTimeout :*: | SeatsToResurrect :*: | LangID :*: | HNil | | Thanks, Joel | | -- | http://wagerlabs.com/ | | | | | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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RE: [Haskell-cafe] GHC ignores RTS options
by Simon Marlow 16 Nov '05

16 Nov '05

On 16 November 2005 08:12, Tomasz Zielonka wrote: > On Wed, Nov 16, 2005 at 08:53:18AM +0100, Dusan Kolar wrote: >> I wonder whether anybody could advise me how to pass >> correctly RTS options to ghc? I've tried > > You have to pass these options to the program, not > to GHC. > > BTW - it would be nice if it was easier to override the default RTS > options when compiling the program. Perhaps a nice task for a newbie > GHC developer? Already possible, see: http://www.haskell.org/ghc/docs/latest/html/users_guide/runtime-control. html#rts-hooks Admittedly it's a bit more fiddly than a command-line flag to GHC, though. Cheers, Simon

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Re: [Haskell-cafe] waitForProcess: sytem call interrupted
by Joel Reymont 16 Nov '05

16 Nov '05

I think runhaskell reports that when the program has crashed violently with a segmentation violation. On Nov 16, 2005, at 1:54 AM, Donald Bruce Stewart wrote: > I've been getting this in lambdabot with waitForProcess since 6.4.1 (I > think). Seems harmless though (I think). Try catching the exception. > > Control.Exception.catch (waitForProcess pid) > (\_ -> return ExitSuccess) -- so just > fake success -- http://wagerlabs.com/

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Re: [Haskell-cafe] waitForProcess: sytem call interrupted
by Joel Reymont 16 Nov '05

16 Nov '05

The thing is that I'm launching threads, not processes. The message is printed by runhaskell now that I think about it. On Nov 16, 2005, at 1:54 AM, Donald Bruce Stewart wrote: > I've been getting this in lambdabot with waitForProcess since 6.4.1 (I > think). Seems harmless though (I think). Try catching the exception. > > Control.Exception.catch (waitForProcess pid) > (\_ -> return ExitSuccess) -- so just > fake success -- http://wagerlabs.com/

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doc/html -> wiki -> xml
by Bulat Ziganshin 16 Nov '05

16 Nov '05

Hello Haskellers, i'm now write documention about Template Haskell in MS Word. when it will be written, i will be glad to publish it in Wiki, so anyone can correct it. and when all be done, it will be great to automatically convert this wiki text to DocBook XML for inserting in GHC documentation can anyone say me about tools/scripts which can be used to do this? or share your ideas - how can i write scripts to do it? -- Best regards, Bulat mailto:bulatz@HotPOP.com

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GHC ignores RTS options
by Dusan Kolar 16 Nov '05

16 Nov '05

Hello, I wonder whether anybody could advise me how to pass correctly RTS options to ghc? I've tried ghc +RTS -K4M --RTS -O program.hs -o aO.out ghc +RTS -K4M -RTS -O program.hs -o aO.out ghc -O program.hs -o aO.out +RTS -K4M ghc -O program.hs +RTS -K4M --RTS -o aO.out and many others, with other sizes (10M, 12M), but program always(!) stops with: Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize' to increase it. Even time of execution is always the same and thus the RTS option on stack size is ignored. What can I do so that the option IS taken into account? My GHC version says: ghc --version The Glorious Glasgow Haskell Compilation System, version 6.4.1 Thanks & regards Dusan

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waitForProcess: sytem call interrupted
by Joel Reymont 16 Nov '05

16 Nov '05

Folks, My program frequently quites (I think) after this message: waitForProcess: sytem call interrupted I think it has to do with my killing the thread that calls connectTo, after a certain timeout. Is there a way to catch this exception so that the program does not crash? My code looks like this: connect :: HostName -> Int -> EngineState () connect host port = do w <- get let secs = timeout_seconds w x <- liftIOTrap $ timeout secs $ connect_ host port let h = case x of (Right x') -> x' trace "Connection established" ... timeout :: forall a.Show a => Int -> IO a -> IO (Either String a) timeout secs fun = do resultVar <- newEmptyMVar threadId <- forkIO $ do result <- try fun let x = case result of Right a -> Right a Left b -> Left (fromIOError b) trace_ $ "timeout: " ++ show x putMVar resultVar x forkIO $ do threadDelay (secs * 1000000) putMVar resultVar (Left "Timeout") maybeResult <- takeMVar resultVar case maybeResult of (Right result) -> return (Right result) (Left result) -> do killThread threadId return (Left result) and fromIOError err = ioeGetErrorString err liftIOTrap :: IO a -> EngineState a liftIOTrap io = do mx <- liftIO (do x <- io return (return x) `catchError` (\e -> return (throwError (fromIOError e)))) mx Thanks, Joel -- http://wagerlabs.com/

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RE: [Haskell-cafe] Re: Bring down the house (was Re: GHC cannot compilemy code)
by Simon Peyton-Jones 15 Nov '05

15 Nov '05

Turns out this is to do with the way that type synonyms are represented. Somewhere there is type a :*: b = HCons a b If you simply use HCons instead of :*: the problem goes away. (Use `HCons` if you want it infix.) This is a bug; using HCons instead is a workaround, but it might reduce your compilation times. Meanwhile I'll look into fixing it. Simoin | -----Original Message----- | From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Joel | Reymont | Sent: 09 November 2005 19:27 | To: Haskell Cafe | Subject: [Haskell-cafe] Re: Bring down the house (was Re: GHC cannot compilemy code) | | Shae (#haskell) figured out that this is called for and that GHC has | trouble deriving for large tuples. I have no idea what type of a | performance hit this is gonna be but I hope it's resolved at compile- | time and there's no impact afterwards. | | type TableInfo = TableInfo1 :*: TableInfo2 | | type TableInfo1 = | AvgPot :*: | NumPlayers :*: | Waiting :*: | PlayersFlop :*: | TableName :*: | TableID :*: | GameType :*: | InfoMaxPlayers :*: | RealMoneyTable :*: | LowBet :*: | HighBet :*: | HNil | | type TableInfo2 = | MinStartMoney :*: | MaxStartMoney :*: | GamesPerHour :*: | TourType :*: | TourID :*: | BetType :*: | CantReturnLess :*: | AffiliateID :*: | NIsResurrecting :*: | MinutesForTimeout :*: | SeatsToResurrect :*: | LangID :*: | HNil | | Thanks, Joel | | -- | http://wagerlabs.com/ | | | | | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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Download binary file
by Jorge Guerra 15 Nov '05

15 Nov '05

Hi everyone, I'm trying to download a binary file (an mp3) from a given URL, at the moment I've found two possible solutions: 1) Use the Network.Socket library from ghc to get the file. The problem with this is that I'll have to deal with the HTTP protocol (done), and read the Handle in binary mode however I don't understand how to do this, in particular how to deal with the buffer (Prt?). 2) Use a system program like wget in linux systems. But I don't know how to call a system command from haskell, and besides I wan't my program to be portable at least between windows and linux. Any sugestions? Sorry for my newbie question. Thanks. -- Jorge E. Guerra D. Departamento de Computación y Tecnología de la Información Universidad Simón Bolívar

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Re: [Haskell-cafe] Two questions: lazy evaluation and Church-Rosser
by Ezra Cooper 15 Nov '05

15 Nov '05

Gregory, Church-Rosser is proved in any good text on lambda calculus, such as Barendregt [1]. Some rather detailed notes on that book are at [2]. Lazy evaluation is often formalized as "call-by-need." Try [3]. Ezra [1] Barendregt. The Lambda Calculus <http://www.amazon.com/exec/obidos/ASIN/0444875085> [2] <http://www.andrew.cmu.edu/user/cebrown/notes/barendregt.html> [3] Maraist, Odersky, and Wadler, "A call-by-need lambda-calculus." Journal of Functional Programming 8(3):275-317 (May 1998). <http://homepages.inf.ed.ac.uk/wadler/topics/call-by-need.html> On Nov 15, 2005, at 5:30 AM, Gregory Woodhouse wrote: > This is surely a dumb question, but where can I find a proof of the > Church-Rosser theorem? > > Now, a totally(?) separate question: I've been trying to do some > background reading on lambda calculus, and have found discussions of > strict evaluation strategies (call-by-value and call-by-name) but > have yet to find an appropriate framework for modeling lazy evaluation > (much less infinite lists and comprehensions). Can anyone point me in > the right direction?

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Semantics for FP?
by Gregory Woodhouse 15 Nov '05

15 Nov '05

First of all, I'm very new to Haskell (but very impressed). I remember having a lot of fun with Lisp as an undergrad, and recently started working with Scheme (and having a great time at it), and so I decided to look into Haskell. Like everyone else, I was totally impressed by the two line quicksort -- and hooked. Unfortunately(?), though, FP seems to pose a bit of a challenge from a semantic point of view. I remember being very impressed with "Dynamic Logic" (Harel et al.), and it really changed my way of thinking about programming languages. But are Kripke structures even of any relevance to Haskell and FP? Well, in order to think it through, I've been experimenting with the idea of reduction providing the basic accessibility relation. That's why I've been asking seemingly off-topic questions about lambda calculus and C-R (well- definedness). === Gregory Woodhouse gregory.woodhouse(a)sbcglobal.net "The whole of science is nothing more than a refinement of everyday thinking." -- Albert Einstein

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warning HEAP: creating uncommited range
by Joel Reymont 14 Nov '05

14 Nov '05

Folks, Does this ring a bell with anyone? logon.exe is a binary that I built with -O -debug and ran from within gdb on Windows. warning HEAP:[logon.exe] warning: Failing creating uncommitted range (7fbfc000 for 5000) Thanks, Joel -- http://wagerlabs.com/

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Re: [Haskell] Making Haskell more open
by Gour 14 Nov '05

14 Nov '05

Sven Panne (Sven.Panne(a)aedion.de) wrote: > * DocBook XML can be transformed into a very rich collection of output > formats: XHTML, HTML Help, DVI, PS, PDF, FO, plain text, etc. etc. txt2tags has the following backends: HTML, XHTML, SGML, LaTeX, Lout, man, Magic Point, Moin Moin, Page Maker 6.0 & plain text. > * But what's more important: Compared to the more exotic markup mechanisms > proposed, it is well-known and extremely well documented. There are tons of > web sites, books, articles, etc. etc. about DocBook XML. Proposing more > arcane technologies will drastically reduce the amount of people actually > contributing to an Open Source project, a fact which is easily overlooked. But don't forget, as it was already stated, get the whole working-chain ready for authoring in Docbook is not at all ready and for one not proficient in emacs with SGML mode it is very difficult to write texts with so many tags. otoh, e.g. for 'txt2tags' python is the only requirement and it is therefore multi-platform soulution where one can start writing documentation in 15min. Besides that, 'txt2tags-like technology' is already in use for some time - e.g AFT (http://www.maplefish.com/todd/aft.html) dating back in '99 and XMLmind XML Editor has plugin which supports (similar) markup called APT (http://www.xmlmind.com/xmleditor/_distrib/doc/apt/apt_format.html) quote: "Aptconvert is an OpenSource command-line tool that can be used to convert the APT format to HTML, XHTML, PDF, PostScript, (MS Word loadable) RTF, DocBook SGML and DocBook XML." However, the main point in using such tool is productivity & simplicity. How many tags from DocBook DTD are actually used in GHC manual and how many of them are required for HTML output? Sincerely, Gour -- Registered Linux User | #278493 GPG Public Key | 8C44EDCD

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Re: [Haskell] Making Haskell more open
by Gour 14 Nov '05

14 Nov '05

Wolfgang Jeltsch (wolfgang(a)jeltsch.net) wrote: > The font size is much smaller than the font size of other webpages. So if I > would change the default font size to give good results with the Haskell > website, all other websites would have their text in very large letters. Well, haskell.org has smaller font size for the links, but the my preferred portal site (www.iskon.hr) has even smaller. However, pressing 'Ctrl +' to increase font size is, imoho, not such a big task :-) > The question is if HTML is sufficient. In addition, HTML is at some points > not well thought-out. True, but considering the present situation, it is all what is required. Sincerely, Gour -- Registered Linux User | #278493 GPG Public Key | 8C44EDCD

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Re: [Haskell] Making Haskell more open
by Gour 13 Nov '05

13 Nov '05

Wolfgang Jeltsch (wolfgang(a)jeltsch.net) wrote: > The most important question is: Does txt2tags use logical markup? A kind of, e.g. = title = == subtitle == === subsub...=== if this is logical ;) Sincerely, Gour -- Registered Linux User | #278493 GPG Public Key | 8C44EDCD

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Re: [Haskell] Making Haskell more open
by Gour 13 Nov '05

13 Nov '05

Wolfgang Jeltsch (wolfgang(a)jeltsch.net) wrote: > In addition, one could argue that since newsgroups were specifically > designed for discussions, newsgroup software allows proper mangagement > of threads but, well, current e-mail programs might do this in similar > quality. >From the most plain mailers like pine & mutt, to the gui-mailers (kmail, evolution), all have threading support. Sincerely, Gour p.s. I am moving this reply to cafe. -- Registered Linux User | #278493 GPG Public Key | 8C44EDCD

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Please explain behavior of setBit
by Murray Gross 13 Nov '05

13 Nov '05

Here is my trivial program: import Bits main = putStr (show(bit 0::Int)++" "++show (mybit 0)) mybit:: Int -> Int mybit x = setBit (bit 0) x The output (with GHC-5) is 1 1 My question: Why is (bit 0) equal to 1 and not 0? That first bit is set regardless of the value of x (I have tried several), although in each case, the bit I expect to be set is also set (e.g., mybit 4 yields 17). Thanks in advance for assistance. Murray Gross

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RE: [Haskell-cafe] Re: FPS: Finalizers not running (was Memoryusageoutside of the Haskell heap)
by Simon Marlow 12 Nov '05

12 Nov '05

On 07 November 2005 12:07, Donald Bruce Stewart wrote: > simonmar: >> Finalizers aren't guaranteed to be run. In particular, if the main >> thread exits, then we don't run any outstanding finalizers. This >> change was made recently, but it turned out that even prior to 6.4 >> we couldn't guarantee to run all outstanding finalizers. >> >> Does this explain it, or is there something else going on? >> >> BTW, when you addForeignPtrConcFinalizer to a ForeignPtr created with >> mallocForeignPtr, you're *creating* a finalizer, it doesn't have one >> to start with. It's pretty expensive to do this. > > Ah, right, I see. It's: > > mallocForeignPtr = doMalloc undefined > where doMalloc :: Storable b => b -> IO (ForeignPtr b) > doMalloc a = do > IO $ \s -> > case newPinnedByteArray# size s of { (# s, mbarr# #) > -> (# s, ForeignPtr (byteArrayContents# > (unsafeCoerce# mbarr#)) > (MallocPtrNoFinalizer mbarr#) #) } > where (I# size) = sizeOf a > > So the GC will take care of these thingies? > Now, this probably means that the problem is somewhere else in > Joelr's code. Yes, mallocForeignPtr's are implemented using pinned GC'd memory, with no finalizer (unless you add one). That's why they're nice and fast. It looks like you have an old version of GHC.ForeignPtr there - it has a bug in it, please cvs update to the latest version. Cheers, Simon

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`typeof' is not a (visible) method of class `Typeable' ?
by WANG Meng 12 Nov '05

12 Nov '05

Hi All, While I was trying to declare Language.Haskell.TH.Exp as an instance of "Typeable", ghci 6.4 yields this error. It does not allow me to define an instance of "typeof". Does anybody know what should be the right way of doing this? Thanks. -W-M- @ @ | \_/

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Re: Making Haskell more open
by Nils Anders Danielsson 11 Nov '05

11 Nov '05

On Fri, 11 Nov 2005, Tomasz Zielonka <tomasz.zielonka(a)gmail.com> wrote: [Moved to cafe.] > How about an integrated newsgroup+mailinglist+forum. If we had a > two-way newsgroup+mailinglist integration, people could use it also > as a forum, for example through gmail.google.com. But I don't use > fora, so I probably talk nonsense. I think Gmane has everything you're looking for (bidirectional mail-to-news gateway, you can read and post via a web page, and quite a few Haskell mailing lists are already archived there; see http://dir.gmane.org/gmane.comp.lang.haskell.general, for instance). I've hardly used it, though, so I can't tell whether it works well. -- /NAD

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throwDyn typing "fun"
by Einar Karttunen 11 Nov '05

11 Nov '05

Hello It seems that the type of throwDyn and throwDynTo are dangerously close. ThrowDyn works in with any of the arguments of throwDynTo, which can cause evil situations. throwDyn :: Typeable exception => exception -> b Which means e.g. "throwDyn someThreadId SomeException" will work when you wanted to say "throwDynTo someThreadId SomeException" and they both have types which unify with IO (). I think using a class Typeable => DynamicException a where ... and throwDyn :: DynamicException a => a -> b could make more sense. - Einar Karttunen

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RE: [Haskell-cafe] Re: FPS: Finalizers not running (wasMemoryusageoutside of the Haskell heap)
by Simon Marlow 10 Nov '05

10 Nov '05

On 10 November 2005 14:56, Jan-Willem Maessen wrote: > On Nov 9, 2005, at 4:46 AM, Ketil Malde wrote: > >> Sebastian Sylvan wrote: >> >>> On 11/8/05, Jan-Willem Maessen <jmaessen(a)alum.mit.edu> wrote: >>> >>>> Just wanted to let people know that I've been working on improving >>>> Data.HashTable, with the help of Ketil Malde's badly performing >>>> code >>>> >>>> >> Always happy to help, of course - bad performance R us:-) > > I think that if I can get unsafeFreeze/unsafeThaw to work reliably, > it'll finally outperform Data.Map on your example. I haven't yet > played with the hash function, which looks kind of bad; there may be > hope for improvement there as well. > >>> Request: Data.HashTable.Immutable >>> >> I'm not sure you really want that - do you wish to copy a large >> array each time you do an update? >> Freezing and thawing might be a good idea, though. > > A true read-only hash table, with a freeze for the mutable version, > but NO THAW, could potentially be useful. I seem to recall that hbc > had an immutable hash table (along with a derivable Hashable class), > where the content was specified as in an array comprehension. The unsafeFreeze/unsafeThaw trick can be used to speed up DiffArrays, which in turn could be used to provide a good immutable HashTable implementation. I'm pretty sure this would be a profitable approach. It's possible that DiffArrays need more work than just unsafeFreeze/unsafeThaw to make them efficient, though. Cheers, Simon

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Parameterizing on type
by Joel Reymont 10 Nov '05

10 Nov '05

Folks, How can I create a generic pickler that's parameterized on type and constructor? I define types like this: newtype AvgPot = AvgPot Word64 deriving (Show, Typeable) newtype NumberOfPlayers = NumberOfPlayers Word16 deriving (Show, Typeable) and then have a lot of boiler-plate code like this, a pickler for each type: puAvgPot :: PU AvgPot puAvgPot = wrap (\a -> AvgPot a, \(AvgPot b) -> b) endian where data PU a = PU { appP :: (a, [Word8]) -> [Word8], appU :: [Word8] -> (a, [Word8]) } wrap :: (a -> b, b -> a) -> PU a -> PU b What I would like to have is a generic pickler that's parameterized on constructor and type. These can and will be the same, though. I want something like this, how can it be done in Template Haskell or otherwise? pickler :: PU T pickler Con pa = wrap (\a -> Con a, \(Con b) -> b) pa Thanks, Joel -- http://wagerlabs.com/

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GHC cannot compile my code
by Joel Reymont 09 Nov '05

09 Nov '05

Folks, I'm on Mac OSX 10.4.3 with 1Gb of memory and GHC 6.4.1. I'm using HList to define 92 structures in a module. I'm not using classes. There's some nesting going on (see below). Few datypes above are data, mostly they are newtypes around Word32s, Strings, and lists of those. I have 40 newtypes that wrap HLists and homogeneous lists of HList types, 52 are type aliases around HLists. Both with and without -O ghc cannot compile my module. I run out of physical memory within 2-3 minutes and then it's just swapping (I think) and the system becomes totally unresponsive. Any ideas how to remedy this? I shudder at thinking about compiling this on Windows with 256Mb of memory. I will try to split the module into smaller modules and will report my findings. Thanks, Joel P.S. Some example types: newtype Tables = Tables [TableInfo] deriving (Show, Typeable) type TableInfo = AvgPot :*: NumPlayers :*: Waiting :*: PlayersFlop :*: TableName :*: TableID :*: GameType :*: InfoMaxPlayers :*: RealMoneyTable :*: LowBet :*: HighBet :*: MinStartMoney :*: MaxStartMoney :*: GamesPerHour :*: TourType :*: TourID :*: BetType :*: CantReturnLess :*: AffiliateID :*: NIsResurrecting :*: MinutesForTimeout :*: SeatsToResurrect :*: LangID :*: HNil -- http://wagerlabs.com/

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Request for subject suggestions for a series of informal top 10 Haskell articles
by Kenneth Hoste 08 Nov '05

08 Nov '05

Greetings, As you all might know, the Haskell community has it's own informal magazine, The Monad.Reader (http://haskell.org/tmrwiki) I'm planning to write (with some support from the frequent users of #haskell @ irc.freenode.net) a series of articles for TMR, which describe some aspect of Haskell. Because of the informal (but serious and thorough) style of TMR, I'd like to do this using a top 10 list regarding some subject. Every article will list 10 of most famous, most frequently used or most usefull things regarding that subject. I'd like to ask for suggestions on each subject when I'm writing the article on this mailing list, because I don't know the Haskell world very well (I've only been working with it for a year know, in my spare time). This first mail is intented to ask for suggestions regarding future subjects for the articles. Suggestions are welcome by replying, or by adding them to the 'take 10 [1..]'-wiki at http://haskell.org/tmrwiki/TopTenHaskell . Also other suggestions or remarks are very welcome. I hope this series of articles can provide a source of information for both new and experienced users, because you there's always room to discover new aspects of your favourite language. Kenneth a.k.a. boegel

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Inferred type less polymorphic than expected
by Joel Reymont 08 Nov '05

08 Nov '05

Folks, How do I fix this? data Prop = forall a b.(Eq a, Show a) => Attr a := a data Attr a = Attr String (a -> Dynamic, Dynamic -> Maybe a) (PU a) type Props = M.Map String (Int, Prop) instance Ord (Int, Prop) where compare (a, _) (b, _) | a == b = EQ | a > b = GT | otherwise = LT makeAttr :: Typeable a => String -> PU a -> Attr a makeAttr name pickler = Attr name (toDyn, fromDynamic) pickler ... props :: Props -> PU Props props m = props' $ sort $ M.toList m where props' [] = lift [] props' ((_, (Attr _ _ pp := _)):xs) = wrap (\(a, b) -> a : b, \(a : b) -> (a, b)) (pair pp (props' xs)) ./Script/Prop.hs:80:10: Inferred type is less polymorphic than expected Quantified type variable `a' is mentioned in the environment: props' :: [(a1, Prop)] -> PU [a] (bound at ./Script/Prop.hs: 79:10) When checking an existential match that binds $dEq :: {Eq a} $dShow :: {Show a} pp :: PU a The pattern(s) have type(s): [(a1, Prop)] The body has type: PU [a] In the definition of `props'': props' ((_, (Attr _ _ pp := _)) : xs) = wrap (\ (a, b) -> a : b, \ (a : b) -> (a, b)) (pair pp (props' xs)) In the definition of `props': props m = props' $ (sort $ (Data.Map.toList m)) where props' [] = lift [] props' ((_, (Attr _ _ pp := _)) : xs) = wrap (\ (a, b) -> a : b, \ (a : b) -> (a, b)) (pair pp (props' xs)) Thanks, Joel -- http://wagerlabs.com/

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Re: [Haskell-cafe] Inferred type less polymorphic than expected
by Joel Reymont 08 Nov '05

08 Nov '05

This gets me pretty close. I now have to figure out how to return a PU Props instead of a PU [Prop] which is what it's returning. Still, it's a huge step forward. props :: Props -> PU Props props m = props' $ sort $ M.toList m where props' [] = lift [] props' ((_, (_, x)):xs) = wrap (\(a, b) -> a : b, \(a : b) -> (a, b)) (pair (prop x) (props' xs)) ./Script/Prop.hs:82:10: Couldn't match `Props' against `[Prop]' Expected type: PU Props Inferred type: PU [Prop] In the expression: props' $ (sort $ (Data.Map.toList m)) In the definition of `props': props m = props' $ (sort $ (Data.Map.toList m)) where props' [] = lift [] props' ((_, (_, x)) : xs) = wrap (\ (a, b) -> a : b, \ (a : b) -> (a, b)) (pair (prop x) (props' xs)) Big thanks to Andrew and Malcolm on #haskell for pointing me in the right direction! Thanks, Joel On Nov 8, 2005, at 5:23 PM, Andrew Pimlott wrote: > You might have better luck getting if you send a complete example, > since > it's hard for me to figure out exactly what this code is supposed > to do. > However, I'll take a quick stab. > > On Tue, Nov 08, 2005 at 04:46:56PM +0000, Joel Reymont wrote: >> props :: Props -> PU Props >> props m = props' $ sort $ M.toList m >> where props' [] = lift [] >> props' ((_, (Attr _ _ pp := _)):xs) = >> wrap (\(a, b) -> a : b, >> \(a : b) -> (a, b)) >> (pair pp (props' xs)) >> >> >> ./Script/Prop.hs:80:10: >> Inferred type is less polymorphic than expected >> Quantified type variable `a' is mentioned in the environment: >> props' :: [(a1, Prop)] -> PU [a] (bound at ./Script/Prop.hs: >> 79:10) > > Recall that pp is a (PU a) for some a. However, the inferred type for > props' is fully polymorphic in a. It might help first of all to write > down the type you expect for props', and then add type annotations to > different pieces until you find the one that's going awry. > > Andrew -- http://wagerlabs.com/

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\Parsec\Token.hs
by Sara Kenedy 08 Nov '05

08 Nov '05

Dear all, I run file Token.hs in hugs98\libraries\Text\ParserCombinator\Parsec\Token.hs, but it displays this error ERROR : 64 - Syntax error in data type definition (unexpected '.') Anyone know how to fix this? Thanks.

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RE: [Haskell-cafe] Type classes and hFoldr from HList
by Ralf Lammel 07 Nov '05

07 Nov '05

Hi Greg, Since hfoldr is right-associative, I prefer to reorder your list of functions as follows: > test = HCons (length::String -> Int) (HCons ((+1)::(Int->Int)) (HCons ((*2)::(Int->Int)) HNil)) Note that I also annotated length with its specific type. (If you really wanted to leave things more polymorphic, you would need to engage in TypeCast.) Providing a specific Apply instance for (.) is not necessary, strictly necessary. We could try to exploit the normal function instance for Apply. Let me recall that one here for convenience: >instance Apply (x -> y) x y > where > apply f x = f x Let me also recall the hFoldr instances: >class HList l => HFoldr f v l r | f v l -> r > where > hFoldr :: f -> v -> l -> r >instance HFoldr f v HNil v > where > hFoldr _ v _ = v >instance ( HFoldr f v l r > , Apply f (e,r) r' > ) > => HFoldr f v (HCons e l) r' > where > hFoldr f v (HCons e l) = apply f (e,hFoldr f v l) To fit in (.), we would flip and uncurry it. So we could try: comp' = hFoldr (uncurry (flip (.))) (id::Int -> Int) test This wouldn't work. The trouble is the required polymorphism of the first argument of hFoldr. The type of that argument as such is polymorphic. However, this polymorphism does not survive type class parameterization. You see this by looking at the HCons instance of HFoldr. The different occurrences of "f" would need to be used at different types. This would only work if the type class parameter f were instantiated by the polymorphic type of (uncurry (flip (.))). (And even then we may need something like TypeCast.) What you can do is define a dedicated *type code* for composition. comp = hFoldr (undefined::Comp) (id::Int -> Int) test data Comp instance Apply Comp (x -> y,y -> z) (x -> z) where apply _ (f,g) = g . f Ralf > -----Original Message----- > From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe- > bounces(a)haskell.org] On Behalf Of Greg Buchholz > Sent: Sunday, November 06, 2005 7:01 PM > To: haskell-cafe(a)haskell.org > Subject: [Haskell-cafe] Type classes and hFoldr from HList > > > I was playing around with the HList library from the paper... > > Strongly typed heterogeneous collections > http://homepages.cwi.nl/~ralf/HList/ > > ...and I thought I'd try to fold the composition function (.) through a > heterogeneous list of functions, using hFoldr... > > >{-# OPTIONS -fglasgow-exts #-} > >{-# OPTIONS -fallow-undecidable-instances #-} > > > >import CommonMain > > > >main = print $ comp "abc" > > > >test = HCons ((+1)::(Int->Int)) (HCons ((*2)::(Int->Int)) (HCons length > HNil)) > > > >comp = hFoldr (.) id test > > > >instance Apply (a -> b -> c -> d) (a, b) (c -> d) > > where > > apply f (a,b) = f a b > > ...but it fails with the following type error... > > ]Compiling Main ( compose.hs, interpreted ) > ] > ]compose.hs:10:7: > ] No instances for (Apply ((b -> c) -> (a -> b) -> a -> c) > ] (Int -> Int, r) > ] ([Char] -> a3), > ] Apply ((b -> c) -> (a -> b) -> a -> c) (Int -> Int, > r1) r, > ] Apply ((b -> c) -> (a -> b) -> a -> c) ([a2] -> > Int, a1 ->a1) r1) > ] arising from use of `hFoldr' at compose.hs:10:7-12 > ] Probable fix: > ] add an instance declaration for (Apply ((b -> c) -> (a -> b) -> a - > > c) > ] (Int -> Int, r) > ] ([Char] -> a3), > ] Apply ((b -> c) -> (a -> b) -> a - > > c) > ](Int -> Int, r1) r, > ] Apply ((b -> c) -> (a -> b) -> a - > > c) > ]([a2] -> Int, a1 -> a1) r1) > ] In the definition of `comp': comp = hFoldr (.) id test > > ...Anyway, I couldn't quite tell whether I was using hFoldr incorrectly, > or if I needed to have more constraints placed on the construction of > "test", or if needed some sort of type-level function that resolves... > > Apply ((b -> c) -> (a -> b) -> a -> c) > > ...into (a -> c), or something else altogether. I figured someone might > be able to help point me in the right direction.

2 1

Information on B-Tree IO implemenations
by Scott Weeks 07 Nov '05

07 Nov '05

Hello all, (I'm resending this because I sent the first one without being a member of the list and I'm assuming it bounced) I'm a newbie and while I grasp some of the basics of FP I have yet to really understand the guts of Haskell. The type system is starting to clear up for me and so are Monads but I have a long way to go. For a project that I'm working on I need to implement a B-Tree or similar disk based data structure for storing large amounts of data. I feel like I'm getting it and then I get hung up on disk IO operations and trying to figure out how they should fit into the mix. I'm not necessarily looking for someone to point me at an implementation (although I wouldn't mind) but if someone could point me in the direction of some material that could shed a light on things I would be much obliged. I've read some Okasaki and found a promising paper called "Database Manipulation in Haskell 1.3" by Kevin Hammond and Phil Trinder but while they talk to the data structures themselves they don't quite get around to mentioning how they achieve the IO part of the equation. Thanks, Scotty Weeks

2 2

RE: Re[2]: [Haskell-cafe] Re: FPS: Finalizers not running (wasMemoryusageoutside of the Haskell heap)
by Simon Marlow 07 Nov '05

07 Nov '05

On 07 November 2005 14:02, Bulat Ziganshin wrote: > Hello Simon, > > Monday, November 07, 2005, 4:16:54 PM, you wrote: > >> Yes, mallocForeignPtr's are implemented using pinned GC'd memory, >> with no finalizer (unless you add one). That's why they're nice and >> fast. > > Simon, can you please write some docs about all these foreign stuff > and their interaction with pure Haskell code? i see some bits of this > information in these newsgroups regularly (for example, are you > remember discussion about using lots of hashtables in program?), but > there is no definitive source > > there is no need to write full-fledged doc right now, just > "implementation notes" as the list of peculiarities will be great for > the start You're right, it would be good to have this folklore stuff written down. I've added some notes to the mallocForeignPtr docs for now. Cheers, Simon

1 0

Monadifying pickler combinators
by Joel Reymont 07 Nov '05

07 Nov '05

Folks, I'm trying to monadify http://research.microsoft.com/~akenn/fun/ picklercombinators.pdf appU is easy but I can't figure out the appP. Is it actually possible? The clever trick seems to be the passing of (b -> a) into sequ for use in appP. -- instance Monad (PU s) where return a = PU snd (\s -> (a, s)) -- how do I do appP below? pa >>= k = PU (\(b, s) -> let pb = k a in appP pa (a, ??? -- this is good (\s -> let (a, s1) = appU pa s pb = k a in appU pb s1) Thanks, Joel -- http://wagerlabs.com/

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RE: [Haskell-cafe] Trashing of memory: How to troubleshoot and fix?
by Simon Marlow 07 Nov '05

07 Nov '05

On 07 November 2005 14:16, Joel Reymont wrote: > Well, I was suspecting FPS but I removed all FPS usage and went with > regular lists. The program still crashes. I did not see a "malloc: > memory exhausted" error from ghci this time, it just crashed with an > application error while writing to some random memory location. > > I built a separate exe (this is Windows) and ran it in gdb for a > segmentation violation in with this stack trace: > > ?? () > s7yw_info () > ?? () If you are pretty certain that you aren't doing anything unsafe, then this is a bug in GHCi. If you can provide us with a reproducible test case, I'll look into it. Cheers, Simon

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RE: [Haskell-cafe] Trashing of memory: How to troubleshoot and fix?
by Simon Marlow 07 Nov '05

07 Nov '05

On 05 November 2005 10:10, Joel Reymont wrote: > This is a I came up with a "scripting" environment for poker server > people to excercise their server. All it basically does is compose > and parse binary packets and let scripters send and receive them. > > The issue I have is that the "script" runs fine on Mac OSX (1Gb of > memory, though 6Gb VM) and runs out of memory on a Windows machine > with 512Mb of memory and 768Mb of VM. The memory error is from malloc > which leads me to believe memory fragmentation could be an issue. > Running on Windows is a customer requirement. GHC very rarely calls malloc(), so this is likely to be caused by heavy memory use in the C++ part of your app. It would be interesting to find out though: you can run gdb on the binary and get a backtrace when the memory error occurs (compiling the Haskell app with -debug will help). > I was wondering if peak memory usage was the issue but jugding from > the GC stats it does not seem to be that high. Maybe I'm wrong. What > do you guys make of this? > > ./logon +RTS -p -sblah > > GC summary: > -- > 5,695,379,620 bytes allocated in the heap > 1,274,038,800 bytes copied during GC > 69,790,544 bytes maximum residency (53 sample(s)) > > 20433 collections in generation 0 (230.29s) > 53 collections in generation 1 ( 5.15s) > > 152 Mb total memory in use > > INIT time 0.00s ( 0.04s elapsed) > MUT time 91.13s (250.79s elapsed) > GC time 235.44s (607.31s elapsed) > RP time 0.00s ( 0.00s elapsed) > PROF time 0.00s ( 0.00s elapsed) > EXIT time 0.00s ( 0.00s elapsed) > Total time 326.57s (858.14s elapsed) GC load is *very* high. But as you can see, GHC's storage manager is only using 152Mb peak - if you're running out with 512Mb, then something else is using the rest. To improve performance, I would first try to optimise the program to reduce the allocation rate, get any low-hanging fruit, and then tweak the GC settings. Most of your GC is generation 0 collections, which suggests that your program is allocating a lot of temporary memory and not getting much work done. Also, note that you got these figures from a version of the program compiled for profiling, which will have higher memory requirements than normal due to the profiling overheads. > --- > Time allocation and profiling report: > ---- > total time = 85.58 secs (4279 ticks @ 20 ms) > total alloc = 2,941,143,704 bytes (excludes profiling > overheads) > > COST CENTRE MODULE %time %alloc > > exp/evalU/cmd Script.Engine 50.0 66.4 > connect Main 14.1 11.1 > CAF Script.Engine 10.3 5.4 > exp/if Script.Engine 8.8 4.8 > send Main 6.4 6.7 > expect Main 5.8 2.7 > exp/evalU/sz Script.Engine 1.4 1.4 > startSSL Script.Engine 1.3 0.1 > --- Seems like you need to look at evalU: > cmd' <- {-# SCC "exp/evalU/cmd" #-}return $ evalU packet appU > -- unpickle command this is where most of the time/alloc seems to be going. Also, just looking at this line of code reminds me of SimonM's 203rd law of Haskell optimisation: when writing 'return $ E', consider writing 'return $! E' instead. Cheers, Simon

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RE: [Haskell-cafe] Re: FPS: Finalizers not running (was Memory usageoutside of the Haskell heap)
by Simon Marlow 07 Nov '05

07 Nov '05

On 06 November 2005 18:38, Joel Reymont wrote: > You need to do something like this to force them to run, apparently > > main = do foo $ Prelude.concat $ replicate 100 data_ > > Just triggering the GC with performGC doesn't do it. > > The really odd thing is that if I setup a C finalizer (see below) > then it's triggered once and the whole thing crashes with a bus > error. Duncan reported that it segfaulted for him as well. > > installFinalizer fps@(P.PS fp _ _) = > addForeignPtrFinalizer finalizer fp > > foreign import ccall unsafe "finalizer" finalizer :: FinalizerPtr > Word8 > > where the finalizer itself is > > #include <stdio.h> > > void finalizer(char *p) { > printf("--- Finalized: %x\n", p); > } This crash is due to driver error, I'm afraid. You should have written: foreign import ccall unsafe "&finalizer" finalizer :: FinalizerPtr Word8 (note the "&"). Cheers, Simon

1 0

Memory usage outside of the Haskell heap
by Joel Reymont 07 Nov '05

07 Nov '05

Folks, How can I profile memory usage outside of the Haskell heap? I'm using FastStrings for everything and some folks on #haskell suspect it might be causing my problems. hGet :: Handle -> Int -> IO FastString hGet _ 0 = return empty hGet h i = do fp <- mallocForeignPtr i l <- withForeignPtr fp $ \p-> hGetBuf h p i return $ PS fp 0 l I do this a lot and the finalizers might not be running or something like that. Thanks, Joel -- http://wagerlabs.com/

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RE: [Haskell-cafe] Re: FPS: Finalizers not running (was Memory usageoutside of the Haskell heap)
by Simon Marlow 07 Nov '05

07 Nov '05

Finalizers aren't guaranteed to be run. In particular, if the main thread exits, then we don't run any outstanding finalizers. This change was made recently, but it turned out that even prior to 6.4 we couldn't guarantee to run all outstanding finalizers. Does this explain it, or is there something else going on? BTW, when you addForeignPtrConcFinalizer to a ForeignPtr created with mallocForeignPtr, you're *creating* a finalizer, it doesn't have one to start with. It's pretty expensive to do this. Cheers, Simon On 07 November 2005 01:42, Donald Bruce Stewart wrote: > joelr1: >> David, >> >> I followed your suggestion and I think the finalizers for FPS are not >> running. > > Here are some experiments. Sometimes I can get the finalizers to run > as > expected, but only when putting memory pressure on the Haskell heap > with > normal haskell values. Works with 6.4.1 and 6.5 on OpenBSD or Linux. > > So here we generate a bunch of lists inside Haskell, then pack them. > Our > finalisers get run nicely as expected: > > import qualified Data.FastPackedString as P > import Foreign.Concurrent > import Data.Word > import Data.Char > > data_ = [ replicate 5000 i | i <- [1..100] ] :: [[Word8]] > > main = do > foo data_ > putStrLn "" > > foo [] = return () > foo (x:xs) = do > let fps = P.packWords x > installFinalizer fps > putStr "." > foo xs > > installFinalizer fps@(P.PS fp _ _) = > addForeignPtrFinalizer fp $ putStr (show.ord.P.head $ fps) > > > pill00$ ./a.out > 100 > > ..................................................1234567891011121314151 617181920212223242526272829303132333435363738394041424344454647484950... ........................................51525354555657585960616263646566 6768697071727374757677787980818283848586878889909192....... > > Now, if we instead allocate only outside the Haskell heap (with an > mmap packed > string), then we see something different: > > import qualified Data.FastPackedString as P > import Foreign.Concurrent > import Data.Word > import Data.Char > > main = do > foo 100 > putStrLn "" > > foo 0 = return () > foo n = do > fps <- P.mmapFile "/home/dons/tmp/tests/128k" > installFinalizer fps > putStr "." > foo (n-1) > > installFinalizer fps@(P.PS fp _ _) = > addForeignPtrFinalizer fp $ putStr (show.ord.P.head $ fps) > > No finalisers (even though more data is allocated)! > > $ ./a.out > > ........................................................................ .............. > > The GHC rts doesn't know how big the packed string is. It just sees > the few > bytes of the packed string (as dcoutts pointed out on irc). > > Strangely, the same effect is seen with P.readFile, which (from > darcs) allocates as so: > > mallocForeignPtr :: Int -> IO (ForeignPtr Word8) > mallocForeignPtr l = when (l > 1000000) performGC >> > mallocForeignPtrArray l > > where here mallocForeignPtrArray ends up calling > GHC.Prim.newPinnedByteArray# (i.e. on the Haskell heap). Hmm. I don't > understand that then, as the memory is > in the Haskell heap, yet still no finalisers are run. > > If we do something expensive with the packed string, then finalizers > get run: > > foo n = do > fps <- P.readFile "/home/dons/tmp/tests/128k" > installFinalizer fps > > -- unpack the string into a normal Haskell list: > forkIO (Control.Exception.evaluate ((length . P.unpack) fps) > >> return ()) putStr "." > foo (n-1) > > Also interestingly, calling unsafeFinalize didn't help. > > Simon, any thoughts on this? Is there some way we can ensure memory > outside the Haskell heap gets counted for its full weight? Also, why > don't we see any finalizers run with the pinned arrays? > > -- Don > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe

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RE: [Haskell-cafe] Re: Fixup too large
by Simon Marlow 07 Nov '05

07 Nov '05

On 04 November 2005 20:06, Joel Reymont wrote: > I was able to work around this by adding -O > > On Nov 4, 2005, at 6:57 PM, Joel Reymont wrote: > >> What does this mean exactly? >> >> ghc -prof --make -auto-all -o logon -package Script Logon.hs >> Chasing modules from: Logon.hs >> Compiling Main ( Logon.hs, Logon.o ) >> /tmp/ghc20361.s:17881:Fixup of 93184 too large for field width of 16 >> bits /tmp/ghc20361.s:17878:Fixup of 93196 too large for field width >> of 16 bits /tmp/ghc20361.s:17874:Fixup of 93160 too large for field >> width of 16 bits Can you send us the offending code? Cheers, Simon

1 0

Type classes and hFoldr from HList
by Greg Buchholz 07 Nov '05

07 Nov '05

I was playing around with the HList library from the paper... Strongly typed heterogeneous collections http://homepages.cwi.nl/~ralf/HList/ ...and I thought I'd try to fold the composition function (.) through a heterogeneous list of functions, using hFoldr... >{-# OPTIONS -fglasgow-exts #-} >{-# OPTIONS -fallow-undecidable-instances #-} > >import CommonMain > >main = print $ comp "abc" > >test = HCons ((+1)::(Int->Int)) (HCons ((*2)::(Int->Int)) (HCons length HNil)) > >comp = hFoldr (.) id test > >instance Apply (a -> b -> c -> d) (a, b) (c -> d) > where > apply f (a,b) = f a b ...but it fails with the following type error... ]Compiling Main ( compose.hs, interpreted ) ] ]compose.hs:10:7: ] No instances for (Apply ((b -> c) -> (a -> b) -> a -> c) ] (Int -> Int, r) ] ([Char] -> a3), ] Apply ((b -> c) -> (a -> b) -> a -> c) (Int -> Int, r1) r, ] Apply ((b -> c) -> (a -> b) -> a -> c) ([a2] -> Int, a1 ->a1) r1) ] arising from use of `hFoldr' at compose.hs:10:7-12 ] Probable fix: ] add an instance declaration for (Apply ((b -> c) -> (a -> b) -> a -> c) ] (Int -> Int, r) ] ([Char] -> a3), ] Apply ((b -> c) -> (a -> b) -> a -> c) ](Int -> Int, r1) r, ] Apply ((b -> c) -> (a -> b) -> a -> c) ]([a2] -> Int, a1 -> a1) r1) ] In the definition of `comp': comp = hFoldr (.) id test ...Anyway, I couldn't quite tell whether I was using hFoldr incorrectly, or if I needed to have more constraints placed on the construction of "test", or if needed some sort of type-level function that resolves... Apply ((b -> c) -> (a -> b) -> a -> c) ...into (a -> c), or something else altogether. I figured someone might be able to help point me in the right direction. Thanks, Greg Buchholz

1 0

Families of type classes
by Klaus Ostermann 06 Nov '05

06 Nov '05

Hi all, I am not a Haskell expert, and I am currently exploring type classes and need some advice. I want to define a family of mutually recursive types as a collection of type classes and then I want to be able to map these collections of types to a set of other types using instance declarations. For example, I have a type family for graphs, consisting of the types "Node" and "Edge". In another part of my application I have the types "Person" and "Likes" (a pair of persons), and I want to map the roles "Node" and "Edge" to "Person" and "Likes", respectively. It seems to me that functional dependencies could be a way to model it (maybe it can also be done much simpler, but I don't know how). Here is what I tried: class (Node n, Edge e) => Graph g n e | g -> n, g -> e where class Node n where isConnectedTo :: Graph g n e => g -> n -> e -> Bool class Edge e where n1 :: Graph g n e => g -> e -> n n2 :: Graph g n e => g -> e -> n type Person = String type Likes = (Person, Person) data DummyGraph = DummyGraph String instance Graph DummyGraph Person Likes where instance Node Person where isConnectedTo g n (p1,p2) = (p1 == n) || (p2 == n) instance Edge Likes where n1 g (p1,p2) = p1 n2 g (p1,p2) = p2 This "DummyGraph" thing is supposed to be used as a kind of "family object" which stands for a particular type class family. However, this is not yet quite right because I get the error message Couldn't match the rigid variable `e' against `(a, b)' `e' is bound by the type signature for `isConnectedTo' Expected type: e Inferred type: (a, b) When checking the pattern: (p1, p2) In the definition of `isConnectedTo': isConnectedTo g n (p1, p2) = (p1 == n) || (p2 == n) Similar error messages occur in the instance declaration for Edge/Likes. I don't understand exactly what my error is. Maybe I would need a completely different strategy to model this. Any help would be appreciated! Regards, Klaus

4 5

Information on B-Tree IO implemenations
by Scott Weeks 06 Nov '05

06 Nov '05

Hello all, I'm a newbie and while I grasp some of the basics of FP I have yet to really understand the guts of Haskell. The type system is starting to clear up for me and so are Monads but I have a long way to go. For a project that I'm working on I need to implement a B-Tree or similar disk based data structure for storing large amounts of data. I feel like I'm getting it and then I get hung up on disk IO operations and trying to figure out how they should fit into the mix. I'm not necessarily looking for someone to point me at an implementation (although I wouldn't mind) but if someone could point me in the direction of some material that could shed a light on things I would be much obliged. I've read some Okasaki and found a promising paper called "Database Manipulation in Haskell 1.3" by Kevin Hammond and Phil Trinder but while they talk to the data structures themselves they don't quite get around to mentioning how they achieve the IO part of the equation. Thanks, Scotty Weeks

1 0

Trashing of memory: How to troubleshoot and fix?
by Joel Reymont 05 Nov '05

05 Nov '05

Folks, This is a I came up with a "scripting" environment for poker server people to excercise their server. All it basically does is compose and parse binary packets and let scripters send and receive them. The issue I have is that the "script" runs fine on Mac OSX (1Gb of memory, though 6Gb VM) and runs out of memory on a Windows machine with 512Mb of memory and 768Mb of VM. The memory error is from malloc which leads me to believe memory fragmentation could be an issue. Running on Windows is a customer requirement. I'm sending and receiving deeply nested structures although that is not my call as the server is in C++. Most of the time just one or two fields will be needed after the command is unpickled. Most of the commands are converted to strings and written to a Chan for logging, though. I'm trying to launch 1000 scripts (separate threads) which just connect to the server, login and disconnect. The big issue is that the production scripts will run for hours, playing against one another. If I the maximum that I can handle is about 200 scripts that do nothing that I failed the project. I was wondering if peak memory usage was the issue but jugding from the GC stats it does not seem to be that high. Maybe I'm wrong. What do you guys make of this? ./logon +RTS -p -sblah GC summary: -- 5,695,379,620 bytes allocated in the heap 1,274,038,800 bytes copied during GC 69,790,544 bytes maximum residency (53 sample(s)) 20433 collections in generation 0 (230.29s) 53 collections in generation 1 ( 5.15s) 152 Mb total memory in use INIT time 0.00s ( 0.04s elapsed) MUT time 91.13s (250.79s elapsed) GC time 235.44s (607.31s elapsed) RP time 0.00s ( 0.00s elapsed) PROF time 0.00s ( 0.00s elapsed) EXIT time 0.00s ( 0.00s elapsed) Total time 326.57s (858.14s elapsed) %GC time 72.1% (70.8% elapsed) Alloc rate 62,497,307 bytes per MUT second Productivity 27.9% of total user, 10.6% of total elapsed --- Time allocation and profiling report: ---- total time = 85.58 secs (4279 ticks @ 20 ms) total alloc = 2,941,143,704 bytes (excludes profiling overheads) COST CENTRE MODULE %time %alloc exp/evalU/cmd Script.Engine 50.0 66.4 connect Main 14.1 11.1 CAF Script.Engine 10.3 5.4 exp/if Script.Engine 8.8 4.8 send Main 6.4 6.7 expect Main 5.8 2.7 exp/evalU/sz Script.Engine 1.4 1.4 startSSL Script.Engine 1.3 0.1 --- expect -- receives command and unpickles it from a FastPackedString. send -- pickles the command into a FastPackedString. hGet from FPS: --- hGet :: Handle -> Int -> IO FastString hGet _ 0 = return empty hGet h i = do fp <- mallocForeignPtr i l <- withForeignPtr fp $ \p-> hGetBuf h p i return $ PS fp 0 l -- The code for send: --- send :: Command -> EngineState () send cmd@(Command kind props) = do liftIO $ yield w <- get let (_, cmd') = checkEncryption cmd send_ cmd' trace $ "Sent: " ++ show (kindOf cmd') tracecmd cmd' --- The code for expect: --- expect :: [CmdType] -> EngineState () expect kind = do w <- get let h = socket w secs = timeout_seconds w (Right fps) <- liftIO $ timeout secs $ P.hGet h 4 trace $ "Size: " ++ show (P.unpackWords fps) state <- liftIO $ hIsEOF h trace $ "Connection closed: " ++ show state (Right size', _) <- {-# SCC "exp/evalU/sz" #-}return $ evalU fps appU let size = fromIntegral $ (unLE size' :: Word16) - 4 (Right packet) <- liftIO $ timeout secs $ P.hGet h size guard $ size == P.length packet cmd' <- {-# SCC "exp/evalU/cmd" #-}return $ evalU packet appU -- unpickle command case cmd' of (Left s, _) -> do trace $ "Error: " ++ s throwError $ "Cannot parse: " ++ show (P.unpackWords packet) (Right _, _) -> do return () let (Right cmd'', _) = cmd' let kind' = kindOf cmd'' let vars = (cmdKind := kind'):(propsOf cmd'') vars'= map (\p -> (attrName p, p)) vars -- update world {-# SCC "exp/putWorld" #-}put $ w { cmd = cmd'', cmdVars = M.fromList vars' } -- move on {-# SCC "processCbks" #-}processCallbacks {-# SCC "exp/if" #-}if elem kind' (skip w) then tracecmd cmd'' >> expect kind -- keep going else match kind cmd'' -- http://wagerlabs.com/

1 1

handling rank 2 types
by Andrew Pimlott 04 Nov '05

04 Nov '05

I am trying to use a rank 2 type to enforce a condition on a data structure. For the purpose of this message, I am trying to ensure that a list is empty (ignoring the possibility of bottom elements): > {-# OPTIONS -fglasgow-exts #-} > import Control.Monad > newtype Empty = Empty (forall a. [a]) I want a function > listToEmpty :: [v] -> IO Empty > listToEmpty l = liftM Empty (mapM no l) where > no :: a -> IO a' > no x = fail "element found" But this gives a "less polymorphic" error. I think the problem is that ghc will not instantiate the "a'" in "IO a'" as a higher-rank type because it occurs within a type contructor. I believe this is the restriction referred to at the end of 7.4.9[1]. If I instead write > uncheckedListToEmpty :: [v] -> Empty > uncheckedListToEmpty l = Empty (map no l) where > no :: a -> a' > no x = error "element found" it compiles, because "v'" can be instantiated as "forall v. Rule v", and even pass through map with the higher-rank type. Is there any way to make ghc accept the first definition? I found this workaround: > newtype Any = Any { unAny :: forall a. a } > listToEmptyAny :: [v] -> IO Empty > listToEmptyAny l = liftM (\l -> Empty (map unAny l)) (mapM no l) where > no :: a -> IO Any > no x = fail "element found" But needing a newtype wrapper Empty was bad enough; do I really need one for every intermediate result (that is inside another type constructor) as well? I could probably define a generic family of wrappers > newtype Forall = Forall (forall a. a) > newtype Forall1 c1 = Forall1 (forall a. c1 a) > newtype Forall2 c1 c2 = Forall2 (forall a. c1 c2 a) ... But I would still have to use them everywhere. Any other tricks? Andrew [1] http://haskell.org/ghc/docs/latest/html/users_guide/type-extensions.html#un…

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Re: [Haskell] specification of sum
by ajb＠spamcop.net 04 Nov '05

04 Nov '05

(Moving this to the cafe.) G'day all. Quoting Cale Gibbard <cgibbard(a)gmail.com>: > We already do rely on them in most cases. Of course, not every > property can be proved by the compiler, but many pieces of code are > going to assume quite a lot. Agreed. > I think that the assumption that (+) and (*) in Num define something > like a ring on the given type is a sensible one. I'm not so certain. Octonian multiplication, to pick one example, is not associative, but I'd like to be able to use (*) nonetheless. Cheers, Andrew Bromage

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Fixup too large
by Joel Reymont 04 Nov '05

04 Nov '05

What does this mean exactly? ghc -prof --make -auto-all -o logon -package Script Logon.hs Chasing modules from: Logon.hs Compiling Main ( Logon.hs, Logon.o ) /tmp/ghc20361.s:17881:Fixup of 93184 too large for field width of 16 bits /tmp/ghc20361.s:17878:Fixup of 93196 too large for field width of 16 bits /tmp/ghc20361.s:17874:Fixup of 93160 too large for field width of 16 bits -- http://wagerlabs.com/

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Catching an escaping exception
by Joel Reymont 04 Nov '05

04 Nov '05

How can I catch this exception and translate it into an error within my monad? The exception is going to ghci and is not being caught in the monad. I'm interested in catching it and failing the monad gracefully. Exception: <interactive>: connect: does not exist (Connection refused) Types follow... type EngineState = ErrorT String (StateT World IO) type EngineResult = IO (Either String (), World) connect :: [Prop] -> HostName -> Int -> EngineState () connect env h p = do w <- get let secs = timeout_seconds w (Right h) <- liftIO $ timeout secs $ connect_ h p trace "Connection established" ... connect_ :: HostName -> Int -> IO Handle connect_ h p = connectTo h $ PortNumber $ fromIntegral p timeout :: forall a.Int -> IO a -> IO (Either String a) timeout seconds action = ... Thanks, Joel -- http://wagerlabs.com/

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RE: [Haskell-cafe] handling rank 2 types
by Ralf Lammel 04 Nov '05

04 Nov '05

In a type system like MLF, your original code may type check. Let's do an experiment. We replace the IO monad by the Id(entity) monad. We actually replace the Id newtype also to become true type-level identity. So we get: -- -- This is like your 2nd say unchecked... sample -- fooBar :: [v] -> Empty fooBar l = Empty (map no l) where no :: a -> a' no x = error "element found" But the problem is not about "a higher-rank type occurring with a type constructor", as you guess. It is rather about functions with classic rank-1 types. To see this, insert $ for the application of Empty: fooBar :: [v] -> Empty fooBar l = Empty $ (map no l) where no :: a -> a' no x = error "element found" You get the same type error as for the original monadic code. What you could do is define a suitably typed application operator (likewise, a suitably typed liftM). (With MLF the various types would be admitted by a more general type.) In the non-monadic example, we need: -- Use app instead of ($) app :: ((forall a. [a]) -> c) -> (forall b. [b]) -> c app f x = f x BTW, what operations are we supposed to perform on the content of Empty; what's the real purpose for introducing this independent type variable "a'"? Parametric polymorphism seems to suggest that we can't do much. You can observe the length of the list. That's it, more or less. Why not store the length directly rather than having this superficially polymorphic list? I am a little bit lost. You wonder how you can generally solve this sort of problem? - You seem to spot the wrapping approach: wrap foralls and unpack at application time. This makes particularly sense for polymorphic *functions*. - The other approach is to use consistently rank-2 combinators. I probably don't get what you try to do. Ralf > -----Original Message----- > From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe- > bounces(a)haskell.org] On Behalf Of Andrew Pimlott > Sent: Thursday, November 03, 2005 8:35 PM > To: haskell-cafe(a)haskell.org > Subject: [Haskell-cafe] handling rank 2 types > > I am trying to use a rank 2 type to enforce a condition on a data > structure. For the purpose of this message, I am trying to ensure > that a list is empty (ignoring the possibility of bottom elements): > > > {-# OPTIONS -fglasgow-exts #-} > > import Control.Monad > > newtype Empty = Empty (forall a. [a]) > > I want a function > > > listToEmpty :: [v] -> IO Empty > > listToEmpty l = liftM Empty (mapM no l) where > > no :: a -> IO a' > > no x = fail "element found" > > But this gives a "less polymorphic" error. I think the problem is > that ghc will not instantiate the "a'" in "IO a'" as a higher-rank > type because it occurs within a type contructor. I believe this is > the restriction referred to at the end of 7.4.9[1]. If I instead > write > > > uncheckedListToEmpty :: [v] -> Empty uncheckedListToEmpty l = Empty > > (map no l) where > > no :: a -> a' > > no x = error "element found" > > it compiles, because "v'" can be instantiated as "forall v. Rule v", > and even pass through map with the higher-rank type. > > Is there any way to make ghc accept the first definition? I found > this > workaround: > > > newtype Any = Any { unAny :: forall a. a } listToEmptyAny :: [v] -> > > IO Empty listToEmptyAny l = liftM (\l -> Empty (map unAny l)) (mapM > > no l) where > > no :: a -> IO Any > > no x = fail "element found" > > But needing a newtype wrapper Empty was bad enough; do I really need > one for every intermediate result (that is inside another type > constructor) as well? I could probably define a generic family of > wrappers > > > newtype Forall = Forall (forall a. a) newtype Forall1 c1 = Forall1 > > (forall a. c1 a) newtype Forall2 c1 c2 = Forall2 (forall a. c1 c2 a) > ... > > But I would still have to use them everywhere. Any other tricks? > > Andrew > > [1] http://haskell.org/ghc/docs/latest/html/users_guide/type- > extensions.html#universal-quantification > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe

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RE: [Haskell-cafe] handling rank 2 types
by Simon Peyton-Jones 04 Nov '05

04 Nov '05

| But this gives a "less polymorphic" error. I think the problem is that | ghc will not instantiate the "a'" in "IO a'" as a higher-rank type | because it occurs within a type contructor. I believe this is the | restriction referred to at the end of 7.4.9[1]. If I instead write I think that is indeed the heart of your problem. Actually I'm writing a paper right now about how to lift this restriction. An out of date version is here, http://research.microsoft.com/%7Esimonpj/papers/boxy/ that gives the general idea, but a much better version will be done in a week's time. It's not fully implemented yet, but I'll keep your message as an example to try when it is. Simon -cafe

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newbie help
by Abhijit Ray 04 Nov '05

04 Nov '05

Hi I just started on haskell , i am using the yet another haskell tutorial by Hal Daume I wrote the following program and it dint compile. what's wrong with it module Main where import IO main = do hSetBuffering stdin LineBuffering let testList = makeList let sum = foldr (+) 0 testList putStrLn "Sum is " ++ show(sum) makeList = do putStrLn "enter a num" num <- getLine let nbr = read num if nbr == 0 then do return [] else do all <- makeList return (nbr : all) ---------------------------------------------- the error i get is Chasing modules from: Sum.hs Compiling Main ( Sum.hs, Sum.o ) Sum.hs:6: Couldn't match `[a]' against `IO ()' Expected type: [a] Inferred type: IO () In the application `putStrLn "Sum is "' In the first argument of `(++)', namely `putStrLn "Sum is "' Sum.hs:9: Couldn't match `[b]' against `IO [a]' Expected type: [b] Inferred type: IO [a] In the third argument of `foldr', namely `testList' In the definition of `sum': sum = foldr (+) 0 testList ----------------------------- Thanks, Abhijit Ray

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Threads talking back to parent
by Joel Reymont 04 Nov '05

04 Nov '05

Folks, I'm launching thousands of threads that send and receive commands. I would like the launching thread to keep a log of all the commands sent and received, in proper order. This would mean that each time a command is sent and received in the child thread it would need to be sent back to parent who would log the command on a first-come first-serve basis. How would I implement this in Haskell? Thanks, Joel -- http://wagerlabs.com/

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