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Literate program implementing text editor
by Eric 28 Jul '08

28 Jul '08

Hi all, I wanted to embark on a Haskell program that implements a simple text editor. Before doing so, however, I thought that I should ask: Does anyone know of a literate Haskell program already in existence that does the job? Eric M.

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Control.Concurrent.forkIO versus Control.Parallel.par
by Mario Blažević 28 Jul '08

28 Jul '08

Hello. I have a question about parallel computation in Haskell. After browsing the GHC library documentation, I was left with impression that there are two separate mechanisms for expressing concurrency: Control.Parallel.par for pure computations and Control.Concurrent.forkIO for computations in IO monad. This dichotomy becomes a problem when one tries to use concurrency from a monad transformer, though I'm sure that's not the only such situation. One cannot assume that the base monad is IO so forkIO cannot be used, while Control.Parallel.par won't run monads. My first solution was to replace the base monad class for the monad transformer by the following ParallelizableMonad class: ---------------------------------------------------------------------------- class Monad m => ParallelizableMonad m where parallelize :: m a -> m b -> m (a, b) parallelize ma mb = do a <- ma b <- mb return (a, b) instance ParallelizableMonad Identity where parallelize (Identity a) (Identity b) = Identity (a `par` (b `pseq` (a, b))) instance ParallelizableMonad IO where parallelize ma mb = do va <- newEmptyMVar vb <- newEmptyMVar forkIO (ma >>= putMVar va) forkIO (mb >>= putMVar vb) a <- takeMVar va b <- takeMVar vb return (a, b) ---------------------------------------------------------------------------- I tested this solution, and it worked for IO computations in the sense that they used both CPUs. The test also ran slower on two CPUs that on one, but that's beside the point. Then I realized that par can, in fact, be used on any monad, it just needs a little nudge: ---------------------------------------------------------------------------- parallelize :: m a -> m b -> m (a, b) parallelize ma mb = let a = ma >>= return b = mb >>= return in a `par` (b `pseq` liftM2 (,) a b) ---------------------------------------------------------------------------- However, in this version the IO monadic computations still appear to use only one CPU. I cannot get par to parallelize monadic computations. I've used the same command-line options in both examples: -O -threaded and +RTS -N2. What am I missing?

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multicore programming ...
by Galchin, Vasili 28 Jul '08

28 Jul '08

Hello, I have written quite a bit of multi-threaded code in ANSI C and C++ using mainly Posix threads and some using Win32 API threads. IMO now seems to be a huge opportunity for FPLs to shine .. In any case, now there seems to be an emerging crisis in the computer industry in multithread scalability over large multicore: http://www.hackinthebox.org/modules.php?op=modload&name=News&file=article&s…. This is kind of a "wrag" quote. Do others have more substantial URLs on programming large multi-cores? Kind regards, Vasili

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library for zip compression?
by John MacFarlane 27 Jul '08

27 Jul '08

Haskellers, Is there a library for compressing and uncompressing zip archives? I see zlib and bzlib on HackageDB, but unless I'm mistaken these won't help with a .zip archive. (See http://zlib.net/zlib_faq.html#faq11.) Any help here would be appreciated. John

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Re: [Haskell] ANN: Hipmunk 0.1 and HipmunkPlayground 0.1
by Antoine Latter 27 Jul '08

27 Jul '08

On Sat, Jul 26, 2008 at 9:50 PM, Felipe Lessa <felipe.lessa(a)gmail.com> wrote: > 6.8.1). > > You may get Cabal packages for both on Hackage at: > - http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Hipmunk > - http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HipmunkPlayground > Felipe, I'm getting the following error trying to cabal-install HipmunkPlayground: +++++ Building HipmunkPlayground-0.1... [1 of 1] Compiling Main ( ./Playground.hs, dist/build/HipmunkPlayground/HipmunkPlayground-tmp/Main.o ) Linking dist/build/HipmunkPlayground/HipmunkPlayground ... ld: duplicate symbol _deRefStablePtr in /Library/Frameworks/GHC.framework/Versions/608/usr/lib/ghc-6.8.2.20080211/libHSrts.a(Stable.o) and /Users/alatter/.cabal/lib/Hipmunk-0.1/ghc-6.8.2.20080211/libHSHipmunk-0.1.a(Space_stub.o) collect2: ld returned 1 exit status cabal: Error: some packages failed to install: HipmunkPlayground-0.1 failed during the building phase. The exception was: exit: ExitFailure 1 +++++ I simply typed "cabal install HipmuckPlayground". Should I need to do anything else? I'm running Mac OS 10.5 on Intel. Does this error look useful to anyone? -Antoine

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ANNOUNCE: Sun Microsystems and Haskell.org joint project on OpenSPARC
by Duncan Coutts 26 Jul '08

26 Jul '08

http://haskell.org/opensparc/ I am very pleased to announce a joint project between Sun Microsystems and the Haskell.org community to exploit the high performance capabilities of Sun's latest multi-core OpenSPARC systems via Haskell! http://opensparc.net/ Sun has donated a powerful 8 core SPARC Enterprise T5120 Server to the Haskell community, and $10,000 to fund a student, to further develop support for high performance Haskell on the SPARC. The aim of the project is to improve the SPARC native code generator in GHC and to demonstrate and improve the results of parallel Haskell benchmarks. The student will work with a mentor from Haskell.org and an adviser from Sun's SPARC compiler team. ** We are now inviting applications from students ** Please forward this announcement to any and all mailing lists where you think interested students might be lurking. Further details for students may be found below, and on the project website. Haskell and Multi-core Systems ------------------------------ The latest generation of multi-core machines pose a number of problems for traditional languages and parallel programming techniques. Haskell, in contrast, supports a wealth of approaches for writing correct parallel programs: traditional explicit threads and locks (forkIO and MVars), pure parallel evaluation strategies (par) and also Software Transactional Memory (STM). GHC has supported lightweight preemptable threads for a long time, and for the last couple of years it has been able to take advantage of machines with multiple CPUs or CPU cores. The GHC runtime has also recently gained a parallel garbage collector. OpenSPARC --------- We think the UltraSPARC T1/T2 architecture is a very interesting platform for Haskell. In particular the way that each core multiplexes many threads as a way of hiding memory latency. Memory latency is a performance bottleneck for Haskell code because the execution model uses a lot of memory indirections. Essentially, when one thread blocks due to a main memory read, the next thread is able to continue. This is in contrast to traditional architectures where the CPU core would stall until the result of the memory read was available. This approach can achieve high utilisation as long as there is enough parallelism available. The Project ----------- GHC is increasingly relying on its native code backend for high performance. Respectable single-threaded performance is a prerequisite for decent parallel performance. The first stage of the project therefore is to implement a new SPARC native code generator, taking advantage of the recent and ongoing infrastructure improvements in the C-- and native layers of the GHC backend. There is some existing support for SPARC in the native code generator but it has not kept up with changes in the GHC backend in the last few years. Once the code generator is working we will want to get a range of single threaded and parallel benchmarks running and look for various opportunities for improvement. There is plenty of ongoing work on the generic parts of the GHC backend and run-time system so the project will focus on SPARC-specific aspects. The UltraSPARC T1/T2 architecture supports very fast thread synchronisation (by taking advantage of the fact that all threads share the same L2 cache). We would like to optimise the synchronisation primitives in the GHC libraries and run-time system to take advantage of this. This should provide the basis for exploring whether the lower synchronisation costs make it advantageous to use more fine-grained parallelism. The Server ---------- The T5120 server has a T2 UltraSPARC processor with 8 cores running at 1.2GHz. Each core multiplexes 8 threads giving 64 hardware threads overall. It comes equipped with 32GB of memory. It also has two 146GB 10k RPM SAS disks. http://www.sun.com/servers/coolthreads/t5120/ http://www.sun.com/processors/UltraSPARC-T2/ This server is a donation to the whole Haskell community. We will make accounts available on the same basis as the existing community server as soon as is practical. Our friends at Chalmers University of Technology are kindly hosting the server on our behalf. We will encourage people to use the server for building, testing and benchmarking their Haskell software on SPARC, under both Solaris and Linux. Student applications -------------------- This is a challenging and exciting project and will need a high calibre student. Familiarity with Haskell is obviously important as is some experience with code generation for RISC instruction sets. The summer is now upon us so we do not expect students to be able to work 3 months all in one go. We are inviting students to suggest their own schedule when they apply. This may involve blocks of time in the next 9 months or so. It should add up to the equivalent of 3 months full time work. The application process is relatively informal. Students should send their application to: opensparc(a)community.haskell.org The deadline for applications in Friday 5th September 2008. If that deadline likely to be a problem for you then do get in touch. The application should detail skills and experience. Applications will be reviewed by a panel including the mentor, the adviser from Sun and a number of other Haskell.org community members who have helped with reviewing student projects in the past. The review will be partly interactive; students can expect to get questions and feedback from the reviewers. Students are welcome to contact myself or anyone else to help improve the quality of their application or if they have any questions. The $10k student funding will be paid in three phases, at the beginning ($3k), an intermediate point ($3k) and at the end ($4k). The exact timing will depend on the agreed schedule. The intermediate and final payments will be subject to positive reviews from the mentor. Duncan (project coordinator)

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Hi Nathan ....
by Galchin, Vasili 26 Jul '08

26 Jul '08

Hi Nathan, I am in Houston and want to start a serious Haskell "dialog/group" in the US Southeast! ... Let's rock because Haskell rocks!!!! Very kind regards, Vasili

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ANN: list-extras 0.2.0
by wren ng thornton 26 Jul '08

26 Jul '08

hello all~ After some talks with Aditya Mahajan I've overhauled the Data.List.Extras.Argmax module so it's not quite so braindead. Since it breaks backwards compatibility so soon after the initial announcement, I figured it was worth a mention. I also changed the case of the module's name, so beware on case-sensitive file systems. As always, the code and latest documentation is available from: http://code.haskell.org/~wren/ -- Live well, ~wren

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FPers in Northwest Arkansas?
by Nathan Bloomfield 25 Jul '08

25 Jul '08

Greetings, Haskell-cafe. I am interested in joining or starting a functional programming interest group in my area. Are there any haskellers in the Northwest Arkansas region? Nathan Bloomfield

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Italian Haskellers Summer Meeting?
by Pasqualino 'Titto' Assini 25 Jul '08

25 Jul '08

As a prerequisite for atttending is proficiency in "la bella lingua del si" (also known as Italian) I think I will just write the rest of this message in it. Ottimi, ma non particolarmente abbondanti, haskeller italiani, abbiamo avuto una piccola discussione su #haskell.it circa la possibilita' di organizzare un incontro estivo. Non credo che ne sia stato mai organizzato uno e quindi vorrei intanto che mi faceste sapere: - se vi interessa - dove siete/sarete d'agosto - che formato debba avere l'incontro Riguardo quest'ultimo punto, direi che ci sono almeno tre possibilita' : a) Ritiro spirituale. Luogo: rifugio di montagna, monastero benedettino. Gli adepti giungono al luogo designato dopo un lungo percorso a piedi attraverso regioni desertiche. Hanno barbe lunghe ed occhi severi ma in cui brilla la luce di una pura fede monoidale. Riunitisi davanti ad un semplice pasto gli adepti spezzano il pane e bevono il vino e si scambiano parabole illuminanti circa la vera natura del Monoide, della Monade e del Funtore Applicativo. Un neofita, che non sa spiegare la differenza fra left e right fold, viene giudicato impuro e ritualmente lapidato. b) Scampagnata fuori porta Luogo: ridente localita' marina od agreste. Gli haskeller arrivano alla spicciolata su una spiaggia animata. Hanno costumi colorati e capelli rasta. Qualcuno ha portato i bambini, tutti hanno portato la paletta ed il secchiello. Si fanno castelli di sabbia, qualcuno passa una canna, si divide una pizza e si chiacchiera' in liberta di haskell, zen e viaggi in motocicletta. L'atmosfera si rabbuia pero' improvvisamente quando viene scoperto un infiltrato provocatore che non sa spiegare la differenza fra left e right fold. Sommariamente giudicato da un tribunale del popolo, l'infelice viene affogato ed abbandonato sulla spiaggia, nell'indifferenza dei bagnanti che continuano a giocare a solitario sui telefonini. c) Seminario accademico Luogo: tetra aula universitaria. Serie presentazioni accademiche si susseguono senza posa. Per ragioni di principio nessuno dei relatori usa power point e riempiono le lavagne nere con suggestivi ma incomprensibili sgorbi. Si suda copiosamente nel caldo estivo e l'olezzo di accademici poco lavati riempie la stanza. Un dottorando dell'universita' di Pisa emoziona l'auditorio, dimostrando in maniera inconfutabile la mirabile corrispondenza fra monoidi destrorsi e logica lineare. Un addottorato del politecnico di Torino, geloso, cerca di staccargli un occhio con un gessetto. Un neofita, che non sa spiegare la differenza fra left e right fold, russa in un angolo. Personalmente, vista la stagione, suggerirei di: - Se c'e' disponibilita' a passare un paio di giorni insieme optare per l'opzione a. Paolino ha proposto a questo proposito di riunirci in un rifugio delle Apuane. - Se invece vogliamo fare una cosa in giornata allora andrei per l'opzione b e suggerirei di vederci sulla spiaggia di Monterosso (5 Terre). Come data, suggerirei l'11 agosto (o 11-12 in caso di opzione a). Per registrarsi, proporre date/luoghi etc, proporrei di utilizzare la pagina wiki dedicata: http://www.haskell.org/haskellwiki/ItaloHaskell/Summer_2008 A presto, titto P.S. Io saro' offline per una settimana a partire da domenica. -------------------------------- Pasqualino "Titto" Assini PhD 25 Heath Road - Wivenhoe CO79PT - Colchester - U.K.

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