February 2009 - Haskell-Cafe

Fwd: Re: [Haskell-cafe] speed: ghc vs gcc
by Khudyakov Alexey 21 Feb '09

21 Feb '09

Oh I've again sent mail to wrong address ---------- Forwarded Message ---------- On Saturday 21 February 2009 02:42:11 you wrote: > On Sat, Feb 21, 2009 at 12:22 AM, Bulat Ziganshin > <bulat.ziganshin(a)gmail.com > > > wrote: > > > > Hello Khudyakov, > > > > Saturday, February 21, 2009, 2:07:39 AM, you wrote: > > > I have another question. Why shouldn't compiler realize that `sum > > > > [1..10^9]' > > > > > is constant and thus evaluate it at compile time? > > > > since we expect that compilation will be done in reasonable amount of > > time. you cannot guarantee this for list-involving computation > > it would be nice to have a compiler that can run forever, incrementally > generating faster and faster versions of the same program, until you press > a key or a timeout is reached. > > then you just let it run before you get to bed ;-) > > you could even pass it in a test data set to which it must be optimized; > after the program is compiled, the compiler runs and profiles it, measures > the results, and does another pass to make it faster. > I've just remembered another but related approach to optimization. It uses genetic algorithm to determine close to the best set of optimization options. Alternatively it could be used to find badly interacting options, pessimizations. Implementation for gcc is here: http://www.coyotegulch.com/products/acovea/ In fact I didn't tried it but I liked the idea. -- Khudaykov Alexey

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Haskell Weekly News: Issue 106 - February 21, 2009
by Brent Yorgey 21 Feb '09

21 Feb '09

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20090221 Issue 106 - February 21, 2009 --------------------------------------------------------------------------- Welcome to issue 106 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements HWEB. Eric Macaulay, following a little [2]prodding by Neil Mitchell, has released version 0 of [3]HWEB, a small tool for producing literate Haskell programs. Cabal-1.6.0.2 and cabal-install-0.6.2. Duncan Coutts [4]announced point-releases of the Cabal library and the cabal-install command line tool. These releases include a number of fixes and minor improvements, and are expected to be included with ghc-6.10.2. Barrie 0.3.1. Fraser Wilson [5]announced a hackage release of [6]Barrie, an implementation of an idea for supporting state based, user-driven GUIs. Yogurt-0.3. Martijn van Steenbergen [7]announced the release of [8]Yogurt-0.3, a MUD client library for Haskell. This version improves over 0.2 in several ways, including support for GHC 6.10, no more unsafeCoerce needed, new support for forking threads, and various refactorings. wxFruit-0.1.2. Henk-Jan van Tuyl [9]announced an [10]update of [11]wxFruit, a graphical user interface that combines some of the power and versatility of wxHaskell with the elegance and simplicity of Fruit. The new version works with GHC 6.10, and also includes a demo game, PaddleBall. Interested parties, take note: the position of developer/maintainer for this library is currently open. Paper draft: "Denotational design with type class morphisms". Conal Elliott [12]announced a [13]draft of a new paper, "Denotational design with type class morphisms". Feedback is appreciated, especially if in time for the March 2 ICFP deadline. Crypto 4.2.0 & Related News. Creighton Hogg [14]announced the release of version 4.2.0 of the [15]Crypto library. Creighton will also betaking over maintenance of the library from Dominic Steinitz. The Typeclassopedia, and request for feedback. Brent Yorgey [16]announced a [17]first draft of an article entitled 'The Typeclassopedia', a "starting point for the student of Haskell wishing to gain a firm grasp of its standard type classes." Comments and feedback are encouraged! hslibsvm-2.88.0.1 - A FFI binding to LibSVM. S. Guenther [18]announced the [19]hlibsvm package, a set of Haskell bindings to the C++ [20]libsvm library. spacepart-0.1.0.0 (was called data-spacepart). Corey O'Connor [21]announced a new release of the [22]spacepart package, supporting space-partitioning data structures. The new release includes many bug fixes and some code cleanup. pqueue-mtl, stateful-mtl. Louis Wasserman [23]announced two new packages, [24]stateful-mtl and [25]pqueue-mtl. stateful-mtl provides an ST monad transformer, several useful operations on generic monad transformers, and a monad transformer intended to cleanly externally wrap operations on a mutable array (including resizing operations). pqueue-mtl provides implementations of several structures supporting a generic 'single-in, single-out' paradigm (encapsulated in a typeclass named Queuelike), including stacks, queues, and several implementations of priority queues. haha-0.1 - Animated ascii lambda. Sebastiaan Visser [26]announced [27]haha, a very minimal vector based ascii art library written just for fun. If you've always wanted to have a full-color rotating vector based ascii art lambda on your terminal, now is your chance! Discussion Darcs and Google Summer of Code. Eric Kow [28]floated the idea of having darcs apply to the Google Summer of Code as a separate mentoring organization, and discussed several ideas for student projects. Jobs Postdoctoral Research Position at Yale University. Paul Hudak [29]announced the availability of a postdoctoral research position at Yale University. The successful candidate will apply modern, high-level programming language ideas (such as embodied in Haskell) to help design and implement a language for the control of BGP-based network routers, with the goal of realizing high-level networking protocols for traffic engineering, security, and related networking concerns. Blog noise [30]Haskell news from the [31]blogosphere. * GHC / OpenSPARC Project: [32]Triage. * Manuel M T Chakravarty: [33]Mark your Haskell tweets with #haskell. * Gregg Reynolds: [34]Performance Economics. * Alex Mason: [35]AVar released (three times). * Sean Leather: [36]The strict danger of switching from pure to monadic Template Haskell. * Mads Lindstrom: [37]Using Mutable Arrays for Faster Sorting. * Conal Elliott: [38]Denotational design with type class morphisms. A draft of Conal's new paper. * Jesse Andrews: [39]Getting Tiled with XMonad. * happstack.com: [40]SOCALFP Presentation Slides: "Happstack is better than X". * Luke Palmer: [41]Dependent types are ridiculously easy. * GHC / OpenSPARC Project: [42]Thunderbirds are go. * Brent Yorgey: [43]Typeclassopedia---a generic response. * Alex Mason: [44]ASTM updates. * London Haskell Users Group: [45]Lemmih: LHC - past, present and future. * Eric Kow (kowey): [46]announcing: burrito tutorial support group. Laden with burrito tutorial guilt? The burrito tutorial support group can help. * Alex Mason: [47]ASTM: redundant STMish fun. * happstack.com: [48]Announcing the launch of the Patch-Tag blog. * Colin Ross: [49]XML parsing with Haskell. * Brent Yorgey: [50]The Typeclassopedia---request for feedback. * Sean Leather: [51]Incremental fold, a design pattern. * Manuel M T Chakravarty: [52]Comparison of type families with functional dependencies.. A nice summary comparison of these two Haskell language features. * Random permutations and sorting: [53]Heinrich Apfelmus. * A day with xmonad: [54]Colin Adams. * Antoine Latter: [55]MaybeT - The CPS Version. * Gregg Reynolds: [56]Intergalactic Telefunctors and Quantum Entanglement. * Gregg Reynolds: [57]In Praise of Elitism. * Dan Piponi (sigfpe): [58]Beyond Monads. A generalization of monads to parameterized monads. * Well-Typed.Com: [59]Cabal ticket #500. Quotes of the Week * KetilMalde: No, those are quite outdated by now. The new horsemen of the programming apocalypse are, of course, IO, MutableState, LazyMemoryLeak, and Bottom. * skorpan: i love the layout of lyah. makes me feel like having some chunky bacon. * lilac: * lilac looks forward to Cale explaining category theory by analogy to Call of Duty * byorgey: _|_ ... is a party pooper * idnar: enlarge your context in just seven days with all-natural herbal supplements! * mmorrow: gah, i'm so used to haskell i forgot a return stmt in C and was trying to figure out where the segfault was happening for 20 minutes About the Haskell Weekly News New editions are posted to [60]the Haskell mailing list as well as to [61]the Haskell Sequence and [62]Planet Haskell. [63]RSS is also available, and headlines appear on [64]haskell.org. To help create new editions of this newsletter, please see the information on [65]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [66]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://neilmitchell.blogspot.com/2009/01/small-scripts-with-haskell.html 3. http://mathmeth.com/eem/hweb/quickstart.shtml 4. http://www.haskell.org//pipermail/haskell-cafe/2009-February/056153.html 5. http://article.gmane.org/gmane.comp.lang.haskell.general/16882 6. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/barrie 7. http://article.gmane.org/gmane.comp.lang.haskell.general/16869 8. http://code.google.com/p/yogurt-mud/ 9. http://article.gmane.org/gmane.comp.lang.haskell.cafe/53341 10. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/wxFruit 11. http://www.haskell.org/haskellwiki/WxFruit 12. http://article.gmane.org/gmane.comp.lang.haskell.cafe/53166 13. http://conal.net/papers/type-class-morphisms/ 14. http://article.gmane.org/gmane.comp.lang.haskell.cafe/53029 15. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Crypto 16. http://article.gmane.org/gmane.comp.lang.haskell.cafe/52964 17. http://www.cis.upenn.edu/~byorgey/papers/typeclassopedia-draft-090216.pdf 18. http://article.gmane.org/gmane.comp.lang.haskell.cafe/52961 19. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hslibsvm 20. http://www.csie.ntu.edu.tw/~cjlin/libsvm/ 21. http://article.gmane.org/gmane.comp.lang.haskell.cafe/52951 22. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/spacepart 23. http://article.gmane.org/gmane.comp.lang.haskell.cafe/52920 24. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/stateful%2Dmtl 25. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/pqueue%2Dmtl 26. http://article.gmane.org/gmane.comp.lang.haskell.cafe/52865 27. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/haha 28. http://www.haskell.org//pipermail/haskell-cafe/2009-February/056057.html 29. http://article.gmane.org/gmane.comp.lang.haskell.cafe/53103 30. http://planet.haskell.org/ 31. http://haskell.org/haskellwiki/Blog_articles 32. http://ghcsparc.blogspot.com/2009/02/triage.html 33. http://justtesting.org/post/80211621 34. http://syntax.wikidot.com/blog:10 35. http://axman6.homeip.net/blog/2009/02/avar-released.html 36. http://feedproxy.google.com/~r/splonderzoek/~3/sD_bp8yKBxc/strict-danger-of… 37. http://lindstroem.wordpress.com/2009/02/19/using-mutable-arrays-for-faster-… 38. http://conal.net/blog/posts/denotational-design-with-type-class-morphisms/ 39. http://overstimulate.com/articles/why-xmonad 40. http://blog.happstack.com/2009/02/18/socalfp-presentation-slides-happstack-… 41. http://lukepalmer.wordpress.com/2009/02/18/dependent-types-are-ridiculously… 42. http://ghcsparc.blogspot.com/2009/02/thunderbirds-are-go.html 43. http://byorgey.wordpress.com/2009/02/17/typeclassopedia-a-generic-response/ 44. http://axman6.homeip.net/blog/2009/02/astm-updates.html 45. http://www.londonhug.net/2009/02/17/lemmih-lhc-past-present-and-future/ 46. http://koweycode.blogspot.com/2009/02/announcing-burrito-tutorial-support.h… 47. http://axman6.homeip.net/blog/2009/02/astm-redundant-stmish-fun.html 48. http://blog.happstack.com/2009/02/16/announcing-the-launch-of-the-patch-tag… 49. http://vcolin.com/2009/02/16/xml-parsing-haskell/ 50. http://byorgey.wordpress.com/2009/02/16/the-typeclassopedia-request-for-fee… 51. http://feedproxy.google.com/~r/splonderzoek/~3/tj_MkKqIlkQ/incremental-fold… 52. http://justtesting.org/post/78667708 53. http://apfelmus.nfshost.com/random-permutations.html 54. http://colina.demon.co.uk/?q=node/534 55. http://panicsonic.blogspot.com/2009/02/maybet-cps-version.html 56. http://syntax.wikidot.com/blog:9 57. http://syntax.wikidot.com/blog:8 58. http://blog.sigfpe.com/2009/02/beyond-monads.html 59. http://blog.well-typed.com/2009/02/cabal-ticket-500/ 60. http://www.haskell.org/mailman/listinfo/haskell 61. http://sequence.complete.org/ 62. http://planet.haskell.org/ 63. http://sequence.complete.org/node/feed 64. http://haskell.org/ 65. http://haskell.org/haskellwiki/HWN 66. http://code.haskell.org/~byorgey/code/hwn/

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Showing >100% CPU usage of parallel code
by Jim Burton 21 Feb '09

21 Feb '09

Hi, I copied the program below from a reddit post of dons'. I have a dual core laptop with ubuntu hardy and ghc 6.10.1. I can see the difference when I run the program with +RTS -N2 but CPU always says 100%. I'd like an example that shows >100 -- is it not showing >100 because of my timeformat or because of the program? If it's the latter can you point me to an example that will use more cpu? Here's the output: $ cat /proc/cpuinfo | grep processor | wc -l 2 $ export TIMEFORMAT="%E real,%U user,%S sys, %P cpu" $ ghc -O2 --make Par.hs -threaded $ time ./Par 1405006117752879898543142606244511569936384005711076 2.330 real,2.328 user,0.000 sys, 99.92 cpu $ time ./Par +RTS -N2 1405006117752879898543142606244511569936384005711076 1.504 real,2.316 user,0.016 sys, 100.00 cpu Here's the program: ---------------- import Control.Parallel main = a `par` b `par` c `pseq` print (a + b + c) where a = ack 3 10 b = fac 42 c = fib 34 fac 0 = 1 fac n = n * fac (n-1) ack 0 n = n+1 ack m 0 = ack (m-1) 1 ack m n = ack (m-1) (ack m (n-1)) fib 0 = 0 fib 1 = 1 fib n = fib (n-1) + fib (n-2) -------------------- Thanks, Jim -- View this message in context: http://www.nabble.com/Showing-%3E100--CPU-usage-of-parallel-code-tp22137081… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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A typeclass for Data.Map etc?
by Eugene Kirpichov 21 Feb '09

21 Feb '09

Greetings, Is there a typeclass for mappings with a Data.Map-like interface, with stuff like: empty, insert, insertWithKey, unionWith etc. ? And, probably, a similar typeclass for mutable mappings like Data.Hashtable. Looks like such a thing would be useful; as for now, I see at least two applications: Data.Map and Data.Trie (bytestring-trie) - it's a pity that they have rather similar interfaces, but the latter lacks many methods and some are named in a different way. Also, Data.Map has some inconsistensies, too: for instance, it has an insertWith' but lacks a unionWith'. "One typeclass for all" would eliminate these inconsistencies. I'm asking mainly because I've been wondering why noone has yet written a mutable hashtable package with a MArray-like interface, I wrote a small thing myself and I am unsure as to what interface it should have. -- Eugene Kirpichov

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RE: "first class" tuples?
by Brian Bloniarz 20 Feb '09

20 Feb '09

Wolfgang Jeltsch wrote: > Make , an infix operator. Then even the syntax (,) works without further ado. > Make , right-associative, for example. Then you can write (a1,...,an) which > means (a1,(a2,(...,an))). You just need one data declaration: > > data (a,b) = (a,b) > > However, this has the problem that it leads to more partially-defined values > than with today's tuples. For example, you could have a *triple* (a,_|_). > > So maybe we should treat tuple syntax completely as special syntax (as it is > today) and define our tuple types so that tuples don't end with the last > element (as above) but with an explicit empty tuple (like lists end in a > nil). This would also give use 1-tuples. We would need the unit type () for > empty tuples. Then we define a cons type which has a strictness annotation: > > data head :# tail = head :# !tail Lennart Augustsson wrote: > Look at the HList stuff by Oleg and others and you'll find the kind of > tuples you suggest. One thing about HList: the HCons type is lazy in its second element, so HList tuples can be more partially-defined than normal tuples. Anybody know the rationale for this? I'm curious whether it could be changed, or if any code depends on it. -Brian _________________________________________________________________ Access your email online and on the go with Windows Live Hotmail. http://windowslive.com/online/hotmail?ocid=TXT_TAGLM_WL_HM_AE_Access_022009

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Trying to install Cabal
by David 20 Feb '09

20 Feb '09

Hi! I've just installed ghc (v 6.10.1) for Windows, and it seems to be installed correctly, and now I'm trying to install Cabal (v1.6.0.2), but I'm getting the following error message (along with a lot of warnings about a deprecated something-or-other, which I assume I can ignore): C:\Temp>runghc Setup configure -p Distribution\Simple\Utils.hs:1:11: Warning: -fffi is deprecated: use -XForeignFunctionInterface or pragma {-# LANGUAGE ForeignFunctionInterface#-} instead Distribution\Simple\Utils.hs:4:15: Warning: -fffi is deprecated: use -XForeignFunctionInterface or pragma {-# LANGUAGE ForeignFunctionInterface#-} instead Distribution\Simple\InstallDirs.hs:1:11: Warning: -fffi is deprecated: use -XForeignFunctionInterface or pragma {-# LANGUAGE ForeignFunctionInterface#-} instead Distribution\Simple\InstallDirs.hs:4:15: Warning: -fffi is deprecated: use -XForeignFunctionInterface or pragma {-# LANGUAGE ForeignFunctionInterface#-} instead During interactive linking, GHCi couldn't find the following symbol: SHGetFolderPathA@20 This may be due to you not asking GHCi to load extra object files, archives or DLLs needed by your current session. Restart GHCi, specifying the missing library using the -L/path/to/object/dir and -lmissinglibname flags, or simply by naming the relevant files on the GHCi command line. Alternatively, this link failure might indicate a bug in GHCi. If you suspect the latter, please send a bug report to: glasgow-haskell-bugs(a)haskell.org Am I missing a dependency, or is ghc not installed properly, or am I doing something else wrong? Thanks, David.

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Error installing pkg 'HDBC-sqlite3'
by David 20 Feb '09

20 Feb '09

I've encountered another problem while trying to install 'HDBC-sqlite3'. I did the install "manually", instead of using Cabal, and during the build phase, received the following error message: D:\Apps\ghc\ghc-6.10.1\HDBC-sqlite3-2.1.0.0>runghc Setup build Preprocessing library HDBC-sqlite3-2.1.0.0... Database\HDBC\Sqlite3\Statement.hsc:41:21: sqlite3.h: No such file or directory Database\HDBC\Sqlite3\Statement.hsc: In function `main': Database\HDBC\Sqlite3\Statement.hsc:137: error: `SQLITE_NULL' undeclared (first use in this function) Database\HDBC\Sqlite3\Statement.hsc:137: error: (Each undeclared identifier is reported only once Database\HDBC\Sqlite3\Statement.hsc:137: error: for each function it appears in.) Database\HDBC\Sqlite3\Statement.hsc:148: error: `SQLITE_ROW' undeclared (first use in this function) Database\HDBC\Sqlite3\Statement.hsc:149: error: `SQLITE_DONE' undeclared (first use in this function) Database\HDBC\Sqlite3\Statement.hsc:150: error: `SQLITE_ERROR' undeclared (first use in this function) compiling dist\build\Database\HDBC\Sqlite3\Statement_hsc_make.c failed Is the file 'sqlite3.h' missing? Or am I doing something wrong? Thanks, David.

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foreign export space-leaks?
by James Ge 20 Feb '09

20 Feb '09

first I wrote a silly haskell program: --- a program to walk through very long list ---- data Silly = A !Int | B !Int deriving (Show) main = go [a + b | a <- [0..10000], b <- [0..10000]] where go [] = do putStrLn $ "completed." go (x:xs) = do case even x of True -> putStrLn $ show (A x) False -> putStrLn $ show (B x) go xs ---------- end of the program ----------- upper program ran well, and consumed fixed memory (2.8M watched by top). but when I exported the main to C and host the whole haskell program in C, memory consumption increased CONSTANTLY. what I did are: 1) explicit name the module to `Silly' and rename `main' to `call_me_back' 2) write a c wrapper following guildlines here(http://www.haskell.org/ ghc/docs/latest/html/users_guide/ffi-ghc.html#hs-exit): --- c wrapper code begins ---- #include <stdio.h> #include "HsFFI.h" #ifdef __GLASGOW_HASKELL__ #include "Silly_stub.h" #endif #ifdef __GLASGOW_HASKELL__ extern void __stginit_Silly ( void ); #endif int main() { hs_init(0, 0); #ifdef __GLASGOW_HASKELL__ hs_add_root(__stginit_Silly); #endif call_me_back(); hs_exit(); return 0; } ---- wrapper code ends ----- then I compiled them together: ---- Makefile section begins ----- ghc -O2 --make Silly.hs ghc -O2 --make Silly_wrapper.c ghc -O2 -o Silly.out *.o ./Silly -----Makefile sect ends ----------- this program consumed memory constantly until the process being terminated by OS because of `out of memory'. I guess this must have something to do with GC (although i tried import hs_perform_gc declared in HsFFI.h and called the function, but i didn't see any change), do you have ideas? Thanks in advance, jge

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Fwd: [Haskell-cafe] speed: ghc vs gcc
by Alberto G. Corona 20 Feb '09

20 Feb '09

I think that a higuer level language has better opportunities to optimize, specially if the compiler is coded in its own language. for example I guess that a good type dependent implementation would evaluate the sum[1..10^9::Int] at compilation time. I reality haskell is much much faster than c in some cases that now are not considered, but it is fair to remember that haskell outperfromed all the rest in those old benchmarks with did´t care to print the results. This may seem trivial now, but at the time surprised the benchmark people. 2009/2/21 Khudyakov Alexey <alexey.skladnoy(a)gmail.com> On Friday 20 February 2009 16:29:29 Bulat Ziganshin wrote: > > Hello haskell-cafe, > > > > since there are no objective tests comparing ghc to gcc, i made my own > > one. these are 3 programs, calculating sum in c++ and haskell: > > > > main = print $ sum[1..10^9::Int] > > > > ... skipped ... > > The discussion is mostly about low level optimizations such as loop > unrolling > etc. > > I have another question. Why shouldn't compiler realize that `sum > [1..10^9]' > is constant and thus evaluate it at compile time? > > -- > Khudakov Alexey > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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Paper draft: "Denotational design with type class morphisms"
by Conal Elliott 20 Feb '09

20 Feb '09

I have a draft paper some of you might enjoy, called "Denotational design with type class morphisms". Abstract: Type classes provide a mechanism for varied implementations of standard interfaces. Many of these interfaces are founded in mathematical tradition and so have regularity not only of *types* but also of *properties* (laws) that must hold. Types and properties give strong guidance to the library implementor, while leaving freedom as well. Some of the remaining freedom is in *how* the implementation works, and some is in *what* it accomplishes. To give additional guidance to the *what*, without impinging on the *how*, this paper proposes a principle of *type class morphisms* (TCMs), which further refines the compositional style of denotational semantics. The TCM idea is simply that *the instance's meaning is the meaning's instance*. This principle determines the meaning of each type class instance, and hence defines correctness of implementation. In some cases, it also provides a systematic guide to implementation, and in some cases, valuable design feedback. The paper is illustrated with several examples of type, meanings, and morphisms. You'll find the paper at http://conal.net/papers/type-class-morphisms/ . I'd sure appreciate feedback on it, especially if in time for the *March 2* ICFP deadline. Pointers to related work would be particularly appreciated, as well as what's unclear and what could be cut. This draft is an entire page over the limit, so I'll have to do some trimming before submitting. Enjoy, and thanks! - Conal

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