- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Data.Array.Accelerate initialization timings
by Paul Sujkov 23 Feb '12

23 Feb '12

Ah, it seems that I see now what's going wrong way. I'm not using the 'run' function from the CUDA backend, and so by default I guess the code is interpreted (the test backend used for semantics check). However, it's not perfectly clear how to use CUDA backend explicitly. If you have any suggestions, it would be a great help! On 20 February 2012 16:06, Alex Gremm <algremm(a)googlemail.com> wrote: > Hi Paul, > > even though I just started reading about Accelerate, it seems to me that > you didn't use the "use" method which according to [1] initiates > asynchronous data transfer from host to GPU. > > > Cheers, > Alex > > [1]: http://www.cse.unsw.edu.au/%7Echak/papers/acc-cuda.pdf > On 20/02/12 14:46, Paul Sujkov wrote: > > Hi everyone, > > > > since accelerate mail list seems to be defunct, I'm trying to ask > > specific questions here. The problem is: array initialization in > > Data.Array.Accelerate takes a 10x amount of time in contrast to both > > Data.Array and bare C++ CUDA array initialization. This can be due to > > Data.Array.Accelerate having two backends (however, it's own tests show > > that my nVidia card is CUDA-capable), but I'm not aware of how can I > > profile GPU to check whether it is used or not. Anyway, here's code: > > > > http://hpaste.org/64036 > > > > both generateArray (DIM3) and generateArray1 (DIM1) take the same amount > > of time to initialize array. I'd say the problem is in GPU memory > > copying time, but here's bare C++ code: > > > > http://hpaste.org/64037 > > > > which does exactly the same, but 10 times faster. I'm wandering what am > > I doing wrong and how to check if I really am. Thanks in advance if > > anyone can point me on my mistakes! > > > > -- > > Regards, Paul Sujkov > > > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > -- Regards, Paul Sujkov

3 2

Haskell Weekly News: Issue 216
by Daniel Santa Cruz 23 Feb '12

23 Feb '12

Welcome to issue 216 of the HWN, a newsletter covering crowdsourced links for the Haskell community. This release covers the week of February 12 to 18, 2012. You can find the HTML version at: http://contemplatecode.blogspot.com/2012/02/haskell-weekly-news-issue-216.h… Quotes of the Week * monochrom: the selfish program's motive is to fool the programmer * WilliamByrd: Oleg is an emissary from some advanced alien race. Working with him is both exhausting and enlightening. * CodeWeaverX: do-block, or do-not-block. There is no try-catch-block. Top Reddit Stories * Where is Hackage 2.0? Domain: self.haskell, Score: 66, Comments: 42 On Reddit: [1] http://goo.gl/uXq10 Original: [2] http://goo.gl/uXq10 * Haskell Performance Patters [HTML slideshow] Domain: blog.johantibell.com, Score: 52, Comments: 13 On Reddit: [3] http://goo.gl/Y5tCb Original: [4] http://goo.gl/T9zZI * Concatenative, Row-Polymorphic Programming in Haskell (re: Why Concatenative Programming Matters) Domain: github.com, Score: 41, Comments: 21 On Reddit: [5] http://goo.gl/0w83b Original: [6] http://goo.gl/aw22p * Neil Mitchell - Shake: A Better Make Domain: neilmitchell.blogspot.com, Score: 37, Comments: 7 On Reddit: [7] http://goo.gl/MeFQ1 Original: [8] http://goo.gl/4HM0d * Why concatenative programming matters. Domain: evincarofautumn.blogspot.com, Score: 37, Comments: 23 On Reddit: [9] http://goo.gl/Udpdt Original: [10] http://goo.gl/VvUvt * GSOC 2012 Project Proposal - GHCi in the web browser Domain: apfelmus.nfshost.com, Score: 36, Comments: 34 On Reddit: [11] http://goo.gl/KS6d8 Original: [12] http://goo.gl/epgTZ * Yesod Blog :: Call for GSoC: expand the reach of Haskell with interactive websites and good persistence Domain: yesodweb.com, Score: 31, Comments: 20 On Reddit: [13] http://goo.gl/1HQ9d Original: [14] http://goo.gl/bxKIC * hxournal - A pen notetaking program written in Haskell Domain: ianwookim.org, Score: 25, Comments: 16 On Reddit: [15] http://goo.gl/4UG5E Original: [16] http://goo.gl/kQOMh * Type checking by theorem proving in IDRIS: Brady [pdf, 29 slides] Domain: cs.st-andrews.ac.uk, Score: 25, Comments: 33 On Reddit: [17] http://goo.gl/qAD5L Original: [18] http://goo.gl/mhdlC * Using Lawvere theories to combine effects Domain: blog.sigfpe.com, Score: 24, Comments: 0 On Reddit: [19] http://goo.gl/4IHq7 Original: [20] http://goo.gl/QS1aO * BayHac '12 Domain: haskell.org, Score: 23, Comments: 0 On Reddit: [21] http://goo.gl/nuxUm Original: [22] http://goo.gl/NCQGy * Hope for Haskell: making Hackage and cabal-install more awesome Domain: github.com, Score: 22, Comments: 23 On Reddit: [23] http://goo.gl/E9MmZ Original: [24] http://goo.gl/sLpkp * Thoughts on Haskell Development Domain: self.haskell, Score: 21, Comments: 77 On Reddit: [25] http://goo.gl/Qdt4b Original: [26] http://goo.gl/Qdt4b * Relating Category Theory to Programming Language Theory - MathOverflow Domain: mathoverflow.net, Score: 21, Comments: 1 On Reddit: [27] http://goo.gl/wA9E2 Original: [28] http://goo.gl/6Ox5n * The Other Prelude — any activity here? It seems like a worthwhile project. Domain: haskell.org, Score: 18, Comments: 13 On Reddit: [29] http://goo.gl/j94fj Original: [30] http://goo.gl/kwGCm Top StackOverflow Questions * Covariance / Contravariance in Haskell? votes: 24, answers: 2 Read on SO: [31] http://goo.gl/wBjaP * Haskell for someone who already knows some category theory votes: 17, answers: 1 Read on SO: [32] http://goo.gl/ms4dE * Haskell libraries overview and their quality [closed] votes: 16, answers: 1 Read on SO: [33] http://goo.gl/H3Rwg * Haskell existential quantification in detail votes: 12, answers: 1 Read on SO: [34] http://goo.gl/uiJZG * Derivative Towers and how to use the vector-space package (haskell) votes: 11, answers: 1 Read on SO: [35] http://goo.gl/lkPEl * Why doesn't Scala have an IO Monad? votes: 10, answers: 1 Read on SO: [36] http://goo.gl/dyTte * How to let a function [a] -> [a] operate on [(a,Int)]? votes: 9, answers: 2 Read on SO: [37] http://goo.gl/Js3As * Speed up runhaskell votes: 9, answers: 4 Read on SO: [38] http://goo.gl/yc3qo * Unnecessary type juggling to define Data.Void (package “void” on Hackage)? votes: 8, answers: 1 Read on SO: [39] http://goo.gl/FCmyv * Lazy vs eager evaluation and double linked list building votes: 8, answers: 3 Read on SO: [40] http://goo.gl/Z55Og Until next time, Daniel Santa Cruz References 1. http://www.reddit.com/r/haskell/comments/pn2oh/where_is_hackage_20/ 2. http://www.reddit.com/r/haskell/comments/pn2oh/where_is_hackage_20/ 3. http://blog.johantibell.com/2012/02/slides-from-haskell-performance.html 4. http://www.reddit.com/r/haskell/comments/pry5h/haskell_performance_patters_… 5. https://github.com/leonidas/codeblog/blob/master/2012/2012-02-17-concatenat… 6. http://www.reddit.com/r/haskell/comments/ptji8/concatenative_rowpolymorphic… 7. http://neilmitchell.blogspot.com/2012/02/shake-better-make.html 8. http://www.reddit.com/r/haskell/comments/plv2b/neil_mitchell_shake_a_better… 9. http://evincarofautumn.blogspot.com/2012/02/why-concatenative-programming-m… 10. http://www.reddit.com/r/haskell/comments/pmcav/why_concatenative_programmin… 11. http://apfelmus.nfshost.com/blog/2012/02/14-summer-of-code-proposal.html 12. http://www.reddit.com/r/haskell/comments/ppdgq/gsoc_2012_project_proposal_g… 13. http://www.yesodweb.com/blog/2012/02/call-for-gsoc-2012 14. http://www.reddit.com/r/haskell/comments/pqudh/yesod_blog_call_for_gsoc_exp… 15. http://ianwookim.org/hxournal 16. http://www.reddit.com/r/haskell/comments/por66/hxournal_a_pen_notetaking_pr… 17. http://www.cs.st-andrews.ac.uk/~eb/writings/idris-stp.pdf 18. http://www.reddit.com/r/haskell/comments/pp6i3/type_checking_by_theorem_pro… 19. http://blog.sigfpe.com/2012/02/using-lawvere-theories-to-combine.html 20. http://www.reddit.com/r/haskell/comments/pm46y/using_lawvere_theories_to_co… 21. http://www.haskell.org/haskellwiki/BayHac2012 22. http://www.reddit.com/r/haskell/comments/puzxx/bayhac_12/ 23. https://github.com/DanBurton/Blog/blob/master/Markdown/Hope.md 24. http://www.reddit.com/r/haskell/comments/pswbp/hope_for_haskell_making_hack… 25. http://www.reddit.com/r/haskell/comments/ppf7p/thoughts_on_haskell_developm… 26. http://www.reddit.com/r/haskell/comments/ppf7p/thoughts_on_haskell_developm… 27. http://mathoverflow.net/questions/4235/relating-category-theory-to-programm… 28. http://www.reddit.com/r/haskell/comments/put1g/relating_category_theory_to_… 29. http://www.haskell.org/haskellwiki/The_Other_Prelude 30. http://www.reddit.com/r/haskell/comments/ppwst/the_other_prelude_any_activi… 31. http://stackoverflow.com/questions/9302739/covariance-contravariance-in-has… 32. http://stackoverflow.com/questions/9252488/haskell-for-someone-who-already-… 33. http://stackoverflow.com/questions/9286799/haskell-libraries-overview-and-t… 34. http://stackoverflow.com/questions/9259921/haskell-existential-quantificati… 35. http://stackoverflow.com/questions/9313994/derivative-towers-and-how-to-use… 36. http://stackoverflow.com/questions/9345008/why-doesnt-scala-have-an-io-monad 37. http://stackoverflow.com/questions/9324862/how-to-let-a-function-a-a-operat… 38. http://stackoverflow.com/questions/9326097/speed-up-runhaskell 39. http://stackoverflow.com/questions/9261490/unnecessary-type-juggling-to-def… 40. http://stackoverflow.com/questions/9277176/lazy-vs-eager-evaluation-and-dou…

1 0

Haskell development in Mac OS X after Gatekeeper
by Tom Murphy 23 Feb '12

23 Feb '12

Does anyone know what this will mean for the future of Haskell development in OS X?: http://www.apple.com/macosx/mountain-lion/security.html I'm particularly interested in what it'll mean for 0) Distributing non-Cocoa-built apps, even if you're approved by Apple 1) Writing software for widespread use (a security setting is to only run software from the App Store, and I'd like to have my software function on users' computers.) 1.0) Aren't you unable to put software under the GPL or certain other open-source licenses on the App Store? amindfv / Tom

8 19

Toronto Haskell Users Meetup
by Christopher Olah 22 Feb '12

22 Feb '12

Hey All, There's going to be a Toronto Haskell Users Meetup at hacklab on March 7th starting at 7pm. Come by and meet your fellow Haskellers! http://thug1.eventbrite.com/ This will be the first one. I'm really looking forward to meeting other Haskellers in person! Haskell Users of Toronto, unite! Chris http://colah.ca PS. Thoughts about where else I should mention this are appreciated.

1 0

Monad laws in presence of bottoms
by Roman Cheplyaka 22 Feb '12

22 Feb '12

I just realised that many common monads do not obey the monad laws when it comes to bottoms. E.g. for the Reader monad: undefined >>= return /= undefined return () >>= undefined /= undefined return () >>= const undefined /= undefined return undefined >>= \x -> case x of () -> return () /= undefined Not a long time ago David Barbour argued on this list that bottoms should be ignored when checking the monad laws. Is that the commonly accepted interpretation of the laws? Is there any other interpretation in which the Reader monad obeys the laws? -- Roman I. Cheplyaka :: http://ro-che.info/

6 15

Re: [Haskell-cafe] Streaming to JuicyPixels
by Vincent Berthoux 22 Feb '12

22 Feb '12

Hi, I can understand your performance problems, I bumped into them before the first release of Juicy Pixels and took a long time to get 'correct' performance out of the box, and the IDCT is not the only 'hot point', I got problems with intermediate data structure as well. Any list has proven a bit problematic performance wise, so I rewrote some things which would have been easily implemented with forM_ or mapM_ with manual recursion. I didn't knew STT existed, so it open a new area of reflection for the streaming Jpeg decoder, instead of using the (remaining >> getBytes) combo, staying in the Get monad might help. The reason to expose the ST monad is that I use it internally to mutate the final image directly, and I'd prefer to avoid freezing/unfreezing the underlying array. So in order to give access to the intermediate representation, a type could be (STT s (StateT JpegDecodingState Get) (MutableImage s PixelYCbCr8)) (the Jpeg decoder only produce (Image PixelYCbCr8 internally)). This should allow a freeze then a color conversion. As it would induce performance loss, this version should exist alongside current implementation. This is not trivial, but it's far from impossible. For the IDCT implementation, I don't think a package make much sense, if you want to use it, just grab it and customize the interface to your needs :). Regards Vincent Berthoux Le 21 février 2012 06:16, Myles C. Maxfield <myles.maxfield(a)gmail.com> a écrit : Hello, and thanks for the quick reply. > > You're right that using (remaining >> getBytes) won't work for streaming, > as it would pull the rest of the stream into a buffer, thereby delaying > further processing until the image is completely downloaded. :-( > > I'm a little unclear about what you mean about the use of the ST monad. > There is an STT<http://hackage.haskell.org/packages/archive/STMonadTrans/0.2/doc/html/Contr…> monad > transformer, so you could wrap that around Get. Is that what you're > referring to? > > As an aside: I didn't realize that JuicyPixels existed, so I wrote a JPEG > decoder specifically designed for streaming - it doesn't request a byte of > input unless it has to, uses a StateT (wrapped around Attoparsec) to keep > track of which bit in the current byte is "next", and does the Huffman > decoding in-line. However, I didn't use ST for the IDCT, so my own decoder > has serious performance problems. This prompted me to start searching > around for a solution, and I came across JuicyPixels, which already exists > and is much faster than my own implementation. I'm hoping to get rid of my > own decoder and just use JuicyPixels. If you're curious, my own code is > here: https://github.com/litherum/jpeg. > > Is it reasonable to extend JuicyPixels to fit my use case? It sounds like > JuicyPixels wouldn't work so well as it stands. I'd be happy to do whatever > work is necessary to help out and get JuicyPixels usable for me. However, > if that would require a full (or near-full) rewrite, it might make more > sense for me to use my own implementation with your IDCT. Is there a way we > can share just the IDCT between our two repositories? Perhaps making a new > IDCT8 library that we can both depend on? > > As for what API I'd like to be able to use, just a "Get DynamicImage" > should suffice (assuming it has streaming semantics as described above). It > would be really nice if it was possible to get at the incomplete image > before the stream is completed (so the image could slowly update as more > data arrives from the network), but I'm not quite sure how to elegantly > express that. Do you have any ideas? > > I think that having 2 native jpeg decoders (Actually 3, because of this > package <http://hackage.haskell.org/package/jpeg>) is detrimental to the > Haskell community, and I would really like to use JuicyPixels :D > > Thanks, > Myles C. Maxfield > > > On Mon, Feb 20, 2012 at 3:01 PM, Vincent Berthoux < > vincent.berthoux(a)gmail.com> wrote: > >> Hi, >> >> I can expose the low level parsing, but you would only get the >> chunks/frames/sections of the image, Cereal is mainly used to parse the >> structure of the image, not to do the raw processing. For the raw >> processing, I rely on `remaining >> getBytes` to be able to manipulate data >> at bit level or to feed it to zlib, and the documentation clearly state >> that remaining doesn't work well with runGetPartial, so no read ahead, but >> even worse for streaming :). >> >> To be fair, I never thought of this use case, and exposing a partially >> decoded image would impose the use of the ST Monad somehow, and Serialize >> is not a monad transformer, making it a bit hard to implement. >> >> By curiosity what kind of API would you hope for this kind of >> functionality? >> >> Regards >> >> Vincent Berthoux >> >> Le 20 février 2012 22:08, Myles C. Maxfield <myles.maxfield(a)gmail.com> a >> écrit : >> >> Hello, >>> I am interested in the possibility of using JuicyPixels for streaming >>> images from the web. It doesn't appear to expose any of its internally-used >>> Serialize.Get functionality, which is problematic for streaming - I would >>> not like to have to stream the whole image into a buffer before the decoder >>> can start decoding. Are there any plans on exposing this API, so I can use >>> the runGetPartial function to facilitate streaming? >>> >>> In addition, does the library do much readahead? There's no point in >>> exposing a Get interface if it's just going to wait until the stream is >>> done to start decoding anyway. >>> >>> Thanks, >>> Myles C. Maxfield >>> >> >> >

2 1

Re: [Haskell-cafe] ANN: network-socket-options 0.1
by Joey Adams 22 Feb '12

22 Feb '12

On Wed, Feb 22, 2012 at 5:56 AM, L Corbijn <aspergesoepje(a)gmail.com> wrote: > On Wed, Feb 22, 2012 at 5:58 AM, Joey Adams <joeyadams3.14159(a)gmail.com> wrote: >> I released network-socket-options 0.2, adding setSocketTimeouts and >> setHandleTimeouts. I'll post an announcement in a separate thread >> once the Haddock documentation is generated. >> >> -Joey >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe > > Hi Joey, > > Seeing the large number of getters and setters in this package I was > wondering if it might be improved by using 'StateVar's from the > StateVar package. > http://hackage.haskell.org/package/StateVar > > Lars > > P.S. It does mention OpenGL (where it's actively used), but replacing > that with 'socket' makes the description seem to fit rather well. Copying to the mailing list. Thanks for pointing out StateVar. However, setSocketOption and getSocketOption (or variants taking raw Fds or GHC FDs) will not have a class for socket options to abstract over. It'd be nicer to see a list of settable options under the SetSockOpt class, and a list of gettable options under the GetSockOpt class. -Joey

1 0

how to add monad-stack to network-conduit
by Alexander V Vershilov 22 Feb '12

22 Feb '12

Hello. I have got next problem: I want to have database connection pool in server based on network-conduit. So I wanted to be able to do > runTCPServer options action > where > action src snk = > pool <- ask > .... > In this situation I can make pool `action's parameter, but in more difficult situations (many methods inside) is would be painfull. Also I wanted to have some kind of State for each thread, e.g. > action src snk = src $= act1 $= act2 $= act3 $$ snk in act1, act2, act3 I want to read and change state. Is it possible? And how to do it if it is? -- Alexander Vershilov

2 2

ANNOUNCE: HaskellDB 2.0: Scrap your SQL strings
by Justin Bailey 22 Feb '12

22 Feb '12

What is it? ======== The HaskellDB library lets you generate SQL queries without writing any actual SQL. Unlike other query generating libraries, you choose the abstraction level. Queries can be built out of independent fragments, just like your programs. Leave hand-written, string-based, SQL libraries behind and check out HaskellDB. Where to get it? ============ You can get it from Hackage (http://hackage.haskell.org/package/haskelldb) or by using cabal (cabal install haskelldb). You also need drivers for your specific database. HaskellDB currently supports the HDBC family of drivers. First, download haskelldb-hdbc (http://hackage.haskell.org/package/haskelldb-hdbc) then get the appropriate package for your database: * ODBC: haskelldb-hdbc-odbc (http://hackage.haskell.org/package/haskelldb-hdbc-odbc) * Postgres: haskelldb-hdbc-postgresql (http://hackage.haskell.org/package/haskelldb-hdbc-postgresql) * Sqllite: haskelldb-hdbc-sqlite3 (http://hackage.haskell.org/package/haskelldb-hdbc-sqlite3) Documentation, Mailing List, Source, etc ======================= Go to http://trac.haskell.org/haskelldb for detailed information. What's New? ========= * New query capabilities: stored procedures, CASTs, query parameters, constants, and more. * Postgres SQL improvements. * Bug fixes around AND and OR associativity. * Query optimization improvements around aggregate expressions. * More tests. Details ===== Back in June 2009, Bjorn Bringert passed maintainership of HaskellDB to me. I've been working this summer to get a release out, which included: * Adding an examples/ directory to the source distribution. * Archiving and consolidating information to http://trac.haskell.org/haskelldb. * Accepting patches for various issues. I have used a lot of ORM & SQL-wrapper libraries during my career and HaskellDB is the first that I've found which does not require you to eventually break the abstraction. Learning to use the the library was a fun challenge but not one that many people are willing to take, when they can easily write SQL by hand. If the library was easier to get started with, I think it would be much more widely used. Help me get HaskellDB better documentation! If you are using HaskellDB and want to help: go to http://trac.haskell.org/haskelldb and write an article, write a blog post, get in touch with me, etc. When I saw that Rails 3.0 uses the "ARel" gem (based on the relational algebra) I groaned - Haskell has had that forever! We need to get the word out! Why 2.0? -------------- Last year Brian Bloniarz contributed an awesome patch which replaced HaskellDB's home-grown record system with the HList library by Oleg Kiselyov (and colleagues). I intended to work with the library for awhile and get a 1.0 release out. Unfortunately, HList proved too daunting for GHC and for me. Compile times went way up, and I could not isolate it enough to give GHC HQ a repro case. Even worse, HList required too many Oleg units for me to comprehend. I could usually fix compile errors, but found myself struggling to extend HaskellDB's functionality. In the end I felt I needed to back the patch out. I really hated to lose some of the functionality but in the end maintainability won out. At that point I had pushed a few patches with a v1.0 cabal file, so I thought it best to make this release 2.0. Who am I? --------------- I started using HaskellDB in early 2009. I use it more as a query-generating library than for executing SQL statements. I have written a largish system for generating a data-access layer in PHP from query descriptions in HaskellDB. Yes, I'm using Haskell to write PHP ... dirty! Unmaintained & Unrelated Packages ----------------------------------------------------- A couple of haskelldb related packages on Hackage are not maintained by me: * haskelldb-hdbc-mysql - This project was created and uploaded independent of me. Contact the author for specifics. However, the haskelldb-hdbc-odbc library is maintained by me and can be used to talk to MySQL. * HSQL (haskelldb-hsql, etc) - I cannot get this backend to compile on my platform. HSQL seems unmaintained so I have let the drivers decay. You'll notice I have not uploaded new packages or changed their version dependencies. * haskelldb-flat and haskelldb-dynamic - Both of these packages have suffered serious bitrot and are not maintained any longer.

5 7

Inject cabal version or VCS version as a CPP macro
by Eugene Kirpichov 22 Feb '12

22 Feb '12

Hi, I'd like my program to print something like "this is $program 1.0.4 git 45fea6b" when invoked with --version, or at least just the 1.0.4 part. Can Cabal expose the version as a preprocessor macro by default, or do I have to use Build-Type: Custom and add a preprocessing step of my own? -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/

4 8