Re: [Haskell-cafe] Monadic style with Streams (as in Data.Array.Parallel.Stream)
Hi Mark What style of Stream programming do you have in mind? In Haskell there can be at least four styles of Stream programming depending how you count: There is the stream as infinite-list - see Wouter Swierstra's Data.Stream on Hackage and if you have university affiliation look for the paper Functional Pearl: Streams and Unique Fixed Points by Ralf Hinze. I think comonadic stream programming is within this style - if not that makes five styles... There's Stream fusion (Duncan Coutts, Roman Leshchinskiy, Don Stewart) where the stream programming is an implementation technique for particular data-structures - internally recursion is avoided with a special unfold to get fusion optimizations. Then there is the Arrow Stream processor style of writing transducers, used I think by the Fudgets toolkit - streamproc on Hackage. Possibly not finally, there is Jeremy Gibbons's 'Streaming representation-changers' style which has relation to the Stream fusion style but appears to have different aims - see Arithmetic coding with folds and unfolds with Richard Bird. None of them are monadic I'm afraid. The Arithmetic coding... paper might be relevant if you are working with Huffman coding. http://www.cse.unsw.edu.au/~dons/papers/stream-fusion.pdf http://www.comlab.ox.ac.uk/jeremy.gibbons/publications/ Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GADTs and Scrap your Boilerplate
Hi Oscar, On Sat, May 15, 2010 at 22:19, Oscar Finnsson oscar.finns...@gmail.comwrote: (...) I guess my questions are: 1. Is it possible to combine GADTs with Scrap your Boilerplate? Your GADT encodes an existential datatype. The closest attempt to encode existential types in (something like) SYB that I know of is in Section 5.3 of Alexey's PhD thesis [1]. Having said that, he uses the spine view, which makes the generic view in SYB explicit, but this has never been packaged as a library. So I'm afraid the answer is no. The link above might still be useful for your understanding of why this is a complex problem, though. Cheers, Pedro [1] http://igitur-archive.library.uu.nl/dissertations/2009-0518-200422/UUindex.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GADTs and Scrap your Boilerplate
On Sun, May 16, 2010 at 2:34 AM, Tom Hawkins tomahawk...@gmail.com wrote: I got the GADT data DataBox where DataBox :: (Show d, Eq d, Data d) = d - DataBox [snip] but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: I had a similar difficultly in Atom making a GADT a member of Eq. At one point I had my head wrapped around the reason for the problem, but now it escapes me. However, I remember the solution: I created a function to convert the GADT into another, unGADT type, which was then used to compute (==). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Have you tried using StandaloneDeriving (and DeriveDataTypeable)? According to http://www.haskell.org/ghc/docs/6.12.2/html/users_guide/deriving.html#stand-alone-deriving you can't derive instances for GADTs normally but a standalone derivation will at least attempt to make an instance as if it was an ordinary data type. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Speed of Error handling with Continuations vs. Eithers
On Thu, May 13, 2010 at 8:13 PM, wren ng thornton w...@freegeek.org wrote: Andrea Vezzosi wrote: On Thu, May 13, 2010 at 10:51 AM, wren ng thornton w...@freegeek.org wrote: Andrea Vezzosi wrote: wren ng thornton wrote: With this change [1] I can't notice any difference for your benchmark[2]. Then again, all the runTest calls take 0 msec and I've had no luck making the computation take much time; perhaps your computer can detect a difference. On my machine, with ghc-6.12.1, yours and the original ErrCPS give quite similar results, both ~2x slower than Either. However it's important to note that these results are highly dependent on the monadic expressions being evaluated, with a different benchmark you can get an huge speedup with the CPS versions. That's very curious. After installing Criterion, my machine (OSX 10.5.8 2.8GHz Intel Core2Duo, GHC 6.12.1 with -O2) shows only 1% difference between my ErrCPS and Either on this benchmark. Alas, I can't print kernel density graphs since Crieterion charts are broken on 6.12. It seems buggy that your platform would behave so much differently... I got the measurements from the original code, could you share the code that uses criterion instead? The 1% number was buggy because I hadn't factored the generation of random lists out of the benchmark. But, having fixed that, I still can't replicate your numbers: I get 12us for Either, vs 17us for EitherCPS. http://community.haskell.org/~wren/wren-extras/test/Control/Monad/ErrCPS/CriterionBenchmark.hs Yet another version of the same benchmark, this time using Microbench: http://community.haskell.org/~wren/wren-extras/test/Control/Monad/ErrCPS/MicrobenchBenchmark.hs Microbench seems to replicate your numbers better: 2551.930ns vs 4466.832ns (or 391.86 vs 223.87 calls per second)--- though this is getting into the range where there might be Int overflow issues corrupting the results (a similar problem showed up when benchmarking Data.Trie vs Data.Map), so it may warrant further investigation. That might be the case, i'm on 64bit: sai...@astarte:~$ uname -a Linux astarte 2.6.32-ARCH #1 SMP PREEMPT Tue Feb 23 19:43:46 CET 2010 x86_64 Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz GenuineIntel GNU/Linux sai...@astarte:~$ ./CriterionBenchmark warming up estimating clock resolution... mean is 6.834442 us (80001 iterations) found 1240 outliers among 79998 samples (1.6%) 1131 (1.4%) high severe estimating cost of a clock call... mean is 107.2316 ns (41 iterations) benchmarking Either collecting 100 samples, 1039 iterations each, in estimated 683.8220 ms bootstrapping with 10 resamples mean: 6.563462 us, lb 6.553649 us, ub 6.570454 us, ci 0.950 std dev: 41.74602 ns, lb 23.76971 ns, ub 67.67842 ns, ci 0.950 found 8 outliers among 100 samples (8.0%) 2 (2.0%) low severe 4 (4.0%) high mild 2 (2.0%) high severe variance introduced by outliers: 0.990% variance is unaffected by outliers benchmarking ErrCPS collecting 100 samples, 1 iterations each, in estimated 1.334000 s bootstrapping with 10 resamples mean: 13.14468 ms, lb 13.10442 ms, ub 13.18208 ms, ci 0.950 std dev: 198.3150 us, lb 182.0600 us, ub 220.7957 us, ci 0.950 variance introduced by outliers: 0.993% variance is unaffected by outliers If i'm reading it correctly this gives even worse results: 6us vs. 13ms -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Speed of Error handling with Continuations vs. Eithers
On Fri, 14 May 2010, Derek Elkins wrote: You did it wrong. All you did was Church encode the Either type. Your bind is still doing a case-analysis. All you have to do is use ContT r (Either e). The bind implementation for ContT is completely independent of the underlying monad. It doesn't even require the m in ContT r m to be a functor, let alone a monad. Therefore the ContT bind doesn't do any case-analysis because it doesn't know anything about the underlying monad. One way to look at what is happening is to compare it to Andrzej Filiniski's work in Representing Monads and Representing Layered Monads. What I don't get is that the bind operation for ContT and ErrCPS look so similar to me ContT (stripping off the newtype constructor/destructors): m = k = \c - m (\a - k a c) ErrCPS (stripping off the newtype constructor/destructors): m = f = \err good - m err (\x - f x err good) I don't get why one is slow but not the other? -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Numerical Analysis
On 16/05/2010, at 10:17, Pierre-Etienne Meunier wrote: I've also just noticed a lack in the vector library : multidimensional arrays seem to require indirections like in caml, whereas in C or in Data.Ix, there is a way to avoid this. This is especially important for avoiding cache misses with many dimensions, as well as for providing a clean interface. For instance if a 10x10 matrix is initialized unproperly like Data.Vector.replicate 10 $ Data.Vector.replicate 10 0 The result is a total mess. Surely, every programmer knows that a computer has got memory, and that this memory has to be allocated, but from what I understand of haskell, I would expect the interface and the RTS to do it for me. And an integer multiplication, followed by an addition, is way cheaper than accessing uncached memory. Or maybe I do not understand that pipelines, hyperthreading and all that stuff would give you the same result ? You are quite right that vector only supports nested arrays but not multidimensional ones. This is by design, however - the library's only goal is to provide efficient one-dimensional, Int-indexed arrays. I'm thinking about how to implement multidimensional arrays on top of vector but it's not that easy. While repa is a step in that direction, I also need to support mutable arrays and interoperability with C which complicates things immensely. That said, if all you need is a matrix it's quite easy to implement the necessary index calculations yourself. Also, since you are working with numerics I highly recommend that you use either Data.Vector.Unboxed or Data.Vector.Storable instead of Data.Vector as boxing tends to be prohibitively expensive in this domain. Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monadic style with Streams (as in Data.Array.Parallel.Stream)
On 16/05/2010, at 11:54, Mark Wassell wrote: Hi, This possibly might go against the spirit of what Stream programming is about but I having difficulties converting an imperative algorithm [1] into Haskell and think it would be easier if I was able to write it in a monadic style with operations to read and write from and to the streams. I first tried to approach it by delving into the innards of other Stream functions to devise what I needed. I only got so far and the sticking point was defining the Monad. I then approached it from the Monad side and although what I have is workable, it probably isn't going to perform (for one it uses fromStream and tailS on each read off the front of the stream). Data.Array.Parallel.Stream serves only one purpose: to represent loops produced by DPH in such a way that the compiler is able to optimise them well. Putting a monad on top of that will very very likely break this. To be honest, I'm not sure why you need the monad anyway. I would expect compression/decompression to be pure functions of type Stream Word8 - Stream Word8. In any case, I would urgently recommend not to use Data.Array.Parallel.Stream for anything at this point. This whole subsystem will soon die of old age and be replaced by the much nicer stuff from package vector, specifically Data.Vector.Fusion.Stream and Data.Vector.Fusion.Stream.Monadic. Note that the latter implements monadic streams as described in http://www.cse.unsw.edu.au/~rl/publications/recycling.html. Perhaps those can be useful for you if you really need a monad. Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANN: Monad.Reader Issue 16
Brent Yorgey wrote: I am very pleased to announce that Issue 16 of The Monad.Reader is now available [1]. Issue 16 consists of the following three articles: * Demand More of Your Automata by Aran Donohue * Iteratee: Teaching an Old Fold New Tricks by John W. Lato * Playing with Priority Queues by Louis Wasserman Another great issue of my favorite Haskell magazine! I have a remark on Louis' article. Namely, I think the description of amortization is a bit unfortunate in a persistent setting like Haskell. The inc example will still take O(1) amortized time, but not because costs are saved in advance, you can't save anything when things are persistent. Imagine several clones of you coming from the future and trying to access your current bank account savings... The real reason for O(1) is that the changes to the list are lazy and the cost for the expensive operation is payed as tax by *future* operations that attempt to extract elements further down the list. This means that the amortized bound depends on the available functions for *observing* the data structure, too. Unfortunately, I think this makes the proof of theorem 27 more subtle: you need to make sure that you don't pay more than O(log n) in tax for evaluating the binary number with log n digits to normal form! In other words, each increment might take O(1) time but this could create so many taxes that printing all digits takes a lot longer. To demonstrate the issue, consider the function bunk :: [Bool] - [Bool] bunk (True : bs) = False : bunk bs bunk (False : bs) = True : bunk bs bunk [] = [True] This will take O(1) time when you only look at the head of the list afterwards, i.e. head . bunk . bunk . ... . bunk $ [] is always O(n). But length . bunk . bunk . ... . bunk $ [] will take O(n^2). You'd have to show that this doesn't happen with inc . For more on how to do amortized analysis in a persistent setting, see also Okasaki's book Purely Functional Data Structures. http://www.cs.cmu.edu/~rwh/theses/okasaki.pdf I have collected some mailing lists posts on his debit method here: http://apfelmus.nfshost.com/articles/debit-method.html Regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] executeFile failing on macosx
executeFile is failing for me on Mac OS X 10.5.8, with ghc 6.12.1 when compiling with -threaded. Compiling without -threaded, or running on linux is fine. When compiled with -threaded, the following snippet produces the error: testProg: /bin/echo: executeFile: failed (Operation not supported) import System.Posix.Process main = do forkProcess $ executeFile /bin/echo False [Ok] Nothing Any suggestions for a work around for this would be appreciated. Cheers, -- David Powell ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] executeFile failing on macosx
Hello David, Sunday, May 16, 2010, 7:18:29 PM, you wrote: executeFile is failing for me on Mac OS X 10.5.8, with ghc 6.12.1 when compiling with -threaded. Compiling without -threaded, or running on linux is fine. forkProcess $ executeFile /bin/echo False [Ok] Nothing afair, forkProcess and -threaded shouldn't work together on any Unix. can you try forkIO or forkOS instead? -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Getting a string from url-converted UTF8 input
Hello all! Can somebody please explain wha am I doing in wrong way? === module UrlEncode where import System import Codec.Binary.UTF8.String as SU import Codec.Binary.Url as U import Data.Maybe main :: IO () main = do args - getArgs processWithArgs args processWithArgs (-d:[]) = getLine = putStrLn . maybe SU.decode . U.decode processWithArgs (-e:[]) = getLine = putStrLn . U.encode . SU.encode processWithArgs _ = putStrLn Usage: -e (encode) or -d (decode) === With this script if fed with input: === 1%29%20%D0%B3%D0%B4%D0%B5%20%D0%BD%D1%8B%D0%BD%D1%87%D0%B5%20%D0%BC%D0%BE%D0%B4%D0%BD%D0%BE%20%D0%B1%D1%80%D0%B0%D1%82%D1%8C%20%D0%BA%D0%BD%D0%B8%D0%B6%D0%BA%D0%B8%20%D0%B2%20%D0%B2%D0%B8%D0%B4%D0%B5%20FB2%3F%0D%0A%0D%0A2%29%20%D0%BA%D0%B0%D0%BA%D0%BE%D0%B9%20%D0%B5%D1%81%D1%82%D1%8C%20%D1%81%D0%BE%D1%84%D1%82%20%D0%BD%D0%B0%20%D0%B6%D0%B5%D0%BB%D0%B5%D0%B7%D0%BA%D1%83%20%D1%82%D0%B8%D0%BF%D0%B0%20%D1%82%D0%B5%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%20%D1%81%20Symbian === I am getting the output: === 1) 345 =K=G5 4= 1...@0bl :=86:8 2 2845 FB2? 2) :0:9 5ABL ADB =0 65;57:C B8?0 B5;5D= A Symbian === which is wrong. So what do I miss in encoding the data in UTF? Thank you in advance! -- Eugene Dzhurinsky pgpUPu4ndYSxU.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting a string from url-converted UTF8 input
* Eugene Dzhurinsky b...@redwerk.com [2010-05-16 18:42:08+0300] Hello all! Can somebody please explain wha am I doing in wrong way? [snip] I am getting the output: === 1) 345 =K=G5 4= 1...@0bl :=86:8 2 2845 FB2? 2) :0:9 5ABL ADB =0 65;57:C B8?0 B5;5D= A Symbian === which is wrong. So what do I miss in encoding the data in UTF? I assume you are using GHC 6.12. The trouble is in conversion done by putStrLn. Use one from System.IO.UTF8. Or try to upgrade to GHC 6.12 which respects the locale settings. -- Roman I. Cheplyaka :: http://ro-che.info/ Don't let school get in the way of your education. - Mark Twain ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting a string from url-converted UTF8 input
On Sun, May 16, 2010 at 06:56:58PM +0300, Roman Cheplyaka wrote: I assume you are using GHC 6.12. The trouble is in conversion done by putStrLn. Use one from System.IO.UTF8. Or try to upgrade to GHC 6.12 which respects the locale settings. Hello, Roman! Thank you very much for the hint, it really did help. Unfortunately, there's no port of GHC 6.12 available for FreeBSD now, so I used System.IO.UTF8 -- Eugene Dzhurinsky pgp4pa7EBeen7.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Numerical Analysis
You are quite right that vector only supports nested arrays but not multidimensional ones. This is by design, however - the library's only goal is to provide efficient one-dimensional, Int-indexed arrays. I'm thinking about how to implement multidimensional arrays on top of vector but it's not that easy. While repa is a step in that direction, I also need to support mutable arrays and interoperability with C which complicates things immensely. I understand. What complicates it even more (at least in what I imagine) is that C uses the same syntax for multidimensional and nested arrays, and I do not believe that for instance GHC's FFI allows for array types such as int x[19][3]. Data.Ix allows for indexing arrays with (Int,Int), for instance, but with costly index conversions, constructing lists in the memory for instance. Also, sometimes the user of these libraries may find a better bijection between N and N^2, better in the sense that for his particular problem, a slightly more complicated arithmetic sequence of operations for computing the index would optimize cache misses better. Would it be for instance possible however to generate a default bijection using preprocessing (template haskell ?) ? That said, if all you need is a matrix it's quite easy to implement the necessary index calculations yourself. Also, since you are working with numerics I highly recommend that you use either Data.Vector.Unboxed or Data.Vector.Storable instead of Data.Vector as boxing tends to be prohibitively expensive in this domain. I'm actually thinking about rewriting parts of my code now ! It seems indeed that given how the algorithms are specified for instance in numerical recipes or the papers in its bibliography, unboxing is the only option, since there is no such thing as boxing in cobol and fortran ;-) I was also wondering about how to do linear algebra : an infinite number of types would be needed to express all the constraints on matrix multiplication : we need types such as array of size m * n. Is there a way to generate these automatically with for instance template haskell (again ! But I know nothing of template haskell, neither, sorry !) Cheers, PE ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting a string from url-converted UTF8 input
On Sunday 16 May 2010 18:13:30, Eugene Dzhurinsky wrote: On Sun, May 16, 2010 at 06:56:58PM +0300, Roman Cheplyaka wrote: I assume you are using GHC 6.12. The trouble is in conversion done by putStrLn. Use one from System.IO.UTF8. Or try to upgrade to GHC 6.12 which respects the locale settings. Hello, Roman! Thank you very much for the hint, it really did help. Unfortunately, there's no port of GHC 6.12 available for FreeBSD now, so I used System.IO.UTF8 Is there any problem compiling from source on FreeBSD? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Numerical Analysis
On May 16, 2010, at 4:51 AM, Roman Leshchinskiy wrote: You are quite right that vector only supports nested arrays but not multidimensional ones. This is by design, however - the library's only goal is to provide efficient one-dimensional, Int-indexed arrays. I'm thinking about how to implement multidimensional arrays on top of vector but it's not that easy. While repa is a step in that direction, I also need to support mutable arrays and interoperability with C which complicates things immensely. Indeed; I eventually decided to hand-roll my own package for dealing with N-dimensional arrays using StorableArray under the hood since I needed to be able to pass them to and from Fortran routines. It has some nice features such as arbitrary type-safe cuts and slicing (i.e., you can take index 1 of the first dimension and every 3rd index between 2 and 9 of the third dimension and it will returns a new array with a type that has one fewer dimension), folding, converting to/from lists, mutable and immutable versions, and direct pointer access --- which is just the amount of functionality I needed for my purposes. The problem (and part of the reason I haven't gotten around to uploading it to Hackage) is that the package is not geared around performing efficient computations in Haskell because I have been writing numeric routines themselves in Fortran; its only real purpose was to let me to examine the arrays in Haskell code. As an aside, while there are advantages to writing numerical analysis routines in Haskell, it might be better strategy to instead link in something like LAPACK and provide nice wrappers to it in Haskell, since this way you can harness the work of the experts who have spent a lot of time perfecting their code rather than re-inventing the wheel. One downside of this, though, is that the LAPACK routines only achieve parallelism by making extensive use of Level 3 BLAS routines whenever possible and assuming that they are heavily optimized and parallelized (which they are), so there *might* be cases were a pure Haskell implementation might be able to out-perform them by exploiting even more opportunities parallelism within the algorithm then that provided by the BLAS calls.Another downside is that using LAPACK requires the arrays to be in pinned memory --- though only for the duration of the LAPACK call. Finally, I have been experiencing problems linking Fortran and Haskell code on OSX for reasons that I don't understand, since I have no problem on my Linux machine, I have made sure that all the code is compiled for the 32-bit architecture on my OSX machine, and linking C and Fortran programs on the OSX machine does not result in any problems. Cheers, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
Eventually, I don't think it is a profiling issue.
Maybe a problem with integral. According to a quite recent post on the
reactive mailing list, the following minimal code produces the same problem
:
import FRP.Reactive
import FRP.Reactive.LegacyAdapters
import Control.Applicative
type Velocity = Double
type Position = Double
data Car = Car { vel :: Velocity, pos :: Position } deriving Show
velocity :: Behavior Velocity
velocity = 1
position :: Behavior Position
position = integral (atTimes [0, 0.5 ..]) velocity
car :: Behavior Car
car = Car $ velocity * position
main :: IO ()
main = adaptE $ print $ car `snapshot_` atTimes [0, 0.5..]
1) why is the leak happen?
2) how can I fix this problem?
Some more detailed informations:
* reactive 0.11.4
* GHC 6.12.1
* Gentoo Linux (2.6.32-tuxonice, x86_64) or Ubuntu 9.10 64bits
* compiled with or without -O2 flag
2010/5/16 David Leimbach leim...@gmail.com
On Sat, May 15, 2010 at 8:42 AM, Limestraël limestr...@gmail.com wrote:
Okay,
guess I'll have to bring out the chapter 25 of my Real World Haskell...
I find it's often the most practical chapter that I hit a lot during writes
and changes to my server process I have in Haskell in our control system
code :-)
That plus the information that I had missed that Control.Monad.State
defaulted to the Lazy version (which is consistent, but for some reason it
got by me) helped me to realize why I was leaking so much space in a garbage
collected environment.
I wouldn't have gotten very far with Haskell as this piece of our code
without that chapter. I'd love to see more writing of that sort around
Haskell in book form. One can become fluent in tuning Haskell by trial and
error, but the sharp corners one must bump into are often sharper than in
other languages I've found.
Dave
2010/5/15 Bulat Ziganshin bulat.zigans...@gmail.com
Hello Limestraėl,
Saturday, May 15, 2010, 7:02:38 PM, you wrote:
But when I set my beat to tick every 60 times per second, the
position is well updated, but I clearly see that the display
dramatically slows down after a few seconds of execution. Too heavy
rate for integrate?
it may be due to lot of uncollected garbage that is result of lazy
evaluation. profile program to check its GC times
--
Best regards,
Bulatmailto:bulat.zigans...@gmail.com
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Re: [Haskell-cafe] [reactive] A pong and integrate
As far as I know, it was never possible to make a pong game in
Reactive, at least not with the versions I tried, but I admit a lot of
never versions got released since then. It would be great to see one
though :)
You might want to try Yampa, that works for sure (although you should
mark all your output data strict, as is done in the examples,
otherwise you might also get space leaks or shaky frame rates). Or
Elerea, which comes with a breakout game.
On Sun, May 16, 2010 at 9:30 PM, Limestraël limestr...@gmail.com wrote:
Eventually, I don't think it is a profiling issue.
Maybe a problem with integral. According to a quite recent post on the
reactive mailing list, the following minimal code produces the same problem
:
import FRP.Reactive
import FRP.Reactive.LegacyAdapters
import Control.Applicative
type Velocity = Double
type Position = Double
data Car = Car { vel :: Velocity, pos :: Position } deriving Show
velocity :: Behavior Velocity
velocity = 1
position :: Behavior Position
position = integral (atTimes [0, 0.5 ..]) velocity
car :: Behavior Car
car = Car $ velocity * position
main :: IO ()
main = adaptE $ print $ car `snapshot_` atTimes [0, 0.5..]
1) why is the leak happen?
2) how can I fix this problem?
Some more detailed informations:
* reactive 0.11.4
* GHC 6.12.1
* Gentoo Linux (2.6.32-tuxonice, x86_64) or Ubuntu 9.10 64bits
* compiled with or without -O2 flag
2010/5/16 David Leimbach leim...@gmail.com
On Sat, May 15, 2010 at 8:42 AM, Limestraël limestr...@gmail.com wrote:
Okay,
guess I'll have to bring out the chapter 25 of my Real World Haskell...
I find it's often the most practical chapter that I hit a lot during
writes and changes to my server process I have in Haskell in our control
system code :-)
That plus the information that I had missed that Control.Monad.State
defaulted to the Lazy version (which is consistent, but for some reason it
got by me) helped me to realize why I was leaking so much space in a garbage
collected environment.
I wouldn't have gotten very far with Haskell as this piece of our code
without that chapter. I'd love to see more writing of that sort around
Haskell in book form. One can become fluent in tuning Haskell by trial and
error, but the sharp corners one must bump into are often sharper than in
other languages I've found.
Dave
2010/5/15 Bulat Ziganshin bulat.zigans...@gmail.com
Hello Limestraėl,
Saturday, May 15, 2010, 7:02:38 PM, you wrote:
But when I set my beat to tick every 60 times per second, the
position is well updated, but I clearly see that the display
dramatically slows down after a few seconds of execution. Too heavy
rate for integrate?
it may be due to lot of uncollected garbage that is result of lazy
evaluation. profile program to check its GC times
--
Best regards,
Bulat mailto:bulat.zigans...@gmail.com
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Re: [Haskell-cafe] Monadic style with Streams (as in Data.Array.Parallel.Stream)
Roman Leshchinskiy wrote: On 16/05/2010, at 11:54, Mark Wassell wrote: Hi, This possibly might go against the spirit of what Stream programming is about but I having difficulties converting an imperative algorithm [1] into Haskell and think it would be easier if I was able to write it in a monadic style with operations to read and write from and to the streams. I first tried to approach it by delving into the innards of other Stream functions to devise what I needed. I only got so far and the sticking point was defining the Monad. I then approached it from the Monad side and although what I have is workable, it probably isn't going to perform (for one it uses fromStream and tailS on each read off the front of the stream). Data.Array.Parallel.Stream serves only one purpose: to represent loops produced by DPH in such a way that the compiler is able to optimise them well. Putting a monad on top of that will very very likely break this. To be honest, I'm not sure why you need the monad anyway. I would expect compression/decompression to be pure functions of type Stream Word8 - Stream Word8. In any case, I would urgently recommend not to use Data.Array.Parallel.Stream for anything at this point. This whole subsystem will soon die of old age and be replaced by the much nicer stuff from package vector, specifically Data.Vector.Fusion.Stream and Data.Vector.Fusion.Stream.Monadic. Note that the latter implements monadic streams as described in http://www.cse.unsw.edu.au/~rl/publications/recycling.html. Perhaps those can be useful for you if you really need a monad. Roman Thanks. No, I don't need a Monad and I suspected it was a bad idea. It was really needed for convenience as all I had to go on was a C implementaiton of arithmetic coding (which included a getc part-way through the code block which I hoped to map to something like a get from the stream). However thanks to Stephen I have something better to work from. I will also take a look at Data.Vector.Fusion.Stream. Cheers Mark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
Why isn't it possible to make a Pong with Reactive? Where is the problem?
Conceptually, I don't see where it is. IMO, it's a time-leak issue due to a
Reactive bug, but it is not a limitation of Reactive.
I mean, it's not that it *can't* work, it's that it *should* work, shouldn't
it?
And why would it be more possible with Yampa?
I've already checked Yampa, but I find it much less simple and easy to use
than Reactive.
Moreover, I tried the space invaders sample (the sample that the paper
Yampa Arcade is about), and it lauches but it is completely unusable (I do
have a decent PC, and I get like 5fps and a gun which absolutely doesn't
move correctly). Not very appealing ^^, but maybe the problem is with the
code of the game itself or with my PC, not with Yampa...
I did not look thoroughly at elerea, but at least, when I tried its sample
dungeons of wor it worked properly ;)
I will have a look...
2010/5/16 Peter Verswyvelen bugf...@gmail.com
As far as I know, it was never possible to make a pong game in
Reactive, at least not with the versions I tried, but I admit a lot of
never versions got released since then. It would be great to see one
though :)
You might want to try Yampa, that works for sure (although you should
mark all your output data strict, as is done in the examples,
otherwise you might also get space leaks or shaky frame rates). Or
Elerea, which comes with a breakout game.
On Sun, May 16, 2010 at 9:30 PM, Limestraël limestr...@gmail.com wrote:
Eventually, I don't think it is a profiling issue.
Maybe a problem with integral. According to a quite recent post on the
reactive mailing list, the following minimal code produces the same
problem
:
import FRP.Reactive
import FRP.Reactive.LegacyAdapters
import Control.Applicative
type Velocity = Double
type Position = Double
data Car = Car { vel :: Velocity, pos :: Position } deriving Show
velocity :: Behavior Velocity
velocity = 1
position :: Behavior Position
position = integral (atTimes [0, 0.5 ..]) velocity
car :: Behavior Car
car = Car $ velocity * position
main :: IO ()
main = adaptE $ print $ car `snapshot_` atTimes [0, 0.5..]
1) why is the leak happen?
2) how can I fix this problem?
Some more detailed informations:
* reactive 0.11.4
* GHC 6.12.1
* Gentoo Linux (2.6.32-tuxonice, x86_64) or Ubuntu 9.10 64bits
* compiled with or without -O2 flag
2010/5/16 David Leimbach leim...@gmail.com
On Sat, May 15, 2010 at 8:42 AM, Limestraël limestr...@gmail.com
wrote:
Okay,
guess I'll have to bring out the chapter 25 of my Real World Haskell...
I find it's often the most practical chapter that I hit a lot during
writes and changes to my server process I have in Haskell in our control
system code :-)
That plus the information that I had missed that Control.Monad.State
defaulted to the Lazy version (which is consistent, but for some reason
it
got by me) helped me to realize why I was leaking so much space in a
garbage
collected environment.
I wouldn't have gotten very far with Haskell as this piece of our code
without that chapter. I'd love to see more writing of that sort around
Haskell in book form. One can become fluent in tuning Haskell by trial
and
error, but the sharp corners one must bump into are often sharper than
in
other languages I've found.
Dave
2010/5/15 Bulat Ziganshin bulat.zigans...@gmail.com
Hello Limestraėl,
Saturday, May 15, 2010, 7:02:38 PM, you wrote:
But when I set my beat to tick every 60 times per second, the
position is well updated, but I clearly see that the display
dramatically slows down after a few seconds of execution. Too heavy
rate for integrate?
it may be due to lot of uncollected garbage that is result of lazy
evaluation. profile program to check its GC times
--
Best regards,
Bulatmailto:bulat.zigans...@gmail.com
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Re: [Haskell-cafe] Numerical Analysis
Pierre-Etienne Meunier wrote: I was also wondering about how to do linear algebra : an infinite number of types would be needed to express all the constraints on matrix multiplication : we need types such as array of size m * n. Is there a way to generate these automatically This is already done for you in the package hmatrix-static on Hackage. Erik -- -- Erik de Castro Lopo http://www.mega-nerd.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
Yes, it would be very nice to actually pinpoint why this can't be
done. Is it a bug, is it a design flaw, ... I'm just saying that I'm
not aware of a working Pong game in Reactive. Well actually, someone
did make a Tetris game with it once...
Intuitively I would say Reactive gives the programmer too much power
of what can be done with time, making it all too easy to break
causality. And since that's a physical law that can't be broken
(unless Reactive would create a wormhole somehow), it means you too
easily get delays or deadlocks. But that's just an intuition, I can't
describe this formally. This is a general problem of first class
signals IMHO: too open, not restrictive enough. First class signals
are fine for just animation, but not for complex reactivity.
Yampa gives you access to signal transformers, not the signals
themselves, which is more natural to me as a casual game developer.
Yampa looks like dataflow programming, but I agree that's not
something you want to do in a text editor ;-) (stuff like x - f - y
is easier in a graphical boxes/links editor). Also, a lot of global
state needs to be transfered to all the signal functions (e.g. a
random number seed that can't be used statically, e.g. in dynamic
collections), and an arrow is fine for that, just like a state monad
is.
Well, at least that's what I understand from it. But I understand only
tiny bits of pieces of it all :)
On Sun, May 16, 2010 at 11:41 PM, Limestraël limestr...@gmail.com wrote:
Why isn't it possible to make a Pong with Reactive? Where is the problem?
Conceptually, I don't see where it is. IMO, it's a time-leak issue due to a
Reactive bug, but it is not a limitation of Reactive.
I mean, it's not that it can't work, it's that it should work, shouldn't it?
And why would it be more possible with Yampa?
I've already checked Yampa, but I find it much less simple and easy to use
than Reactive.
Moreover, I tried the space invaders sample (the sample that the paper
Yampa Arcade is about), and it lauches but it is completely unusable (I do
have a decent PC, and I get like 5fps and a gun which absolutely doesn't
move correctly). Not very appealing ^^, but maybe the problem is with the
code of the game itself or with my PC, not with Yampa...
I did not look thoroughly at elerea, but at least, when I tried its sample
dungeons of wor it worked properly ;)
I will have a look...
2010/5/16 Peter Verswyvelen bugf...@gmail.com
As far as I know, it was never possible to make a pong game in
Reactive, at least not with the versions I tried, but I admit a lot of
never versions got released since then. It would be great to see one
though :)
You might want to try Yampa, that works for sure (although you should
mark all your output data strict, as is done in the examples,
otherwise you might also get space leaks or shaky frame rates). Or
Elerea, which comes with a breakout game.
On Sun, May 16, 2010 at 9:30 PM, Limestraël limestr...@gmail.com wrote:
Eventually, I don't think it is a profiling issue.
Maybe a problem with integral. According to a quite recent post on the
reactive mailing list, the following minimal code produces the same
problem
:
import FRP.Reactive
import FRP.Reactive.LegacyAdapters
import Control.Applicative
type Velocity = Double
type Position = Double
data Car = Car { vel :: Velocity, pos :: Position } deriving Show
velocity :: Behavior Velocity
velocity = 1
position :: Behavior Position
position = integral (atTimes [0, 0.5 ..]) velocity
car :: Behavior Car
car = Car $ velocity * position
main :: IO ()
main = adaptE $ print $ car `snapshot_` atTimes [0, 0.5..]
1) why is the leak happen?
2) how can I fix this problem?
Some more detailed informations:
* reactive 0.11.4
* GHC 6.12.1
* Gentoo Linux (2.6.32-tuxonice, x86_64) or Ubuntu 9.10 64bits
* compiled with or without -O2 flag
2010/5/16 David Leimbach leim...@gmail.com
On Sat, May 15, 2010 at 8:42 AM, Limestraël limestr...@gmail.com
wrote:
Okay,
guess I'll have to bring out the chapter 25 of my Real World
Haskell...
I find it's often the most practical chapter that I hit a lot during
writes and changes to my server process I have in Haskell in our
control
system code :-)
That plus the information that I had missed that Control.Monad.State
defaulted to the Lazy version (which is consistent, but for some reason
it
got by me) helped me to realize why I was leaking so much space in a
garbage
collected environment.
I wouldn't have gotten very far with Haskell as this piece of our code
without that chapter. I'd love to see more writing of that sort around
Haskell in book form. One can become fluent in tuning Haskell by trial
and
error, but the sharp corners one must bump into are often sharper than
in
other languages I've found.
Dave
2010/5/15 Bulat Ziganshin bulat.zigans...@gmail.com
Hello Limestraėl,
Re: [Haskell-cafe] executeFile failing on macosx
On Mon, May 17, 2010 at 1:33 AM, Bulat Ziganshin bulat.zigans...@gmail.comwrote: Hello David, Sunday, May 16, 2010, 7:18:29 PM, you wrote: executeFile is failing for me on Mac OS X 10.5.8, with ghc 6.12.1 when compiling with -threaded. Compiling without -threaded, or running on linux is fine. forkProcess $ executeFile /bin/echo False [Ok] Nothing afair, forkProcess and -threaded shouldn't work together on any Unix. can you try forkIO or forkOS instead? Hi Bulat, Both, forkIO and forkOS fail in the same way for me with -threaded. I believe this is because macosx requires the process to only have a single thread when doing an execv(), which I thought was the purpose of forkProcess? Cheers, -- David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] executeFile failing on macosx
Works fine on 10.6.3. If you run with +RTS -N2, though, you'll get forking not supported with +RTS -Nn greater than 1 The reason for this is that forking won't copy over the threads which means that the Haskell IO manager stops working (you'd have to somehow reinitialise the RTS while leaving heap and runtime stacks in tact -- very tricky). I'm using http://hackage.haskell.org/package/process to run external processes. I haven't had any problems with it. On 17 May 2010 00:06, David Powell da...@drp.id.au wrote: On Mon, May 17, 2010 at 1:33 AM, Bulat Ziganshin bulat.zigans...@gmail.com wrote: Hello David, Sunday, May 16, 2010, 7:18:29 PM, you wrote: executeFile is failing for me on Mac OS X 10.5.8, with ghc 6.12.1 when compiling with -threaded. Compiling without -threaded, or running on linux is fine. forkProcess $ executeFile /bin/echo False [Ok] Nothing afair, forkProcess and -threaded shouldn't work together on any Unix. can you try forkIO or forkOS instead? Hi Bulat, Both, forkIO and forkOS fail in the same way for me with -threaded. I believe this is because macosx requires the process to only have a single thread when doing an execv(), which I thought was the purpose of forkProcess? Cheers, -- David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Push the envelope. Watch it bend. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ShowList magic
Hi.
I'm a Haskell newbie and there's a bit of Haskell code that I don't
understand how it works. In the prelude, defining the class Show, the
function showList is implemented twice, one for String and another one
for other lists:
showList cs = showChar '' . showl cs
where showl= showChar ''
showl ('':cs) = showString \\\ . showl cs
showl (c:cs) = showLitChar c . showl cs
and
showList [] = showString []
showList (x:xs) = showChar '[' . shows x . showl xs
where showl [] = showChar ']'
showl (x:xs) = showChar ',' . shows x .
showl xs
The thing is... how does Haskell «know» which to execute? It works
even for the blank string:
Prelude show
\\
Prelude show []
[]
Salud,
Abby
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Re: [Haskell-cafe] What makes Haskell difficult as .NET?
On May 15, 2010, at 5:40 AM, Daryoush Mehrtash wrote: the speaker talks about F# on .Net platform. Early on in the talk he says that they did F# because haskell would be hard to make as a .Net language.Does anyone know what features of Haskell make it difficult as .Net language? Laziness is the obvious one: a plain integer type in an ML-like language can map directly onto a .Net primitive value type, whereas Int in Haskell has to map onto something boxed. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] executeFile failing on macosx
Indeed System.Process does work for me. I had avoided it because it is a little more awkward to use it when you want the actual PIDs. I don't understand why System.Process.runProcess works for me, but executeFile does not. I did find this issue (for python) http://bugs.python.org/issue6800which I think is the same thing I'm hitting and they also claim it is fixed in macosx 10.6. Anyway, I'll work with System.Process for now. Thanks for your help. -- David On Mon, May 17, 2010 at 9:41 AM, Thomas Schilling nomin...@googlemail.comwrote: Works fine on 10.6.3. If you run with +RTS -N2, though, you'll get forking not supported with +RTS -Nn greater than 1 The reason for this is that forking won't copy over the threads which means that the Haskell IO manager stops working (you'd have to somehow reinitialise the RTS while leaving heap and runtime stacks in tact -- very tricky). I'm using http://hackage.haskell.org/package/process to run external processes. I haven't had any problems with it. On 17 May 2010 00:06, David Powell da...@drp.id.au wrote: On Mon, May 17, 2010 at 1:33 AM, Bulat Ziganshin bulat.zigans...@gmail.com wrote: Hello David, Sunday, May 16, 2010, 7:18:29 PM, you wrote: executeFile is failing for me on Mac OS X 10.5.8, with ghc 6.12.1 when compiling with -threaded. Compiling without -threaded, or running on linux is fine. forkProcess $ executeFile /bin/echo False [Ok] Nothing afair, forkProcess and -threaded shouldn't work together on any Unix. can you try forkIO or forkOS instead? Hi Bulat, Both, forkIO and forkOS fail in the same way for me with -threaded. I believe this is because macosx requires the process to only have a single thread when doing an execv(), which I thought was the purpose of forkProcess? Cheers, -- David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Push the envelope. Watch it bend. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ShowList magic
On 17 May 2010 12:56, Abby Henríquez Tejera parad...@gmail.com wrote:
I'm a Haskell newbie and there's a bit of Haskell code that I don't
understand how it works. In the prelude, defining the class Show, the
function showList is implemented twice, one for String and another one
for other lists:
showList cs = showChar '' . showl cs
where showl = showChar ''
showl ('':cs) = showString \\\ . showl cs
showl (c:cs) = showLitChar c . showl cs
This is the default implementation; if an instance doesn't define
showList then this value is used.
showList [] = showString []
showList (x:xs) = showChar '[' . shows x . showl xs
where showl [] = showChar ']'
showl (x:xs) = showChar ',' . shows x .
showl xs
This is how the Show instance for Char defines showList (i.e. it
overrides the default one).
There would then be something like:
instance (Show a) = Show [a] where
show = showList
So, depending on the type used, it will either use the special ..
method (for String = [Char]) or the default one (or another special
one if another data type overrides the default implementation for
Show).
See http://book.realworldhaskell.org/read/using-typeclasses.html for
more information.
--
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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[Haskell-cafe] ANN: cil-0.0.1
CIL [1] is an OCaml library that parses and compiles C down to a simplified subset to ease different forms of static analysis. Frama-C [2] augments CIL with a property specification language (ACSL), which can capture design contracts for C functions. Frama-C's Jessie plugin uses the Why [3] software verification platform, which itself uses several different SMT solvers and proof assistances to verify ACSL function contracts -- a very cool platform, I encourage anyone interested in the verification of C programs to check it out. This Hackage library [4] is an interface to the Frama-C environment. Specifically, it provides equivalent CIL and ACSL data types, allowing CIL and ACSL based analyzers to be written in Haskell. The library installs a Frama-C/OCaml plugin, which dumps the CIL database into Haskell. Internally, both the OCaml and Haskell sides of the interface are generated by a script (GenCIL.hs) that parses the contents of the CIL type definitions (cil_types.mli). Currently it only works for the most basic C programs. A bug in either the generated OCaml plugin or Frama-C causes issues [5]. -Tom [1] http://cil.sourceforge.net/ [2] http://frama-c.com/ [3] http://why.lri.fr/ [4] http://hackage.haskell.org/package/cil [5] http://bts.frama-c.com/view.php?id=481 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
