[Haskell-cafe] Re: sendfile leaking descriptors on Linux?
Brandon S. Allbery KF8NH wrote: On Feb 5, 2010, at 02:56 , Bardur Arantsson wrote: [--snip--] Broken pipe is normally handled as a signal, and is only mapped to an error if SIGPIPE is set to SIG_IGN. I can well imagine that the SIGPIPE signal handler isn't closing resources properly; a workaround would be to use the System.Posix.Signals API to ignore SIGPIPE, but I don't know if that would work as a general solution (it would depend on what other uses of pipes/sockets exist). It was a good idea, but it doesn't seem to help to add installHandler sigPIPE Ignore (Just fullSignalSet) to the main function. (Given the package name I assume System.Posix.Signals works similarly to regular old signals, i.e. globally per-process.) This is really starting to drive me round the bend... One further thing I've noticed: When compiling on my 64-bit machine, ghc issues the following warnings: Linux.hsc:41: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Those lines are: 39: -- max num of bytes in one send 40: maxBytes :: Int64 41: maxBytes = fromIntegral (maxBound :: (#type ssize_t)) and 44: foreign import ccall unsafe sendfile64 c_sendfile 45: :: Fd - Fd - Ptr (#type off_t) - (#type size_t) - IO (#type ssize_t) This looks like a typical 32/64-bit problem, but normally I would expect any real run-time problems caused by a problematic conversion in the FFI to crash the whole process. Maybe I'm wrong about this... Cheers, ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] a beginner question: decorate-op-undecorate
Hello Aran Changing to an explicit sum type rather than using Either might subsequent functions that process a Binding cleaner: data Binding = BoundVar Var Value | PossiblyBound Var [Value] Naturally you might want to consider a better constructor name than 'PossiblyBound'. -- As an open question to the list - the above change can be seen as a 'denormalisation' of the data type (adding redundancy), does anyone know of a reference that covers such things? The only thing I can think of close is David S. Wile's Abstract syntax from concrete syntax... Thanks Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal fun (not)
On 6 February 2010 03:33, Ivan Miljenovic ivan.miljeno...@gmail.com wrote: If you upgrade a library, it will break all other libraries that depend upon it. ghc-pkg list will tell you which libraries are broken and need to be rebuilt. I think you mean ghc-pkg check. Peter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal fun (not)
On 6 February 2010 19:23, Peter Robinson thaldy...@gmail.com wrote: I think you mean ghc-pkg check. Yes, I do. Whoops :s -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com Charles de Gaulle - The better I get to know men, the more I find myself loving dogs. - http://www.brainyquote.com/quotes/authors/c/charles_de_gaulle.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Simulation of interconnect network
2010/2/5 Roger King rogerking...@yahoo.com: I am building a simulator for an interconnect network for a multiprocessor computer. I would like to develop it in Haskell as an opportunity to learn Haskell. The network will have a number of routers with input ports and output ports and crossbars between them. I would like to simulate the protocol. This would be an event driven simulator. It would be at a high level, leaving out many details. I would like it to be fast and be able to run it on several processors. Crossbar is certainly easier using lazy lists of events. Like those used in Hawk: http://eprints.kfupm.edu.sa/66296/1/66296.pdf Event-driven approach is good for asynchronous behaviour, like combinatorial logic etc. For single-clock clocked logic (and crossbar is certainly that kind of device) lazy lists are simpler to write and reason about. I would like to know if you have any advice. Has anyone done this before? Are there any discrete event simulators written in Haskell? http://hackage.haskell.org/package/hasim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] safe lazy IO or Iteratee?
I've put my benchmarking code online at: http://inmachina.net/~jwlato/haskell/research-iteratee.tar.bz2 unpack it so you have this directory structure: ./iteratee ./research-iteratee/ Also download my criterionProcessor programs. The darcs repo is at http://inmachina.net/~jwlato/haskell/criterionProcessor/ to use it, go into the criterionProcessor directory, edit the testrunner.hs script for your environment, and run it. This runs all the benchmarks. Then you can use the CritProc program (build with cabal) to generate pictures. I'm pretty sure you need Chart HEAD in order to build CritProc (I hacked my Chart install, but I think the only important change has been applied to HEAD). I make no guarantees that these will all build properly, it's basically a work-in-progress dump. John On Fri, Feb 5, 2010 at 10:25 PM, John Millikin jmilli...@gmail.com wrote: Benchmark attached. It just enumerates a list until EOF is reached. An interesting thing I've noticed is that IterateeMCPS performs better with no optimization, but -O2 gives IterateeM the advantage. Their relative performance depends heavily on the chunk size -- for example, CPS is much faster at chunk size 1, but slower with 100-element chunks. On Fri, Feb 5, 2010 at 08:56, John Lato jwl...@gmail.com wrote: On Fri, Feb 5, 2010 at 4:31 PM, Valery V. Vorotyntsev valery...@gmail.com wrote: John Lato jwl...@gmail.com wrote: Both designs appear to offer similar performance in aggregate, although there are differences for particular functions. I haven't yet had a chance to test the performance of the CPS variant, although Oleg has indicated he expects it will be higher. @jwlato: Do you mind creating `IterateeCPS' tree in http://inmachina.net/~jwlato/haskell/iteratee/src/Data/, so we can start writing CPS performance testing code? I'm working on the CPS version and will make it public when it's done. It may take a week or so; this term started at 90 and has picked up. I have several benchmark sources that aren't public yet, but I can put them online for your perusal. AFAICS, you have benchmarks for IterateeM-driven code already: http://inmachina.net/~jwlato/haskell/iteratee/tests/benchmarks.hs Those will make more sense when I've added the context of the codebases in use. There are several more sets of output that I simply haven't published yet, including bytestring-based variants. John Millikin jmilli...@gmail.com wrote: I wrote some criterion benchmarks for IterateeM vs IterateeCPS, and the CPS version was notably slower. I don't understand enough about CPS to diagnose why, but the additional runtime was present in even simple cases (reading from a file, writing back out). That's very interesting. I wonder if I'll see the same, and if I'd be able to figure it out myself... Did you benchmark any cases without doing IO? Sometimes the cost of the IO can overwhelm any other measurable differences, and also disk caching can affect results. Criterion should highlight any major outliers, but I still like to avoid IO when benchmarking unless strictly necessary. @jmillikin: Could you please publish those benchmarks? +1 John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: sendfile leaking descriptors on Linux?
On Sat, Feb 06, 2010 at 09:16:35AM +0100, Bardur Arantsson wrote: Brandon S. Allbery KF8NH wrote: On Feb 5, 2010, at 02:56 , Bardur Arantsson wrote: [--snip--] Broken pipe is normally handled as a signal, and is only mapped to an error if SIGPIPE is set to SIG_IGN. I can well imagine that the SIGPIPE signal handler isn't closing resources properly; a workaround would be to use the System.Posix.Signals API to ignore SIGPIPE, but I don't know if that would work as a general solution (it would depend on what other uses of pipes/sockets exist). It was a good idea, but it doesn't seem to help to add installHandler sigPIPE Ignore (Just fullSignalSet) to the main function. (Given the package name I assume System.Posix.Signals works similarly to regular old signals, i.e. globally per-process.) This is really starting to drive me round the bend... Have you seen GHC ticket #1619? http://hackage.haskell.org/trac/ghc/ticket/1619 One further thing I've noticed: When compiling on my 64-bit machine, ghc issues the following warnings: Linux.hsc:41: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long unsigned int’ Those lines are: 39: -- max num of bytes in one send 40: maxBytes :: Int64 41: maxBytes = fromIntegral (maxBound :: (#type ssize_t)) and 44: foreign import ccall unsafe sendfile64 c_sendfile 45: :: Fd - Fd - Ptr (#type off_t) - (#type size_t) - IO (#type ssize_t) This looks like a typical 32/64-bit problem, but normally I would expect any real run-time problems caused by a problematic conversion in the FFI to crash the whole process. Maybe I'm wrong about this... To convert those '#' constants, hsc2hs preprocessor constructs a C file things like 'printf(%d, sizeof(ssize_t))' to use the system's C compiler and avoid having the encode the ABI of every platform (to be able to know the memory layout of the structures). So that message comes from that C file, not from your Haskell one. At runtime it really doesn't matter. -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Using ShowS or Difference Lists
Hi,
Just wondering whether I can use ShowS or tupling or Difference Lists to speed
up the following code?
It's basic text processing. It takes in a list of Lines where each Line is a
list of Words and intersperses between them then concatenates them into a
longer String. Note that there is a recursive call and the ++ operator.
Thanks
Mark
-- Function: joinLines
-- Joins the Words within Lines together with whitespace and newline characters
-- Argument: Lines to pad with whitespace and newlines
-- Evaluate: The processed and concatenated String
joinLines :: [Line] - String
joinLines (l:[]) = concat (intersperse l)
joinLines (l:ls) = (concat (intersperse l)) ++ ('\n':joinLines ls)
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Re: [Haskell-cafe] a beginner question: decorate-op-undecorate
From: Aran Donohue aran.dono...@gmail.com Hi Haskell-Cafe, Consider a data type such as data Binding = Binding Var (Either Value [Value]) representing a variable bound either to a fixed value or that has a list of possible values. I'd like to perform an operation on say, the fixed-value members of a list of bindings. Data.Either has partitionEithers---I'd essentially like to use partitionEithers, but in a way that it peeks into the value field of the binding. For the sake of argument, let's say I can't or can't modify Binding to move the Either to the outside. I think that partitionEithers is leading you down the wrong trail. If what you want to do is modify some values inside the binding, I would start with this: mapVal :: (Either Value [Value] - Either Value [Value]) - Binding - Binding mapVal f (Binding v e) = Binding v (f e) mapLeft :: (a - b) - Either a c - Either b c mapLeft f = either (Left . f) Right -- mapRight is just fmap, but for symmetry mapRight :: (b - c) - Either a b - Either a c mapRight = fmap modifyFixed :: (Value - Value) - Binding - Binding modifyFixed f b = mapVal (mapLeft f) b modifyList :: ([Value] - [Value]) - Binding - Binding modifyList f b = mapVal (mapRight f) b -- note that modifyFixed and modifyList have very nice point-free representations -- modifyFixed = mapVal . mapLeft -- modifyList = mapVal . mapRight Now to apply this to a list: modifyFixedBindings :: (Value - Value) - [Binding] - [Binding] modifyFixedBindings f binds = map (modifyFixed f) binds -- or point-free modifyFixedBindings' = map . modifyFixed In my opinion, this would be more idiomatic if Binding were polymorphic: data Binding' k v = Binding' k v instance Functor (Binding' k) where fmap f (Binding' k v) = Binding' k (f v) type Binding2 = Binding' Var (Either Value [Value]) now mapVal is just fmap, and these functions are: modifyFixed2 :: (Val - Val) - [Binding2] - [Binding2] modifyFixed2 = fmap . fmap . mapLeft modifyList2 :: ([Val] - [Val]) - [Binding2] - [Binding2] modifyList2 = fmap . fmap . mapRight I've typed out all the steps for clarity, but to be honest, I wouldn't bother with the Fixed and List variants, unless you're going to use them frequently. I would do just: mapVals :: (Either Value [Value] - Either Value [Value]) - [Binding] - [Binding] mapVals f = map (\(Binding var val) - Binding var (f val)) and leave it at that, using mapVals with the either function when necessary. I would consider making Binding polymorphic, though, so you can write the Functor instance. You may also want to look at Data.Traversable. Cheers, John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using ShowS or Difference Lists
Am Samstag, den 06.02.2010, 23:12 +1030 schrieb Mark Spezzano:
Hi,
Just wondering whether I can use ShowS or tupling or Difference Lists to
speed up the following code?
It's basic text processing. It takes in a list of Lines where each Line
is a list of Words and intersperses between them then concatenates
them into a longer String. Note that there is a recursive call and the
++ operator.
Thanks
Mark
-- Function: joinLines
-- Joins the Words within Lines together with whitespace and newline
characters
-- Argument: Lines to pad with whitespace and newlines
-- Evaluate: The processed and concatenated String
joinLines :: [Line] - String
joinLines (l:[]) = concat (intersperse l)
joinLines (l:ls) = (concat (intersperse l)) ++ ('\n':joinLines ls)
You should use the existing library functions and leave the
optimisations to their implementor:
import Data.List
joinLines :: [[String]] - String
joinLines = intercalate \n . map (intercalate )
Now you can easily switch to the faster ByteString library by simply
changing the import statement.
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Re: [Haskell-cafe] Using ShowS or Difference Lists
On Sat, Feb 06, 2010 at 11:12:40PM +1030, Mark Spezzano wrote:
-- Function: joinLines
-- Joins the Words within Lines together with whitespace and newline
characters
-- Argument: Lines to pad with whitespace and newlines
-- Evaluate: The processed and concatenated String
joinLines :: [Line] - String
joinLines (l:[]) = concat (intersperse l)
joinLines (l:ls) = (concat (intersperse l)) ++ ('\n':joinLines ls)
Why not just
joinLines = unlines . map unwords
This should be as fast as you may get using lists of lists of
lists of Chars :).
--
Felipe.
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Re: [Haskell-cafe] a beginner question: decorate-op-undecorate
Hi John I'm not sure about making Binding polymorphic to get Functor, Traversable, Foldable... While I think you're correct that partitionEithers might not be a useful example to draw from in this case, I'd assume that Binding would be part of a larger syntax-tree, thus there might not be a appropriate single leaf to make the tree polymorphic on. Felipe Lessa's point - to use Uniplate or one of the Generics packages - might be a better candidate for implementing traversals. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using ShowS or Difference Lists
Am Samstag 06 Februar 2010 13:42:40 schrieb Mark Spezzano:
Hi,
Just wondering whether I can use ShowS or tupling or Difference Lists to
speed up the following code?
It's basic text processing. It takes in a list of Lines where each Line
is a list of Words and intersperses between them then concatenates
them into a longer String. Note that there is a recursive call and the
++ operator.
Thanks
Mark
-- Function: joinLines
-- Joins the Words within Lines together with whitespace and newline
characters -- Argument: Lines to pad with whitespace and newlines
-- Evaluate: The processed and concatenated String
joinLines :: [Line] - String
joinLines (l:[]) = concat (intersperse l)
joinLines (l:ls) = (concat (intersperse l)) ++ ('\n':joinLines ls)
joinLines = init . unlines . map unwords
joinLines = concat . intersperse \n . map unwords
joinLines = intercalate \n . map unwords
joinLines = intercalate \n . map (intercalate )
it should be pretty good already, if that's a performance bottleneck, you
might need to switch to (Lazy) ByteStrings. I don't think ShowS or
difference lists would be any faster.
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[Haskell-cafe] Re: cabal fun (not)
On Feb 6, 3:33 am, Ivan Miljenovic ivan.miljeno...@gmail.com wrote: On 6 February 2010 01:05, Johannes Waldmann waldm...@imn.htwk-leipzig.de wrote: so please please please have cabal install fail with some error message if (that is, before) the install would break anything. - J. If you upgrade a library, it will break all other libraries that depend upon it. ghc-pkg list will tell you which libraries are broken and need to be rebuilt. Yes, I think that's the current behaviour what Johannes described yet he suggest this to be sub-optimal. A warning about breakage would be good before the breakage has happened. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com Joan Crawford - I, Joan Crawford, I believe in the dollar. Everything I earn, I spend. -http://www.brainyquote.com/quotes/authors/j/joan_crawford.html ___ Haskell-Cafe mailing list haskell-c...@haskell.orghttp://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: sendfile leaking descriptors on Linux?
Felipe Lessa wrote: On Sat, Feb 06, 2010 at 09:16:35AM +0100, Bardur Arantsson wrote: Brandon S. Allbery KF8NH wrote: On Feb 5, 2010, at 02:56 , Bardur Arantsson wrote: [--snip--] Broken pipe is normally handled as a signal, and is only mapped to an error if SIGPIPE is set to SIG_IGN. I can well imagine that the SIGPIPE signal handler isn't closing resources properly; a workaround would be to use the System.Posix.Signals API to ignore SIGPIPE, but I don't know if that would work as a general solution (it would depend on what other uses of pipes/sockets exist). It was a good idea, but it doesn't seem to help to add installHandler sigPIPE Ignore (Just fullSignalSet) to the main function. (Given the package name I assume System.Posix.Signals works similarly to regular old signals, i.e. globally per-process.) This is really starting to drive me round the bend... Have you seen GHC ticket #1619? http://hackage.haskell.org/trac/ghc/ticket/1619 I hadn't. I guess the conclusion is that SIG_PIPE is ignored by default anyway. So much for that. During yet another bout of debugging, I've added even more I am here instrumentation code to the SendFile code, and the culprit seems to be threadWaitWrite. Here's the bit of code I've modified: sendfile :: Fd - Fd - Ptr Int64 - Int64 - IO Int64 sendfile out_fd in_fd poff bytes = do putStrLn PRE-threadWaitWrite threadWaitWrite out_fd putStrLn AFTER threadWaitWrite sbytes - c_sendfile out_fd in_fd poff (fromIntegral bytes) putStrLn $ AFTER c_sendfile; result was: ++ (show sbytes) if sbytes = -1 then do errno - getErrno if errno == eAGAIN then sendfile out_fd in_fd poff bytes else throwErrno Network.Socket.SendFile.Linux else return (fromIntegral sbytes) This is the output when a file descriptor is lost: --- AFTER sendfile: sbytes=27512 DIFFERENCE: 627264520 remaining=627264520, bytes=627264520 PRE-threadWaitWrite Got request for CONTENT for objectId=1700,f2150400 Serving file 'X'... Sending 625838080 bytes... in_fd=13 --- So I have to conclude that threadWaitWrite is doing *something* which causes the thread to die when the PS3 kills the connection. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Category Theory woes
On Tue, 02 Feb 2010 09:16:03 -0800, Creighton Hogg wrote: 2010/2/2 Álvaro García Pérez agar...@babel.ls.fi.upm.es You may try Pierce's Basic Category Theory for Computer Scientists or Awodey's Category Theory, whose style is rather introductory. Both of them (I think) have a chapter about functors where they explain the Hom functor and related topics. I think Awodey's book is pretty fantastic, actually, but I'd avoid Pierce. Unlike Types and Programming Languages, I think Basic Category Theory... is a bit eccentric in its presentation and doesn't help the reader build intuition. I have written an overview of various category theory books, which you may find useful, at the following site: Learning Haskell through Category Theory, and Adventuring in Category Land: Like Flatterland, Only About Categories http://dekudekuplex.wordpress.com/2009/01/16/learning-haskell-through-category-theory-and-adventuring-in-category-land-like-flatterland-only-about-categories/ Hope this helps. -- Benjamin L. Russell -- Benjamin L. Russell / DekuDekuplex at Yahoo dot com http://dekudekuplex.wordpress.com/ Translator/Interpreter / Mobile: +011 81 80-3603-6725 Furuike ya, kawazu tobikomu mizu no oto. -- Matsuo Basho^ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: sendfile leaking descriptors on Linux?
Bardur Arantsson wrote: (sorry about replying-to-self) During yet another bout of debugging, I've added even more I am here instrumentation code to the SendFile code, and the culprit seems to be threadWaitWrite. I think I've pretty much confirmed this. I've changed the code again. This time to: sendfile :: Fd - Fd - Ptr Int64 - Int64 - IO Int64 sendfile out_fd in_fd poff bytes = do putStrLn PRE-threadWaitWrite -- threadWaitWrite out_fd -- putStrLn AFTER threadWaitWrite sbytes - c_sendfile out_fd in_fd poff (fromIntegral bytes) putStrLn $ AFTER c_sendfile; result was: ++ (show sbytes) if sbytes = -1 then do errno - getErrno if errno == eAGAIN then do threadDelay 100 sendfile out_fd in_fd poff bytes else throwErrno Network.Socket.SendFile.Linux else return (fromIntegral sbytes) That is, I removed the threadWaitWrite in favor of just adding a threadDelay 100 when eAGAIN is encountered. With this code, I cannot provoke the leak. Unfortunately this isn't really a solution -- the CPU is pegged at ~50% when I do this and it's not exactly elegant to have a hardcoded 100 ms delay in there. :) I'm hoping that someone who understands the internals of GHC can chime in here with some kind of explanation as to if/why/how threadWaitWrite can fail in this way. Anyone? Cheers, ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Category Theory woes
On Sun, 07 Feb 2010 01:38:08 +0900 Benjamin L. Russell dekudekup...@yahoo.com wrote: On Tue, 02 Feb 2010 09:16:03 -0800, Creighton Hogg wrote: 2010/2/2 Álvaro García Pérez agar...@babel.ls.fi.upm.es You may try Pierce's Basic Category Theory for Computer Scientists or Awodey's Category Theory, whose style is rather introductory. Both of them (I think) have a chapter about functors where they explain the Hom functor and related topics. I think Awodey's book is pretty fantastic, actually, but I'd avoid Pierce. Unlike Types and Programming Languages, I think Basic Category Theory... is a bit eccentric in its presentation and doesn't help the reader build intuition. I have written an overview of various category theory books, which you may find useful, at the following site: Learning Haskell through Category Theory, and Adventuring in Category Land: Like Flatterland, Only About Categories http://dekudekuplex.wordpress.com/2009/01/16/learning-haskell-through-category-theory-and-adventuring-in-category-land-like-flatterland-only-about-categories/ Hope this helps. It does. Does anybody have any opinions on Pitt, Category Theory and Computer Science ? Brian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] safe-lazy-io on GHC 6.12?
After convincing myself the hard way that you can't be lazy across strict monadic results (by writing myself a foldrM -- yeah, I'm still a beginner), I noticed the recent discussion of safe-lazy-io vs. iteratee with interest. The safe-lazy-io package seems much easier to understand than iteratee, but it doesn't compile on GHC 6.12 (and I haven't had any luck in figuring out how to update it myself). The Hackage build log shows the same build result I'm getting [1]; is there any chance of it getting updated to work on 6.12? [1] http://hackage.haskell.org/packages/archive/safe-lazy-io/0.1/logs/failure/ghc-6.12 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] safe-lazy-io on GHC 6.12?
On Sat, 6 Feb 2010 11:38:25 -0600, Tom Tobin korp...@korpios.com wrote: After convincing myself the hard way that you can't be lazy across strict monadic results (by writing myself a foldrM -- yeah, I'm still a beginner), I noticed the recent discussion of safe-lazy-io vs. iteratee with interest. The safe-lazy-io package seems much easier to understand than iteratee, but it doesn't compile on GHC 6.12 (and I haven't had any luck in figuring out how to update it myself). The Hackage build log shows the same build result I'm getting [1]; is there any chance of it getting updated to work on 6.12? Right, updating it is on my todo list. However I have a little dilemma, safe-lazy-io has a local version of hGetContents because I needed a version which do not hide exceptions. However the latest version of hGetContents seems to no longer catch exceptions (am I right?), if so it might be preferable to just use the new hGetContents. Or not? -- Nicolas Pouillard http://nicolaspouillard.fr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using ShowS or Difference Lists
As other people have mentioned, you are duplicating library
functionality. But nobody has actually talked about the performance
characteristics of your code.
Fortunately for you, the calls to (++) in your recursion are
right-associative, so you don't have an asymptotic problem where your
program gets slower and slower for large inputs; it should stay
linear.
But you are wasting some work. In particular, (concat (intersperse
l)) produces a String, and then (++) duplicates all of the cons
cells in that string as it rebuilds it so that the tail connects with
the next string.
So there is a potential benefit to using a difference list, albeit
only by around a 2x factor.
-- ryan
On Sat, Feb 6, 2010 at 4:42 AM, Mark Spezzano
mark.spezz...@chariot.net.au wrote:
Hi,
Just wondering whether I can use ShowS or tupling or Difference Lists to
speed up the following code?
It's basic text processing. It takes in a list of Lines where each Line is a
list of Words and intersperses between them then concatenates them into a
longer String. Note that there is a recursive call and the ++ operator.
Thanks
Mark
-- Function: joinLines
-- Joins the Words within Lines together with whitespace and newline
characters
-- Argument: Lines to pad with whitespace and newlines
-- Evaluate: The processed and concatenated String
joinLines :: [Line] - String
joinLines (l:[]) = concat (intersperse l)
joinLines (l:ls) = (concat (intersperse l)) ++ ('\n':joinLines ls)
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Re: [Haskell-cafe] a beginner question: decorate-op-undecorate
One way or the other, this has been a very productive question for getting good pointers on what to read about next... Thanks again. Aran On Sat, Feb 6, 2010 at 8:18 AM, Stephen Tetley stephen.tet...@gmail.comwrote: Hi John I'm not sure about making Binding polymorphic to get Functor, Traversable, Foldable... While I think you're correct that partitionEithers might not be a useful example to draw from in this case, I'd assume that Binding would be part of a larger syntax-tree, thus there might not be a appropriate single leaf to make the tree polymorphic on. Felipe Lessa's point - to use Uniplate or one of the Generics packages - might be a better candidate for implementing traversals. Best wishes Stephen ___ 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] Re: sendfile leaking descriptors on Linux?
me too. 2010/2/5 MightyByte mightyb...@gmail.com: I've been seeing a steady stream of similar resource vanished messages for as long as I've been running my happstack app. This message I get is this: socket: 58: hClose: resource vanished (Broken pipe) I run my app from a shell script inside a while true loop, so it automatically gets restarted if it crashes. This incurs no more than a few seconds of down time. Since that is acceptable for my application, I've never put much effort into investigating the issue. But I don't think the resource vanished error results in program termination. When I have looked into it, I've had similar trouble reproducing it. Clients such as wget and firefox don't seem to cause the problem. If I remember correctly it only happens with IE. On Fri, Feb 5, 2010 at 2:56 AM, Bardur Arantsson s...@scientician.net wrote: Jeremy Shaw wrote: Actually, We should start by testing if native sendfile leaks file descriptors even when the whole file is sent. We have a test suite, but I am not sure if it tests for file handle leaking... I should have posted this earlier, but the exact message I'm seeing in the case where the Bad Client disconnects is this: hums: Network.Socket.SendFile.Linux: resource vanished (Broken pipe) Oddly, I haven't been able to reproduce this using a wget client with a ^C during transfer. When I disconnect wget with ^C or pkill wget or even pkill -9 wget, I get this message: hums: Network.Socket.SendFile.Linux: resource vanished (Connection reset by peer) (and no leak, as observed by lsof | grep hums). So there appears to be some vital difference between the handling of the two cases. Another observation which may be useful: Before the sendfile' API change (Handle - FilePath) in sendfile-0.6.x, my code used withFile to open the file and to ensure that it was closed. So it seems that withBinaryFile *should* also be fine. Unless the Broken pipe error somehow escapes the scope without causing a close. I don't have time to dig more right now, but I'll try to see if I can find out more later. Cheers, ___ 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] cannot post to haskellmode-em...@projects.haskell.org
Hi, all my posts to the haskellmode-emacs list (using the address in the subject) are being rejected with the error: 451 451 Temporary local problem - please try later (state 18) (after several retries by the Google smtp server, which i use as a smarthost). Any idea of what could be causing this problem? Thanks! jao -- There are two ways to write error-free programs; only the third one works. - Alan Perlis, Epigrams in Programing ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cannot post to haskellmode-em...@projects.haskell.org
On 7 February 2010 07:39, Jose A. Ortega Ruiz j...@gnu.org wrote: all my posts to the haskellmode-emacs list (using the address in the subject) are being rejected with the error: 451 451 Temporary local problem - please try later (state 18) (after several retries by the Google smtp server, which i use as a smarthost). I have been experiencing this often too recently when trying to post to haskell-platform list. I wonder if some of the googlemail smtp servers got blacklisted on projects.haskell.org because of spam? Jens ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: data-ordlist-0.2
I have released data-ordlist 0.2, with a number of changes: 1. The module name is now Data.List.Ordered, instead of Data.OrdList 2. Three bugfixes: (ack!) insertSet and insertBag assumed reverse-ordered lists, nub failed to remove duplicates. Thanks to Topi Karvonen for reporting the first problem. 3. One semantic change: old_nubBy f == new_nubBy (not . f). The new version is better keeping with the spirit of the rest of the library, and makes the old nub bug much more obvious. Now nubBy is the greedy algorithm that returns a sublist such that for all binary predicates: isSortedBy pred (nubBy pred xs) == True 4. Improved documentation, I hope! Please consider taking a look and letting me know what you think. http://hackage.haskell.org/package/data-ordlist Cheers, Leon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
