June 2014 - Haskell-Cafe

accessing a ByteArray from FFI
by Mihaly Barasz 25 Jun '14

25 Jun '14

Hello, I want to access the contents of a Data.Vector.Primitive from FFI. I came up with the following so far: {-# LANGUAGE ForeignFunctionInterface #-} module FFIExample (exampleFn) where import Control.Monad.Primitive (touch) import Control.Monad.ST (runST) import Data.Primitive.Addr (Addr(..)) import Data.Primitive.ByteArray (mutableByteArrayContents) import qualified Data.Vector.Primitive as P import qualified Data.Vector.Primitive.Mutable as PM import GHC.Ptr (Ptr(..), plusPtr) import Data.Word (Word64) foreign import ccall unsafe "my_external_fn" myExternalFn :: Ptr Word64 -> Int -> Int exampleFn :: P.Vector Word64 -> Int exampleFn v = runST $ do PM.MVector off len mba <- P.unsafeThaw v let ptr = case mutableByteArrayContents mba of Addr addr -> Ptr addr `plusPtr` off result = myExternalFn ptr len result `seq` touch mba return result This seems to work, but I have questions that I haven't been able to find the answers to on my own: 1. Is this actually OK to do? I guess that this wouldn't be OK if the foreign import were "safe", as then the GC could move the contents of the byte array while the foreign function is running. But is it safe like this? 2. If the answer to the previous question is no, then is there a way to do it properly? Or there is just no way to pass an unpinned byte array to a foreign call? What about foreign import prim? 3. If the answer to Q1 is no, then would it be OK if the underlying byte array were pinned? 4. Any other simplifications? Pointers to resources on these topics would be more than welcome! But, I haven't been able to find any. Thanks, Mihaly

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Fwd: 自动回复：Re: ANN: hmatrix-0.16
by Dominic Steinitz 25 Jun '14

25 Jun '14

Hello Cafe, Everytime I post something via gmane I get what I assume is spam - see below. Is this a gmane feature or a haskell-cafe feature? Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com Begin forwarded message: > From: <zhangliu529(a)sina.com> > Subject: 自动回复：Re: [Haskell-cafe] ANN: hmatrix-0.16 > Date: 22 June 2014 11:37:49 BST > To: <dominic(a)steinitz.org> > > 您发的邮件我已收到，我将尽快给您答复。

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ANN: hmatrix-0.16
by Alberto Ruiz 24 Jun '14

24 Jun '14

Hi! I am happy to announce the release of hmatrix-0.16, a Haskell package for matrix computations and numeric linear algebra. New features: - BSD3 license. The modules depending on GSL have been moved to a new package hmatrix-gsl (GPL). Now hmatrix depends only on BLAS/LAPACK. - Simpler reexport modules with improved documentation and usage examples. There are a few API changes but the traditional modules are also exposed for backwards compatibility. - Alternative interface using type-level literals for static dimension checking and inference (work in progress). - Initial support for sparse linear systems. - Minor improvements and bug fixes (see the changelog for details). http://hackage.haskell.org/package/hmatrix https://github.com/albertoruiz/hmatrix Some examples: http://dis.um.es/~alberto/hmatrix/hmatrix.html Suggestions, contributions, and bug reports are welcome. Thanks! Alberto

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ANN: Graphics.OpenSCAD
by Mike Meyer 24 Jun '14

24 Jun '14

Graphics.OpenSCAD provides an algebraic data type for creating OpenSCAD 3d models, as well a a function to generate an OpenSCAD program from a data structure. OpenSCAD is a "programmers" CAD tool. It provides a declarative language for 3d models with a primitive functional language for doing computation. The Graphics.OpenSCAD module tries to preserve the declarative parts by providing tools for building data structures that match the OpenSCAD declarative models, then embedding that in a powerful, modern functional language. The critical problem with OpenSCAD is the error handling. At it's best, it will say "syntax error" and provide sufficient location information to easily find the error. At times, the location information points outside the file. Errors in dealing with variables may have no error messages, or messages that are easy to overlook, resulting in models that are radically different from what was expected with no way to determine the problem except searching the complete program text. Graphics.OpenSCAD attempts to solve that by leveraging Haskell's type system as far as possible. While not every run-time OpenSCAD error can be detected in Haskell, as many as possible are. Hackage page with pointers to source and documentation: http://hackage.haskell.org/package/OpenSCAD

1 0

how to upgrade to a new version of Haskell?
by Johan Larson 24 Jun '14

24 Jun '14

I am currently running an old installation of the Haskell environment from 2012, and I would like to upgrade. Can I just grab the installer from https://www.haskell.org/platform/windows.html and run it? This is on Windows. -- Johan Larson -- Toronto, Canada

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New Assistant Professorship in Nottingham
by Graham Hutton 23 Jun '14

23 Jun '14

Dear all, The School of Computer Science at the University of Nottingham in the UK is seeking to appoint a new Assistant Professor: http://www.nottingham.ac.uk/jobs/currentvacancies/ref/SCI181514 Applications in the area of the Functional Programming (FP) lab would be most welcome. The FP lab is keen to receive applications from candidates with an excellent publication record, experience in combining theory with practice, and the ability to secure external funding to support their research. Further information about the FP lab is available from: http://fp.cs.nott.ac.uk The deadline for applications is Friday 22nd August 2014. The advert mentions computer vision, but the position is open to applicants from any area of Computer Science. Best wishes, Graham Hutton -- Prof Graham Hutton Functional Programming Lab School of Computer Science University of Nottingham, UK http://www.cs.nott.ac.uk/~gmh This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system, you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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hayoo doesn't find the Kleisli arrow?
by Erik Rantapaa 23 Jun '14

23 Jun '14

I just happen to notice that this query comes back empty in Hayoo: (a -> m b) -> (b -> m c) -> (a -> m c) Hoogle is able to find (>=>), and I'm wondering if its a bug or...?

2 1

Pathological overloaded function
by Simon Yarde 23 Jun '14

23 Jun '14

Could anyone chip in with examples of a pathological overloaded functions in relation to the GHC Guide 6.2: > Overloaded functions are not your friend: > Haskell's overloading (using type classes) is elegant, neat, etc., etc., but it is death to performance if left to linger in an inner loop. How can you squash it? > > Give explicit type signatures: > Signatures are the basic trick; putting them on exported, top-level functions is good software-engineering practice, anyway. (Tip: using -fwarn-missing-signatures can help enforce good signature-practice). http://lambda.haskell.org/platform/doc/current/ghc-doc/users_guide/faster.h… Best Regards, Simon

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cabal-install failure
by Magicloud Magiclouds 23 Jun '14

23 Jun '14

Hi, This is a box that used to work well. But today, I found that I could not install anything by cabal. I removed ~/.ghc and ~/.cabal to start all userspace thing from the beginning. I used Setup.hs to install Cabal, and bootstrap.sh to install cabal-install. All succeeded. Then I tried to install data-default-class, I got following. Notice the ld fail near the end. Versions: OS: Ubuntu Precise; ghc 7.8.2; Cabal/cabal-install: latest from github. % cabal install -v3 data-default-class Searching for ghc in path. Found ghc at /usr/local/bin/ghc ("/usr/local/bin/ghc",["--numeric-version"]) /usr/local/bin/ghc is version 7.8.2 looking for tool ghc-pkg near compiler in /usr/local/bin found ghc-pkg in /usr/local/bin/ghc-pkg ("/usr/local/bin/ghc-pkg",["--version"]) /usr/local/bin/ghc-pkg is version 7.8.2 ("/usr/local/bin/ghc",["--supported-languages"]) ("/usr/local/bin/ghc",["--info"]) Reading installed packages... ("/usr/local/bin/ghc-pkg",["dump","--global","-v0"]) ("/usr/local/bin/ghc-pkg",["dump","--user","-v0"]) ("/usr/local/bin/ghc",["--print-libdir"]) Reading available packages... Warning: The package list for the local repo '/home/local/ANT/shida/.cabal/packages/cabal-src/' is missing. The repo is invalid. Resolving dependencies... targets: data-default-class constraints: base installed ghc-prim installed integer-gmp installed stanzas data-default-class preferences: strategy: PreferAllLatest [__0] trying: data-default-class-0.0.1 (user goal) [__1] trying: base-4.7.0.0/installed-018... (dependency of data-default-class-0.0.1) [__2] trying: rts-1.0/installedbuil... (dependency of base-4.7.0.0/installed-018...) [__3] trying: integer-gmp-0.5.1.0/installed-dc4... (dependency of base-4.7.0.0/installed-018...) [__4] next goal: ghc-prim (dependency of base-4.7.0.0/installed-018...) [__4] trying: ghc-prim-0.3.1.0/installed-948... [__5] done Ready to install data-default-class-0.0.1 Waiting for install task to finish... Extracting /home/local/ANT/shida/.cabal/packages/ hackage.haskell.org/data-default-class/0.0.1/data-default-class-0.0.1.tar.gz to /tmp/data-default-class-0.0.1-19534... Updating data-default-class.cabal with the latest revision from the index. Using internal setup method with build-type Simple and args: ["configure","--verbose=3","--ghc","--prefix=/home/local/ANT/shida/.cabal","--bindir=/home/local/ANT/shida/.cabal/bin","--libdir=/home/local/ANT/shida/.cabal/lib","--libsubdir=x86_64-linux-ghc-7.8.2/data-default-class-0.0.1","--libexecdir=/home/local/ANT/shida/.cabal/libexec","--datadir=/home/local/ANT/shida/.cabal/share","--datasubdir=x86_64-linux-ghc-7.8.2/data-default-class-0.0.1","--docdir=/home/local/ANT/shida/.cabal/share/doc/x86_64-linux-ghc-7.8.2/data-default-class-0.0.1","--htmldir=/home/local/ANT/shida/.cabal/share/doc/x86_64-linux-ghc-7.8.2/data-default-class-0.0.1/html","--haddockdir=/home/local/ANT/shida/.cabal/share/doc/x86_64-linux-ghc-7.8.2/data-default-class-0.0.1/html","--sysconfdir=/home/local/ANT/shida/.cabal/etc","--enable-split-objs","--user","--dependency=base=base-4.7.0.0-018311399e3b6350d5be3a16b144df9b","--disable-tests","--exact-configuration","--disable-benchmarks"] Configuring data-default-class-0.0.1... creating dist Searching for ghc in path. Found ghc at /usr/local/bin/ghc ("/usr/local/bin/ghc",["--numeric-version"]) /usr/local/bin/ghc is version 7.8.2 looking for tool ghc-pkg near compiler in /usr/local/bin found ghc-pkg in /usr/local/bin/ghc-pkg ("/usr/local/bin/ghc-pkg",["--version"]) /usr/local/bin/ghc-pkg is version 7.8.2 ("/usr/local/bin/ghc",["--supported-languages"]) ("/usr/local/bin/ghc",["--info"]) Reading installed packages... ("/usr/local/bin/ghc-pkg",["dump","--global","-v0"]) ("/usr/local/bin/ghc-pkg",["dump","--user","-v0"]) ("/usr/local/bin/ghc",["--print-libdir"]) Dependency base ==4.7.0.0: using base-4.7.0.0 Searching for alex in path. Cannot find alex on the path Searching for ar in path. Found ar at /usr/bin/ar Searching for c2hs in path. Cannot find c2hs on the path Searching for cpphs in path. Cannot find cpphs on the path Searching for ffihugs in path. Cannot find ffihugs on the path Searching for gcc in path. Found gcc at /usr/bin/gcc ("/usr/bin/gcc",["-dumpversion"]) /usr/bin/gcc is version 4.6 Searching for greencard in path. Cannot find greencard on the path Searching for haddock in path. Found haddock at /usr/local/bin/haddock ("/usr/local/bin/haddock",["--version"]) /usr/local/bin/haddock is version 2.14.2 Searching for happy in path. Cannot find happy on the path Searching for hmake in path. Cannot find hmake on the path Searching for hpc in path. Found hpc at /usr/local/bin/hpc ("/usr/local/bin/hpc",["version"]) /usr/local/bin/hpc is version 0.67 looking for tool hsc2hs near compiler in /usr/local/bin found hsc2hs in /usr/local/bin/hsc2hs ("/usr/local/bin/hsc2hs",["--version"]) /usr/local/bin/hsc2hs is version 0.67 Searching for HsColour in path. Cannot find HsColour on the path Searching for hugs in path. Cannot find hugs on the path Searching for jhc in path. Cannot find jhc on the path Searching for ld in path. Found ld at /usr/bin/ld Environment: [("COLORFGBG","12;default;8"),("COLORTERM","rxvt-xpm"),("DBUS_SESSION_BUS_ADDRESS","unix:abstract=/tmp/dbus-5El0U8sCi8,guid=09290436e309789f9814dffc00000406"),("DEFAULTS_PATH","/usr/share/gconf/xmonad.default.path"),("DESKTOP_SESSION","xmonad"),("DISPLAY"," 10.69.208.185:0"),("EDITOR","vim"),("GDMSESSION","xmonad"),("GPG_AGENT_INFO","/tmp/gpg-KKH3WT/S.gpg-agent:5467:1"),("GREP_COLOR","1;32"),("GREP_OPTIONS","--color=auto --exclude-dir=.cvs --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn"),("GTK_IM_MODULE","xim"),("HOME","/home/local/ANT/shida"),("LANG","C.UTF-8"),("LC_ALL","C.UTF-8"),("LC_CTYPE","C.UTF-8"),("LESS","-R"),("LOGNAME","shida"),("LSCOLORS","Gxfxcxdxbxegedabagacad"),("MANDATORY_PATH","/usr/share/gconf/xmonad.mandatory.path"),("NODE_PATH","/usr/lib/nodejs:/usr/lib/node_modules:/usr/share/javascript"),("OLDPWD","/home/local/ANT/shida/src/git/cabal/cabal-install"),("PAGER","less"),("PATH","/usr/local/heroku/bin:.:/home/local/ANT/shida/.cabal/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/lib/lightdm/lightdm:/usr/local/bin:/usr/bin:/bin"),("PULSE_SERVER","10.69.208.185"),("PWD","/home/local/ANT/shida"),("QT_IM_MODULE","xim"),("SHELL","/usr/bin/zsh"),("SHLVL","1"),("SSH_AGENT_PID","14748"),("SSH_AUTH_SOCK","/tmp/ssh-NeRVrYb14746/agent.14746"),("TERM","rxvt-unicode-256color"),("UBUNTU_MENUPROXY","libappmenu.so"),("USER","shida"),("VISUAL","vim"),("WINDOWID","14683293"),("XAUTHORITY","/home/local/ANT/shida/.Xauthority"),("XDG_CONFIG_DIRS","/etc/xdg/xdg-xmonad:/etc/xdg"),("XDG_DATA_DIRS","/usr/share/xmonad:/usr/local/share/:/usr/share/"),("XDG_SEAT_PATH","/org/freedesktop/DisplayManager/Seat1"),("XDG_SESSION_COOKIE","05ca21f0ee7e6a10e18260ac00001d83-1402975930.974487-843139146"),("XDG_SESSION_PATH","/org/freedesktop/DisplayManager/Session0"),("XMODIFIERS","@im=ibus"),("ZSH","/home/local/ANT/shida/.oh-my-zsh"),("_","/home/local/ANT/shida/.cabal/bin/cabal")] ("/usr/local/bin/ghc",["-c","/tmp/19534.c","-o","/tmp/19534.o"]) ("/usr/bin/ld",["-x","-r","/tmp/19534.o","-o","/tmp/19535.o"]) Searching for lhc in path. Cannot find lhc on the path Searching for lhc-pkg in path. Cannot find lhc-pkg on the path Searching for nhc98 in path. Cannot find nhc98 on the path Searching for pkg-config in path. Found pkg-config at /usr/bin/pkg-config ("/usr/bin/pkg-config",["--version"]) /usr/bin/pkg-config is version 0.26 Searching for strip in path. Found strip at /usr/bin/strip Searching for tar in path. Found tar at /bin/tar Searching for uhc in path. Cannot find uhc on the path Using Cabal-1.21.0.0 compiled by ghc-7.8 Using compiler: ghc-7.8.2 Using install prefix: /home/local/ANT/shida/.cabal Binaries installed in: /home/local/ANT/shida/.cabal/bin Libraries installed in: /home/local/ANT/shida/.cabal/lib/x86_64-linux-ghc-7.8.2/data-default-class-0.0.1 Private binaries installed in: /home/local/ANT/shida/.cabal/libexec Data files installed in: /home/local/ANT/shida/.cabal/share/x86_64-linux-ghc-7.8.2/data-default-class-0.0.1 Documentation installed in: /home/local/ANT/shida/.cabal/share/doc/x86_64-linux-ghc-7.8.2/data-default-class-0.0.1 Configuration files installed in: /home/local/ANT/shida/.cabal/etc No alex found Using ar found on system at: /usr/bin/ar No c2hs found No cpphs found No ffihugs found Using gcc version 4.6 found on system at: /usr/bin/gcc Using ghc version 7.8.2 found on system at: /usr/local/bin/ghc Using ghc-pkg version 7.8.2 found on system at: /usr/local/bin/ghc-pkg No greencard found Using haddock version 2.14.2 found on system at: /usr/local/bin/haddock No happy found Using haskell-suite found on system at: haskell-suite-dummy-location Using haskell-suite-pkg found on system at: haskell-suite-pkg-dummy-location No hmake found Using hpc version 0.67 found on system at: /usr/local/bin/hpc Using hsc2hs version 0.67 found on system at: /usr/local/bin/hsc2hs No hscolour found No hugs found No jhc found Using ld found on system at: /usr/bin/ld No lhc found No lhc-pkg found No nhc98 found Using pkg-config version 0.26 found on system at: /usr/bin/pkg-config Using strip found on system at: /usr/bin/strip Using tar found on system at: /bin/tar No uhc found ("/usr/bin/gcc",["/tmp/19534.c","-o","/tmp/19534","-D__GLASGOW_HASKELL__=708","-Dlinux_BUILD_OS=1","-Dx86_64_BUILD_ARCH=1","-Dlinux_HOST_OS=1","-Dx86_64_HOST_ARCH=1","-Idist/build/autogen","-I.","-I/usr/local/lib/ghc-7.8.2/base-4.7.0.0/include","-I/usr/local/lib/ghc-7.8.2/integer-gmp-0.5.1.0/include","-I/usr/local/lib/ghc-7.8.2/include","-L/usr/local/lib/ghc-7.8.2/base-4.7.0.0","-L/usr/local/lib/ghc-7.8.2/integer-gmp-0.5.1.0","-L/usr/local/lib/ghc-7.8.2/ghc-prim-0.3.1.0","-L/usr/local/lib/ghc-7.8.2/rts-1.0"]) Using internal setup method with build-type Simple and args: ["build","--verbose=3"] Component build order: library creating dist/build creating dist/build/autogen Building data-default-class-0.0.1... Preprocessing library data-default-class-0.0.1... Building library... creating dist/build Environment: [("COLORFGBG","12;default;8"),("COLORTERM","rxvt-xpm"),("DBUS_SESSION_BUS_ADDRESS","unix:abstract=/tmp/dbus-5El0U8sCi8,guid=09290436e309789f9814dffc00000406"),("DEFAULTS_PATH","/usr/share/gconf/xmonad.default.path"),("DESKTOP_SESSION","xmonad"),("DISPLAY"," 10.69.208.185:0"),("EDITOR","vim"),("GDMSESSION","xmonad"),("GPG_AGENT_INFO","/tmp/gpg-KKH3WT/S.gpg-agent:5467:1"),("GREP_COLOR","1;32"),("GREP_OPTIONS","--color=auto --exclude-dir=.cvs --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn"),("GTK_IM_MODULE","xim"),("HOME","/home/local/ANT/shida"),("LANG","C.UTF-8"),("LC_ALL","C.UTF-8"),("LC_CTYPE","C.UTF-8"),("LESS","-R"),("LOGNAME","shida"),("LSCOLORS","Gxfxcxdxbxegedabagacad"),("MANDATORY_PATH","/usr/share/gconf/xmonad.mandatory.path"),("NODE_PATH","/usr/lib/nodejs:/usr/lib/node_modules:/usr/share/javascript"),("OLDPWD","/home/local/ANT/shida/src/git/cabal/cabal-install"),("PAGER","less"),("PATH","/usr/local/heroku/bin:.:/home/local/ANT/shida/.cabal/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/lib/lightdm/lightdm:/usr/local/bin:/usr/bin:/bin"),("PULSE_SERVER","10.69.208.185"),("PWD","/home/local/ANT/shida"),("QT_IM_MODULE","xim"),("SHELL","/usr/bin/zsh"),("SHLVL","1"),("SSH_AGENT_PID","14748"),("SSH_AUTH_SOCK","/tmp/ssh-NeRVrYb14746/agent.14746"),("TERM","rxvt-unicode-256color"),("UBUNTU_MENUPROXY","libappmenu.so"),("USER","shida"),("VISUAL","vim"),("WINDOWID","14683293"),("XAUTHORITY","/home/local/ANT/shida/.Xauthority"),("XDG_CONFIG_DIRS","/etc/xdg/xdg-xmonad:/etc/xdg"),("XDG_DATA_DIRS","/usr/share/xmonad:/usr/local/share/:/usr/share/"),("XDG_SEAT_PATH","/org/freedesktop/DisplayManager/Seat1"),("XDG_SESSION_COOKIE","05ca21f0ee7e6a10e18260ac00001d83-1402975930.974487-843139146"),("XDG_SESSION_PATH","/org/freedesktop/DisplayManager/Session0"),("XMODIFIERS","@im=ibus"),("ZSH","/home/local/ANT/shida/.oh-my-zsh"),("_","/home/local/ANT/shida/.cabal/bin/cabal")] ("/usr/local/bin/ghc",["--make","-v","-fbuilding-cabal-package","-O","-split-objs","-static","-dynamic-too","-dynosuf","dyn_o","-dynhisuf","dyn_hi","-outputdir","dist/build","-odir","dist/build","-hidir","dist/build","-stubdir","dist/build","-i","-idist/build","-i.","-idist/build/autogen","-Idist/build/autogen","-Idist/build","-optP-include","-optPdist/build/autogen/cabal_macros.h","-package-name","data-default-class-0.0.1","-hide-all-packages","-package-db","dist/package.conf.inplace","-package-id","base-4.7.0.0-018311399e3b6350d5be3a16b144df9b","-XHaskell98","Data.Default.Class"]) Glasgow Haskell Compiler, Version 7.8.2, stage 2 booted by GHC version 7.8.1 Using binary package database: /usr/local/lib/ghc-7.8.2/package.conf.d/package.cache Using binary package database: /home/local/ANT/shida/.ghc/x86_64-linux-7.8.2/package.conf.d/package.cache Using package config file: dist/package.conf.inplace wired-in package ghc-prim mapped to ghc-prim-0.3.1.0-948744e1f99cc8bcc7c7d3ba60c7c2d8 wired-in package integer-gmp mapped to integer-gmp-0.5.1.0-dc47f6b546fc171f67a7f7d311684a99 wired-in package base mapped to base-4.7.0.0-018311399e3b6350d5be3a16b144df9b wired-in package rts mapped to builtin_rts wired-in package template-haskell mapped to template-haskell-2.9.0.0-dcc8c210fb02937e104bc1784d7b0f06 wired-in package dph-seq not found. wired-in package dph-par not found. Hsc static flags: wired-in package ghc-prim mapped to ghc-prim-0.3.1.0-948744e1f99cc8bcc7c7d3ba60c7c2d8 wired-in package integer-gmp mapped to integer-gmp-0.5.1.0-dc47f6b546fc171f67a7f7d311684a99 wired-in package base mapped to base-4.7.0.0-018311399e3b6350d5be3a16b144df9b wired-in package rts mapped to builtin_rts wired-in package template-haskell mapped to template-haskell-2.9.0.0-dcc8c210fb02937e104bc1784d7b0f06 wired-in package dph-seq not found. wired-in package dph-par not found. *** Chasing dependencies: Chasing modules from: *Data.Default.Class Stable obj: [] Stable BCO: [] Ready for upsweep [NONREC ModSummary { ms_hs_date = 2014-06-23 03:29:30.794067064 UTC ms_mod = data-default-class-0.0.1:Data.Default.Class, ms_textual_imps = [import (implicit) Prelude] ms_srcimps = [] }] *** Deleting temp files: Deleting: compile: input file ./Data/Default/Class.hs Created temporary directory: /tmp/ghc19596_0 *** Checking old interface for data-default-class-0.0.1:Data.Default.Class: [1 of 1] Compiling Data.Default.Class ( Data/Default/Class.hs, dist/build/Data/Default/Class.o ) *** Parser: *** Renamer/typechecker: *** Desugar: Result size of Desugar (after optimization) = {terms: 0, types: 0, coercions: 0} *** Simplifier: Result size of Simplifier = {terms: 0, types: 0, coercions: 0} *** Specialise: Result size of Specialise = {terms: 0, types: 0, coercions: 0} *** Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}): Result size of Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}) = {terms: 0, types: 0, coercions: 0} *** Float inwards: Result size of Float inwards = {terms: 0, types: 0, coercions: 0} *** Simplifier: Result size of Simplifier = {terms: 0, types: 0, coercions: 0} *** Simplifier: Result size of Simplifier = {terms: 0, types: 0, coercions: 0} *** Simplifier: Result size of Simplifier = {terms: 0, types: 0, coercions: 0} *** Demand analysis: Result size of Demand analysis = {terms: 0, types: 0, coercions: 0} *** Worker Wrapper binds: Result size of Worker Wrapper binds = {terms: 0, types: 0, coercions: 0} *** Simplifier: Result size of Simplifier = {terms: 0, types: 0, coercions: 0} *** Float out(FOS {Lam = Just 0, Consts = True, PAPs = True}): Result size of Float out(FOS {Lam = Just 0, Consts = True, PAPs = True}) = {terms: 0, types: 0, coercions: 0} *** Common sub-expression: Result size of Common sub-expression = {terms: 0, types: 0, coercions: 0} *** Float inwards: Result size of Float inwards = {terms: 0, types: 0, coercions: 0} *** Simplifier: Result size of Simplifier = {terms: 0, types: 0, coercions: 0} *** Tidy Core: Result size of Tidy Core = {terms: 4, types: 7, coercions: 2} writeBinIface: 2 Names writeBinIface: 16 dict entries writeBinIface: 2 Names writeBinIface: 16 dict entries *** CorePrep: Result size of CorePrep = {terms: 4, types: 7, coercions: 2} *** Stg2Stg: *** CodeOutput: *** New CodeGen: *** CPSZ: *** CPSZ: *** Splitter: /usr/local/lib/ghc-7.8.2/ghc-split /tmp/ghc19596_0/ghc19596_2.split_s /tmp/ghc19596_0/ghc19596_4.split /tmp/ghc19596_0/ghc19596_4.split *** Assembler: /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -c -o dist/build/Data/Default/Class_o_split/Class__1.o /tmp/ghc19596_0/ghc19596_4.split__1.s *** Assembler: /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -c -o dist/build/Data/Default/Class_o_split/Class__2.o /tmp/ghc19596_0/ghc19596_4.split__2.s *** Linker: /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -nostdlib -Wl,-r -nodefaultlibs '-Wl,--build-id=none' -o dist/build/Data/Default/Class.o /tmp/ghc19596_0/ghc19596_5.ldscript /usr/bin/ld: error: cannot find dist/build/Data/Default/Class_o_split/Class__1.o /usr/bin/ld: error: cannot find dist/build/Data/Default/Class_o_split/.o::Class(void) collect2: ld returned 1 exit status *** Deleting temp files: Deleting: /tmp/ghc19596_0/ghc19596_5.ldscript /tmp/ghc19596_0/ghc19596_4.split__1.s /tmp/ghc19596_0/ghc19596_4.split__2.s /tmp/ghc19596_0/ghc19596_4.split /tmp/ghc19596_0/ghc19596_3.c /tmp/ghc19596_0/ghc19596_2.split_s /tmp/ghc19596_0/ghc19596_1.split_s Warning: deleting non-existent /tmp/ghc19596_0/ghc19596_3.c Warning: deleting non-existent /tmp/ghc19596_0/ghc19596_1.split_s *** Deleting temp dirs: Deleting: /tmp/ghc19596_0 /usr/local/bin/ghc returned ExitFailure 1 Failed to install data-default-class-0.0.1 Updating world file... cabal: Error: some packages failed to install: data-default-class-0.0.1 failed during the building phase. The exception was: ExitFailure 1 -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

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Problems with Parallel N Queens using Control.Parallel.Strategy
by bruce li 22 Jun '14

22 Jun '14

Hello, Cafe, I'm currently reading Parallel and Concurrent Programming in Haskell. I tried to implement an n-queens problem as an exercise, but a little bit overwhelmed by the strategy mystery. The code is listed at http://pastebin.com/ySgc3VSR. I implemented the higher order skeleton of search and try to add parallelism. My original idea was spawning a few threads while the search tree was small and each thread handles the following expansion of the tree. Hence, I gave a "maxDepth" variable to restrict the parallelism. But this did not go very well if I set the maxDepth to very small value, say, 2, 3, 4 etc. The speed up was very small. Viewing in threadscope, it seems there was very small amount of parallelism. Then I tried to let it go, which means I set the tree depth to a value larger than the maximum possible depth, say 20. Then it speeds up about 1.4 times on 2-cores. Viewing in threadscope, it seems the 2 cores are fully utilized. But the report is a bit annoying: SPARKS: 4686728 (100456 converted, 3461 overflowed, 0 dud, 4540817 GC'd, 41994 fizzled) with no restrictions on the parallelism, a lot of sparks are not converted and are GC'd. I wonder if there is some way to further improve the results, reducing un-convereted sparks and achieving better speed-up ratio. Thanks.

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