January 2013 - Glasgow-haskell-users

ANNOUNCE: GHC 7.6.2 Release Candidate 1
by Ian Lynagh 20 Mar '13

20 Mar '13

We are pleased to announce the first release candidate for GHC 7.6.2: http://www.haskell.org/ghc/dist/7.6.2-rc1/ This includes the source tarball, installers for Windows, and bindists for Windows, Linux, OS X and FreeBSD, on x86 and x86_64. We plan to make the 7.6.2 release early in 2013. Please test as much as possible; bugs are much cheaper if we find them before the release! Thanks Ian, on behalf of the GHC team

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Validate of GHC HEAD freezes on FreeBSD
by Kazu Yamamoto 04 Feb '13

04 Feb '13

Hello, The "validate" script against GHC HEAD freezes on FreeBSD 9.1. After sync-all, I did as follow: ---------------------------------------------------------------- % config_args="--with-iconv-includes=/usr/local/include --with-iconv-libraries=/usr/local/lib --with-gmp-includes=/usr/local/include --with-gmp-libraries=/usr/local/lib --with-gcc=/usr/local/bin/gcc47" CPUS=10 sh validate ---------------------------------------------------------------- This stopped quickly due to this problem: http://hackage.haskell.org/trac/ghc/ticket/7592 Then I executed "validate" with "--no-clean" again. ---------------------------------------------------------------- % config_args="--with-iconv-includes=/usr/local/include --with-iconv-libraries=/usr/local/lib --with-gmp-includes=/usr/local/include --with-gmp-libraries=/usr/local/lib --with-gcc=/usr/local/bin/gcc47" CPUS=10 sh validate --no-clean ---------------------------------------------------------------- GHC could be compiled and tests started. But this resulted in: ---------------------------------------------------------------- cd ../../libraries/base/tests && '/usr/home/kazu/work/ghc/bindisttest/install dir/bin/ghc' -fforce-recomp -dcore-lint -dcmm-lint -dno-debug-output -no-user-package-db -rtsopts -fno-ghci-history -o qsemn001 qsemn001.hs >qsemn001.comp.stderr 2>&1 cd ../../libraries/base/tests && ./T5962 </dev/null >T5962.run.stdout 2>T5962.run.stderr cd ../../libraries/base/tests && ./5943 </dev/null >5943.run.stdout 2>5943.run.stderr cd ../../libraries/base/tests && ./T7034 </dev/null >T7034.run.stdout 2>T7034.run.stderr cd ../../libraries/base/tests && ./qsem001 </dev/null >qsem001.run.stdout 2>qsem001.run.stderr cd ../../libraries/base/tests && ./qsemn001 </dev/null >qsemn001.run.stdout 2>qsemn001.run.stderr Wrong exit code (expected 0 , actual 9 ) Stdout: Stderr: *** unexpected failure for Chan002(normal) ---------------------------------------------------------------- And waiting for something forever. Does anyone understand what happened? Note that I can build GHC HEAD by typing "gmake" (v3.82 installed by the ports system) twice. This is a serious problem for us since we want to merge our code to GHC HEAD. "validate" against GHC with our code on Linux and Mac passed so far. But "validate" against even vanilla GHC freezes. P.S. On FreeBSD, I applied the following patch for validate since unused-but-set-variable is not available. diff --git a/mk/validate-settings.mk b/mk/validate-settings.mk index 399bf0e..378a3e6 100644 --- a/mk/validate-settings.mk +++ b/mk/validate-settings.mk @@ -13,7 +13,7 @@ HADDOCK_DOCS = YES # Debian doesn't turn -Werror=unused-but-set-variable on by default, so # we turn it on explicitly for consistency with other users ifeq "$(GccLT46)" "NO" -SRC_CC_WARNING_OPTS += -Werror=unused-but-set-variable +#SRC_CC_WARNING_OPTS += -Werror=unused-but-set-variable # gcc 4.6 gives 3 warning for giveCapabilityToTask not being inlined SRC_CC_WARNING_OPTS += -Wno-error=inline endif --Kazu

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GHC compilation error (re-post).
by Caitlin 02 Feb '13

02 Feb '13

Hi all. I wrote the following test program: bar x = x * x on a Win32 (SP3) machine using the Haskell Platform and GHC-7.6.1 (standalone) and I have noticed the same frustrating errors. Any suggestions would be most appreciated. Thanks, ~Caitlin C:\>ghci GHCi, version 7.4.2: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Prelude> Prelude> :l bar [1 of 1] Compiling Main ( bar.hs, interpreted ) *** Exception: CreateDirectory ".": permission denied (Access is denied.) > > :l bar.hs [1 of 1] Compiling Main ( bar.hs, interpreted ) *** Exception: CreateDirectory ".": permission denied (Access is denied.) > > :l "C:\\bar.hs" [1 of 1] Compiling Main ( C:\bar.hs, interpreted ) *** Exception: CreateDirectory "C:\\": permission denied (Access is denied.) > >

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ANNOUNCE: GHC version 7.6.2
by Ian Lynagh 02 Feb '13

02 Feb '13

============================================================= The (Interactive) Glasgow Haskell Compiler -- version 7.6.2 ============================================================= The GHC Team is pleased to announce a new patchlevel release of GHC, 7.6.2. This release fixes a number of bugs relative to 7.6.1, so we recommend upgrading. Full release notes are here: http://www.haskell.org/ghc/docs/7.6.2/html/users_guide/release-7-6-2.html How to get it ~~~~~~~~~~~~~ The easy way is to go to the web page, which should be self-explanatory: http://www.haskell.org/ghc/ We supply binary builds in the native package format for many platforms, and the source distribution is available from the same place. Packages will appear as they are built - if the package for your system isn't available yet, please try again later. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below). On-line GHC-related resources ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Relevant URLs on the World-Wide Web: GHC home page http://www.haskell.org/ghc/ GHC developers' home page http://hackage.haskell.org/trac/ghc/ Haskell home page http://www.haskell.org/ Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms we support, and the people responsible for them, is here: http://hackage.haskell.org/trac/ghc/wiki/Contributors Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: http://hackage.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ We welcome new contributors. Instructions on accessing our source code repository, and getting started with hacking on GHC, are available from the GHC's developer's site run by Trac: http://hackage.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at http://www.haskell.org/mailman/listinfo/glasgow-haskell-users http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see http://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: http://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: http://www.haskell.org/ghc/reportabug

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Proposal to extend FieldPat in Template Haskell
by Iavor Diatchki 30 Jan '13

30 Jan '13

Hello, (sorry for the repost, I forgot to add a subject.) I was just doing some work with Template Haskell and I noticed that the AST does not have support for record puns and wild-cards. I know that these could be desugared into ordinary record patterns but I think that it would be more convenient for users (and also more consistent with the rest of the AST) if we provided direct support for them. So I propose to change: type FieldPat = (Name, Pat) to data FieldPat = RecordFileldP Name Pat -- x = P | RecordPunP Name -- x | RecordWildP -- .. Would there be any objections to doing so? If not, I'd be happy to have a go at making the change. -Iavor

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(no subject)
by Iavor Diatchki 29 Jan '13

29 Jan '13

Hello, I was just doing some work with Template Haskell and I noticed that the AST does not have support for record puns and wild-cards. I know that these could be desugared into ordinary record patterns but I think that it would be more convenient for users (and also more consistent with the rest of the AST) if we provided direct support for them. So I propose to change: type FieldPat = (Name, Pat) to data FieldPat = RecordFileldP Name Pat -- x = P | RecordPunP Name -- x | RecordWildP -- .. Would there be any objections to doing so? If not, I'd be happy to have a go at making the change. -Iavor

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Extended periods of "waking up thread %d on cap %d"
by Ben Gamari 29 Jan '13

29 Jan '13

Recently I've been benchmarking my concurrent Gibbs sampler[1] on a largish multicore machine. I've been using GHC HEAD due to various GC-related fixes that are present. One thing that I've noticed in looking over the event logs is that there are large durations (tens of milliseconds) when HECs appear to be constantly bombarded with wake-ups from other capabilities. In these periods, the eventlog will be filled with blocks of messages such as this snippet from one benchmark run[2] (long repeated blocks marked with ellipses, a few irrelevant messages have been omitted yet not marked, see eventlog for full log), 28.320958s HEC 7: running thread 293 ... 28.391802s HEC 6: running thread 209 28.392070s HEC 6: waking up thread 284 on cap 7 28.392302s HEC 6: waking up thread 284 on cap 7 28.392579s HEC 6: waking up thread 284 on cap 7 28.392808s HEC 6: waking up thread 284 on cap 7 . . . 28.405971s HEC 16: waking up thread 284 on cap 7 28.406026s HEC 15: waking up thread 284 on cap 7 28.406080s HEC 12: waking up thread 284 on cap 7 28.406091s HEC 23: waking up thread 284 on cap 7 28.406095s HEC 6: waking up thread 284 on cap 7 28.406095s HEC 23: waking up thread 284 on cap 7 28.406225s HEC 16: waking up thread 284 on cap 7 . . . 28.490449s HEC 7: stopping thread 293 (thread yielding) 28.490454s HEC 7: waking up thread 284 on cap 7 28.490454s HEC 7: waking up thread 284 on cap 7 28.490455s HEC 7: waking up thread 284 on cap 7 28.490456s HEC 7: waking up thread 284 on cap 7 28.490456s HEC 7: waking up thread 284 on cap 7 28.490457s HEC 7: waking up thread 284 on cap 7 28.490458s HEC 7: waking up thread 284 on cap 7 . . . 28.491841s HEC 7: waking up thread 284 on cap 7 28.491850s HEC 7: migrating thread 284 to cap 0 28.491968s HEC 7: running thread 293 . . . In other words, it appears that HEC 7 took a vacation of more than a millisecond as it tried (ultimately unsuccessfully) to wake up thread 284. These blocks are easy to spot in this event log and quite difficult to explain. In this case I was being silly and spawned a few too many capabilities (30 capabilities whereas the machine has 24 real cores, 2 threads per core due to hyperthreading; I was running 24 threads). That being said, even under more reasonable conditions[3] (where I was running 24 capabilities with 20 threads on the same 24-core machine) I still see problems waking up. For example, from 32.293455s to 32.327349s see numerous attempts by many HECs to wake-up thread 517 on cap 12. In this period, cap 12 briefly runs thread 537 (32.326781s) but while running HEC 17 attempts to wake up 517 again. All-in-all, something seems a bit strange. Any ideas what might be going on here? I've CC'd Edward Yang (who I understand has recently been doing a rework on the scheduler) and Simon Marlow. Thanks, - Ben [1] https://github.com/bgamari/bayes-stack [2] http://goldnerlab.physics.umass.edu/~bgamari/Benchmark-wakeup.eventlog [3] http://goldnerlab.physics.umass.edu/~bgamari/Benchmark-wakeup-smaller.event…

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How to get started with a new backend?
by Jason Dagit 29 Jan '13

29 Jan '13

I would like to explore making a backend for .NET. I've done a lot of background reading about previous .NET and JVM attempts for Haskell. It seems like several folks have made significant progress in the past and, with the exception of UHC, I can't find any code around the internet from the previous efforts. I realize that in total it's a huge undertaking and codegen is only one of several significant hurdles to success. I would like to get a very, very, very simple translation working inside GHC. If all I can compile and run is fibonacci, then I would be quite happy. For my first attempt, proof of concept is sufficient. I found a lot of good documentation on the ghc trac for how the compilation phases work and what happens in the different parts of the backend. The documentation is excellent, especially compared to other compilers I've looked at. When I started looking at how to write the code, I started to wonder about the "least effort" path to getting something (anything?) working. Here are some questions: * Haskell.NET seems to be dead. Does anyone know where their code went? * Did lambdavm also disappear? (JVM I know, but close enough to be useful) * Would it make sense to copy&modify the -fvia-C backend to generate C#? The trac claims that ghc can compile itself to C so that only standard gnu C tools are needed to build an unregistered compiler. Could I use this trick to translate programs to C#? * What stage in the pipeline should I translate from? Core? STG? Cmm? * Which directories/source files should I look at to get familiar with the code gen? I've heard the LLVM codegen is relatively simple. * Any other advice? Thank you in advance! Jason

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Fastest way to reload module with GHC API
by JP Moresmau 28 Jan '13

28 Jan '13

Hello, I just want to be sure of what's the fastest way to reload a module with the GHC API. I have a file whose path is fp I load the module with: addTarget Target { targetId = TargetFile fp Nothing, targetAllowObjCode = True, targetContents = Nothing } Then I load the module load LoadAllTargets And when I want to reload the module (the contents of fp have changed) I do: removeTarget (TargetFile fp Nothing) load LoadAllTargets and then I rerun my initial code (addTarget, load) This works well, I don't get any errors about duplicates, the information I extract from the module is updated properly. But is it the most efficient, or can I achieve the same thing faster (I'm looking at improving the performance of my BuildWrapper code and by consequence of EclipseFP)? Thanks! -- JP Moresmau http://jpmoresmau.blogspot.com/

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Size of crosscompiled exectuable
by Nathan Hüsken 28 Jan '13

28 Jan '13

Hey, A simple hello world application has 1Mb in by 64 bit ubunut machine. When I stript it, is has about 750kb. When I build a cross compiler for android (arm), the executable has a asize of about 10MB, stripped about 5MB. That is huge, five times the size on my linux sysem. Why is this? Can I do something about it? Thanks! Nathan

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