July 2015 - ghc-devs - Haskell.org

RE: vectorisation code?
by Simon Peyton Jones 12 Sep '16

12 Sep '16

Austin, (or anyone else) Manuel says: | > Would it be ok if we left it in the repo, but CPP'd it out so that | we | > didn't compile everything? (The DPH library is in the same state at | > the moment.) | > | > It might suffer bit-rot, but it’d still be there for resurrection. | | Sure, that’s ok. Could you action this? Just avoid compiling anything in 'vectorise/', using (I suppose) cpp to create a stub where necessary. Leave enough comments to explain! Simon | | I hope everything is fine in Cambridge! | Manuel | | > | -----Original Message----- | > | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of | > | Manuel M T Chakravarty | > | Sent: 16 January 2015 02:58 | > | To: Richard Eisenberg | > | Cc: ghc-devs(a)haskell.org Devs | > | Subject: Re: vectorisation code? | > | | > | [Sorry, sent from the wrong account at first.] | > | | > | We currently don’t have the resources to work on DPH. I would | > | obviously prefer to leave the code in, in the hope that we will be | > | able to return to it. | > | | > | Manuel | > | | > | > Richard Eisenberg <eir(a)cis.upenn.edu>: | > | > | > | > Hi devs, | > | > | > | > There's a sizable number of modules in the `vectorise` | > | subdirectory of GHC. I'm sure these do all sorts of wonderful | > | things. But what, exactly? And, does anyone make use of these | wonderful things? | > | > | > | > A quick poking through the code shows a tiny link between the | > | vectorise code and the rest of GHC -- the function `vectorise` | > | exported from the module `Vectorise`, which is named in exactly | one | > | place from SimplCore. From what I can tell, the function will be | > | called only when `-fvectorise` is specified, and then it seems to | > | interact with a {-# VECTORISE #-} pragma. However, `{-# VECTORISE | > | #-}` doesn't appear in the manual at all, and `-fvectorise` is | > | given only a cursory explanation. It seems these work with DPH... | > | which has been disabled, no? Searching online finds several hits, | > | but nothing more recent than 2012. | > | > | > | > I hope this question doesn't offend -- it seems that | > | vectorisation probably has amazing performance gains. Yet, the | > | feature also seems unloved. In the meantime, compiling (and | > | recompiling, and | > | recompiling...) the modules takes time, as does going through | them | > | to propagate changes from elsewhere. If this feature is truly | > | orphaned, unloved, and unused at the moment, is it reasonable to | > | consider putting it on furlough? | > | > | > | > Thanks, | > | > Richard | > | > _______________________________________________ | > | > ghc-devs mailing list | > | > ghc-devs(a)haskell.org | > | > http://www.haskell.org/mailman/listinfo/ghc-devs | > | | > | _______________________________________________ | > | ghc-devs mailing list | > | ghc-devs(a)haskell.org | > | http://www.haskell.org/mailman/listinfo/ghc-devs

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arc land changes author
by Joachim Breitner 19 Dec '15

19 Dec '15

Hi, I was just about to apply a DR by David. First I ran $ arc patch D390 which put me on a feature branch. Then I reworded the commit with $ git commit --amend and then I tried to land it with $ arc land Luckily I also passed --hold... It even asked me if I want to land the commit although I am not the author: This branch has revision 'D390: Reorder GHC.List; fix performance regressions' but you are not the author. Land this revision by dfeuer? [y/N] y But it still put me in the author field: $ git show HEAD commit a387c359b99667ce55016de3816b5d9873a155db Author: Joachim Breitner <mail(a)joachim-breitner.de> Date: Wed Oct 29 08:17:05 2014 +0100 Reorder GHC.List; fix performance regressions Summary: Rearrange some oddly placed code. (and undid my commit message changes....) Did I do something wrong? Anyways, it said something along the lines of Cleaning up feature branch... (Use `git checkout -b 'arcpatch-D390' 'a3ceb0e7f44d53f728fb8bd0dfb4c97297818029'` if you want it back.) so with $ git commit --amend -C a3ceb0e7f44d53f728fb8bd0dfb4c97297818029 I was able to get the edited commit message with the right author back. Greetings, Joachim -- Joachim “nomeata” Breitner mail(a)joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata(a)joachim-breitner.de • GPG-Key: 0xF0FBF51F Debian Developer: nomeata(a)debian.org

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A GHC Library
by Richard Eisenberg 08 Dec '15

08 Dec '15

Hi devs, It has struck me that we have a vast trove of documentation about GHC in the form of academic papers, but little organization to this trove. The papers are scattered across authors' websites, and sometimes it is hard to remember what a paper is titled when searching for it. I have thus started a wiki page here: https://ghc.haskell.org/trac/ghc/wiki/Library I would love for this page to be the Definitive List of GHC-related papers. The list I've included is, of course, woefully short, but it is a starting point. Please add to it! Have you written a GHC paper? If so, make sure it's included. Thanks, Richard

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utils/hp2ps/Main.c:88: possible missing break ?
by David Binderman 15 Sep '15

15 Sep '15

Hello there, [utils/hp2ps/Main.c:88] -> [utils/hp2ps/Main.c:91]: (warning) Variable 'iflag' is reassigned a value before the old one has been used. 'break;' missing? Source code is switch( *(*argv + 1) ) { case '-': iflag = -1; case '+': default: iflag = 1; } Suggest add missing break. Regards David Binderman

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the platform has outgrown Travis-CI
by Mark Lentczner 09 Sep '15

09 Sep '15

I finally figured out what was wrong with the Travis CI build for Haskell Platform, and got it all working w/hvr's .debs of GHC (for the boot compiler)... and ran smack into this: Your test run exceeded 50 minutes. SO... I'd like to find another CI solution. Is phabricator.haskell.org an option? Can we / should we create a project there? - Mark

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Cabal and simultaneous installations of the same package
by Simon Peyton Jones 29 Aug '15

29 Aug '15

Dear Cabal developers You'll probably have seen the thread about the Haskell Platform. Among other things, this point arose: | Another thing we should fix is the (now false) impression that HP gets in | the way of installing other packages and versions due to cabal hell. People mean different things by "cabal hell", but the inability to simultaneously install multiple versions of the same package, compiled against different dependencies is certainly one of them, and I think it is the one that Yitzchak is referring to here. But some time now GHC has allowed multiple versions of the same package (compiled against different dependencies) to be installed simultaneously. So all we need to do is to fix Cabal to allow it too, and thereby kill of a huge class of cabal-hell problems at one blow. But time has passed and it hasn't happened. Is this because I'm misunderstanding? Or because it is harder than I think? Or because there are much bigger problems? Or because there is insufficient effort available? Or what? Unless I'm way off beam, this "multiple installations of the same package" thing has been a huge pain forever, and the solution is within our grasp. What's stopping us grasping it? Simon

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Deleting sync-all
by Thomas Miedema 20 Aug '15

20 Aug '15

Hello ghc-devs, I would like to delete the file sync-all <https://ghc.haskell.org/trac/ghc/wiki/Building/SyncAll> from the GHC repository. It should not have been necessary to use it for about a year now. To get the sources <https://ghc.haskell.org/trac/ghc/wiki/Building/GettingTheSources>: git clone --recursive git://git.haskell.org/ghc.git cd ghc git clone git://git.haskell.org/ghc-tarballs.git # Windows only To update an existing tree <https://ghc.haskell.org/trac/ghc/wiki/WorkingConventions/Git/Submodules#Upd…>: git pull --rebase git submodule update --init To update an existing tree <https://ghc.haskell.org/trac/ghc/wiki/WorkingConventions/Git/Submodules#git…>, without the possibility to forget to run `git submodule update --init`: git config --global alias.pullall '!f(){ git pull --ff-only "$@" && git submodule update --init --recursive; }; f' # Run once git pullall --rebase Please speak up if you want those 1000 lines of buggy Perl a.k.a. sync-all to stay for some reason, or if you have questions about a certain git submodules workflow. The source code (./boot no longer suggests it) and the wiki are already sync-all free, except for a few historical pages. Discussion period: 1 month. Thomas

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Typechecker / OverloadedStrings question 7.8 vs. 7.10
by Michael Karg 03 Aug '15

03 Aug '15

Hi devs, in the followin snippet: {-# LANGUAGE OverloadedStrings #-} import Data.Char (isAlphaNum) import Data.ByteString.Char8 as BS (all) main = print $ check str where check = BS.all (\x -> x `elem` valid || isAlphaNum x) -- Line 7 valid = "$_-" -- :: String -- Line 8 str = "foo_bar123" GHC 7.10 fails with the following errors (whereas 7.8 compiles without complaining): ghc --make "Testcase.hs" [1 of 1] Compiling Main ( Testcase.hs, Testcase.o ) Testcase.hs:7:31: No instance for (Foldable t0) arising from a use of ‘elem’ The type variable ‘t0’ is ambiguous (...) Testcase.hs:8:15: No instance for (Data.String.IsString (t0 Char)) arising from the literal ‘"$_-"’ The type variable ‘t0’ is ambiguous (...) Uncommenting the -- :: String type annotation (line 8) makes the snippet acceptable to the typechecker however. So Foldable [] and [Char] should be possible to infer, given the evidence of 'isAlphaNum x', as obviously happens with GHC 7.8. My question is, how or why does the 7.10 typechecker behave differently? Is this intentional, or does this qualify for a trac ticket? Thanks for looking into this, Michael PS: The ByteString part is just there since the snippet is taken out of one of my projects. The following (modified) code only typechecks on 7.10 with both type annotations uncommented: {-# LANGUAGE OverloadedStrings #-} import Data.Char (isAlphaNum) main = print $ check str where check = all (\x -> x `elem` valid || isAlphaNum x) valid = "$_-" -- :: String str = "foo_bar123" -- :: String The errors here are (1) no instances for Foldable and (2) no instances for IsString.

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Building GHC master with GHC 7.6
by Ben Gamari 02 Aug '15

02 Aug '15

Hello everyone, Earlier today I merged a clean-up [1] to the master branch which removed some #ifdefs which ensured that the tree could be built with GHC 7.6 Thomas Miedema correctly pointed out that some nightly builders may not be on GHC 7.8 yet. Do any of the nightly builders call in this category? If so, would it be possible to upgrade? Cheers, - Ben [1] https://phabricator.haskell.org/D904

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Fundep question
by Gabor Greif 31 Jul '15

31 Jul '15

Hi all, say I want to instantiate class Dep (a :: k) b | a -> b as instance Dep x y => Dep (Just x) (Maybe y) Is this supposed to work? I get "The coverage condition fails" errors. For simple cases like instance Dep True Bool etc. it seems to work fine. Thanks and cheers, Gabor

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