June 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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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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Handling overflow and division by zero
by Nikita Karetnikov 27 Jul '15

27 Jul '15

Haskell is often marketed as a safe (or safer) language, but there's an issue that makes it less safe as it could be. I'm talking about arithmetic overflows and division by zero. The safeint package tries to address this, but it only supports the Int type because (as I understand it) there are no useful primitives for other common types defined in Data.Int and Data.Word. I've tried adding Int64 support to safeint just to see how it would work without primops. Here's a snippet (I haven't tested this code well, so it may be wrong, sorry about that): shiftRUnsigned :: Word64 -> Int -> Word64 shiftRUnsigned = shiftR -- http://git.haskell.org/ghc.git/blob/HEAD:/compiler/codeGen/StgCmmPrim.hs#l9… plusSI64 :: SafeInt64 -> SafeInt64 -> SafeInt64 plusSI64 (SI64 a) (SI64 b) = if c == 0 then SI64 r else overflowError where r = a + b c = (fromIntegral $ (complement (a `xor` b)) .&. (a `xor` r)) `shiftRUnsigned` ((finiteBitSize a) - 1) -- http://git.haskell.org/ghc.git/blob/HEAD:/compiler/codeGen/StgCmmPrim.hs#l9… minusSI64 :: SafeInt64 -> SafeInt64 -> SafeInt64 minusSI64 (SI64 a) (SI64 b) = if c == 0 then SI64 r else overflowError where r = a - b c = (fromIntegral $ (a `xor` b) .&. (a `xor` r)) `shiftRUnsigned` ((finiteBitSize a) - 1) -- https://stackoverflow.com/a/1815371 timesSI64 :: SafeInt64 -> SafeInt64 -> SafeInt64 timesSI64 (SI64 a) (SI64 b) = let x = a * b in if a /= 0 && x `div` a /= b then overflowError else SI64 x I may be wrong, but my understanding is that new primops could reduce overhead here. If so, would a patch adding them be accepted? Are there any caveats? In the safeint package, would it be reasonable to return an Either value instead of throwing an exception? Or would it be too much? I haven't created a wiki page or ticket because I don't know much, so I want to get some feedback before doing so. That would be my first patch to GHC (if ever), so maybe I'm not the best candidate, but I've been thinking about it for too long to ignore. :\

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Backporting srcLoc to the GHC 7.10 branch
by Michael Snoyman 15 Jul '15

15 Jul '15

It looks like the srcLoc change[1] is something that some of our (FP Complete's) customers would be quite interested in getting access to sooner rather than later. Would there be any possibility of getting that patch merged into the 7.10 branch of GHC? I'm not sure if I'd try my luck at actually including it in 7.10.1, but would it be on the table for 7.10.2? We do of course have the option of backporting it ourselves and including it in a custom GHC we provide customers, but we generally try to stay as close to upstream as possible. [1] https://ghc.haskell.org/trac/ghc/ticket/9049

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Right way to turn off dynamic linking in build.mk
by Johan Tibell 07 Jul '15

07 Jul '15

Some times when I play around with GHC I'd like to turn off dynamic linking to make GHC compile faster. I'm not sure what the right way to do this in build.mk. It's made confusing by the conditional statements in that file: GhcLibWays = $(if $(filter $(DYNAMIC_GHC_PROGRAMS),YES),v dyn,v) This line make me worry that if I don't put DYNAMIC_GHC_PROGRAMS = NO in the right place in build.mk it wont "take". There's also this one: ifeq "$(PlatformSupportsSharedLibs)" "YES" GhcLibWays += dyn endif Seeing this makes me wonder if DYNAMIC_GHC_PROGRAMS = NO DYNAMIC_BY_DEFAULT = NO is enough or if the build system still sniffs out the fact that my platform supports dynamic linking. Could someone please give an authoritative answer to how to turn off dynamic linking? -- Johan

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Abstract FilePath Proposal
by Herbert Valerio Riedel 05 Jul '15

05 Jul '15

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello *, What? ===== We (see From: & CC: headers) propose, plain and simple, to turn the currently defined type-synonym type FilePath = String into an abstract/opaque data type instead. Why/How/When? ============= For details (including motivation and a suggested transition scheme) please consult https://ghc.haskell.org/trac/ghc/wiki/Proposal/AbstractFilePath Suggested discussion period: 4 weeks -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJVjXkZAAoJELo8uj/+IrV0WXUP/0romoKazwLbQpaMAKgCNZon BsY8Di44w6rkbdBXoky0xZooII8LJJyQfexH0BLRYEVLZFy0+LB8XzpPt8Ekg526 YlY4x0qFm9oiJbJDMqHUnb6z6Lr2KxzBcV37drTPbltUA+HB49DUVkkPbvHimpL2 28SIyhAr4fN6fLpGcFAkv6Rcs0mkvnTp7vsC0HNyshmGi6qQ+C+eB4mklQzWOPcn koHZ2wtI8AJmyTdHKcXKAIFM0r+xl4MJ5445IvDjvIuGXZCzybXMw9Ss/4wSG3VN qSIJVEDGZXrBCc12fPxPEB0Bqx9MIVytjplXKIo8rFrk93h3at9t9kDM26z+9PZ5 KYnEdjRKF4KL4j+3xqJDOEJT15GVRbGRRzb9A8xH0YIQ0S3Q3pt1PAfla1Hss75+ NRQgfowZYryL9dfCkAj2XNfdQ+pUk25N3bNig11se+zjk2JO77QRM0u3GOYZ9+CU tSlwhtIMF32xnjgQyWE5yBBiEg3/Y+S+809tVaPseUEzkQJXMGq5TFxBrN6bj1Vm awr6QghThKjeoRwky5bmFn/gept/lbYN6VV5B6gNznGP5xgFrmvVtmjbQJBRMYCv aEUnrYqxkkbIddJjD5gl771/LWH4M2F1yBgJjfiZw2paEVAXKxEr327LsbOQaPdb HjIPRrJbVK9AABo4AZ/Y =lg0o -----END PGP SIGNATURE-----

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ANNOUNCE: GHC 7.10.2 Release Candidate 1
by Austin Seipp 04 Jul '15

04 Jul '15

We are pleased to announce the first release candidate for GHC 7.10.2: https://downloads.haskell.org/~ghc/7.10.2-rc1 https://downloads.haskell.org/~ghc/7.10.2-rc1/docs/html/ This includes the source tarball and bindists for Windows, Mac OS X, and Debian Linux. FreeBSD and Solaris binaries will follow soon. These binaries and tarballs have an accompanying SHA256SUMS file signed by my GPG key id (0x3B58D86F). We plan to make the 7.10.2 final release at the end of this coming week - so please test as much as possible; bugs are much cheaper if we find them before the release! -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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