- Glasgow-haskell-users

Re: -O in 6.8.1-candidate
by Serge D. Mechveliani 20 Oct '07

20 Oct '07

On Sat, Oct 20, 2007 at 03:25:04PM +0100, Duncan Coutts wrote: > On Fri, 2007-10-19 at 10:54 -0300, Isaac Dupree wrote: > > > How can user who does not modify Cabal file choose between all three of > > -O0, -O and -O2? > > They cannot. Cabal currently only support a binary notion of > optimisations. So it's either -O0 or -O. > As I understand, the Cabal developers claim that a user of an applied package p does not need to change anything in the file p.cabal. But there is a contradition here. For example, a user may need to build p via p.cabal under GHC and once under -Onot and next time under -O2. Suppose also that once the user needs to build p under -prof -auto-all and next time -- under -prof only. How can one do all this without intruding into p.cabal ? Personally, I would like better if the default for Cabal does not set any GHC options, and a user to be invited to edit the field `ghc-options:' in the .cabal file. This way, it looks simpler and less confusive. Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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GHC benchmarks
by Ketil Malde 19 Oct '07

19 Oct '07

Hi, I've recently implemented some benchmarks for my library, and while I expected a slowdown for 64-bit code, I'm a bit bit surprised by the results. In summary: with 64 bit ghc 6.6.1, my benchmark runs in ~160 seconds with 32 bit ghc 6.6, it runs in ~ 95 seconds Most of the time is traversing a list of elements, doing a few numerical calculations. Presumably this is due to increased code size due to 8-byte pointers? I'll add some more benchmarks, but just wondered whether this was to be expeced, and, if so, whether I perhaps should be running a 32 bit version of GHC? I tried to Google for other benchmark results, but couldn't find any. Are there any particular GHC options I should use for compiling 64-bit code? I'll install 6.8 RSN, perhaps that will improve things? Oh, and if anybody wants to play with it, it should be possible to install Data.Binary and HXT, and then: darcs get http://malde.org/~ketil/bio cd bio make bench -k -- If I haven't seen further, it is by standing in the footprints of giants

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ghc --make-parallel ?
by Johannes Waldmann 18 Oct '07

18 Oct '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Can ghc execute compilations in parallel? (With GNU make, I'd say "make -j 2" but how to achieve this with "ghc --make" ?) Thanks - J. Waldmann. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4-svn0 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFHF0FB3ZnXZuOVyMIRAv0LAKCu8Ub2Cbb9xGNlfVNhLAKdwe/vXQCfUG0l RokmawVrEibckG7QknybMkg= =eQQY -----END PGP SIGNATURE-----

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Command Line Arguments
by Paulo J. Matos 18 Oct '07

18 Oct '07

As an Haskell beginner, and considering this may be compiler dependent, I shall ask it on this list. How can I access command line arguments from my main function in my Main module? Cheers, -- Paulo Jorge Matos - pocm at soton.ac.uk http://www.personal.soton.ac.uk/pocm PhD Student @ ECS University of Southampton, UK

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Prevent optimization from tempering with unsafePerformIO
by Bernd Brassel 18 Oct '07

18 Oct '07

Hello to all who have given me hints an suggestions about this topic whether directly by mail or over the mailing list. I do now have a much more concrete idea of how to optimize my programs. Thanks for your time! Bernd

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6.8.1-candidate tested
by Serge D. Mechveliani 18 Oct '07

18 Oct '07

Dear GHC developers, I have tested ghc-6.8.0.20071015-src.tar.bz2 on DoCon and on Dumatel. It looks all right (except the bug-candidate for -O which is common to all GHC versions and which I recently reported ). On DoCon, ghc-6.8.0.20071015 1) builds the project 2-3 times faster than ghc-6.6.1, 2) its produced .a code is 1.6 times larger, 3) the test runs 1.4 times faster, 4) the minimal space (2500 Kb) for the test running remains. This looks all right. Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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-O bug?
by Serge D. Mechveliani 18 Oct '07

18 Oct '07

Dear GHC developers, The point (1) below looks like a bug (in all GHC versions!). (1) -O for demo-test. Take (the public) docon-2.10 build it under -O, install, and build also under -O its test program by cd demotest ghc $doconCpOpt -O --make Main Either the latter compilation will loop forever or it will take an unnaturally large resource. Yes, the functions T_.test, T_tt are defined in rather a particular way (see them). I always build this test under -Onot, because compiling with optimization has not much sense for this part. But slill. (2) -O2 In my DoCon programs, -O2 was always worse than -O: the code is about 1.3 times larger and 1.2 times slower. There are some particular points in my programs. For example, almost everywhere I set Integer rather than Int, I do not recall others, now. In never complained on (1) and (2) because did not recall of them and because they do not bite me in practice, so far. ----------------- Serge Mechveliani mechvel(a)botik.ru

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bug in 6.8.1-candidate
by Serge D. Mechveliani 17 Oct '07

17 Oct '07

Dear GHC developers, this is a bug report on ghc-6.8.1-candidate. The archive http://botik.ru/pub/local/Mechveliani/ghcBugs/bug-6.8.0-sep28.zip contains a project for which `making' under ghc-6.8.0.20070928-src produces a report of kind ---------------------------------------------------- ... <many modules compiled> GBasFld_.hs: ... ghc-6.8.0.20070928: panic! (the 'impossible' happened) (GHC version 6.8.0.20070928 for i386-unknown-linux): initC: srt_lbl Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug ---------------------------------------------------- unzip it, please, and see install.txt. Then, see GBasFld_.hs, it is small, and it looks like ghc cannot compile it. In ghc-6.6.1, this project works all right. The project can easily be reduced to the size of about a single GBasFld_.hs module (see install.txt). Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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empty export warning
by Serge D. Mechveliani 17 Oct '07

17 Oct '07

People, here is a more precise report about empty _export_ in ghc-6.8.1-candidate: I use -------------------------------- module M1 (f, module M2) where import M2 () f = ... -------------------------------- in the situation when M1 imports some instances from M2 and reexports these instances. And ghc-6.8.1-candidate reports "Warning: The export item `module M2' exports nothing" 1) Can I fix anything here? 2) Should this warning be different? Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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Prevent optimization from tempering with unsafePerformIO
by Bernd Brassel 17 Oct '07

17 Oct '07

Hello, I am writing a compiler from the functional logic language Curry to Haskell. As the result is a real extension of Haskell, there has to be SOME side effect involved. Unfortunately, this seems to prevent me from using any of ghc's optimizations on the resulting code. I have tried for some time to invoke the no-inline pragmata, but they seem to have no effect at all. Recently at ICFP, Neil Mitchell told me that there definitely is a way to avoid this problem. But does anybody know how? Thanks for your help! Bernd Brassel

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