June 2008 - Glasgow-haskell-users

desperately seeking RULES help
by Conal Elliott 09 Jun '08

09 Jun '08

I'm trying to do some fusion in ghc, and I'd greatly appreciate help with the code below (which is simplified from fusion on linear maps). I've tried every variation I can think of, and always something prevents the fusion. Help, please! Thanks, - Conal {-# OPTIONS_GHC -O2 -Wall -fglasgow-exts -ddump-simpl -ddump-simpl-stats #-} -- {-# OPTIONS_GHC -ddump-simpl-iterations #-} module F where -- | Domain of a linear map. class AsInt a where toInt :: a -> Int fromInt :: Int -> a {-# RULES "toInt/fromInt" forall m. toInt (fromInt m) = m #-} {-# INLINE onInt #-} onInt :: AsInt a => (Int -> Int) -> (a -> a) onInt f = fromInt . f . toInt test :: AsInt a => (Int -> Int) -> (Int -> Int) -> (a -> a) test h g = onInt h . onInt g -- The desired result: -- -- test h g -- == onInt h . onInt g -- == (fromInt . h . toInt) . (fromInt . g . toInt) -- == \ a -> (fromInt . h . toInt) ((fromInt . g . toInt) a) -- == \ a -> (fromInt . h . toInt) (fromInt (g (toInt a))) -- == \ a -> fromInt (h (toInt (fromInt (g (toInt a))))) -- == \ a -> fromInt (h (g (toInt a)))

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Missing Data.Map library? GHC 6.8.2 under OS X
by Thomas Krauss 09 Jun '08

09 Jun '08

I seem to be having trouble using GHC 6.8.2 and OS X (10.5). It seems that any use of anything from Data.Map results in a link error like Undefined symbols: "___stginit_containerszm0zi1zi0zi1_DataziMap_", referenced from: ___stginit_Main_ in tst_parse.o ld: symbol(s) not found Has anyone else seen this? I tried reinstalling the package from haskell.org, but no luck.

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Building ndp Problem
by Dominic Steinitz 09 Jun '08

09 Jun '08

I wanted to try out data parallel haskell. I followed the instructions on http://haskell.org/haskellwiki/Data_Parallel_Haskell/PackageNDP but I get the following error: > dom@lagrange:~/ghc/libraries> make make.library.ndp > make: *** No rule to make target `build.library.ndp', needed by `make.library.ndp'. Stop. BTW when I built ghc, I had the following problem with happy (and alex). It kept telling me I needed dvips but dvips is already installed. In the end I used --nodeps. > dom@lagrange:~/happy> rpmbuild -ta happy-1.17.tar.gz > error: Failed build dependencies: > dvips is needed by happy-1.17-1.i586 > dom@lagrange:~/happy> rpmlocate dvips > /usr/bin/dvips > dom@lagrange:~/happy> rpm --query -f /usr/bin/dvips > texlive-2007-69 > dom@lagrange:~/happy> dvips --version > dvips(k) 5.96 > kpathsea version 3.5.6 > Copyright (C) 2005 Radical Eye Software. > There is NO warranty. You may redistribute this software > under the terms of the GNU General Public License > and the Dvips copyright. > For more information about these matters, see the files > named COPYING and dvips.h. > Primary author of Dvips: T. Rokicki; -k maintainer: T. Kacvinsky/ S. Rahtz. > rpmbuild -ta --nodeps happy-1.17.tar.gz

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*BSD support in 6.8.3
by Simon Marlow 07 Jun '08

07 Jun '08

Hi Folks, 6.8.3 is nearing release, and we have an outstanding bug affecting the GHCi on the BSDs: http://hackage.haskell.org/trac/ghc/ticket/2013 We need someone to help out with this. The patch in the ticket apparently works, but can't be committed as is because it isn't correctly #ifdef'd and will presumably break other platforms. Also it needs to be tested on OpenBSD/NetBSD in addition to FreeBSD. I don't have access to a *BSD machine right now, and I don't have the time available to set one up. If someone can donate a temporary account then that would be helpful, but most helpful would be if someone could work with us to get this bug fixed in time for 6.8.3 (i.e. the next few days). Otherwise, we have to release with the bug still in, which would be bad. Cheers, Simon

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Mutually recursive modules
by Richard Giraud 06 Jun '08

06 Jun '08

Hello I've been doing some work with mutually recursive modules (MRMs). I'm familiar with the section in the User's Guide on how to do this and have successfully worked with MRMs with simple dependencies. However, I have created a set of MRMs that I can't seem to get to compile because of type issues. I can get the code to compile by combining all of the modules into a single, monolithic module; however, this breaks the conceptual design that I'm going for. I may also be able to break the modules into smaller pieces that will compile, though I'm not sure about this and it, too, would break the conceptual design. Does the current {-# SOURCE #-}/.hs-boot scheme allow for compilation of arbitrary MRMs? Or are there known cases where it doesn't work? If there are cases where it doesn't work, are there other options? Someone in Haskell Cafe mentioned that GHC 6.2 used a different scheme for MRMs (.hi-boot). Is it still possible to use this? Would it allow for compilation of arbitrary MRMs? I can create a minimal case as an example, if it would be useful. Thanks, Richard

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automatically deriving Functor Re[2]: [Haskell-cafe] automatically deriving Map and Filter on datatypes etc.
by Bulat Ziganshin 05 Jun '08

05 Jun '08

Hello Neil, Thursday, June 5, 2008, 8:54:51 PM, you wrote: >> PS Why isn't Functor derivable? > Derive can do it: http://www.cs.york.ac.uk/~ndm/derive > I believe that Twan (the author of Functor deriving in Derive) is > trying to get this suggested for Haskell' as a proper deriving. dear GHC developers, may be it's a good idea to add such facility to ghc? [as one more H98 extension] -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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Build and runtime errors
by Tom Cody 05 Jun '08

05 Jun '08

I've attached a log of the 'make install' on advice from Igloo. I get the following when trying to building from source with the documentation install enabled: #Hacks: /usr/bin/install -c -m 644 base/dist/doc/html/*/*.css /usr/local/share/doc/ghc/libraries /usr/bin/install: cannot stat `base/dist/doc/html/*/*.css': No such file or directory make[1]: *** [install] Error 1 make[1]: Leaving directory `/home/cody/Desktop/ghc-6.9.20080603/libraries' make: *** [install] Error 2 However, if I comment out lines 386 -394 in the libraries makefile, it all installs perfectly. But then I get this runtime error every time I use any GHC file: ghc-6.9.20080603: panic! (the 'impossible' happened) (GHC version 6.9.20080603 for i386-unknown-linux): interactiveUI:setBuffering2 _________________________________________________________________ http://clk.atdmt.com/UKM/go/msnnkmgl0010000007ukm/direct/01/

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Having trouble with parallel Haskell
by Bryan O'Sullivan 05 Jun '08

05 Jun '08

I intended to write a half chapter or so about parallel programming in Haskell for the book I'm working on, but I've been coming to the conclusion that the time is not yet ripe for this. I hope it will be helpful if I share my experiences here. Specifically, I was planning to write about parallel programming in pure code: use of "par" and programming with strategies. The most substantial problem is that the threaded RTS in GHC 6.8.2 is very crashy in the face of "par": about 90% of my runs fail with a segfault or an assertion failure. Simon Marlow mentioned that this bug is fixed, but I've been unsuccessful in building a GHC 6.8.3 release candidate snapshot so far, so I can't verify this. When a run does go through, I have found it surprisingly difficult to actually get both cores of a dual-core system to show activity. As there are no tools I can use to see what is happening, I am stumped. It is of course quite likely that I am doing something wrong that results in unexpected dependencies, but I cannot find a means to gaining insight into the problem. As an example, I have a simple parallel quicksort that is very conservative in its sparking, and I get no joy out of it on a dual-core machine: it mostly sticks to a single core. This wouldn't be a problem if I had some way to spot the presumed data dependency that is serialising the code, but no joy. <b

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-fvia-C for libHSbase, etc.?
by Donn Cave 05 Jun '08

05 Jun '08

I'm building GHC on NetBSD-amd64, and among other things need to deal with the problem described in #2305 - native code misses the __RENAME (__asm) directive in NetBSD include files, and ends up linking to the wrong externals. The author of #2305 reports that -fvia-C avoids this problem, so I built the ghc 5/31 distribution I've been working on, with GhcLibHcOpts=-O -Rghc-timing -fgenerics -fvia-C (i.e., add -fvia-C compile option for library build.) Does that seem like a reasonable solution? It does seem to work, but I'm wondering if there are issues we can expect with performance etc.? thanks, -- Donn Cave <donn(a)avvanta.com>

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Re: Having trouble with parallel Haskell
by Donnie Jones 05 Jun '08

05 Jun '08

Hello Bryan, 2008/6/4 Bryan O'Sullivan <bos(a)serpentine.com>: > I intended to write a half chapter or so about parallel programming in > Haskell for the book I'm working on, but I've been coming to the > conclusion that the time is not yet ripe for this. I hope it will be > helpful if I share my experiences here. > > Specifically, I was planning to write about parallel programming in pure > code: use of "par" and programming with strategies. > > The most substantial problem is that the threaded RTS in GHC 6.8.2 is > very crashy in the face of "par": about 90% of my runs fail with a > segfault or an assertion failure. Simon Marlow mentioned that this bug > is fixed, but I've been unsuccessful in building a GHC 6.8.3 release > candidate snapshot so far, so I can't verify this. > > When a run does go through, I have found it surprisingly difficult to > actually get both cores of a dual-core system to show activity. As > there are no tools I can use to see what is happening, I am stumped. It > is of course quite likely that I am doing something wrong that results > in unexpected dependencies, but I cannot find a means to gaining insight > into the problem. Although my Google Summer of Code project was not selected, I decided to go ahead and work on the Parallel Profiling Tools for GHC this Summer, with the help of Simon Marlow of course, for my Master's thesis. The work is nowhere near complete, as I just began working on it a couple of weeks ago. I was able to run the ParSort.hs program in your original post with my modified version of GHC HEAD that now supports parallel profiling. Hopefully, by the end of the Summer, Haskell's support for parallel profiling will be vastly improved. This is the example test I performed: ghc -parprof -threaded -o ParSort --make ParSort.hs time ./ParSort 1000000 +RTS -pN -N6 -RTS We have 1000000 elements to sort. Sorted all 1000000 elements. 28.04362s elapsed. real 0m36.060s user 0m44.107s sys 0m0.708s I have attached an Postscript file containing a graph that visualizes the parallel profiling data from the above test. A lot of work still needs to be done, but I just wanted to let you know that improvements are expected soon. Btw, ParSort.hs was taking advantage of both cores on my machine. Thank you. __ Donnie Jones

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