May 2007 - Glasgow-haskell-users

partially applied type synonyms
by Arie Peterson 05 Mar '12

05 Mar '12

Dear list, Is there a good reason that partially applied type synonyms cannot be made instances of classes? - A simple example would be making the identity type 'Id' ("type Id x = x") instance of 'Monad'. This would eliminate the need for some silly occurrences of 'runIdentity', and perhaps narrow the gap between monads and monad transformers. - The reason I complain about this now is a more involved example, where introducing a newtype to work around the restriction is not an option. Well, not as far as I can see now, anyway. Partially applied type synonyms are, in a sense, the anonymous functions at the type level, and one might argue that they deserve the same 'first-class member status' as the lambda at the value level. Kind regards, Arie Peterson

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ghci and ghc -threaded broken with pipes & forking
by John Goerzen 29 Dec '08

29 Dec '08

Hi, I've been hitting my head against a wall for the past couple of days trying to figure out why my shell-like pipeline code kept hanging. I found fd leakage (file descriptors not being closed), which disrupts EOF detection and can lead to deadlocks. I just couldn't find the problem. I finally tried compiling my test with ghc instead of running it in ghci. And poof, it worked fine the first time. I tried asking on #haskell, and got the suggestion that ghci uses -threaded. I tried compiling my test program with ghc -threaded, and again, same deadlock. My program never calls forkIO or forkOS or any other threading code. You can see my test case with: darcs get '--tag=glasgow ml' http://darcs.complete.org/hsh ghc -fglasgow-exts --make -o test2 test2.hs That'll run fine. If you add -threaded, it will hang. Ideas? Thanks, -- John

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readArray is faster than unsafeRead
by Scott Dillard 01 Jul '07

01 Jul '07

Hello, I'm writing some matrix multiplication and inversion functions for small matrices (3x3 and 4x4 mostly, for 3d graphics, modeling, simulation, etc.) I noticed that the matrix multiplication was a bottleneck so I set out to optimize and found that using unsafeRead instead of (!) (or readArray in stateful code) helped a lot. So then I went to optimize my gaussian elimination function and found just the opposite. unsafeRead is slower than readArray. This struck me as very odd considering that readArray calls unsafeRead. If there is a "good" reason why the compiler optimized readArray better than unsafeRead, I'd like to know what it is so that I can make all my array code safe as well as fast. (By "good" reason I mean something deterministic and repeatable, not just luck.) On the otherhand, if this is a fluke, I'm inclined to think that it's not the safe code which is freakishly fast, but the unsafe code which is needlessly slow. That is, something about my program is hindering optimization of the unsafe code. What is it? Attached is the profiling results and a test program with a handful of matrix multiplication and gaussian elimination functions to illustrate what I've seen. This happens both on amd64 and intel core architectures. Thanks for any insight, Scott

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ghc6.6 on ps3 - compile error in StgCRun
by Tristan Allwood 24 Jun '07

24 Jun '07

Hi, I'm trying to build ghc-6.6 on a sony ps3, but have hit a problem: ------------------------------------------------------------------------ == make all -r; in /home/tora/ghc/ghc-6.6/rts ------------------------------------------------------------------------ ../compiler/ghc-inplace -optc-O -optc-Wall -optc-W -optc-Wstrict-prototypes -optc-Wmissing-prototypes -optc-Wmissing-declarations -optc-Winline -optc-Waggregate-return -optc-Wbad-function-cast -optc-I../includes -optc-I. -optc-Iparallel -optc-DCOMPILING_RTS -optc-fomit-frame-pointer -optc-DNOSMP -optc-fno-strict-aliasing -H16m -O -optc-O2 -optc-DNOSMP -static -I. -#include HCIncludes.h -fvia-C -dcmm-lint -c StgCRun.c -o StgCRun.o /tmp/ghc12557_0/ghc12557_0.s: Assembler messages: /tmp/ghc12557_0/ghc12557_0.s:12:0: Error: junk at end of line, first unrecognized character is `@' /tmp/ghc12557_0/ghc12557_0.s:16:0: Error: junk at end of line, first unrecognized character is `@' make[1]: *** [StgCRun.o] Error 1 make: *** [stage1] Error 1 The ps3 is running YDL, and to bootstrap the ghc build I managed to install a powerpc ghc6.6 on the system (downloaded a deb from http://packages.debian.org/cgi-bin/download.pl?arch=powerpc&file=pool%2Fmai… then alien'ed it to get an rpm which seems to work - though ghci is non-functioning) The sources I'm trying to build are the standard ghc http://www.haskell.org/ghc/dist/6.6/ghc-6.6-src.tar.bz2 (and extralibs) >uname -a Linux ebony 2.6.16-20061110.ydl.2ps3 #1 SMP Tue Dec 5 12:35:42 EST 2006 ppc64 ppc64 ppc64 GNU/Linux Any tips / pointers / advice greatfully recieved; TIA, Tristan Allwood

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ghc configure
by C.M.Brown 23 Jun '07

23 Jun '07

Hi, I've noticed that when you run ./configure on a ghc build lot's of repetition occurs. A lot of the time the same checks are being performed for each configure file in the ghc hierarchy. Could it be possible if some of these checks could be done once at a high level and then subsequent configures could refer to these checks to speed up configuration time? It's just configuring ghc on a mac G4 is a very time consuming process in it's own right! Thanks, Kind regards, Chris.

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"GHC as a library" stalls when nobody is consuming it's output
by Mads Lindstrøm 08 Jun '07

08 Jun '07

Hi all While trying to implement a GUI for GHCi, I have run into an annoying concurrency problems. I think "GHC as a library" is at fault, as it stalls (maybe some deadlock) when nobody is consuming it's output. This message is a literate Haskell program, which illustrates the problem. This test-program starts a thread which prints an 'A' on stderr every second. Then it wait three seconds (meanwhile the 'A's are printing), and runs, via "GHC as a library", the following Haskell code "[1..]". If I start the program as: ./IsGhcBlocking >/dev/null everything works fine and the 'A' keeps coming out on stderr. However, if I do: ./IsGhcBlocking | sleep 10 I only see three 'A's. I believe that is because the sleep-command, do not consume any input. The program was tested on Debian Etch running GHC 6.6. > module Main where > Compile with: ghc -threaded -package ghc-6.6 --make IsGhcBlocking.lhs > import qualified GHC as GHC > import qualified Outputable as GHC > import qualified Packages as GHC > import qualified DynFlags as GHC > import qualified ErrUtils as GHC > > import System.IO > import Control.Concurrent > -- the path of our GHC 6.6 installation > path :: FilePath > -- path = "c:\\ghc-6.6" > path = "/usr/lib/ghc-6.6/" > > main :: IO() > main = do let printAs = do threadDelay (10^6) > hPutStrLn stderr "A" > printAs > forkOS printAs -- forkIO gives the same result > threadDelay (10^6 * 3) > session <- initializeSession > GHC.runStmt session "[1..]" > return () > > initializeSession = > do session <- GHC.newSession GHC.Interactive (Just path) > > -- initialize the default packages > dflags0 <- GHC.getSessionDynFlags session > let myLogAction _ locSpec style errMsg = hPutStrLn stderr showMsg where > showMsg = GHC.showSDoc $ GHC.withPprStyle style $ GHC.mkLocMessage locSpec errMsg > dflags1 = dflags0 { GHC.log_action = myLogAction } > (dflags2, packageIds) <- GHC.initPackages dflags1 > GHC.setSessionDynFlags session dflags2{GHC.hscTarget=GHC.HscInterpreted} > GHC.setContext session [] [] > return session The stalling becomes a problem, when one wants to interrupt "GHC as a library"'s runStmt function. One could interrupt "GHC as a library" with Panic.interruptTargetThread (see http://article.gmane.org/gmane.comp.lang.haskell.glasgow.user/12289) However, as "GHC as a library" locks up (stalls, deadlocks) there is no way of executing Panic.interruptTargetThread. Some people may suggest that I should always consume the output from "GHC as a library". But that is easier said than done. Many GUI libraries (including WxHaskell, which I am using) only allows for one active thread at a time (see http://wxhaskell.sourceforge.net/faq.html) Thus my GUI cannot simultaneously tell "GHC as a library" to interrupt it's execution and read it's output. For thus wondering how I can run both a GUI and "GHC as a library", if WxHaskell is not happy about threading, the answer is that I run the GUI and "GHC as a library" in separate processes. Greetings, Mads Lindstrøm

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ghc-6.6.1 for FreeBSD/amd64 binary distribution
by Gregory Wright 05 Jun '07

05 Jun '07

Hi, I have put a binary distribution of ghc-6.6.1 for FreeBSD/amd64 at http://www.haskell.org/ghc/dist/6.6.1/ghc-6.6.1-x86_64-unknown- freebsd.tar.bz2 No documentation or ghci. The former might be easily remedied although using FreeBSD's docbook chain, as suggested in the wiki, fails when asked to generate printable docs. The latter seems to be a bigger project since my naive interpretation of the problem is that we need data relocations across a 2GB boundary. The binary works well enough to build itself and darcs. There are only sixteen unexpected test suite failures thus far. I am ignoring these for the moment while I get back to thinking about ghci. Note that you need to install libgmp to use the compiler. libgmp from the ports collection works fine. Best Wishes, Greg

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GHC Extensibility
by Monique Monteiro 03 Jun '07

03 Jun '07

Hi (this message is mainly intended to the GHC Team), is there any plan to improve GHC's extensibility by providing a simpler way to integrante new backends? I worked at Haskell.NET project in the past, when we integrated successfully a .NET code generator to GHC 6.2.2. As it wasn't stable enough, we didn't integrate it to the main branch. However, I've been trying to integrate our code generator to 6.6.1 and I've not been able to compile it up to now, due to several changes in GHC's code! I haven't yet figured out how to call the .NET code generator from GHC 6.6.1's main function. Further, it would be great if there was a better extensibility mechanism (such as a "plugin" infrastructure, for example) in which it wasn't necessary to use "#ifdef"along the code. Also, it would be very useful if this mechanism/API was well documented. Of course, this is only a suggestion. Best regards. -- __________________________________________________________ Monique Monteiro, MSc MCP .NET Framework 2.0 / SCJP / IBM OOAD Project Manager Recife Microsoft Innovation Center +55 81 34198137 http://www.cin.ufpe.br/~mlbm http://thespoke.net/blogs/moniquelouise/default.aspx monique(a)qualiti.com.br MSN: monique_louise(a)msn.com

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6.6.1 for windows
by Adrian Hey 01 Jun '07

01 Jun '07

Hello, Can we expect a 6.6.1 binary and/or installer for windows sometime? Thanks -- Adrian Hey

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[slightly OT] ghc-6.6.1 on OpenBSD/i386: internal error (Storage.c)
by Matthias Kilian 31 May '07

31 May '07

Hi, I'm currently working on updating the GHC port to 6.6.1 for OpenBSD, and when I run the testsuite (ghc-regress), all test cases for the way "threaded1", i.e. debug + threaded bail out with an assertion failure: Blocks: 132 live + 123 free = 255 total (508 around) conc010: internal error: ASSERTION FAILED: file Storage.c, line 1174 The numbers vary slightly, but there's always a total of 255 and 508 blocks around, except for one test case (con012), where there are a total of 763 blocks (1016 around). What puzzles me a little bit is the fact that this does *not* happen on amd64 (aka x86_64) but only on i386 so far. So does this ring a bell for anyone? I didn't find anything similar in the archives or in the bug tracker. Ciao, Kili -- CRM114 isn't ugly like PERL. It's a whole different kind of ugly. -- John Bowker

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