- Glasgow-haskell-users

Request for help: 6.6.1 bugs
by Simon Marlow 02 Feb '07

02 Feb '07

Hi Folks, To give you a rough idea of how GHC activity is ramping up, take a look at the number of tickets assigned to recent milestones: 6.4.2: 27 tickets 6.6: 48 tickets 6.6.1: 107 tickets (61 open) 6.8: 134 tickets (117 open) We're focussed on getting 6.6.1 out of the door at the moment. We still have 61 open tickets though, so this message is a plea for help: if you have some time to spare, and would like to help out, please get involved! Here is a query that gives you the list of bugs milestoned for 6.6.1 with no current owner: http://hackage.haskell.org/trac/ghc/query?status=new&status=assigned&status… I've also listed the bugs at the end of this message. Some of the bugs we've marked as low priority (blue background), those are the ones we consider would be "nice to fix" but not essential for 6.6.1 (some of these are quite easy, incedentally). The protocol is, if you start working on a bug then claim it by setting yourself as the owner. Other guidelines for working on GHC can be found here: http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions in particular see the section at the end of that page about use of the bug tracker. If you need permission to modify tickets, please ask either myself or Ian. Cheers, Simon open tickets for 6.6.1 with no owner: 742 Graphics.SOE runs very slowly under win32. 804 Signal handlers always installed, evem in a DLL 933 Separate compilation fails with existential records 955 more object-code blow-up in ghc-6.6 vs. ghc-6.4.2 (both with optimization) 957 No way to use -lgmp from a non-standard location 970 GHCi crashes under Windows Millenium 976 GHCi crashes on Windows 98 987 X11: foreign declarations use Haskell types instead of C ones 1010 ghci crashes when running out of heap. 1014 Mangled module name in __stginit_Module symbol 1025 -ddump-minimal-imports works wrongly 1035 Win32 package doesn't appear in the online library docs 1044 library docs on web have broken link 1075 ghci unhandled exception on startup (memory access violation) 1076 runhaskell crash with .hi/.o files in the directory 1082 Documentation missing from MacOS PPC binary 1093 Windows: haddock-html fields are wrong in package.conf 1109 lockFile: fd out of range 1110 Setting PATH needed in Windows Vista 1128 The impossible happened, code commented 604 Windows installer: use WiX 609 Useful optimisation for set-cost-centre 831 GHCi user interface bug 839 Generate documentation for built-in types and primitve operations 850 threaded RTS uses SIGALRM 956 improving error messages #1 998 Tab-completion of filenames does not work in GHCi 6.6 1077 documentation error and omission 1095 make boot under includes/ doesn't run make depend 1096 More make boot / make depend problems 1098 Broken link in the User's Guide 1117 [2,4..10] is not a good list producer 1119 openBinaryFile: does not exist (No such file or directory) i386-unknown-linux 629 IO library locking doesn't count readers

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Problems building GHC
by Rodrigo Geraldo 31 Jan '07

31 Jan '07

Hi! I start to "hack" GHC, and, I 've tried to build it, but the build return this error message : ./compiler/stage1/ghc-inplace -o stage2/ghc -H64m -Onot -fasm -package ghc -Ist age2 -cpp -fglasgow-exts -fno-generics -Rghc-timing -I. -IcodeGen -InativeGen -I parser -Rghc-timing -Onot -fasm -DGHCI -DBREAKPOINT -threaded stage2/main /Main.o stage2/main/Main.o(.text+0x233c):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverPhases_showsPrec1_closure' stage2/main/Main.o(.text+0x2567):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverPhases_showsPrec1_info' stage2/main/Main.o(.text+0x25c2):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverPhases_showsPrec1_info' stage2/main/Main.o(.text+0x3978):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverPhases_haskellishzusrczusuffixes_closure' stage2/main/Main.o(.text+0x3c57):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverPhases_haskellishzusrczusuffixes_closure' stage2/main/Main.o(.text+0x454e):ghc1888_0.hc: undefined reference to `ghczm6zi6 _GHC_zdwsetSessionDynFlags_closure' stage2/main/Main.o(.text+0x4552):ghc1888_0.hc: undefined reference to `ghczm6zi6 _GHC_zdwload_closure' stage2/main/Main.o(.text+0x4566):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverPipeline_zdwcompileFile_closure' stage2/main/Main.o(.text+0x456a):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverMkDepend_zdwdoMkDependHS_closure' stage2/main/Main.o(.text+0x4572):ghc1888_0.hc: undefined reference to `ghczm6zi6 _InteractiveUI_zdwinteractiveUI_closure' stage2/main/Main.o(.text+0x457a):ghc1888_0.hc: undefined reference to `ghczm6zi6 _Packages_zdwdumpPackages_closure' stage2/main/Main.o(.text+0x5b4e):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverMkDepend_zdwdoMkDependHS_info' stage2/main/Main.o(.text+0x5bb8):ghc1888_0.hc: undefined reference to `ghczm6zi6 _InteractiveUI_zdwinteractiveUI_info' stage2/main/Main.o(.text+0x5bef):ghc1888_0.hc: undefined reference to `ghczm6zi6 _InteractiveUI_zdwinteractiveUI_info' stage2/main/Main.o(.text+0x66ce):ghc1888_0.hc: undefined reference to `ghczm6zi6 _Packages_zdwdumpPackages_info' stage2/main/Main.o(.text+0x5760):ghc1888_0.hc: undefined reference to `ghczm6zi6 _DriverPipeline_zdwcompileFile_info' stage2/main/Main.o(.text+0x5890):ghc1888_0.hc: undefined reference to `ghczm6zi6 _GHC_zdwload_info' stage2/main/Main.o(.text+0x58c4):ghc1888_0.hc: undefined reference to `ghczm6zi6 _GHC_zdwsetTargets_info' stage2/main/Main.o(.text+0x689b):ghc1888_0.hc: undefined reference to `ghczm6zi6 _GHC_zdwsetSessionDynFlags_info' collect2: ld returned 1 exit status <<ghc: 9924096 bytes, 3 GCs, 89824/89824 avg/max bytes residency (1 samples), 62 M in use, 0.02 INIT (0.00 elapsed), 0.03 MUT ( 17.44 elapsed), 0.00 GC (0.00 elap sed) :ghc>> make[3]: *** [stage2/ghc] Error 1 make[3]: Leaving directory `/c/ghc-build/ghc-6.6/compiler' make[2]: *** [stage2/ghc] Error 2 make[2]: Leaving directory `/c/ghc-build/ghc-6.6/compiler' make[1]: *** [stage2] Error 2 make[1]: Leaving directory `/c/ghc-build/ghc-6.6' make: *** [bootstrap2] Error 2 I've tried to build GHC using mSYS and MinGW under MS windows xp... Does anyone have any idea of how can I solve this problem? Thanks a lot! Rodrigo Ribeiro

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(no subject)
by TFP 2007 31 Jan '07

31 Jan '07

Dear Colleagues, Apologies in advance for the "p.m." ommission. This is a kind reminder that the deadline for extended abstract submissions to TFP 2007 is tomorrow, Feb. 1 at 11:59 p.m. EST. We are also pleased to announce that the TFP 2007 invited speaker is John McCarthy, Stanford University. For further details, please visit our website at: http://cs.shu.edu/tfp2007/ . The TFP 2007 program committee looks forward to receiving your submissions! Best wishes, Marco ************************************************************************************ Dr. Marco T. Morazan TFP 2007 Program Committee Chair http://cs.shu.edu/tfp2007/

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TFP 2007 Submission Deadline is Tomorrow
by TFP 2007 31 Jan '07

31 Jan '07

Dear Colleagues, This is a kind reminder that the deadline for extended abstract submissions to TFP 2007 is tomorrow, Feb. 1 at 11:59 EST. We are also pleased to announce that the TFP 2007 invited speaker is John McCarthy, Stanford University. For further details, please visit our website at: http://cs.shu.edu/tfp2007/ . The TFP 2007 program committee looks forward to receiving your submissions! Best wishes, Marco ************************************************************************************ Dr. Marco T. Morazan TFP 2007 Program Committee Chair http://cs.shu.edu/tfp2007/

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hrm...
by John Meacham 29 Jan '07

29 Jan '07

so I have this simple bit of code, which should be fast but seems to be being compiled to something very slow. > import Data.Word > import Data.Bits > > fhb :: Word -> Word > fhb w = b1 .|. b2 where > b2 = if 0xFFFF0000 .&. w /= 0 then 0x2 else 0 > b1 = if 0xFF00FF00 .&. w /= 0 then 0x1 else 0 what it compiles to is something involving Integers, lots of coercions and other nasty stuff when it should consist of a couple of primitive operations. John -- John Meacham - ⑆repetae.net⑆john⑈

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HEAD ghci crash on ppc OS X
by David Kirkman 28 Jan '07

28 Jan '07

I just built ghc from HEAD on OS X (ppc), and get the following error when starting ghci: ---start [15:15:15][david@isengard]$ compiler/stage2/ghc-inplace --interactive ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.7, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. ghc-6.7(9972,0xa000ed88) malloc: *** error for object 0x3807ff8: pointer being reallocated was not allocated ghc-6.7(9972,0xa000ed88) malloc: *** set a breakpoint in szone_error to debug malloc: failed on request for 11359964 bytes; message: ocAllocateJumpIslands ---end despite the suggestion, a breakpoint in szone_error catches nothing. But a breakpoint in malloc_printf (both szone_error and malloc_printf in the OS, not ghc) gives the following backtrace for an rts compiled with the -g flag: --start Breakpoint 1, 0x9012bb94 in malloc_printf () (gdb) bt #0 0x9012bb94 in malloc_printf () #1 0x90018388 in szone_realloc () #2 0x90018098 in realloc () #3 0x00e6f5c4 in stgReallocBytes (p=0x901a4df4, n=11359964, msg=0xfd9704 "ocAllocateJumpIslands") at RtsUtils.c:209 #4 0x00e97cbc in ocAllocateJumpIslands (oc=0x2b005d0, count=372, first=14502) at Linker.c:1598 #5 0x00e98954 in loadObj (path=0x2e63268 "/Network/Sid/Users/david/ ghc-crap/ghc/libraries/base/HSbase.o") at Linker.c:3743 #6 0x005b660c in s1wt_info () #7 0x00e8a220 in schedule (initialCapability=0x901a4df4, task=0x2e63268) at Schedule.c:608 #8 0x00c60e18 in main (argc=-1877324300, argv=0x3807ff8) at Main.c:105 (gdb) --end The call to failing call to stgReallocBytes occurs at line 1598 of Linker.c, in the following context: --start Linker.c, lines 1597 --> 1602 oc->image -= misalignment; oc->image = stgReallocBytes( oc->image, misalignment + aligned + sizeof (ppcJumpIsland) * count, "ocAllocateJumpIslands" ); oc->image += misalignment; --end oc->image is allocated at line 1326 of Linker.c (listing below), and then never modified until misalignment is subtracted from it at line 1598. Both the comment in the code fragment below, and the actual code in the fragment above seem to indicate that oc->image should be offset by misalignment. --start Linker.c, lines 1315 --> 1327 # elif defined(darwin_HOST_OS) // In a Mach-O .o file, all sections can and will be misaligned // if the total size of the headers is not a multiple of the // desired alignment. This is fine for .o files that only serve // as input for the static linker, but it's not fine for us, // as SSE (used by gcc for floating point) and Altivec require // 16-byte alignment. // We calculate the correct alignment from the header before // reading the file, and then we misalign oc->image on purpose so // that the actual sections end up aligned again. oc->misalignment = machoGetMisalignment(f); oc->image = stgMallocBytes(oc->fileSize + oc->misalignment, "loadObj(image)"); # else ---end The comment above seems to be begging for a oc->image += oc->misalignment; statement right after the call to stgMallocBytes. But I'm assuming it must normally be done someplace else -- I just can't figure out where. Anyway, I've verified that os->image is still pointing to the value returned from stgMallocBytes when misalignment (non-zero) is subtracted from it just before the call to stgReallocBytes. So in my build at least, the execution path is not hitting whatever part of the code that should be applying the misalignment offset to oc->image. Let me know if there is any more information I can give. -david k.

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ANN: regex-tdfa 0.56
by Chris Kuklewicz 27 Jan '07

27 Jan '07

Greetings, My new regular expression backend "regex-tdfa" is passing all the tests I have been throwing at it, so it is time to share the good news. First up: Where is it? Version 0.56 is in my "stable" location at > darcs get --partial darcs.haskell.org:/home/darcs/packages/regex-tdfa The version that will get updated and broken more often is "unstable" at > darcs get --partial darcs.haskell.org:/home/darcs/packages/regex-unstable/regex-tdfa It needs a slightly updated regex-base package (version >= 0.80) at > darcs get --partial darcs.haskell.org:/home/darcs/packages/regex-unstable/regex-base It has only been tested (on Max OS X) with GHC 6.6 and depends on base >= 2.0 for Data.ByteString, Data.ByteString.Lazy, and Data.Sequence. ** What does regex-tdfa do? It runs POSIX regular expression searches correctly. No other regular expression backend for Haskell does this correctly. The regular expression can be chosen to be from a String, ByteString, ByteString.Lazy, or (Data.Seq Char). Independent of that choice the searched text can also be any of those types. ** Properties and benefits of regex-tdfa: It follows a known standard: POSIX. (If you find that it disagrees with the standard then I will fix it.) It is written in Haskell, so there is no C library to compile and install. Though it is currently only written for GHC 6.6, it could be ported to any other compiler with only minor changes. (I expect that if you drop the polymorphic MPTC interface of regex-base it could be made Haskell98). It works with Unicode since it can be used on [Char] (and it works if there are '\NUL' characters around). It is lazy in the regular expression: it only builds the DFA if you use it, and only builds the state it needs, which are memoized in a lazy Trie. It is lazy in the searched text, and the pure function that searches the text only evaluates the text until the next match is done and does not hold onto the initial text. Thus you could efficiently search a [Char] up to the size of the Position type, which is an Int for now. It is free, the regex-tdfa library is under a BSD-3 license. ** Does it work? Yes. The regex-posix backend that come with GHC does not run all the searches correctly: it is buggy (example at end of announcement). And the regex-posix backend is also impossibly slow -- the slowest backend by far -- orders of magnitude slower. The regex-tre backend that wraps the TRE library has exposed this very fast library to the harsh gaze of QuickCheck. The lesson from QuickCheck is to never use regex-tre because the TRE library (version 0.7.4) is buggy. For regex-tdfa backend I took/stole ideas from Ville Laurikari's Master thesis which describes the algorithm that TRE uses. And I made a pure Haskell implementation that now passes all the tests at http://www.research.att.com/~gsf/testregex/testregex.html and follows the notes at http://www.research.att.com/~gsf/testregex/re-interpretation.html and passes those tests as well. And it "passes" QuickCheck tests which actually just compare the answers that regex-posix, regex-tre, and regex-tdfa since I do not have a bug free reference implementation to compare against. ** Why the name TDFA? Tagged Deterministic Finite Automata. The Tagged part is from Ville Laurikari's thesis work. ** Speed: If you do not care only about the match as a whole and not about subexpression matching then you can set the captureGroups ExecOption to False: makeMyRegex = makeRegex defaultCompOpt myExecOpt where myExecOpt = defaultExecOpt { captureGroups = False } And redefine (=~) and (=~~) to use makeMyRegex instead of makeRegex: (=~) :: (RegexMaker Regex CompOption ExecOption source,RegexContext Regex source1 target) => source1 -> source -> target (=~) s r = let re = makeMyRegex r :: Regex in match re s (=~~) :: (RegexMaker Regex CompOption ExecOption source,RegexContext Regex source1 target,Monad m)=> source1 -> source -> m target (=~~) s r = let re = makeMyRegex r :: Regex in match re s The benefit to this is speed, as it then proceeds to run all matches of "b(..?c)?d" against a large test file *faster* than the the TRE C library backend. My compliments to those who worked on ghc and -O2. It even runs nearly as fast as regex-dfa in this mode. Thus regex-dfa is (mostly) obsolete. If you use the default and capture the subgroups then the speed is reduced by a factor of about 4. This is because of the very simple data structures that keep track of the run time state. I intend to improve this aspect of the design now that I have a working algorithm. I have not benchmarked the speed of compiling the regular expression from the String. This compiling is done with very lazy data structures, so the DFA size is really only as big as you actually explore while running the match. ** Examples of bugs in regex-posix and regex-tre: An example for regex-posix: > *Main> "ab" Posix.=~ "((a)|(b)){2,}" :: MatchArray > array (0,3) [(0,(0,2)),(1,(1,1)),(2,(0,1)),(3,(1,1)) The array holds (group #, (match offset, match length)) The 0th group is the whole match "ab". The 2nd group is (a) and it matched the first "a" and the third group is (b) and matched the "b". But the second group is a child of the first group ((a)|(b)) which matched "b". The standard requires that captured groups are nested inside their parents, and here "a" is not not nested inside "b". So the regex-posix C backend that comes with GHC is buggy. The correct answer is, where the second group matched nothing: > *Main> "ab" TDFA.=~ "((a)|(b)){2,}" :: MatchArray > array (0,3) [(0,(0,2)),(1,(1,1)),(2,(-1,0)),(3,(1,1))] An example for regex-tre: "yyyyyy" TRE.=~ "(yyy|(x?)){2,4}" array (0,2) [(0,("yyyyyy",(0,6))),(1,("yyy",(3,3))),(2,("yyy",(3,3)))],"") Here TRE reports that the second group (x?) which should only match "" or "x" somehow matched "yyy". This is even more wrong than the regex-posix bug above. The correct answer, where the second group does not match: array (0,2) [(0,("yyyyyy",(0,6))),(1,("yyy",(3,3))),(2,("",(-1,0)))],"") -- Chris Kuklewicz

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RE: [Haskell-cafe] proposal: HaBench, a Haskell Benchmark Suite
by Simon Peyton-Jones 26 Jan '07

26 Jan '07

| Following up and the threads on haskell and haskell-cafe, I'd like to | gather ideas, comments and suggestions for a standarized Haskell | Benchmark Suite. Great idea. Maybe this can subsume nofib. I recommend reading the nofib paper though: http://citeseer.ist.psu.edu/partain93nofib.html Simon

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ByteArr# - nullByteArr# anyone?
by John Meacham 26 Jan '07

26 Jan '07

I would like to create a datatype that contains some memory managed by the GHC runtime, the natural fit is ByteArr#, however, in the common case, the ByteArr# won't actually have anything in it. would it be possible to have a single constant 'nullByteArr#'? I can't define a top level value of type ByteArr# and creating these values is in very performance critical code so I am not quite sure what to do. It would also be nice if byteArrContents# returned 'nullAddr#' for such byte arrays, but it is not a strict requirement. John -- John Meacham - ⑆repetae.net⑆john⑈

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Re: Replacement for GMP: Update
by Peter Tanski 24 Jan '07

24 Jan '07

On Tue, 23 Jan 2007, John Meacham wrote: > I think the benchmarks are flawed in an important way, I believe, (but > am not positive) that ARPREC uses a special factorized form of > representing numbers, which makes multiplicative type operations > extremely fast, but simple things like addition/subtraction quite > slow. Oh, don't worry. I've given up on ARPREC for the simple reason that *every* operation on small-size operands is very slow to say nothing of the time it would take to initialise ARPREC every time. ARPREC does store numbers using a representation similar to floating point, essentially an array of doubles where: (int)(array[0]) = array_size (int)(array[1]) = no_mantissa_words array[2] = exponent array[ 3 .. ] = mantissa I hope the tests aren't "flawed," in that the main purpose of performing those operations was to see the median-level performance (extreme performance being Integers with operands greater than, 10,000 or 30,000 bits). The crumby graphs do show that I made a low cutoff of 256 bits so the most common Integer-use ( < 128 bits, 4 uint32_t) wasn't even tested. I probably didn't clarify why I tested larger size operands. GHC should have something that is comparable to GMP, and that means speed (and precision) for medium-large operands as well as small operands. > you are only benchmarking multiplicative or similar routines, giving > ARPREC a huge lead, when in practice it might end up being slowest, as > addition/subtraction are extremely more common than multiplication. In the common case it is slowest--but not by much. > Also, how are you choosing the numbers to test with? it is possible > that > some packages are using 'sparse' representations or other specialized > forms if all your numbers happen to be powers of two or something. Random numbers--a different number for each iteration in size. I used a PRNG based on the SNOW2 stream cipher--something I wrote awhile ago, as fast as arc4random and tests well on DIEHARD and other statistical things. The GMP and OpenSSL random number generators were slower and I wanted to use the same generator across libraries. > also, pretty much all uses of integers will be for very small > integers, > we should be careful to not lose sight of speed for the common case > due > to pretty asymtotic bounds. All numbers were the same size, so cases like multiplying a 1024-bit operand by a 256-bit operand weren't tested; that could be a real flaw. It's all very sloppy--just to get an idea of where things generally line up. So, where am I now? I worked on the GHC-Win off and on and then went back to making a uniform API between GHC and the replacement, and I am re-writing the replacement. I thought I would be done several weeks ago but of course little things take over... One area of GHC I would really like to change is the memory-use. ForeignPtr seems to work well but places the full burden of memory management on the Integer library; for SIMD-use (AltiVec, SSE2), the library would require GHC to allocate memory aligned to 16-bytes. Right now, the only choice would be allocatePinned() (in rts/sm/Storage.c), which is 4-byte aligned and it is, of course, pinned so the GC can't move it. Imagine the RTS-memory problems you could have if you wrote a Haskell program using lots of small Integers allocated with, say, an allocatePinned_16() (16-byte aligned). The alternative would be to use normal memory but re-align the operands for the vectorized operations by peeling; o.k., doable (especially easy with AltiVec), but slower. In the meantime I have been working through SSE2 assembler, which doesn't have an addc (add-carry) operation and doesn't set a flag for overflow, so I have been experimenting with a SWAR-like algorithm--essentially the same thing as GMP's Nails--to make the normally 32-bit operands 31 bits with the last bit for a carry flag. Thorkil Naur and others have suggested writing the whole thing as small assembler operations and piece them together in Haskell; I have been looking into that as well but it seems to entail inlining every Integer function--imagine the code bloat. Cheers, Pete

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