February 2004 - Glasgow-haskell-users

config.h namespace clashes
by John Meacham 03 Mar '04

03 Mar '04

The inclusion of the GHC made config.h in HsFFI.h makes it extremely difficult to use autoconf with ones own projects without dealing with horrible name clashes everywhere. Is there some way this can be fixed? perhaps pre-generating the HsFFI.h. although I don't think it is stated explicitly by the FFI report, I would assume that HsFFI.h should not clash with anything that doesn't start with Hs, hs_ or HS_. also, it would be good if config.h could be renamed to something like ghc-config.h, because otherwise the conflict between the names can hide bugs where you get the incorrect config.h or make it tricky to get at the GHC one if it is actually the one you want. John -- --------------------------------------------------------------------------- John Meacham - California Institute of Technology, Alum. - john(a)foo.net ---------------------------------------------------------------------------

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RE: [Haskell] performance tuning Data.FiniteMap
by Simon Peyton-Jones 02 Mar '04

02 Mar '04

[Moving to GHC users list] There are several things that aren't research issues: notably, faster copying, fewer intermediate lists, fewer state-monad-induced intermediate closures. These are things that would move sharply up our priority list if you had a real application that was stumbling on them. What I obviously can't promise is that improving these things would solve your problem -- if, indeed, you turn out to have one! Simon | -----Original Message----- | From: S. Alexander Jacobson [mailto:alex@i2x.com] | Sent: 26 February 2004 23:27 | To: Simon Peyton-Jones | Cc: haskell(a)haskell.org | Subject: RE: [Haskell] performance tuning Data.FiniteMap | | Is fixing GHC arrays a big research job or is it | something that someone can straightforwardly | handle if my site actually gets enough traffic to | warrant it? | | -Alex- | | On Thu, 26 Feb 2004, Simon Peyton-Jones wrote: | | > | But in managing this tradeoff, what is faster: | > | * constructing/destructing e.g. 16 trees (for a 65000 item table) | > | * 2 memcpy of 256 item arrays (perhaps after you primop?) | > | | > | If the later is not dramatically slower than I | > | will bias towards more arrayness. | > | > I doubt the latter is dramatically slower, but you'd have to experiment | > to find out. And GHC is not doing as well as it should on arrays just | > now. (One of the things on our to-do list.) Might vary between | > implementations too. | > | > Simon | > | | _________________________________________________________________ | S. Alexander Jacobson mailto:me@alexjacobson.com | tel:917-770-6565 http://alexjacobson.com

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Happy Question
by Ashley Yakeley 29 Feb '04

29 Feb '04

My hand-written S-expression parser for HScheme is very very slow. Really quite a bit slower than it ought to be. So I'd like to switch to Happy instead. The problem is my parser should be monadic, but the monad type is generalised (basically of the form (context m) => m). Is there a way of switching on monadic-ness, so I can have a monadic happyError, but without giving type signatures to happyThen and happyReturn? Or else allowing a class context for the type signatures? -- Ashley Yakeley, Seattle WA

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RE: Generics... no Tuples > 2 either...
by Simon Peyton-Jones 27 Feb '04

27 Feb '04

Yes, sorry about that. We'll add them shortly. (It's nice to know that someone is using this stuff!) Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Abraham Egnor | Sent: 26 February 2004 22:18 | To: MR K P SCHUPKE | Cc: glasgow-haskell-users(a)haskell.org | Subject: Re: Generics... no Tuples > 2 either... | | I've been frustrated by the same lack of instances; as a stopgap, here's | one for a three-tuple. The pattern is pretty clear and can easily be | extended to whatever size you'd like. | | tupCon = mkConstr 1 "(,,)" Prefix | | instance (Data a, Data b, Data c) => Data (a, b ,c) where | gfoldl k z (a, b, c) = ((z (,,) `k` a) `k` b) `k` c | toConstr _ = tupCon | fromConstr _ = (undefined, undefined, undefined) | dataTypeOf _ = mkDataType [tupCon] | | MR K P SCHUPKE <k.schupke(a)imperial.ac.uk> writes: | > | >Any chance of Data instances for tuples of size | >greater than 2... One of the nice things about generics is | >you can use them by deriving Data on your datatypes - of | >course this doesn't work if you all of a sudden have to | >put a load of boiler-plate in just to use tuples... | > | > Regards, | > Keean Schupke | >_______________________________________________ | >Glasgow-haskell-users mailing list | >Glasgow-haskell-users(a)haskell.org | >http://www.haskell.org/mailman/listinfo/glasgow-haskell-users | > | | | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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Generics... no Tuples > 2 either...
by MR K P SCHUPKE 26 Feb '04

26 Feb '04

Any chance of Data instances for tuples of size greater than 2... One of the nice things about generics is you can use them by deriving Data on your datatypes - of course this doesn't work if you all of a sudden have to put a load of boiler-plate in just to use tuples... Regards, Keean Schupke

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Generics missing Data instances...
by MR K P SCHUPKE 26 Feb '04

26 Feb '04

There appears to be no instance for Double values in the Generics.Basic Also no instance for Ptr. am I not importing the right file, or does this need to be fixed? Regards, Keean Schupke. PS. This is with ghc-6.2

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RE: Why is partition no good list producer?
by Simon Peyton-Jones 25 Feb '04

25 Feb '04

Yes, if partition was implemented as described in the Report, namely as two independent filters, then both would be good producers. But then it would not be a good consumer (because it would consume the list twice). In the GHC library it is implemented as a single traversal producing two lists, so it's a good consumer but not a good producer. I don't know how to do both at once. Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Jan Scheffczyk | Sent: 25 February 2004 09:44 | To: glasgow-haskell-users(a)haskell.org | Subject: Why is partition no good list producer? | | Hi all, | | I'm about to optimize a fairly large Haskell program, which uses | partition quite often (and a fold immediately afterwards). | The GHC User guide section about RULE pragmas says that filter is a | good producer, whereas partition is not mentioned (therefore, I | assume it is not). | | I put a little test program together: | | > fuse1 :: [Bool] -> (Bool,Bool) | > fuse1 xs = (x,y) | > where (fs,gs) = partition id xs | > x = foldr (&&) True fs | > y = foldr (||) False gs | | > fuse2 :: [Bool] -> (Bool,Bool) | > fuse2 xs = (x,y) | > where fs = filter id xs | > gs = filter not xs | > x = foldr (&&) True fs | > y = foldr (||) False gs | | Compiling it via ghc -O and loading the compiled object to ghci | results in: | | Prelude Test> fuse2 (replicate 10000000 False) | (True,False) | (8.19 secs, 241174592 bytes) | Prelude Test> fuse1 (replicate 10000000 False) | (*** Exception: stack overflow | (6.18 secs, 48472660 bytes) | | | I understand the results: Using partition an intermediate list seems | to be build. | But WHY? | | Is it simply because of a missing RULE pragma for partition or is | there a "deeper" reason? | | Cheers, | Jan | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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Why is partition no good list producer?
by Jan Scheffczyk 25 Feb '04

25 Feb '04

Hi all, I'm about to optimize a fairly large Haskell program, which uses partition quite often (and a fold immediately afterwards). The GHC User guide section about RULE pragmas says that filter is a good producer, whereas partition is not mentioned (therefore, I assume it is not). I put a little test program together: > fuse1 :: [Bool] -> (Bool,Bool) > fuse1 xs = (x,y) > where (fs,gs) = partition id xs > x = foldr (&&) True fs > y = foldr (||) False gs > fuse2 :: [Bool] -> (Bool,Bool) > fuse2 xs = (x,y) > where fs = filter id xs > gs = filter not xs > x = foldr (&&) True fs > y = foldr (||) False gs Compiling it via ghc -O and loading the compiled object to ghci results in: Prelude Test> fuse2 (replicate 10000000 False) (True,False) (8.19 secs, 241174592 bytes) Prelude Test> fuse1 (replicate 10000000 False) (*** Exception: stack overflow (6.18 secs, 48472660 bytes) I understand the results: Using partition an intermediate list seems to be build. But WHY? Is it simply because of a missing RULE pragma for partition or is there a "deeper" reason? Cheers, Jan

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RE: inconsistent GHC building documentaion
by Simon Marlow 25 Feb '04

25 Feb '04

> In the "Building the Glasgow Functional Programming Tools > Suite", chapter > 12, Notes for building under Windows > (http://www.haskell.org/ghc/docs/6.2/html/building/winbuild.ht > ml), it is > said: "Install an executable Happy, from > http://www.haskell.org/happy". The > latest version of happy in its website is 1.13. When running > configure in > fptools, however, I get the error: > > configure: error: Happy version 1.14 or later is required to > compile GHC. Firstly, discussion about the development versions of GHC usually take place on cvs-ghc(a)haskell.org rather than here (to avoid confusion). The CVS HEAD currently requires Happy 1.14, which hasn't been released yet. It is available in the source tree (fptools/happy), so to build the CVS HEAD you currently also need to either: (a) check out fptools/happy and use --enable-src-tree-happy when configuring GHC. (b) Build & install Happy separately from CVS Cheers, Simon

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GC behaviour in GHC
by Nivia Q. 24 Feb '04

24 Feb '04

Hello, GHC users, I'm a Computational Engineering student in the University of Pernambuco (Brazil). In my research, I'm working with applications written in Haskell , where time is a critical factor. But there is a pretty high GC overhead I can't understand . Can someone indicate some paper or reference about the GC behaviour in GHC? Thanks, _________________________________________________ Nivia Cruz Quental Graduação em Eng. Computação - UPE Técnica em Telecomunicações - CEFET-PE - Brasil --------------------------------- Yahoo! Mail - O melhor e-mail do Brasil. Abra sua conta agora!

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