- Haskell-Cafe - Haskell.org

RE: UML diagrams of Haskell
by Hal Daume 30 Jun '03

30 Jun '03

There's something like UML, called FAD (Functional Analysis and Design, I believe). It was the topic of Daniel Russell's PhD thesis. See http://www.cs.kent.ac.uk/pubs/2001/1152/index.html for more. -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume > -----Original Message----- > From: haskell-cafe-admin(a)haskell.org > [mailto:haskell-cafe-admin@haskell.org] On Behalf Of Bas van Dijk > Sent: Sunday, June 29, 2003 2:50 PM > To: HaskellCafe Mailinglist > Subject: UML diagrams of Haskell > > > Hi, > > It's maybe a weird question but do there exist UML diagrams > of the Haskell > language. > They don't necessarily have to be UML diagrams, as long as > they show the > different concepts in the language (i.e.: functions, > datatypes, patterns, > etc.) and the relations between them(i.e.: a function > consists of other > functions, functions have a type). > > Bas. > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

1 0

RE: Simple monads
by Hal Daume 29 Jun '03

29 Jun '03

> (a) People could point out to me where I'm still confused, as > revealed by > my code. Is it needlessly complicated? looks pretty reasonable to me :) as to why Unique is in the IO monad is probabyl because if it were in any other monad, you could start the monad twice and thus get a repeat of each ID (if that makes sense). The only way around this is to put it in IO.

7 7

Bom dia haskell-cafe
by Marta 29 Jun '03

29 Jun '03

1 0

Template Haskell question
by Ashley Yakeley 28 Jun '03

28 Jun '03

Can anyone tell me what's wrong with this? -- ghc -fglasgow-exts -c TH.hs module TH where { import Language.Haskell.THSyntax; class HasZero a where { zero :: a; }; aninstance :: TypQ -> Q [Dec]; aninstance t = [d| instance HasZero $t where -- error here { zero = 0; }; |]; $(aninstance [t|Int|]) $(aninstance [t|Integer|]) } $ ghc -fglasgow-exts -c TH.hs TH.hs:14: Malformed context in instance header All I want to do is spin off a number instances for a number of types... -- Ashley Yakeley, Seattle WA

2 1

RE: haskell array access
by Hal Daume 27 Jun '03

27 Jun '03

> At best case for Haskell, 15.5 times slower. The thing about > bounds checking, > in Haskell it's always there. In C, you might have it, you > might not there is > no certainty by the language, only by design and > implementation. So with C, > one is free to live dangerously. If you're using GHC, there's Data.Array.Base.unsafeAt which is the one which doesn't do bounds checking.

1 0

RE: Help with ghci and Yet Another Haskell Tutorial
by Hal Daume 27 Jun '03

27 Jun '03

toUpper is in the Char (or Data.Char) library. You can do: Prelude> :m Data.Char Data.Char> map toUpper "hello world" or specify it completely. Prelude> map Data.Char.toUpper "hello world" I'll fix this reference in YAHT. I believe that Hugs automatically exports toUpper, which is why it was in there to begin with. - Hal -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume -----Original Message----- From: haskell-cafe-admin(a)haskell.org [mailto:haskell-cafe-admin@haskell.org] On Behalf Of Mark Espinoza Sent: Friday, June 27, 2003 7:53 AM To: haskell-cafe(a)haskell.org Subject: Help with ghci and Yet Another Haskell Tutorial Greetings, I am going through the Tutorial using ghc on a redhat 8.0 system. Everything works fine untill I get to the map function: Prelude> map toUpper "hello world" <interactive>:1: Variable not in scope: `toUpper' Prelude> Can anyone tel me what is or might be going on? Thanks. Sincerely, Mark Get your free e-mail address at http://felinemail.zzn.com ___________________________________________________________ Get your own Web-based E-mail Service at http://www.zzn.com _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

1 0

Help with ghci and Yet Another Haskell Tutorial
by Mark Espinoza 27 Jun '03

27 Jun '03

1 0

ELearnChina Conference 2003 - Only 4 Weeks To Go!
by Edwin Jones 27 Jun '03

27 Jun '03

Hey its me again! Ok, there are still a few places left at the best Elearning Event of the year. Please contact me directly for final discounted prices [yes, even lower now] Yours, Edwin Jones www.chinaconferences.net Sales China Conferences Tel +44 131 440 9881 Fax +44 131 440 9882 edwin(a)chinaconferences.net

1 0

RE: haskell array access
by Simon Peyton-Jones 27 Jun '03

27 Jun '03

Several comments 1. In Haskell "mod" is a lot more expensive than "rem", because it involves careful jiggery pokery with the sign of the result. That's why your boxed version was slower (nothing to do with boxing). 2. GHC does indeed optimise away the array access if you aren't careful, and does in Derek's code. Below is a version that avoids doing so, in the same way as the C version, by returning one of the values. 3. Derek correctly points out that gcc does not do array-bound checks. GHC should eliminate them, but it's a non-trivial analysis and GHC does not currently attempt it. You can always use unsafeAt, as Derek does. 4. The UArray stuff builds an array of unboxed Ints, like C. If you use ordinary boxed arrays, the loop has to unbox the Int every time around the loop, which makes it slower (2.6s) With that done, we get ghc -O2 -fliberate-case-threshold20 1.8s gcc -O2 1.4s Seems close enough to me; have not investigated further. The "liberate-case" thing is a practically-undocumented GHC optimisation that switches on with -O2. It specialises a loop that unboxes a free variable (here the array k) so that the unboxing doesn't happen each time round the loop. The threshold at which GHC thinks there is too much code dup is set very low by default, so the flag increases it. Simon ====================== k :: UArray Int Int k = array (0,15) [(i, i+1) | i <- [0 .. 15] ] acc :: Int -> Int -> Int acc r 0 = r acc r n = r `seq` acc (k `unsafeAt` (n `rem` 16)) (n - 1) main :: IO () main = print (acc 0 100000000) ====================== | Anyways, | int main(void){ | int i, k; | int a [16]; | for (i=0; i<=100000000; i++) { | k = a [i % 16]; | } | printf("%d\n",k); | return 0; | } | compiled with MinGW 3.2 -O/-O2/-O3 runs in 1.8s using time. | | int main(void){ | int i, k; | int a [16]; | for (i=0; i<=100000000; i++) { | k = a [i % 16]; | } | printf("%d\n",k); | return 0; | } | | The following (compiled with -O2 -fglasgow-exts and GHC 6.1 i.e. a CVS | version) beats the C version taking only .8s. They don't do the same | thing (the Haskell version "does" more, but prints something different). | Looking at the core/stg/c/asm (the asm and C was quite messy compared | with other times), it certainly doesn't appear to be optimizing this to | print 0, and it does appear (though I'm less sure here) to be doing | everything as it should, but it's really hard to read the assembly, | since we don't use the value we lookup I can easily see gcc dropping it | altogether, though the C GHC spits out is pretty unusual for gcc, so it | may not. | | module Main (main) where | import Data.Array.Unboxed (UArray, array) | import Data.Array.Base (unsafeAt) -- if C doesn't, why should we? | import GHC.Exts | | k :: UArray Int Int | k = array (0,15) [(i, i+1) | i <- [0 .. 15] ] | | acc :: Int# -> Int# | acc 0# = 0# | acc n = (k `unsafeAt` (I# (n `remInt#` 16#))) `seq` acc (n -# 1#) | | main :: IO () | main = print (I# (acc 100000000#)) | | However, I'm am somewhat surprised that I seemingly had to unbox by hand | to get quite close (in fact, better) than C. I expected the following | version to be comparable to the C version (and it is orders of magnitude | faster than the original version which was over 5min when I killed it | (though I think I compiled it with just -O), this version taking 14s). | | module Main (main) where | import Data.Array.Unboxed (UArray, array) | import Data.Array.Base (unsafeAt) -- if C doesn't, why should we? | | k :: UArray Int Int | k = array (0,15) [(i, i+1) | i <- [0 .. 15] ] | | acc :: Int -> Int | acc 0 = 0 | acc n = (k `unsafeAt` (n `mod` 16)) `seq` acc (n - 1) | | main :: IO () | main = print (acc 100000000) | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

2 1

RE: haskell array access
by Hal Daume 27 Jun '03

27 Jun '03

This has been hinted to before: gcc gets rid of the loop. bash-2.05b$ gcc -O3 arr.c -S -o arr.s bash-2.05b$ cat arr.s .file "arr.c" .def ___main; .scl 2; .type 32; .endef .text .align 2 .align 16 .globl _main .def _main; .scl 2; .type 32; .endef _main: pushl %ebp movl %esp, %ebp subl $72, %esp xorl %eax, %eax andl $-16, %esp call __alloca call ___main xorl %eax, %eax .align 16 L7: incl %eax cmpl $100000000, %eax jle L7 leave ret the inside of the loop is exactly: L7: incl %eax cmpl $100000000, %eax jle L7 which doesn't read the array! essentially you are being unfare to ghc by making it seq the array element, but not doing the same to GCC. even with -O0, gcc gets rid of the loop body. one solution: add in the assembly to actually read the array (i'm too lazy and busy to do this). - hal -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume > -----Original Message----- > From: haskell-cafe-admin(a)haskell.org > [mailto:haskell-cafe-admin@haskell.org] On Behalf Of Lex Stein > Sent: Thursday, June 26, 2003 3:46 PM > To: Sven Panne > Cc: haskell-cafe(a)haskell.org > Subject: Re: haskell array access > > > > Great, thanks. Those suggestions narrow the gap from GHC -O being 330x > slower than GCC -O3 to it being 20x slower. Here are the new results: > > gcc -O3 0.54s > ocamlopt 1.11s > ghc -O 10.76s > ocamlc 14.10s > > GHC is still pretty slow for native x86 instruction code. Is > there any way > to further explain the performance gap ? (new code below) > > Thanks! > Lex > > Haskell (GHC) source: > > import Array > k :: Array Int Int > k = Array.array (0,15) [(i, i+1) | i <- [0 .. 15] ] > acc :: Int -> Int > acc 0 = 0 > acc n = seq (k Array.! (n `mod` 16)) (acc (n-1)) > main = do > print (acc 100000000) > > Caml test source: > > let a = Array.make 16 0;; > let rec do1 i z = > if (i>100000000) then z else > do1 (i+1) (z + a.(i mod 16));; > do1 0 0;; > > C (gcc) test source: > > int main () { > int i, k = 0; > int a [16]; > for (i=0; i<100000000; i++) { > k += a [i % 16]; > } > return (k); > } > > > On Fri, 27 Jun 2003, Sven Panne wrote: > > > Well, part of the answer is definitely that the Haskell > program is the > > *only* one which really uses the array elements. :-) I > guess that the > > compilers for the other languages simply remove the array > access from > > the generated code (gcc definitely does, only an empty loop > remains). > > > > Another reason is that the type signatures are missing, so > Integer is > > used instead of Int, which is a bit unfair. Adding > > > > k :: Array Int Int > > acc :: Int -> Int > > > > cuts down the time by more than factor 5 on my machine. > > > > Cheers, > > S. > > > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

2 2