[Haskell-cafe] Re: ghc on Ubuntu Linux?
PS I have always installed ghc first via the Ubuntu package installer followed by a build from ghc 6.8.2 source! Vasili On Sat, May 17, 2008 at 12:01 AM, Galchin, Vasili [EMAIL PROTECTED] wrote: ghc-pkg list gives me [EMAIL PROTECTED]:~$ ghc-pkg list /usr/local/lib/ghc-6.8.2/package.conf: Cabal-1.2.3.0, GLUT-2.1.1.1, HUnit-1.2.0.0, OpenGL-2.2.1.1, QuickCheck-1.1.0.0, array-0.1.0.0, base-3.0.1.0, bytestring-0.9.0.1, cgi-3001.1.5.1, containers-0.1.0.1, directory-1.0.0.0, fgl-5.4.1.1, filepath-1.1.0.0, (ghc-6.8.2), haskell-src-1.0.1.1, haskell98-1.0.1.0, hpc-0.5.0.0, html-1.0.1.1, mtl-1.1.0.0, network-2.1.0.0, old-locale-1.0.0.0, old-time-1.0.0.0, packedstring-0.1.0.0, parallel-1.0.0.0, parsec-2.1.0.0, pretty-1.0.0.0, process-1.0.0.0, random-1.0.0.0, readline-1.0.1.0, regex-base-0.72.0.1, regex-compat-0.71.0.1, regex-posix-0.72.0.2, rts-1.0, stm-2.1.1.0, template-haskell-2.2.0.0, time-1.1.2.0, unix-2.3.0.0, xhtml-3000.0.2.1 I am using version ghc-6.8.2. V On Fri, May 16, 2008 at 11:51 PM, Galchin, Vasili [EMAIL PROTECTED] wrote: Hello, I am running ghc and tools on Ubuntu. I seem to be running into very strange problems between ghc-pkg and the Ubuntu package manager. Suddenly runhaskell Setup.hs configure just stops working ... Are any other ghc/Ubuntu users running into problems? If so, please tell me what problems. This is killing my Haskell work! Regards, Vasili ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Short circuiting and the Maybe monad
On Sat, May 17, 2008 at 1:24 AM, Kim-Ee Yeoh [EMAIL PROTECTED] wrote:
Dan Piponi-2 wrote:
In fact, you can use the Reader monad as a fixed size container monad.
Interesting that you say that. Reader seems to me more as an anti-container
monad.
You just have to think of the environment as an address into an
implicit structure. For example, Bool - a is isomorphic to (a,a).
Thus,
data Diag a = D { p1 :: a, p2 :: a }
to :: Diag a - (Bool - a)
to (D a b) p = if p then a else b
from :: (Bool - a) - Diag a
from f = D (f True) (f False)
Some transformations applied to the monad instance for ((-) Bool) gets you:
instance Monad Diag where
return x = D x x
D a b = f = D (p1 (f a), p2 (f b))
This works for any enumeration.
Here's a more complex example,
data Stream a = a : Stream a
type Nat = Integer
-- we'll pretend this can't ever be negative
to :: Stream a - (Nat - a)
to (a : as) 0 = a
to (a : as) n = to as n
from :: (Nat - a) - Stream a
from f = go 0 where go n = f n : go (n + 1)
shead (a : as) = a
stail (a : as) = as
instance Monad Stream where
return x = x : return x
(a : as) = f = shead (f a) : (as = stail . f)
Assuming I haven't mistyped anything,
to (m = f) n = to (f (to m n)) n
--
Dave Menendez [EMAIL PROTECTED]
http://www.eyrie.org/~zednenem/
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Re: [Haskell-cafe] Re: Write Haskell as fast as C.
Don Stewart [EMAIL PROTECTED] writes: mkAnn :: ByteString - Annotation mkAnn = pick . B.words where pick (_db:up:rest) = pick' up $ getGo rest pick' up' (go:_:ev:_) = Ann (B.copy up') (read $ B.unpack go) (read $ B.unpack ev) getGo = dropWhile (not . B.isPrefixOf (pack GO:)) read $ B.unpack go Looks suspicious. You're unpacking to lists. ByteString performance rule 1: don't unpack to lists. I tend to use this idiom a bit when I want to loop over the characters. The strings being unpacked is an Int and a short (two or three letter) identifier. Doing a 'go' loop would probably be faster, but a lot more work, and I was hoping the String would be deforested or fused or otherwise optimized to the bone. I wonder if the culprit is the last 'read', it reads one from a set of keywords/identifiers, and since they're upper case, I just made a data type with a matching set of nullary constructors, and derived Read for it. I.e: data EvidenceCode = IAC | IUG | IFR | NAC | NR | ... deriving Show Could it be that this derived read instance is somehow very inefficient? -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Couple of formal questions
Creighton Hogg wchogg at gmail.com writes: Where could I find a proof that the initial algebras final coalgebras of CPO coincide? I saw this referenced in the Bananas.. paper as a fact, but am not sure where this comes from Creighton, As promised and I hope this is what you were after. Dominic. http://idontgetoutmuch.wordpress.com/2008/05/12/isomorphic-types/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: ghc on Ubuntu Linux?
Vasili, I have pretty much exactly the same set up as you seem to have. I haven't had a single problem with running configure using cabal. In what sense does it stop working? Cheers, Josef 2008/5/17 Galchin, Vasili [EMAIL PROTECTED]: PS I have always installed ghc first via the Ubuntu package installer followed by a build from ghc 6.8.2 source! Vasili On Sat, May 17, 2008 at 12:01 AM, Galchin, Vasili [EMAIL PROTECTED] wrote: ghc-pkg list gives me [EMAIL PROTECTED]:~$ ghc-pkg list /usr/local/lib/ghc-6.8.2/package.conf: Cabal-1.2.3.0, GLUT-2.1.1.1, HUnit-1.2.0.0, OpenGL-2.2.1.1, QuickCheck-1.1.0.0, array-0.1.0.0, base-3.0.1.0, bytestring-0.9.0.1, cgi-3001.1.5.1, containers-0.1.0.1, directory-1.0.0.0, fgl-5.4.1.1, filepath-1.1.0.0, (ghc-6.8.2), haskell-src-1.0.1.1, haskell98-1.0.1.0, hpc-0.5.0.0, html-1.0.1.1, mtl-1.1.0.0, network-2.1.0.0, old-locale-1.0.0.0, old-time-1.0.0.0, packedstring-0.1.0.0, parallel-1.0.0.0, parsec-2.1.0.0, pretty-1.0.0.0, process-1.0.0.0, random-1.0.0.0, readline-1.0.1.0, regex-base-0.72.0.1, regex-compat-0.71.0.1, regex-posix-0.72.0.2, rts-1.0, stm-2.1.1.0, template-haskell-2.2.0.0, time-1.1.2.0, unix-2.3.0.0, xhtml-3000.0.2.1 I am using version ghc-6.8.2. V On Fri, May 16, 2008 at 11:51 PM, Galchin, Vasili [EMAIL PROTECTED] wrote: Hello, I am running ghc and tools on Ubuntu. I seem to be running into very strange problems between ghc-pkg and the Ubuntu package manager. Suddenly runhaskell Setup.hs configure just stops working ... Are any other ghc/Ubuntu users running into problems? If so, please tell me what problems. This is killing my Haskell work! Regards, Vasili ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: ghc on Ubuntu Linux?
Josef, Did you consistently only use the Ubuntu package manager to install and upgrade all ghc tools including the compiler, cabal?Or did you ever build the ghc compiler from source on your system on top of a Ubuntu package installed ghc like I did? Vasili On Sat, May 17, 2008 at 5:01 AM, Josef Svenningsson [EMAIL PROTECTED] wrote: Vasili, I have pretty much exactly the same set up as you seem to have. I haven't had a single problem with running configure using cabal. In what sense does it stop working? Cheers, Josef 2008/5/17 Galchin, Vasili [EMAIL PROTECTED]: PS I have always installed ghc first via the Ubuntu package installer followed by a build from ghc 6.8.2 source! Vasili On Sat, May 17, 2008 at 12:01 AM, Galchin, Vasili [EMAIL PROTECTED] wrote: ghc-pkg list gives me [EMAIL PROTECTED]:~$ ghc-pkg list /usr/local/lib/ghc-6.8.2/package.conf: Cabal-1.2.3.0, GLUT-2.1.1.1, HUnit-1.2.0.0, OpenGL-2.2.1.1, QuickCheck-1.1.0.0, array-0.1.0.0, base-3.0.1.0, bytestring-0.9.0.1, cgi-3001.1.5.1, containers-0.1.0.1, directory-1.0.0.0, fgl-5.4.1.1, filepath-1.1.0.0, (ghc-6.8.2), haskell-src-1.0.1.1, haskell98-1.0.1.0, hpc-0.5.0.0, html-1.0.1.1, mtl-1.1.0.0, network-2.1.0.0, old-locale-1.0.0.0, old-time-1.0.0.0, packedstring-0.1.0.0, parallel-1.0.0.0, parsec-2.1.0.0, pretty-1.0.0.0, process-1.0.0.0, random-1.0.0.0, readline-1.0.1.0, regex-base-0.72.0.1, regex-compat-0.71.0.1, regex-posix-0.72.0.2, rts-1.0, stm-2.1.1.0, template-haskell-2.2.0.0, time-1.1.2.0, unix-2.3.0.0, xhtml-3000.0.2.1 I am using version ghc-6.8.2. V On Fri, May 16, 2008 at 11:51 PM, Galchin, Vasili [EMAIL PROTECTED] wrote: Hello, I am running ghc and tools on Ubuntu. I seem to be running into very strange problems between ghc-pkg and the Ubuntu package manager. Suddenly runhaskell Setup.hs configure just stops working ... Are any other ghc/Ubuntu users running into problems? If so, please tell me what problems. This is killing my Haskell work! Regards, Vasili ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ghc on Ubuntu Linux?
Galchin, Vasili [EMAIL PROTECTED] wrote: Did you consistently only use the Ubuntu package manager to install and upgrade all ghc tools including the compiler, cabal?Or did you ever build the ghc compiler from source on your system on top of a Ubuntu package installed ghc like I did? On Sat, May 17, 2008 at 5:01 AM, Josef Svenningsson [EMAIL PROTECTED] wrote: I have pretty much exactly the same set up as you seem to have. I haven't had a single problem with running configure using cabal. In what sense does it stop working? SCNR, who is asking questions here? btw: please stop that TOFU A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] A point in favour of -XOverlappingInstances (and -XTypeSynonymInstances)
Token.hs:103:15: Overlapping instances for Show (SourcePos, Tok) arising from a use of `anyToken' at Token.hs:103:15-22 Matching instances: instance (Show a, Show b) = Show (a, b) -- Defined in GHC.Show instance [overlap ok] Show Token -- Defined at Token.hs:(39,0)-(40,23) I was just trying _not_ to show the a of (a,b) -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Performance: MD5
Hi folks. OK, try this: darcs get http://darcs.orphi.me.uk/MyMD5 cd MyMD5 ghc -O2 --make md5sum md5sum some large filename On my PC, it takes 3.5 seconds to compute the MD5 hash of a 10 MB file. For comparison, the md5.exe I downloaded from the Internet does it instantaneously. It's literally so fast I can't even time it. As far as I know, my program always produces the *correct* answer, it just takes far too long to do it. If anybody has any interesting insights as to why my version is so damned slow, I'd like to hear them. (Indeed, a description of the process for tracking the problem down would also be useful!) [Much to my bemusement, when I had a look at the code, I discovered that tucked away in a corner somewhere, it reads a ByteString from disk and instantly converts it to [Word8]. Uh... oops? Anyway, eliminating this changed the numbers I get from the profiler, but it's still far too slow.] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Performance: MD5
Hello Andrew, Saturday, May 17, 2008, 6:51:27 PM, you wrote: If anybody has any interesting insights as to why my version is so damned slow, I'd like to hear them. i equally will be interesting to hear why you think what your program should be as fast as C version? you wrote it in purely functional style. as Don wrote, if you want to reach unoptimized C-like performance, you need to write in C style - with explicit loop processing primitive types. so 1) -funbox-strict-fields 2) don't use tuples as arguments - they are lazy. you may implement strict tuples instead 3) function as a parameter is very bad unless it will be inlined but these are only half-decisions. if you need maximum efficiency, drop all this high-level code and map md5.c to haskell as it was done in Don's bloag -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Performance: MD5
Andrew, I spent a reasonable amount of time making pureMD5 (available on hackage) faster, which mainly ment strictness annoitations and unboxing strict fields, but I also spent a good deal of time with the profiler. One of my early versions was fairly slow due to the converting of the LPS to blocks (an Isabelle proven 'blocks' function) caused O(n) space requirement. I've been meaning to revisit this to optimize more and look closly at GHC core. I'm on vacation now, but when I get back I'll try to make time to look at your code (unless its moot by then). Finally, I encourage anyone interested to make reasonably fast bytestring implementations of SHA algorithms as well - Haskell/Hackage has a number of pure and FFI implementations of MD5 but is a bit lacking in any other cryptographic algorithm. TomMD On Sat, 2008-05-17 at 15:51 +0100, Andrew Coppin wrote: Hi folks. OK, try this: darcs get http://darcs.orphi.me.uk/MyMD5 cd MyMD5 ghc -O2 --make md5sum md5sum some large filename On my PC, it takes 3.5 seconds to compute the MD5 hash of a 10 MB file. For comparison, the md5.exe I downloaded from the Internet does it instantaneously. It's literally so fast I can't even time it. As far as I know, my program always produces the *correct* answer, it just takes far too long to do it. If anybody has any interesting insights as to why my version is so damned slow, I'd like to hear them. (Indeed, a description of the process for tracking the problem down would also be useful!) [Much to my bemusement, when I had a look at the code, I discovered that tucked away in a corner somewhere, it reads a ByteString from disk and instantly converts it to [Word8]. Uh... oops? Anyway, eliminating this changed the numbers I get from the profiler, but it's still far too slow.] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A point in favour of -XOverlappingInstances (and -XTypeSynonymInstances)
On Sat, 2008-05-17 at 15:12 +0200, Achim Schneider wrote: Token.hs:103:15: Overlapping instances for Show (SourcePos, Tok) arising from a use of `anyToken' at Token.hs:103:15-22 Matching instances: instance (Show a, Show b) = Show (a, b) -- Defined in GHC.Show instance [overlap ok] Show Token -- Defined at Token.hs:(39,0)-(40,23) I was just trying _not_ to show the a of (a,b) A point in favour of newtypes newtype Token = Token (SourcePos, Tok) instance Show Token where ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] another Newbie performance question
Hi everybody, I was doing an assignment in Java for my university concerning a program that reads, modifies and writes CSV files, when I suddenly had the idea of implementing parts of this in Haskell for fun. When I finished the Haskell programm, I was disappointed by the performance: To parse a 200k lines CSV file, insert a line (yes I know i could insert a line without parsing the file, that's just an example) at pos. 19 and write the file again, the Java program takes 1.1 seconds while the Haskell program takes 12.5 seconds. I have read Don's blog post but am unsure how to implement his tips into my program, as I am still kind of a Haskell beginner. The source code (40 lines incl. comments and empty lines) and the 200k CSV file I used for testing and a smaller CSV file demonstrating the special easy-to-parse CSV syntax are available on my ftp server, ftp://baah.servegame.org/public/haskell The call syntax is program csv file line to insert e.g. main lang.csv test,this,line I haven't posted the source code here directly because I thought it might be too long. If someone here finds the time to look at my code and give me some hints, that would really be nice. Regards Philip ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Another optimization question
Jeroen, isPrime :: Int - Bool isPrime x = isPrime' x primes where isPrime' x (p:ps) | x == p = True | x p = isPrime' x ps | otherwise = False main = print $ length (filter (== True) (map isPrime [1..5000])) [...] isPrime x = elem x (takeWhile (= x) primes) Here's a couple of things, although I don't know if they account for what you're seeing. All code is untested. 1) A simpler main would be: main = print $ length $ filter isPrime [1..5000] This version manually fuses your map and filter. Of course it's not the same if you're doing anything else besides 'length'. 2) The takeWhile in your second isPrime creates a throwaway list, which doesn't exist in the explicit-recursion isPrime. Unless this gets optimized out, this could be the droid you're looking for. I'd compile with profiling (ghc -O2 --make -prof -auto-all experiment2), and run ./experiment2 +RTS -p -s Find profiling stats in experiment2.prof, and check whether the latter version isn't allocating a lot more. When you feel like Core-diving, it's something specific to look for. 3) Maybe you can get the best of your two versions -- meaning the relative speed of the first and functional style of the second -- by writing your own 'elem' replacement that works on a sorted list. Something like this, with suitably defined elemAsc: -- elemAsc: tests presence of element in an ascending list elemAsc :: (Ord a) = a - [a] - Bool elemAsc ... isPrime x = elemAsc x primes Here's a good habit: abstract things like this out. Read the libraries, and look for better and more abstract patterns. Rinse, repeat. 4) This doesn't explain why the version with real primes was 10x slower. Are you comparing apples to apples? Specifically, comparing both versions of isPrime above using real primes, so both of them have to create the primes list? Does your code for real primes still use [Int] and not [Integer] or (Num t) = [t] ? I haven't invested the time yet to stare at GHC Core until it clicks, excepting a few snippets that have been discussed here. I'm not sure how early in the learning curve it's advisable. Probably depends on your background. Good luck Eulering, John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Another optimization question
On Sat, May 17, 2008 at 8:19 PM, Jeroen [EMAIL PROTECTED] wrote: Hi, I know there's been quite some performance/optimization post lately, so I hope there still room for one more. While solving a ProjectEuler problem (27), I saw a performance issue I cannot explain. I narrowed it down to the following code (never mind that 'primes' is just [1..], the problem is the same or worse with real primes): primes :: [Int] primes = [1..] isPrime :: Int - Bool isPrime x = isPrime' x primes where isPrime' x (p:ps) | x == p = True | x p = isPrime' x ps | otherwise = False main = print $ length (filter (== True) (map isPrime [1..5000])) $ time ./experiment1 5000 real0m4.037s user0m3.378s sys 0m0.060s All good, but if I change isPrime to the simpeler isPrime x = elem x (takeWhile (= x) primes) it takes twice as long: time ./experiment2 5000 real0m7.837s user0m6.532s sys 0m0.141s With real primes, it even takes 10 times as long. I tried looking at the output of ghc -ddump-simpl, as suggested in a previous post, but it's a bit over my head (newby here...). Any suggestions? Just a thought: in your first approach you compare any element of the list once. In second---twice: once to check if = x and second time to check if it is equal to x. That's a hypothesis, but another implementation of isPrime: isPrime x = (== x) $ head $ dropWhile ( x) primes seems to behave closer to your first version than to the second. Note that that does unnecessary comparison as well the find first element = x. yours, anton. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: another Newbie performance question
Philip Müller [EMAIL PROTECTED] wrote: I have read Don's blog post but am unsure how to implement his tips into my program, as I am still kind of a Haskell beginner. Dan, you seem to have opened a big can of worms. If Haskell is successful, it's your fault. Without doing any compiling, staring at core nor profiling myself, I advice that you 1) traverse the list less often. 2) use ByteStrings 3) use an intermediate data structure that has better insert behaviour than a standard list, have a look at Data.Sequence 4) really, really use ByteStrings 5) listen to me if I tell you to use ByteStrings 6) if you already must write in pointless style, please don't also order the functions in a backward way. -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Another optimization question
Am Samstag, 17. Mai 2008 19:52 schrieb anton muhin: On Sat, May 17, 2008 at 8:19 PM, Jeroen [EMAIL PROTECTED] wrote: Hi, I know there's been quite some performance/optimization post lately, so I hope there still room for one more. While solving a ProjectEuler problem (27), I saw a performance issue I cannot explain. I narrowed it down to the following code (never mind that 'primes' is just [1..], the problem is the same or worse with real primes): primes :: [Int] primes = [1..] isPrime :: Int - Bool isPrime x = isPrime' x primes where isPrime' x (p:ps) | x == p = True | x p = isPrime' x ps | otherwise = False main = print $ length (filter (== True) (map isPrime [1..5000])) $ time ./experiment1 5000 real0m4.037s user0m3.378s sys 0m0.060s All good, but if I change isPrime to the simpeler isPrime x = elem x (takeWhile (= x) primes) it takes twice as long: time ./experiment2 5000 real0m7.837s user0m6.532s sys 0m0.141s With real primes, it even takes 10 times as long. I tried looking at the output of ghc -ddump-simpl, as suggested in a previous post, but it's a bit over my head (newby here...). Any suggestions? Just a thought: in your first approach you compare any element of the list once. In second---twice: once to check if = x and second time to check if it is equal to x. That's a hypothesis, I thought so, too, but I couldn't reproduce the behaviour, so I'm not sure what happens. In fact, compiling without optimisations, the first version takes almost twice as long as the second. Compiled with -O2, the second takes about 13% more time. Using a real list of primes, [EMAIL PROTECTED]:~/EulerProblems/Testing ghc --make experiment -o experiment3 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment3 ... [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment3 669 real0m0.222s user0m0.220s sys 0m0.000s [EMAIL PROTECTED]:~/EulerProblems/Testing ghc --make experiment -o experiment4 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment4 ... [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment4 669 real0m0.299s user0m0.290s sys 0m0.000s But [EMAIL PROTECTED]:~/EulerProblems/Testing ghc -O2 --make experiment -o experiment3 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment3 ... [EMAIL PROTECTED]:~/EulerProblems/Testing ghc -O2 --make experiment -o experiment4 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment4 ... [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment3 669 real0m0.053s user0m0.040s sys 0m0.010s [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment4 669 real0m0.257s user0m0.250s sys 0m0.010s Wow! I've no idea what optimising did to the first version, but apparently it couldn't do much for the second. but another implementation of isPrime: isPrime x = (== x) $ head $ dropWhile ( x) primes With -O2, this is about 20% slower than the Jeroen's first version, without optimisations 50% faster. Strange. isPrime :: Int - Bool isPrime x = go primes where go (p:ps) = case compare x p of LT - False EQ - True GT - go ps does best (on my box), with and without optimisations (very very slightly with -O2) for a list of real primes, but not for [1 .. ]. However, more than can be squished out of fiddling with these versions could be gained from a better algorithm. seems to behave closer to your first version than to the second. Note that that does unnecessary comparison as well the find first element = x. yours, anton. perplexed, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Write Haskell as fast as C.
Andrew Coppin [EMAIL PROTECTED] writes: Look closer: it's hardER to read. mean xs = sum xs / fromIntegral (length xs) mean = go 0 0 n where go s l x | x m = s / fromIntegra l | otherwise = go (s+x) (l+1) (x+1 One version makes it instantly clear, at a glance, what is happening. The other requires you to mentally walk round a look, imperative style, to figure out what's happening. It's not a *big* deal, but it's unfortunate. I am new to Haskell and when I first saw the two versions side by side I too was disappointed with the second version. But after reading the great blog post by Don, I realized that the whole problem comes from the fact that lists in Haskell are not like arrays or vectors in other languages: you don't know how long they are before you have found the end. In other words: they behave like a linked lists -- lists that are generated lazily on demand. Because they are generated on demand you *cannot* really know the length beforehand, and thus you *must* traverse the list to its end to count the length. When the list is too big to fit in memory then it's clear that the code *must* let go of the beginning to allow the garbage collector to do its job. You wouldn't be able to work with a 7.5 GiB linked list otherwise. -- Martin Geisler VIFF (Virtual Ideal Functionality Framework) brings easy and efficient SMPC (Secure Multi-Party Computation) to Python. See: http://viff.dk/. pgpgElb902o1M.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell-Cafe Info Page
Hello, Common Lisp is a multiparadigm, general purpose programming language that supports imperative, functional, and object-oriented programming paradigms. Haskell is purely functional. Is this a reason why there is not macro feature in Haskell? I feel the object-oriented paradigm of CL and Scheme is the reason for the macro feature in these two languages. If it's not, then what does the macro feature provide, and why isn't it in Haskell? Douglas___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell-Cafe Info Page
On 2008 May 17, at 14:52, D. Gregor wrote: Common Lisp is a multiparadigm, general purpose programming language that supports imperative, functional, and object-oriented programming paradigms. Haskell is purely functional. Is this a reason why there is not macro feature in Haskell? I feel the object- oriented paradigm of CL and Scheme is the reason for the macro feature in these two languages. If it's not, then what does the macro feature provide, and why isn't it in Haskell? Macros in Lisp have less to do with functional vs. non-functional than with programs and data having precisely the same form (s-expressions). There is a macro facility of the kind you're thinking of in Haskell (Template Haskell), but you have to work with abstract syntax tables which look nothing like the original code. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell-Cafe Info Page
allbery: On 2008 May 17, at 14:52, D. Gregor wrote: Common Lisp is a multiparadigm, general purpose programming language that supports imperative, functional, and object-oriented programming paradigms. Haskell is purely functional. Is this a reason why there is not macro feature in Haskell? I feel the object-oriented paradigm of CL and Scheme is the reason for the macro feature in these two languages. If it's not, then what does the macro feature provide, and why isn't it in Haskell? Macros in Lisp have less to do with functional vs. non-functional than with programs and data having precisely the same form (s-expressions). There is a macro facility of the kind you're thinking of in Haskell (Template Haskell), but you have to work with abstract syntax tables which look nothing like the original code. Also, laziness is used for many of the coding jobs you might use macros for. So there's less need for macros. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell-Cafe Info Page
On Sat, May 17, 2008 at 3:16 PM, Don Stewart [EMAIL PROTECTED] wrote: allbery: On 2008 May 17, at 14:52, D. Gregor wrote: Common Lisp is a multiparadigm, general purpose programming language that supports imperative, functional, and object-oriented programming paradigms. Haskell is purely functional. Is this a reason why there is not macro feature in Haskell? I feel the object-oriented paradigm of CL and Scheme is the reason for the macro feature in these two languages. If it's not, then what does the macro feature provide, and why isn't it in Haskell? Macros in Lisp have less to do with functional vs. non-functional than with programs and data having precisely the same form (s-expressions). There is a macro facility of the kind you're thinking of in Haskell (Template Haskell), but you have to work with abstract syntax tables which look nothing like the original code. Also, laziness is used for many of the coding jobs you might use macros for. So there's less need for macros. Precisely so. For example, macros are often used to implement control operators (e.g. specific kinds of complicated iteration), which is easily done in haskell with normal functions, due to laziness. -- Denis ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Mapping Haskell Concepts To C# 3
I have question on mapping some Haskell concepts to C# 3 ones. Maybe there are not any strict equivalents; yet it helps: 1 - What is the equivalent of Type Constructor in C#? 2 - What is the equivalent of Data Constructor in C#? 3 - What is the logical implementation of pattern matching in C#? (For example using structures with indicator fields or using interfaces and inheritance and dynamically dispatch in calling overloaded methods. Also this question contain a hidden one...GADTs!) Best Regards -- Kaveh Shahbazian email: [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mapping Haskell Concepts To C# 3
2008/5/17 Kaveh Shahbazian [EMAIL PROTECTED]: I have question on mapping some Haskell concepts to C# 3 ones. Maybe there are not any strict equivalents; yet it helps: 1 - What is the equivalent of Type Constructor in C#? Class declaration. Generic ones. E.g. Listint, is a type where the type constructor List has been applied to the type int. 2 - What is the equivalent of Data Constructor in C#? Constructors, I guess. 3 - What is the logical implementation of pattern matching in C#? (For example using structures with indicator fields or using interfaces and inheritance and dynamically dispatch in calling overloaded methods. Also this question contain a hidden one...GADTs!) You can use an abstract base class, and then inherit one class for each constructor (e.g. base class Expression, and concrete subclasses Mul, Add, etc.). Then you can use runtime type reflection to figure out which kind of Expression you have and branch on it. -- Sebastian Sylvan +44(0)7857-300802 UIN: 44640862 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Calling haddock in a portable way
hello, the new version of haddock (2.0.0) needs a new option -B that tells it the GHC lib directory. How do I find out the correct value for this option in a makefile, so that the makefile stays portable? Cheers, Misha ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Next Bay FP Meeting: Bryan O'Sullivan on Concurrent and multicore programming in Haskell
On 5/2/08 8:50 PM, Vimal wrote: On 03/05/2008, Keith Fahlgren [EMAIL PROTECTED] wrote: Hi, Our next BayFP meeting will be this Thursday, May 8th, 2008 at 7:30pm. We'll feature Bryan O'Sullivan on Concurrent and multicore programming in Haskell. Bryan is a co-author of the upcoming O'Reilly book Real Cant wait for the video! How long before the video comes up on the website? The video is now available: http://www.bayfp.org/blog/2008/05/17/video-and-slides-from-bryan-o%e2%80%99sullivans-talk/ HTH, Keith ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Another optimization question
On Sat, May 17, 2008 at 10:40 PM, Daniel Fischer [EMAIL PROTECTED] wrote: Am Samstag, 17. Mai 2008 19:52 schrieb anton muhin: On Sat, May 17, 2008 at 8:19 PM, Jeroen [EMAIL PROTECTED] wrote: Hi, I know there's been quite some performance/optimization post lately, so I hope there still room for one more. While solving a ProjectEuler problem (27), I saw a performance issue I cannot explain. I narrowed it down to the following code (never mind that 'primes' is just [1..], the problem is the same or worse with real primes): primes :: [Int] primes = [1..] isPrime :: Int - Bool isPrime x = isPrime' x primes where isPrime' x (p:ps) | x == p = True | x p = isPrime' x ps | otherwise = False main = print $ length (filter (== True) (map isPrime [1..5000])) $ time ./experiment1 5000 real0m4.037s user0m3.378s sys 0m0.060s All good, but if I change isPrime to the simpeler isPrime x = elem x (takeWhile (= x) primes) it takes twice as long: time ./experiment2 5000 real0m7.837s user0m6.532s sys 0m0.141s With real primes, it even takes 10 times as long. I tried looking at the output of ghc -ddump-simpl, as suggested in a previous post, but it's a bit over my head (newby here...). Any suggestions? Just a thought: in your first approach you compare any element of the list once. In second---twice: once to check if = x and second time to check if it is equal to x. That's a hypothesis, I thought so, too, but I couldn't reproduce the behaviour, so I'm not sure what happens. In fact, compiling without optimisations, the first version takes almost twice as long as the second. Compiled with -O2, the second takes about 13% more time. Why not -O3? Using a real list of primes, What's the size of the real list? [EMAIL PROTECTED]:~/EulerProblems/Testing ghc --make experiment -o expleriment3 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment3 ... [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment3 669 real0m0.222s user0m0.220s sys 0m0.000s [EMAIL PROTECTED]:~/EulerProblems/Testing ghc --make experiment -o experiment4 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment4 ... [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment4 669 real0m0.299s user0m0.290s sys 0m0.000s But [EMAIL PROTECTED]:~/EulerProblems/Testing ghc -O2 --make experiment -o experiment3 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment3 ... [EMAIL PROTECTED]:~/EulerProblems/Testing ghc -O2 --make experiment -o experiment4 [1 of 1] Compiling Main ( experiment.hs, experiment.o ) Linking experiment4 ... [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment3 669 real0m0.053s user0m0.040s sys 0m0.010s [EMAIL PROTECTED]:~/EulerProblems/Testing time ./experiment4 669 real0m0.257s user0m0.250s sys 0m0.010s Wow! I've no idea what optimising did to the first version, but apparently it couldn't do much for the second. but another implementation of isPrime: isPrime x = (== x) $ head $ dropWhile ( x) primes With -O2, this is about 20% slower than the Jeroen's first version, without optimisations 50% faster. Strange. Well, head has its overhead as well. Cf. two variants: firstNotLess :: Int - [Int] - Int firstNotLess s (x:xs) = if x s then firstNotLess s xs else x dropLess :: Int - [Int] - [Int] dropLess s l@(x:xs) = if x s then dropLess s xs else l isPrime :: Int - Bool isPrime x = x == (firstNotLess x primes) isPrime' :: Int - Bool isPrime' x = x == (head $ dropLess x primes) On my box firstNotLess gives numbers pretty close (if not better) than Jeroen's first variant, while head $ dropLess notably worse. isPrime :: Int - Bool isPrime x = go primes where go (p:ps) = case compare x p of LT - False EQ - True GT - go ps does best (on my box), with and without optimisations (very very slightly with -O2) for a list of real primes, but not for [1 .. ]. And what happens for [1..]? However, more than can be squished out of fiddling with these versions could be gained from a better algorithm. Definitely. yours, anton. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Another optimization question
On 2008 May 17, at 16:48, anton muhin wrote: Why not -O3? -O3 doesn't do anything over -O2 in ghc. -fvia-c -optc-O3 *might* be an improvement, or might not. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Calling haddock in a portable way
On 2008.05.17 21:54:53 +0200, Misha Aizatulin [EMAIL PROTECTED] scribbled 0.2K characters: hello, the new version of haddock (2.0.0) needs a new option -B that tells it the GHC lib directory. How do I find out the correct value for this option in a makefile, so that the makefile stays portable? Cheers, Misha Maybe you could do something like call out to a shell and ask it to run 'ghc --print-libdir'? That for me prints to stdout a string like '/usr/lib64/ghc-6.8.2'. -- gwern Rivera Peering Intiso SAMF facsimile Submarine redheads AHPCRC DJC Sears pgpPgoYydlwye.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] another Newbie performance question
On Sat, May 17, 2008 at 5:22 PM, Philip Müller
[EMAIL PROTECTED] wrote:
If someone here finds the time to look at my code and give me some hints,
that would really be nice.
A little experimentation reveals that your main bottleneck is readCSVLine:
readCSVLine = read . (\x - [ ++ x ++ ])
(I just replaced it with (:[]) and it sped up enormously)
Thus, I rewrote it myself instead of with read.
readCSVLine = unfoldr builder
where
builder [] = Nothing
builder xs = Just $ readField xs
readField [] = ([],[])
readField (',':xs) = ([],xs)
readField ('':xs) =
let (l,'':r) = span (/= '') xs
(field,rest) = readField r
And decreased the runtime from 17 seconds to 4.2. It probably admits
an even better implementation, but it's likely that this is not the
bottleneck anymore.
The other thing is that the whole table is stored in memory because of
your call to length csv in doInteraction. This may have been the
intent. But if not, you can cut another 1 second off the runtime by
streaming the file using a function that lazily inserts the line in
the second-to-last position.
insertLine line csv = let (l,r) =
splitLast csv in l ++ [readCSVLine line] ++ r
where
splitLast [x]= ([],[x])
splitLast (x:xs) = let (l,r) = splitLast xs in (x:l,r)
(Note that I got rid of the pos parameter)
Presumably in a real application you are scanning until you see
something and then inserting near that, which is a lazy streamlike
operation.
There are probably a few other tricks you could do, but I think I
identified the main factors.
Luke
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Re: [Haskell-cafe] Calling haddock in a portable way
Maybe you could do something like call out to a shell and ask it to run 'ghc --print-libdir'? That for me prints to stdout a string like '/usr/lib64/ghc-6.8.2'. Yes, this looks like a solution. Thanks a lot! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Another optimization question
Am Samstag, 17. Mai 2008 22:48 schrieb anton muhin: Why not -O3? As far as I know - and Brandon S.Allbery said so, too - -O3 isn't better than -O2. Using a real list of primes, What's the size of the real list? arbitrary, however, since it's [Int], it will actually be at most 105097565 primes long, but since only numbers up to 5000 are checked, only 670 primes will ever be considered - When I check numbers 1 to 5 (5133 primes, so 5134 primes evaluated), with -O0 / -O2, it's Jeroen 1 : 14.5 s / 2.4 s Jeroen 2 : 52.5 s / 49.7 s (== x) . head . dropWhile ( x) : 8.2 s /4.1 s go primes : 5.5 s / 2.5 s So Jeroen 1 is the best to be optimised :) but another implementation of isPrime: isPrime x = (== x) $ head $ dropWhile ( x) primes With -O2, this is about 20% slower than the Jeroen's first version, without optimisations 50% faster. Strange. Well, head has its overhead as well. Cf. two variants: firstNotLess :: Int - [Int] - Int firstNotLess s (x:xs) = if x s then firstNotLess s xs else x dropLess :: Int - [Int] - [Int] dropLess s l@(x:xs) = if x s then dropLess s xs else l isPrime :: Int - Bool isPrime x = x == (firstNotLess x primes) isPrime' :: Int - Bool isPrime' x = x == (head $ dropLess x primes) On my box firstNotLess gives numbers pretty close (if not better) than for primes up to 5, that's 6.8 s / 2.1 s with -O0 / -O2 respectively on mine Jeroen's first variant, while head $ dropLess notably worse. 5.8 s / 2.4 s here. isPrime :: Int - Bool isPrime x = go primes where go (p:ps) = case compare x p of LT - False EQ - True GT - go ps does best (on my box), with and without optimisations (very very slightly with -O2) for a list of real primes, but not for [1 .. ]. And what happens for [1..]? With -O2, Jeroen 1 was best (1.62), nex firstNotLess (1.63), head . dropLess (1.74), then in close succesion Jeroen 2 (1.92), go primes (1.96) and head . dropWhile (1.99), with -O0, it's head . dropWhile (1.7 s, YES, that actually is faster with -O0 than with -O2!), head . dropLess (2.0), Jeroen 2 and firstNotLess (2.1 s), go primes (2.3 s), Jeroen 1 (3.2 s). Weirder and weirder. However, more than can be squished out of fiddling with these versions could be gained from a better algorithm. Definitely. yours, anton. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: ghc on Ubuntu Linux?
Hi Josef, What generates dist/setup-config? When I run runhaskell Setup.hs configure, nothing including dist/setup.config gets generated. ?? Regards, Vasili On Sat, May 17, 2008 at 11:02 AM, Josef Svenningsson [EMAIL PROTECTED] wrote: On Sat, May 17, 2008 at 1:00 PM, Galchin, Vasili [EMAIL PROTECTED] wrote: Josef, E.g. [EMAIL PROTECTED]:~/FTP/Haskell/unix-2.2.0.0$ runhaskell Setup.hs configure Configuring unix-2.3.0.0... Normally copious output ... ??? That's what it should look like! It just means you have a recent version of cabal which doesn't spit out tons of information when configuring. Happily all is well. /Josef ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] more runhaskell question
[EMAIL PROTECTED]:~/FTP/Haskell/unix-2.2.0.0/tests/mlock$ runhaskell Setup.lhs configure --prefix=$HOME Configuring mlock-1.0... [EMAIL PROTECTED]:~/FTP/Haskell/unix-2.2.0.0/tests/mlock$ runhaskell Setup.lhs build Setup.lhs: error reading dist/setup-config; run setup configure command? No dist/setup-config is being generated! what is the setup configure command?? Regards, Vasili ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Another optimization question
Daniel Fischer daniel.is.fischer at web.de writes: Am Samstag, 17. Mai 2008 22:48 schrieb anton muhin: Why not -O3? As far as I know - and Brandon S.Allbery said so, too - -O3 isn't better than -O2. Using a real list of primes, What's the size of the real list? arbitrary, however, since it's [Int], it will actually be at most 105097565 primes long, but since only numbers up to 5000 are checked, only 670 primes will ever be considered - When I check numbers 1 to 5 (5133 primes, so 5134 primes evaluated), with -O0 / -O2, it's Jeroen 1 : 14.5 s / 2.4 s Jeroen 2 : 52.5 s / 49.7 s (== x) . head . dropWhile ( x) : 8.2 s /4.1 s go primes : 5.5 s / 2.5 s So Jeroen 1 is the best to be optimised :) but another implementation of isPrime: isPrime x = (== x) $ head $ dropWhile ( x) primes With -O2, this is about 20% slower than the Jeroen's first version, without optimisations 50% faster. Strange. Well, head has its overhead as well. Cf. two variants: firstNotLess :: Int - [Int] - Int firstNotLess s (x:xs) = if x s then firstNotLess s xs else x dropLess :: Int - [Int] - [Int] dropLess s l@(x:xs) = if x s then dropLess s xs else l isPrime :: Int - Bool isPrime x = x == (firstNotLess x primes) isPrime' :: Int - Bool isPrime' x = x == (head $ dropLess x primes) On my box firstNotLess gives numbers pretty close (if not better) than for primes up to 5, that's 6.8 s / 2.1 s with -O0 / -O2 respectively on mine Jeroen's first variant, while head $ dropLess notably worse. 5.8 s / 2.4 s here. isPrime :: Int - Bool isPrime x = go primes where go (p:ps) = case compare x p of LT - False EQ - True GT - go ps does best (on my box), with and without optimisations (very very slightly with -O2) for a list of real primes, but not for [1 .. ]. And what happens for [1..]? With -O2, Jeroen 1 was best (1.62), nex firstNotLess (1.63), head . dropLess (1.74), then in close succesion Jeroen 2 (1.92), go primes (1.96) and head . dropWhile (1.99), with -O0, it's head . dropWhile (1.7 s, YES, that actually is faster with -O0 than with -O2!), head . dropLess (2.0), Jeroen 2 and firstNotLess (2.1 s), go primes (2.3 s), Jeroen 1 (3.2 s). Weirder and weirder. However, more than can be squished out of fiddling with these versions could be gained from a better algorithm. Definitely. yours, anton. Thanks for the responses so far! I only tested with -O2 and my primes implementation is the Sieve of Eratosthenes and has signature primes :: Integral a = [a] What's also quite strange is that experiment2 is about 10 times time slower than experiment1 when using primes (with the Eratosthenes formula) instead of [1..]. I redid the experiments with -prof and the output was quite revealing: experiment1 (fastest): total time =2.64 secs (132 ticks @ 20 ms) total alloc = 323,356 bytes (excludes profiling overheads) individualinherited COST CENTRE entries %time %alloc %time %alloc MAIN 0 0.00.0 100.0 100.0 main1 0.00.5 0.00.5 CAF 4 0.00.0 100.0 99.0 primes 1 9.8 61.9 9.8 61.9 main 0 0.0 37.190.2 37.1 isPrime5000 90.20.090.20.0 CAF 4 0.00.4 0.00.4 experiment2 (slowest): total time =6.12 secs (306 ticks @ 20 ms) total alloc = 350,473,356 bytes (excludes profiling overheads) individualinherited COST CENTRE entries %time %alloc %time %alloc MAIN 0 0.00.0 100.0 100.0 main 1 0.00.0 0.00.0 CAF 4 0.00.0 100.0 100.0 primes 1 0.00.1 0.00.1 main0 0.00.0 100.0 99.9 isPrime 5000 100.0 99.9 100.0 99.9 CAF 4 0.00.0 0.00.0 Would this be only because isPrime of experiment 2 builds this temporary list (takeWhile) all the time? Jeroen Baekelandt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
