Re: [Haskell-cafe] saner shootout programs
Bulat Ziganshin wrote: Hello Richard, Yes it was just a plausible guess, but not contradicted by the experts. And that was using the Windows version of GHC so other versions may have better optimisation. I don't know how to check, maybe the experts can illuminate the subject? note that my letter was not contradicted too LOL 1. many experts just don't read this list due to its high traffic, write into ghc-users instead Good point. I have started a thread here http://www.haskell.org/pipermail/glasgow-haskell-users/2008-May/014742.html 2. ghc is too large system and no one know all its details. this particular option may be set up 10 years ago and never touched/studied by anyone since then. for example, i'm ghc performance expert [to some degree], but i don't know anything about its build system. all that i can tell is that ghc base library build times don't prohibit use of -O2 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
On Mon, May 12, 2008 at 4:38 AM, Richard Kelsall [EMAIL PROTECTED] wrote: Hello JC, I think you've set yourself a challenge there :) Welcome to Haskell programming. Taking a Shootout entry and playing with it is a great way to learn Haskell. The Shootout provides an example in your favourite previous language for comparison and a small well defined program with exact test results you can pit your wits against. Fame awaits you for a fast and beautiful entry. I'm still learning useful things from the Fasta benchmark. It's surprising how many interesting things you can discover in a small piece of code. It may be fun, but I don't think it would be meaningful. My code will be, most likely, slow, leaving some doubt as to whether it's slow because of the limitations of the compiler or my inexperience. On the other hand, if the experts can't help using malloc, unsafe*, global mutables and IO, I'll be able to conclude that this is probably what it takes to make Haskell run fast :-( ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
On 2008 May 13, at 0:26, J C wrote: On the other hand, if the experts can't help using malloc, unsafe*, global mutables and IO, I'll be able to conclude that this is probably what it takes to make Haskell run fast :-( Very few of the shootout entries have been revisited since most of the improvements to list and stream fusion, etc. in GHC, if I can trust the amount of discussion of shootout entries I've seen on IRC. Some of them are still vintage 6.4.2, which had very little in the way of compiler smarts so hand optimization was crucial. 6.8.2, on the other hand, does much better all by itself as long as you don't e.g. use lists in stupid ways. -- 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] saner shootout programs
J C wrote: [EMAIL PROTECTED] wrote: Hello JC, I think you've set yourself a challenge there :) Welcome to Haskell programming. Taking a Shootout entry and playing with it is a great way to learn Haskell. The Shootout provides an example in your favourite previous language for comparison and a small well defined program with exact test results you can pit your wits against. Fame awaits you for a fast and beautiful entry. I'm still learning useful things from the Fasta benchmark. It's surprising how many interesting things you can discover in a small piece of code. It may be fun, but I don't think it would be meaningful. My code will be, most likely, slow, leaving some doubt as to whether it's slow because of the limitations of the compiler or my inexperience. On the other hand, if the experts can't help using malloc, unsafe*, global mutables and IO, I'll be able to conclude that this is probably what it takes to make Haskell run fast :-( Don't tell the experts who wrote the current shootout entries, but the playing field is tilted radically in favour of us beginners being able to improve on their entries because of new versions of GHC and new tools that have been developed since they wrote their entries. GHC will now automatically perform many of the optimisations that used to have to be done by hand. For example I was surprised to discover the other day when working on Fasta that putting this plain and simple version of splitAt splitAt n (x : xs) = (x : xs', xs'') where (xs', xs'') = splitAt (n-1) xs in my program made it run more quickly than using the built-in version of splitAt which I now know looks like (ug!) this splitAt (I# n#) ls | n# # 0#= ([], ls) | otherwise = splitAt# n# ls where splitAt# :: Int# - [a] - ([a], [a]) splitAt# 0# xs = ([], xs) splitAt# _ [EMAIL PROTECTED] = (xs, xs) splitAt# m# (x:xs) = (x:xs', xs'') where (xs', xs'') = splitAt# (m# -# 1#) xs because I was compiling my splitAt with -O2 optimisation as opposed to the built-in version being compiled with -O. The extra optimisations in -O2 are a new feature of GHC (and -O2 is slower to compile which is why the built-in version doesn't use it, but that doesn't matter for the shootout). You may similarly find various elaborations in the shootout entries that were historically necessary for speed or memory reasons, but which can now be removed because GHC or new libraries do the work for us. Have a go and see what happens to the speed when you change things to make N-body more readable. I would bet money on there being simple tweaks which will make it simultaneously faster and more readable. Richard. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
Well, it would be meaningful for your own experience in learning Haskell. Some time ago somebody took a shot at nbodies using pure immutable structures, and as I recall, got within about 4x the performance of mutable structures. In 6.6, an STArray based approach was maybe 2x slower, but by now it may well be comparable, as Dons pointed out. In fact, lots of the shootout entries could use an overhaul now that 6.8 is running on their machines, as plenty of older, uglier, optimizations are probably preformed as efficiently if not more so by the newer GHC, whose strictness analysis, for example, is consistently and pleasantly surprising. If you take a stab at some of these benchmarks, with some helpful guidance from #haskell, you'll no doubt get a much better sense of how memory and performance works in haskell, and which tweaks are just there for the last 2%. So even if you can't beat the current winners (and given the compiler changes, you may well be able to) you'll still come out ahead in the process. As for the clean entry though, it no doubt relies heavily on uniqueness typing and so is secretly mutating like crazy under the hood. Cheers, S. On Tue, May 13, 2008 at 12:26 AM, J C [EMAIL PROTECTED] wrote: On Mon, May 12, 2008 at 4:38 AM, Richard Kelsall [EMAIL PROTECTED] wrote: Hello JC, I think you've set yourself a challenge there :) Welcome to Haskell programming. Taking a Shootout entry and playing with it is a great way to learn Haskell. The Shootout provides an example in your favourite previous language for comparison and a small well defined program with exact test results you can pit your wits against. Fame awaits you for a fast and beautiful entry. I'm still learning useful things from the Fasta benchmark. It's surprising how many interesting things you can discover in a small piece of code. It may be fun, but I don't think it would be meaningful. My code will be, most likely, slow, leaving some doubt as to whether it's slow because of the limitations of the compiler or my inexperience. On the other hand, if the experts can't help using malloc, unsafe*, global mutables and IO, I'll be able to conclude that this is probably what it takes to make Haskell run fast :-( ___ 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] saner shootout programs
Bulat Ziganshin wrote: Hello Richard, Tuesday, May 13, 2008, 6:10:54 PM, you wrote: because I was compiling my splitAt with -O2 optimisation as opposed to the built-in version being compiled with -O. The extra optimisations in -O2 are a new feature of GHC (and -O2 is slower to compile which is why the built-in version doesn't use it, but that doesn't matter for the shootout). -O2 is very old ghc feature and i think that ghc base library is compiled with -O2 - it's too obvious idea In July 2007 -O2 was documented in GHC as making no difference to the speed of programs : http://www.haskell.org/pipermail/haskell-cafe/2007-July/029118.html and from this thread http://www.haskell.org/pipermail/haskell-cafe/2008-April/042155.html it appears to be currently unused for splitAt. I guess -O2 has however been around for a long time. Richard. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] saner shootout programs
Hello Richard, Tuesday, May 13, 2008, 7:56:36 PM, you wrote: In July 2007 -O2 was documented in GHC as making no difference to the speed of programs : http://www.haskell.org/pipermail/haskell-cafe/2007-July/029118.html it's because ghc is 15 years old and its documentation may be not updated as things changes :) and from this thread http://www.haskell.org/pipermail/haskell-cafe/2008-April/042155.html it appears to be currently unused for splitAt. i've read this thread. it was just assumption - don't believe it before you have checked it -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
Bulat Ziganshin wrote: Hello Richard, In July 2007 -O2 was documented in GHC as making no difference to the speed of programs : http://www.haskell.org/pipermail/haskell-cafe/2007-July/029118.html it's because ghc is 15 years old and its documentation may be not updated as things changes :) and from this thread http://www.haskell.org/pipermail/haskell-cafe/2008-April/042155.html it appears to be currently unused for splitAt. i've read this thread. it was just assumption - don't believe it before you have checked it Hello Bulat, Yes it was just a plausible guess, but not contradicted by the experts. And that was using the Windows version of GHC so other versions may have better optimisation. I don't know how to check, maybe the experts can illuminate the subject? Richard. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
--- On Mon, 5/12/08, PR Stanley [EMAIL PROTECTED] wrote: I don't know Haskell very well, but Paul: I'm not racist but . . . :-) Relevant Haskell humor: Humor/Homework - HaskellWiki: see line 3: http://www.haskell.org/haskellwiki/Humor/Homework Benjamin L. Russell ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
J C wrote: ... If anyone has a version of the N-body benchmark, where the simulation is a type-safe pure function, I would very much like to see and time it. Hello JC, I think you've set yourself a challenge there :) Welcome to Haskell programming. Taking a Shootout entry and playing with it is a great way to learn Haskell. The Shootout provides an example in your favourite previous language for comparison and a small well defined program with exact test results you can pit your wits against. Fame awaits you for a fast and beautiful entry. I'm still learning useful things from the Fasta benchmark. It's surprising how many interesting things you can discover in a small piece of code. Richard. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] saner shootout programs
I don't know Haskell very well, but even I can tell, looking at, for example, the N-body benchmark, that the Haskell code is probably not type-safe, and the tricks used in it would not be usable in a larger program (see below). The task is essentially a pure computation: take a list of bodies having mass, position and velocity; apply Newton laws at discrete intervals for a large number of times; return new positions and velocities. I could write a C++ procedure that performs this task and have some piece of mind regarding its type correctness, exception safety and functional purity: side effects would be local to the procedure, arguments passed as const or by value, the result returned by value, no type casts or new/delete operators used. On the other hand, the Haskell code makes assumptions about the size of double-precision floats (obviously not type-safe). Further, the simulation is not a pure function. It is often argued that one only needs these dirty tricks in the most time-consuming functions. However, if using imperative programming in these inner loop procedures places them in IO monad, the outer loops (the rest of the program - procedures that call it) will have to go there as well. This makes me doubt the Haskell approach to functional programming. If anyone has a version of the N-body benchmark, where the simulation is a type-safe pure function, I would very much like to see and time it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
jhc0033: I don't know Haskell very well, but even I can tell, looking at, for example, the N-body benchmark, that the Haskell code is probably not type-safe, and the tricks used in it would not be usable in a larger program (see below). The task is essentially a pure computation: take a list of bodies having mass, position and velocity; apply Newton laws at discrete intervals for a large number of times; return new positions and velocities. I could write a C++ procedure that performs this task and have some piece of mind regarding its type correctness, exception safety and functional purity: side effects would be local to the procedure, arguments passed as const or by value, the result returned by value, no type casts or new/delete operators used. On the other hand, the Haskell code makes assumptions about the size of double-precision floats (obviously not type-safe). Further, the simulation is not a pure function. It is often argued that one only needs these dirty tricks in the most time-consuming functions. However, if using imperative programming in these inner loop procedures places them in IO monad, the outer loops (the rest of the program - procedures that call it) will have to go there as well. This makes me doubt the Haskell approach to functional programming. If anyone has a version of the N-body benchmark, where the simulation is a type-safe pure function, I would very much like to see and time it. n-body requires updating a global array of double values to be competitive performance-wise, though we haven't really nailed this benchmark yet. The current entry should be considered an older approach to raw performance -- typically we can get good (or better) results in using the ST monad. To improve safety, it should run in the ST monad. A version using ST is here, http://haskell.org/haskellwiki/Shootout/Nbody However, the current fastest program should really be cross-ported to run in ST, for best results. (Similar to the nsieve-bits program): http://shootout.alioth.debian.org/gp4/benchmark.php?test=nsievebitslang=ghcid=0 I suspect the optimisations that weren't happening, that forced nbody to use Foreign.Ptr in the first place are likely obsolete now -- GHC 6.8.2 should do a good job with STUArray Double, in careful hands. Also worth looking at is the other purely functional entry, in Clean, http://shootout.alioth.debian.org/gp4/benchmark.php?test=nbodylang=cleanid=0 translation to Haskell should be fairly straightforward. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
dons: jhc0033: I don't know Haskell very well, but even I can tell, looking at, for example, the N-body benchmark, that the Haskell code is probably not type-safe, and the tricks used in it would not be usable in a larger program (see below). The task is essentially a pure computation: take a list of bodies having mass, position and velocity; apply Newton laws at discrete intervals for a large number of times; return new positions and velocities. I could write a C++ procedure that performs this task and have some piece of mind regarding its type correctness, exception safety and functional purity: side effects would be local to the procedure, arguments passed as const or by value, the result returned by value, no type casts or new/delete operators used. On the other hand, the Haskell code makes assumptions about the size of double-precision floats (obviously not type-safe). Further, the simulation is not a pure function. It is often argued that one only needs these dirty tricks in the most time-consuming functions. However, if using imperative programming in these inner loop procedures places them in IO monad, the outer loops (the rest of the program - procedures that call it) will have to go there as well. This makes me doubt the Haskell approach to functional programming. If anyone has a version of the N-body benchmark, where the simulation is a type-safe pure function, I would very much like to see and time it. n-body requires updating a global array of double values to be competitive performance-wise, though we haven't really nailed this benchmark yet. The current entry should be considered an older approach to raw performance -- typically we can get good (or better) results in using the ST monad. Oh, for those following, the program we're talking about is this one: http://shootout.alioth.debian.org/gp4/benchmark.php?test=nbodylang=ghcid=0 Which I have to argue doesn't /look/ to bad, though the use of Ptr Double to represent mutable arrays of vectors -- following C -- is a bit lower level than we'd like. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
I don't know Haskell very well, but Paul: I'm not racist but . . . :-) even I can tell, looking at, for example, the N-body benchmark, that the Haskell code is probably not type-safe, and the tricks used in it would not be usable in a larger program (see below). The task is essentially a pure computation: take a list of bodies having mass, position and velocity; apply Newton laws at discrete intervals for a large number of times; return new positions and velocities. I could write a C++ procedure that performs this task and have some piece of mind regarding its type correctness, exception safety and functional purity: side effects would be local to the procedure, arguments passed as const or by value, the result returned by value, no type casts or new/delete operators used. On the other hand, the Haskell code makes assumptions about the size of double-precision floats (obviously not type-safe). Further, the simulation is not a pure function. It is often argued that one only needs these dirty tricks in the most time-consuming functions. However, if using imperative programming in these inner loop procedures places them in IO monad, the outer loops (the rest of the program - procedures that call it) will have to go there as well. This makes me doubt the Haskell approach to functional programming. If anyone has a version of the N-body benchmark, where the simulation is a type-safe pure function, I would very much like to see and time it. ___ 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] saner shootout programs
On Sun, May 11, 2008 at 1:40 PM, Don Stewart [EMAIL PROTECTED] wrote: n-body requires updating a global array of double values to be I think the array and any side-effects on it can and should be local to the simulation procedure. competitive performance-wise, though we haven't really nailed this benchmark yet. The current entry should be considered an older approach to raw performance -- typically we can get good (or better) results in using the ST monad. As I understand, a function can use ST, but still be pure. If so, that's the version I'd like to time (assuming it's also type-safe). The only pure functional solution on that page that I found claims to have a huge leak. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] saner shootout programs
jhc0033: On Sun, May 11, 2008 at 1:40 PM, Don Stewart [EMAIL PROTECTED] wrote: n-body requires updating a global array of double values to be I think the array and any side-effects on it can and should be local to the simulation procedure. competitive performance-wise, though we haven't really nailed this benchmark yet. The current entry should be considered an older approach to raw performance -- typically we can get good (or better) results in using the ST monad. As I understand, a function can use ST, but still be pure. If so, Right, its identical to the current solution, but the mutability is guaranteed not to escape the simulation scope. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
