[Haskell-cafe] Re: How to optimize the performance of a code in Haskell?

I forgot to add that changing your definition of Particle and adding some optimization tunings yields an appreciable speedup.

data Particle = Particle { pos, vel :: {-# UNPACK #-} !Vector3, mass, rho, prs :: {-# UNPACK #-} !Scalar }

john$ ghc --make -O2 -fexcess-precision -fforce-recomp sph.hs -funfolding-creation-threshold=600 -funfolding-use-threshold=200 john$ time ./sph 300 real 0m14.963s user 0m14.307s sys 0m0.265s and john$ ghc --make -O2 -fexcess-precision -fvia-c -optc=-O3 -fforce-recomp sph.hs -funfolding-creation-threshold=600 -funfolding-use-threshold=200 john$ time ./sph 300 real 0m13.393s user 0m12.771s sys 0m0.247s which is quite close to the C++ performance. Using ByteStrings instead of Strings for output gets it the rest of the way. If you want to put on your Dons hat, the next steps would be using something like Acovea to fine-tune the compiler options, and/or using DPH. Best, John On Thu, Nov 5, 2009 at 1:49 AM, John Lato wrote:

For me, the Haskell version is about 1.5x slower than the C++ version, 19.6 seconds compared to 12.9.  There wasn't an appreciable difference between -O and -O2.

Which compiler (and version) are you using?

I got:

john$ g++ -O2 -o sph sph.cpp john$ time ./sph 300

real    0m12.914s user    0m11.015s sys     0m0.326s

john$ g++ --version i686-apple-darwin9-g++-4.0.1 (GCC) 4.0.1 (Apple Inc. build 5490) Copyright (C) 2005 Free Software Foundation, Inc.

and

john$ ghc --make -O2 sph.hs john$ time ./sph 300

real    0m19.606s user    0m18.933s sys     0m0.304s

john$ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.10.4

on a recent model MacBook, OSX 10.5.8.

Cheers, John

...

Message: 4 Date: Wed, 04 Nov 2009 17:53:49 +0100 From: Kalman Noel Subject: [Haskell-cafe] Re: How to optimize the performance of a code        in      Haskell? To: Masayuki Takagi Cc: Haskell Cafe Message-ID: <4AF1B19D.2010403@googlemail.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed

(I take it you accidently wrote to fa.haskell, which is just a mirror of -cafe and -beginners, so I'm cc-ing the Café with a full quote.)

Masayuki Takagi:

...

I'm writing fluid simulation programs with SPH(Smoothed particle hydrodynamics) in Haskell and C++. (The purpose that I write in two languages is to make a workflow that first i write in Haskell for rapid prototyping and accuracy then rewrite in C++ for performance.)

I've compared them in performance. Then, although I have already done optimization with profiler, the Haskell code is 20 times slower than the C++ code.

I think the performance of the Haskell code is so slow that there can be room for optimization. I'm happy if the Haskell code work 3 times slower than the C++ code at worst.

How can I make the Haskell code faster? What information should I refer?

The codes are here: http://kamonama.sakura.ne.jp/sph/20091101/sph.hs.zip http://kamonama.sakura.ne.jp/sph/20091101/sph.cpp

To run the code in Haskell: $ ghc --make -O sph.hs $ ./sph 300 (300 is the time step to be conputed)

To run the code in C++: $ g++ -O2 -o sph sph.cpp $ ./sph 300 (300 is the time step to be conputed)

thanks

I've not looked at the code, but you'll want ghc to do better optimizations than -O. -O2 is what you should use in general. Also, number-crunching often profits from -fexcess-precision.