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

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.