Hello, I've created a simple Mandelbrot set generator, using HGL, the source is viewable at: http://pastebin.dqd.cz/cUmg/ 1. The problem is, that it is very slow. It is obvious that what takes the most time is the "mandel" function computation. I have no idea, how it can be improved. 2. What is the easiest way of changing a color and plotting a pixel with it? Do I always have to "create a pen" for it? Isn't there a simple way? Already – using a line to plot a pixel is probably not the best way… Thanks
* On Sun, Feb 14 2010, Vojtěch Knyttl wrote:
1. The problem is, that it is very slow. It is obvious that what takes the most time is the "mandel" function computation. I have no idea, how it can be improved.
Why 1000 iterations? Why is "Infinity" equal to 50? The sequence usually diverges an order of magnitude sooner than you anticipate, and 2 is considered to be a fine value for Infinity (it makes sense if you look at the plot). (Also, "it is obvious what takes the most time"? Did the profiler tell you that, or are you guessing?) If you want a really fast implementation, you are going to lose the simplicity. I wrote a very simple, multi-thread, mathematically-pure (infinity is Infinity, the complex numbers are Complex, etc.) a few weeks ago: http://gist.github.com/291074 It generated this 100M-pixel image in an hour and a half: http://jrock.us/mandelbrot-big.png (Warning: apparently that causes many browsers to crash. Gotta love C programs...) Anyway, not saying this is a good implementation, but it might give you some ideas. (The notable "innovation" is that the set membership is computed in threads, but the image is only generated in the first thread. This is a limitation of the library I used, but I was still able to realize massive speed gains by parallelizing: 8 hours of CPU time in 1.5 hours of wall clock time!) Reading the Google results for "mandelbrot set" is also enlightening, and yields optimizations that you may find useful. But when you start optimizing, you lose "simplicity", so consider first what your goals are -- a simple implementation, or a really fast implementation. Your needs might be met by changing iterations to 50 and "infinity" to 2. So basically, make sure "mandel" is what's slow, then optimize that. But make sure your plotting is also fast enough -- you are plotting as many points are you are calculating, after all. Regards, Jonathan Rockway -- Just "another Haskell hacker"
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Jonathan Rockway -
Vojtěch Knyttl