README

This sample displays a fractal image from a Mandelbrot set. It may be build for single- or multi-core. Before building you should set the DEPTH define in include/circle/screen.h to 16 to increase the number of available colors. Furthermore you should set "loglevel=1" in the file cmdline.txt on the SD card. Otherwise some logging messages may be generated which will overwrite the image.

This sample was chosen because it is well suited to demonstrate the performance gain of a multi-core architecture. On a single-core CPU the whole image is calculated by the only available core. On a multi-core CPU (Raspberry Pi 2/3 only) each of the four available cores calculates a quarter of the fractal image which is much faster.

If you want to run this sample with multiple cores on the Raspberry Pi 2/3 you have to define ARM_ALLOW_MULTI_CORE in include/circle/sysconfig.h.

Please note that the calculation of the Mandelbrot set could be improved very much by choosing other parameters (e.g. MAX_ITERATION) and by implementing it in assembly language using the NEON FPU instructions. This has been done by krom. Please check out his very impressive samples here: 

https://github.com/PeterLemon/RaspberryPi  (in NEON/Fractal and in SMP/NEON/Fractal)