Approximate fractal percolation and compute its Euler characteristic
C++ code to simulate finite approximations of fractal percolation and to analyze their geometry by estimating the expected Euler characteristic, see arXiv:1812.06305
M.A. Klatt and S. Winter (2018) "Geometric functionals of fractal percolation"
More generally the code can simulate pixelated random sets and compute the Minkowski functionals or intrinsic volumes (area, perimeter, and Euler characteristic) as well as their generalization to Minkowski tensors to quantify anisotropy.
Author: Michael Andreas Klatt
Contributor: Steffen Winter
Maintainer: Michael Andreas Klatt (email@example.com)
License: GNU GPLv3
First compile the code using the command
Note that this package uses boost and gsl libraries.
The mean Euler characteristic of fractal percolation can simply be computed by the command
./FractalPercolationMink_NN -n 8 -M 2 -p 0.5 -R 100
for an approximation level n=8 with subdivisions M=2 for a probability of survival p=0.5, where the mean value and standard error of the mean (based on 100 runs) is written to a file in the subfolder "./output/".
Columns in outputfile:
- 1st column: probability of survival p
- 2nd column: mean Euler characteristic
- 3rd column: standard error of the mean
- 4th column: level n of approximation
The parameters can either by chosen via the command line or via a configuration file (default file name 'FractalPercolationMink.conf')
- config_file --- Configuration file to read parameters from
- prefix_of --- Folder for output, i.e. prefix for output files
- p --- Fractal percolation: survival probability
- subdivision --- Fractal percolation: Parameter M of subdivisions
- n_approximations --- Fractal percolation: Level of approximation
- N_runs --- Fractal percolation: Number of simulation runs
- imageout --- Flag whether a pgm image shall be created
- seed --- Seed of the random number generator
There are four executables from which the user can decide to compute the Euler characteristic of
- of either all clusters or only the percolating cluster that spans the system both horizontally and vertically,
- connecting only nearest neighbors (maximum four-fold connected) or also next-to-nearest neighbors (maximum eight-fold connected graph).
All clusters connecting only nearest neighbors
Percolating cluster connecting only nearest neighbors
All clusters connecting nearest neighbors and next-to-nearest neighbors
Percolating cluster connecting nearest neighbors and next-to-nearest next-to-nearest neighbors