StrangelyAttractive

Fortran program to find chaotic-behaving 2d quadratic maps. Examples of pictures it can draw are in the end of this README file.

To compile

0. make sure you have Fortran compiler with Fortran 2008 support. I know that gfortran 4.5 doesn't work, and gfortran 4.8 works.
1. install pgplot from http://www.astro.caltech.edu/~tjp/pgplot/ (or in any other way, like macports);
2. edit top two lines in Makefile, specifying there your Fortran compiler and pgplot linking options;
3. make

To run

./StrangelyAttractive

When the progrom finds a chaotic map, you'll be asked for graphics device. Press '?' to see the list. On Mac OS X try /AQT (if you've installed pgplot with Aquaterm support -- strongly recommended). Another interesting option would be filename.png/PNG, which would create filename.png in the current directory.

To change behaviour

You can edit parameters in the beginning of StrangelyAttractive.f08:

• a_min and a_max specify the range from where the quadratic map coefficients are randomly chosen
• draw_loops -- set to .TRUE. if you want to see the maps with limit loop shown (boring...)
• x0 and y0 -- the initial point; I doubt you can get any different behaviour by changing it
• total_iterations -- the number of iterations to calculate; you probably do not want to touch this, unless your machine is really slow
• last_draw_iteration -- the last iteration to draw (in the drawing the first init_iterations will be skipped). Increasing this value up to, say, 500000, will usually produce really nice pictures, but the drawing will take a lot of time (but if you use png renderer and not on-screen one, it's very fast). Should be less or equal than total_iterations.

Do not touch anything else.

Notes on output devices

You may find the following environmental variables useful:

• PGPLOT_DEV sets the default output device
• PGPLOT_PNG_WIDTH and PGPLOT_PNG_HEIGHT specify the size of PNG image (pgplot's default is 850 x 680)

Examples