Animating the Quantum Drunkard’s Walk (#186)

A recent PPCG challenge titled The Quantum Drunkard’s Walk was about a tiny drunken person for which quantum mechanics apply and who — being drunk — will ran­dom­ly walk in one of the four cardinal directions each step they take.
As they ex­pe­ri­ence the strange world of quanta, they can simultaneously take every path at once and their paths influence each oth­er. The challenge then asked to output all possible positions the quantum drunkard could occupy, all paths they could take in ASCII rep­re­sent­ation.

The ques­tion also states this problem’s equivalence to a cellular automaton, when one removes the story boilerplate.
Cells in this cellular automaton are square and can occupy one of three states: empty, awake or sleeping. Each iteration, all cells change according to three rules.

• An empty cell wakes up iff there is exactly one awake cell amongst its cardinal neighbours, else it stays empty.
• An awake cell goes to sleep.
• A sleeping cell continues to sleep.

Being code golf, the aim was to come up with a minimally sized source code; my attempt required 214 bytes and prints a nested array containing one-length strings (characters), as this output method is cheaper than concatenating all characters to one string.

However, one user took the challenge idea a bit further and created an animated gif showing the walk’s, or cellular automaton’s, progression over time with an increasing num­ber of iterations. My Python program shown in this post does exactly that, generating an animated gif showing the automaton’s progression. I even im­ple­ment­ed rainbow support, possibly improving the automaton’s visual appearance.
Python source code can be downloaded and seen below.

I use the Python Imaging Library to produce all frames and use a shell call to let ImageMagick convert all frames to an animated gif. Animation pa­ram­e­ters are taken via shell arguments, a full list of features follows (also avail­able via the -h flag).

• --iterations N: Number of iterations (initial frame not counted)

• --colorempty C: Empty cell color (#rrggbb)
• --colorawake C: Awake cell color (#rrggbb)
• --colorsleeping C: Sleeping cell color (#rrggbb)
• --rainbow: Use rainbow colors (overrides color settings)
• --scale N: Cell square pixel size

• --convert: Execute ImageMagick’s convert command
• --delay N: Delay be­tween frames in output image.
• --loop N: Gif loops (0 means for indefinite looping)
• --keepfiles: Do not delete files when converting

Source code: animating-the-quantum-drunkards-walk.py

• pingback from #194