Self-Reproducing Automata

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Source code for this applet is available upon request.

Instructions

The controls are displayed below the cellular automata (CA) itself:

Start: Set the automaton in motion. When pressed the Start button will become a Stop button.
Stop: Stop the automaton's motion. When pressed the Stop button will revert to being the Start button.
Step: Perform one step of calculation. This is equivalent to starting and then stopping the automaton after one unit of time has passed.
Reset: Return the automaton to its initial state.
Automaton: Select the automaton to execute: Langton's Loop or the minimal automaton from J. Byl's 1989 paper.
Run to step: A target step (such as step 25) can be input here and when the automaton is started it will run to that step and then stop.
Delay per frame: The automaton will wait for this number of milliseconds per step before proceeding to the next step. This has the effect of slowing the automaton down.
Display Grid: When this checkbox is set, a grid demarking the individual cells will be painted.

Background

Note that in the Langton automata each loop appears to "die" after it has surrounded itself with "child" loops - this death takes the form of the white signals that proceed around the loop disappearing, leaving just the red interior. Steven Levy mentions in Artifical Life that this mimics the life cycle of coral.

Bibliography

S. Levy, Artifical Life, Vintage Books (1993), ISBN 0679743898.
C. Langton, "Self-Reproduction in Cellular Automata", Physica 10D (1984), pp. 135-144.
J. Byl, "Self-Reproduction in Small Cellular Automata", Physica 34D (1989), pp. 295-299.

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J. Scott Hofmann