The Effects of Randomness in Asynchronous 1D Cellular Automata
Yasusi Kanada · 1984
Cellular automata are used as models of emergent computation and artificial life. They are usually simulated under synchronous and deterministic conditions. Thus, they are evolved without the existence of randomness, or noise. However, noise is unavoidable in the real world. The objective of the present paper is to show three major effects caused by the existence or nonexistence of randomness in the computation order, which is a type of environmental noise, experimentally in two-neighbor one-dimensional asynchronous cellular automata (1D-ACA). The first major effect is that certain 1D-ACA, which generate non-chaotic patterns when not randomized, generate "edge-of-chaos " patterns when randomized. Some of these patterns are similar to those generated using Wolfram's class IV automata or coupled map lattices. The second is that certain properties of 1D-ACA, such as mortality of domains of 1's or splitting domains of 0's into two, are fully expressed in their spatio-temporal patterns if the computation order is randomized, though they are only partially expressed if not randomized. The third is that phantom phenomena, which almost never occur if there is no noise, sometimes occur when randomized. The characteristics of patterns generated by several 1DACA are drastically changed from uniform patterns to patterns with multiple or chaotic phases when the randomness is weaken. Several other phenomena are also observed.