Chapter 7: Mechanisms in Programs and Nature

Section 8: The Problem of Satisfying Constraints

Iterative improvement [of constraint satisfaction]

The borders of the regions of black and white in the picture shown here essentially follow random walks and annihilate in pairs so that their number decreases with time like 1/Sqrt[t]. In 2D the regions are more complicated and there is no such simple behavior. Indeed starting from a particular state it is for example not clear whether it is ever possible to reach all other states.

From Stephen Wolfram: A New Kind of Science [citation]