The "ANNEAL" Cellular Automaton
Channel: Moreno Marzolla
Date: 2022-11-22

This movie shows the evolution of the "ANNEAL" Cellular Automaton. ANNEAL is a two-dimensional, binary CA that evolves according to the "twisted majority rule": if the number of black cells B in a 3x3 neighborhood is equal to 4, or greater than 5, then the new color of the central cell is black, otherwise it is white.

Starting from a random initial configuration, ANNEAL produces a set of connected "blobs" with some isolated "speckles" that slowly move and merge. As time goes on, "bays" get filled and "capes" are eroded. At the end, one giant smooth black blob emerges. 

I learned about this automata from the book "Cellular Automata Machines: a new environment for modeling" by Toffoli and Margolus, MIT Press, 1987 (freely downloadable from Norman Margolus' home page here https://people.csail.mit.edu/nhm/ )

The movie has been produced by a GPU program that I proposed as a lab assignment for the High Performance Computing course at the University of Bologna. The text of the assignment can be found here:

https://www.moreno.marzolla.name/teaching/HPC/handouts/cuda-anneal.html

A possible solution is here:

https://www.moreno.marzolla.name/teaching/HPC/solutions/cuda-anneal.cu

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