OCA:Marine

Marine
x=64, y = 64, rule = R2,C2,S4,6-9,B6-8,N@03ddef ! #C [[ THEME Fire ]] #C [[ RANDOMIZE2 RANDSEED 1729 THUMBLAUNCH THUMBNAIL THUMBSIZE 2 GRID ZOOM 6 WIDTH 600 HEIGHT 600 LABEL 90 -20 2 "#G" AUTOSTART PAUSE 2 GPS 8 LOOP 256 ]] LifeViewer-generated pseudorandom soup
Rulestring	R2,C2,S4,6-9,B6-8,N@03ddef
Character	Chaotic

Marine is a higher-range outer-totalistic cellular automaton (abbreviated HROT) with weighted neighbourhood. It was devised by MathAndCode in September 2020.

Rule definition and simulation

Like many outer-totalistic Life-like cellular automata, Marine has two states, runs on a 2d square grid, and the new state of a cell is a function of both the total number of live cells surrounding the cell, and the state of the cell itself. However, its neighbourhood is a 4×4 square, which does not have a cell exactly at the geometric center. To circumvent this issue, Moosey proposed to use a 5×5 square (equivalent to a range-2 neighbourhood of the center c) and assign different weights to the cells instead:

0	0	0	0	0
0	1	1	1	1
0	1	c	1	1
0	1	1	1	1
0	1	1	1	1

Concatenating the rows without c gives 000000111101110111101111 in binary, which equals to 03ddef in hexadecimal. Meanwhile, MathAndCode wrote the rulestring in the usual format for Life-like cellular automata as "B678S46789". Combining neighbourhood and transition function, the valid HROT specification becomes R2,C2,S4,6-9,B6-8,N@03ddef.

In the original introduction, Marine was simulated in a custom website. As LifeViewer began supporting HROT rules in August, later patterns can be shared and viewed easily on the forum thread. Before Golly's support of HROT in version 4.0+ that started in October, CAViewer and Java Square Cell were two means of exploring the rule. For soup-searching, a ruletable (or "apgtable") was written to run this rule in apgsearch, and the results from which are uploaded to Catagolue under the name of "xmarine"; this is linked in External Link below.

Patterns

With the anisotropic neighbourhood definition above, patterns tend to evolve southeastwards; this direction is called downstream.

External Link

• Larger Than Life rule: Marine (discussion thread) at the ConwayLife.com forums

Marine at Adam P. Goucher's Catagolue