Slmake

slmake
Homepage	Click here
Purpose	Slow glider construction
Created by	Adam P. Goucher
Platform	Unix

slmake is a search program first published by Adam P. Goucher in May 2017. It accepts as input a constellation of sufficiently widely separated still lifes, and produces a glider stream that will perform a complete slow glider construction of that constellation, starting from a single block.

It is built atop lifelib, relying on a large (200 megabytes compressed; 800 megabytes uncompressed) collection of precompiled slow salvo recipes found by breadth-first search. In addition to this, there are several 'bespoke' syntheses for unnatural objects such as Snarks and eater2s, which were the result of collaborative human engineering by Chris Cain and others. As such, it is capable of finding recipes not only for Spartan stable circuitry, but also for other useful non-Spartan circuits containing Snarks, syringes, and H-to-MWSS converters, provided that they are separated from other nearby objects by a sufficient amount of empty space.

Strategies

Instead of building the recipe in the order of construction, slmake works in reverse by taking the input pattern and reducing it to a slightly simpler problem. Proceeding inductively, slmake reduces the problem to a single block. In order to prevent it from getting caught in a loop ad infinitum, slmake uses six strategies which guarantee that the descent will terminate (successfully or otherwise):

• split: two objects, one of which is a block, are created from a single object;
• reduce: a single object is created from a simpler object (typically beehive, tub, or block);
• bespoke: a bespoke object (typically a Snark or eater2) is constructed in place;
• tree: by moving a block, the problem is reduced to one with a smaller minimum spanning tree;
• deep: slmake does a 1-step lookahead to see if it can apply another strategy;
• uncover: objects are moved out of the way of a bespoke object to enable its synthesis.

Optimisations

After constructing a slow-salvo recipe, slmake will attempt to reorder the sequence of gliders to defragment the recipe. This will result in a shorter single-channel construction, on the basis that the number of elbow moves is minimised.

Applications

One of slmake's primary uses is to make self-constructing patterns much easier to design and build. Dave Greene used this software to generate the construction recipes involved in the Orthogonoid and Hydra.

External links

• GitLab page for slmake / slsparse

• Slmake at the Life Lexicon