Switch engine

A switch engine (or Corder engine[1]) is a methuselah that was found by Charles Corderman in 1971. It produces a copy of itself after 48 generation, glide-reflected 4 cells northwest (in the case of the starting configuration shown to the right), along with some active junk. If left unattended, the accumulating exhaust overtakes and destroys the engine after 24 cycles, but it can be stabilized to make c/12 diagonal puffers and spaceships.

Switch engine
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Pattern type Methuselah
Number of cells 8
Bounding box 6×4
Lifespan 3911 generations
Final population 842
L/I 488.9
F/I 105.3
F/L 0.215
L/MCPS 391.1
Discovered by Charles Corderman
Year of discovery 1971

A 3-glider synthesis for a clean switch engine was discovered by Luka Okanishi on March 12, 2017, surprisingly late for such a small synthesis.[2]


There are two basic types of stabilized switch engine, both of which were also found by Charles Corderman: the period 288 block-laying switch engine (the more common of the two) and period 384 glider-producing switch engine. These two puffers are the most natural infinite growth patterns in Life, being by far the most common ones to occur from non-symmetric random starting patterns.[3] Switch engine-based puffers, and combinations thereof, are also the only infinite growth patterns observed to have emerged from asymmetric soups on Catagolue.

Because the switch engine lends itself so naturally to infinitely-growing patterns, it appears in many of the smallest known superlinear growth patterns, including the mosquitoes, catacryst, metacatacryst, Gotts dots, and 26-cell quadratic growth. Patterns giving rise to block-laying switch engines can be seen under infinite growth, and one giving rise to a glider-producing switch engine is shown under time bomb.

In addition to the puffers based on a single switch engine, puffers such as Noah's ark can be created by combining two switch engines. Such puffers are generally quite dirty. However, it is also possible to create Corderships made of switch engines that interact to remove their combined exhaust. These move at c/12 diagonally and are thus the slowest known spaceships in Life other than the adjustable ships. Such spaceships can be constructed by combining as few as two switch engines.

'Swimmer' tracks

Like Herschels, switch engines can be supported by conduits made out of well-separated still lifes.[4] These 'swimmer tracks' were discovered by David Bell in 2005, and can be any length. Stable converters have been constructed that convert Herschels to switch engines and back[5]. Much faster, smaller and more efficient Herschel-to-swimmer converters can now be constructed with new technology, particularly Snark reflectors.[6]

Stable pattern

The stable pattern that results from the switch engine has 842 cells. It consists of 60 blocks, 33 beehives (including one honey farm), 50 blinkers (including eight traffic lights), 12 gliders, 11 boats, 11 loaves, four ships, two long boats, two ponds, and two tubs.

Generation 3911

See also


  1. "Corder engine". The Life Lexicon. Stephen Silver. Retrieved on June 10, 2009.
  2. Luka Okanishi (March 12, 2017). Re: Thread For Your Accidental Discoveries (discussion thread) at the ConwayLife.com forums
  3. "Census - Catagolue". Retrieved on September 28, 2015.
  4. Dave Greene (September 6, 2005). "Bobsled run update". Game of Life News. Retrieved on September 21, 2014.
  5. Dave Greene (June 17, 2007). "A New Kind of Signal". Work in Progress blog. Retrieved on September 21, 2014.
  6. Dave Greene (March 25, 2017). "Re: Implications of a Three-Glider Switch Engine". Retrieved on February 13, 2018.
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