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2010 July 30

Gemini guns

Dave Greene has recently built a number of guns, which periodically emit oblique Geminoid spaceships. These are the first guns in the history of Life to produce oblique spaceships, and the largest Life constructions (by area). The largest gun has an area of 17 square miles!

The largest gun is a 'laser gun', i.e. it produces all the spaceships in the same phase. Dave Greene hoped that this would improve HashLife performance; unfortunately, current processing power is insufficient for Golly to 'run away' at exponential speeds.

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One of Dave Greene's Geminoid guns, showing three emerged spaceships.

In order to make such a gun, he had to alter the instruction tape, to circumvent a few problems. Firstly, one of the problems was the fact that the Gemini hatchlings would try to destroy the gun. A rather inelegant (albeit successful) method was to place a configuration of eaters in the vicinity, to absorb all gliders from the destruction arm. Due to the ease of implementation, this was his method of choice. Another possibility would be to alter the recipe completely, so that the elbows are restored to their original positions, instead of being annihilated.

Dave Greene and Paul Chapman are currently contemplating how to reduce the size of Gemini, by reducing the number of channels from 12. They have considered reducing the number of elementary salvos from four to three, which would facilitate a 9-channel Geminoid. Hartmut Holzwart has an alternative idea: to compress the tape by constructing the offspring conduit-by-conduit, instead of catalyst-by-catalyst. He has also considered the possibility of replacing the destruction arm with a p46 equivalent; this would occupy less space and thus be quicker to construct.