Salvo

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A salvo is a collection of spaceships (usually gliders) that are all coming from the same direction.[1] A salvo is generally aimed at a target to produce a specific reaction -- for example, in a sliding-block memory or a slide gun, a salvo might move a block or other still life a step closer to the salvo source, or a step farther away. Or two or more salvos may collide with each other to construct a complex object.

A synchronized salvo is a salvo in which the target reaction requires all spaceships to be in specific locations and timings relative to each other. A different, and probably less useful, construction reaction will occur if any single spaceship arrives at the construction site even a few ticks too soon or too late.

By contrast, a slow salvo is a salvo in which the individual spaceships are far enough apart that precise timing becomes irrelevant. Any collision reaction affecting the nth spaceship has settled down into a stable or periodic intermediate target, by the time the (n+1)st spaceship arrives.

A P1 slow salvo is a slow salvo in which the intermediate settled-down stages are all period 1 (i.e., stable.) It is conjectured that any glider-constructible object can be produced by a P1 slow salvo aimed at a single block or other small still life -- though the number of gliders needed may be very large.

Conversely, a P2 slow salvo may have intermediate stages containing P2 oscillators, allowing constructions with significantly fewer gliders on average. P3 and higher slow salvos are technically possible, but higher periods do not appear to make much difference to construction efficiency in Life, where higher-period oscillators are relatively rare in random ash.

  • If a P1 slow salvo is divided into two parts, the later group of gliders can always be delayed by any number of ticks relative to the earlier group, without changing the eventual construction reaction. In the P2 case, it is generally only safe to delay such a group by an even number of ticks -- though there will be exceptions for any specific gliders that are aimed at P1 intermediate targets.

A monochromatic slow salvo is a slow salvo which contains only gliders of a single color.[2] For example, half-baked knightships reconstruct their glider seed constellations using monochromatic slow salvos.

Similarly, a monoparity slow salvo is a slow salvo which contains only gliders of the same shape -- i.e., even or odd parity. The intermediate targets for this type of slow salvo can be P1 or P2, but P2 targets have two completely separate and non-interchangeable phases. A phase-0 blinker is a different target than a phase-1 blinker, for example, and the two targets would require completely different construction recipes. Even-step variants of the engineless Caterpillar use slow salvos that are both monochromatic and monoparity.[3]

A freeze-dried salvo (or sometimes frozen salvo) is a constellation of stationary objects, which, being hit by a glider or activated by other means, produces a slow salvo with required parameters. In other words, a freeze-dried salvo is essentially a slow salvo seed.[4]

References

  1. Dave Greene (February 24, 2006). "New results from Glue 2". Conway's Life: Work in Progress. Retrieved on June 13, 2009.
  2. Dave Greene (April 18, 2014). "Re: Serizawa - Linear Self Replicator.". Retrieved on July 29, 2014.
  3. Michael Simkin (June 26, 2015). "Re: David Bell's engineless caterpillar idea revisited". Retrieved on August 4, 2015.
  4. Michael Simkin (September 2, 2016). "Re: Freeze-Dried Slow Salvos". Retrieved on September 6, 2016.