Difference between revisions of "Gun"
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==True-period guns== | ==True-period guns== | ||
A '''true-period gun''' (as opposed to a [[#Pseudo-period guns|pseudo-period gun]]) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism that oscillates with period equal to n. True period n guns are known to exist for all periods greater than 61<ref>{{Cite web|url=http://www.radicaleye.com/lifepage/patterns/bhept/bhept.html|title=My Experience with B-heptominos in Oscillators|author=Dave Buckingham|accessdate=May 14, 2009|date=October 12, 1996)}}</ref>, but only a few smaller periods have been achieved, namely [[Period-20 glider gun|20]], [[True_period_22_gun|22]], [[True_period_24_gun|24]], [[Gosper_glider_gun|30]], [[Period-36_Glider_Gun|36]], [[Period-40 glider gun|40]], [[P44_pi-heptomino_hassler|44]], [[Period-45_glider_gun|45]], [[New gun 1|46]], [[True_period_24_gun|48]], [[Period-50 glider gun|50]], 54, 55, 56, 57, 58, [[Period-59_glider_gun|59]], [[Period-60_glider_gun|60]] and [[Period-61_glider_gun|61]]. Credits for these small period guns are as follows: p30, p46 and p60 by [[Bill Gosper]] in [[:Category:patterns found in 1970|1970]]-[[:Category:patterns found in 1971|1971]], p44 by [[David Buckingham]] in [[:Category:patterns found in 1992|1992]], p50 by [[Dean Hickerson]] in [[:Category:patterns found in 1996|1996]], p24 and p48 by [[Noam Elkies]] in [[:Category:patterns found in 1997|1997]], p54 and p56 by [[Dietrich Leithner]] in early [[:Category:patterns found in 1998|1998]], p55 by [[Stephen Silver]] in late 1998, p22 by [[David Eppstein]] in [[:Category:patterns found in 2000|2000]], p36 by [[Jason Summers]] in [[:Category:patterns found in 2004|2004]], p59 by [[Adam P. Goucher]] in [[:Category:patterns found in 2009|2009]], p45 by [[Matthias Merzenich]] in [[:Category:patterns found in 2010|2010]], p40 by Adam P. Goucher and Matthias Merzenich in March [[:Category:patterns found in 2013|2013]], | A '''true-period gun''' (as opposed to a [[#Pseudo-period guns|pseudo-period gun]]) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism that oscillates with period equal to n. True period n guns are known to exist for all periods greater than 61<ref>{{Cite web|url=http://www.radicaleye.com/lifepage/patterns/bhept/bhept.html|title=My Experience with B-heptominos in Oscillators|author=Dave Buckingham|accessdate=May 14, 2009|date=October 12, 1996)}}</ref>, but only a few smaller periods have been achieved, namely [[Period-20 glider gun|20]], [[True_period_22_gun|22]], [[True_period_24_gun|24]], [[Gosper_glider_gun|30]], [[Period-36_Glider_Gun|36]], [[Period-40 glider gun|40]], [[P44_pi-heptomino_hassler|44]], [[Period-45_glider_gun|45]], [[New gun 1|46]], [[True_period_24_gun|48]], [[Period-50 glider gun|50]], 54, 55, 56, 57, 58, [[Period-59_glider_gun|59]], [[Period-60_glider_gun|60]] and [[Period-61_glider_gun|61]]. Credits for these small period guns are as follows: p30, p46 and p60 by [[Bill Gosper]] in [[:Category:patterns found in 1970|1970]]-[[:Category:patterns found in 1971|1971]], p44 by [[David Buckingham]] in [[:Category:patterns found in 1992|1992]], p50 by [[Dean Hickerson]] in [[:Category:patterns found in 1996|1996]], p24 and p48 by [[Noam Elkies]] in [[:Category:patterns found in 1997|1997]], p54 and p56 by [[Dietrich Leithner]] in early [[:Category:patterns found in 1998|1998]], p55 by [[Stephen Silver]] in late 1998, p22 by [[David Eppstein]] in [[:Category:patterns found in 2000|2000]], p36 by [[Jason Summers]] in [[:Category:patterns found in 2004|2004]], p59 by [[Adam P. Goucher]] in [[:Category:patterns found in 2009|2009]], p45 by [[Matthias Merzenich]] in [[:Category:patterns found in 2010|2010]], p40 by Adam P. Goucher and Matthias Merzenich in March [[:Category:patterns found in 2013|2013]], p20 by Matthias Merzenich and Noam Elkies in May 2013, p61 by 'AbhpzTa' in April 2016, p58 by 'thunk' and Matthias Merzenich in April 2016, and p57 by Matthias Merzenich in April 2016. | ||
==Guns in Life-like cellular automata== | ==Guns in Life-like cellular automata== | ||
Revision as of 02:30, 17 April 2016
A gun is a stationary pattern that repeatedly emits spaceships (or rakes) forever. By far the most common type of guns are glider guns, which emit gliders (the most well-known of which is the Gosper glider gun); however, guns that emit spaceships of other speeds, including c/2 orthogonal, 2c/5 orthogonal, and c/12 diagonal, have also been created.
History
The first gun to be discovered, the Gosper glider gun, was found by Bill Gosper in 1970, being the first known pattern in Conway's Game of Life to exhibit infinite growth. Since then, many guns have been constructed with various periods and that fire spaceships of various speeds. Due to simple glider syntheses of the standard spaceships many c/2 spaceship guns are known. The first gun that did not fire gliders or c/2 spaceships was a Cordergun (a gun that fires Corderships) constructed by Jason Summers in July, 1999[1] based on a synthesis of a variation of the 7-engine Cordership by Stephen Silver. In March, 2003 Noam Elkies completed the synthesis of 60P5H2V0 which Dave Greene used to construct the first 2c/5 spaceship gun in April of the same year.
In July, 2010 Dave Greene constructed a few guns for a geminoid spaceship.[2] These are the first guns that shoot obliquely-traveling spaceships and are, in terms of their bounding boxes, the largest patterns constructed in Life.
On February 17, 2013 Josh Ball discovered a simple c/7 orthogonal spaceship, loafer. Adam P. Goucher found a synthesis for loafer later that day, allowing the construction of c/7 orthogonal spaceship guns.
Barrels
It is not uncommon for glider guns to have multiple barrels; that is, streams of gliders that come out along multiple different paths. For example, the B-52 bomber is said to be double-barreled because it produces two streams of gliders (one toward the northwest and another toward the southeast). Gunstar and its variants all have four barrels, and P94S contains a whopping 12 barrels. Given a gun with multiple barrels, one can eliminate barrels by simply placing an eater 1 in the path of the unwanted glider streams.
Pseudo-period guns
A pseudo-period gun (as opposed to a true-period gun) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism that oscillates with a period different from n -- this period will necessarily be a multiple of n. Pseudo period n glider guns are known to exist for all periods greater than or equal to 14, with smaller periods being impossible. The first pseudo period 14 gun was built by Dietrich Leithner in 1995.
True-period guns
A true-period gun (as opposed to a pseudo-period gun) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism that oscillates with period equal to n. True period n guns are known to exist for all periods greater than 61[3], but only a few smaller periods have been achieved, namely 20, 22, 24, 30, 36, 40, 44, 45, 46, 48, 50, 54, 55, 56, 57, 58, 59, 60 and 61. Credits for these small period guns are as follows: p30, p46 and p60 by Bill Gosper in 1970-1971, p44 by David Buckingham in 1992, p50 by Dean Hickerson in 1996, p24 and p48 by Noam Elkies in 1997, p54 and p56 by Dietrich Leithner in early 1998, p55 by Stephen Silver in late 1998, p22 by David Eppstein in 2000, p36 by Jason Summers in 2004, p59 by Adam P. Goucher in 2009, p45 by Matthias Merzenich in 2010, p40 by Adam P. Goucher and Matthias Merzenich in March 2013, p20 by Matthias Merzenich and Noam Elkies in May 2013, p61 by 'AbhpzTa' in April 2016, p58 by 'thunk' and Matthias Merzenich in April 2016, and p57 by Matthias Merzenich in April 2016.
Guns in Life-like cellular automata
Due to the existence of some small spaceships in Life-like cellular automata with birth at two live neighbours (B2), many low-period spaceship guns have been found using tools such as WinLifeSearch. In contrast, there are very few rules without B2 that are known to contain guns. The following is a list of rules without B2 that have known guns:
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See also
References
- ↑ "Game of Life Status page". Retrieved on October 15, 2010.
- ↑ Adam P. Goucher (July 30, 2010). "Gemini guns". Retrieved on October 15, 2010.
- ↑ Dave Buckingham (October 12, 1996)). "My Experience with B-heptominos in Oscillators". Retrieved on May 14, 2009.
External links
- Gun at the Life Lexicon