Sliding block memory: Difference between revisions
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{{Glossary}} | {{Glossary}} | ||
A '''sliding block memory''' is a memory register whose value is stored as the position of a [[block]]. | A '''sliding block memory''' is a memory register whose value is stored as the position of a [[block]]. The block can be moved by means of [[glider]] collisions. See [[block pusher]] for an example. | ||
In Conway's original formulation, as part of his proof of the existence of a [[universal computer]] in Life, two gliders were used to pull the block inwards by three diagonal spaces as shown below, and thirty gliders were used to push it out by the same amount. | In Conway's original formulation, as part of his proof of the existence of a [[universal computer]] in Life, two gliders were used to [[pull]] the block inwards by three diagonal spaces as shown below, and thirty gliders were used to [[push]] it out by the same amount. | ||
{{EmbedViewer | {{EmbedViewer | ||
|pname = | |pname = originalsbmpull | ||
|viewerconfig = #C [[ THUMBNAIL THUMBSIZE 2 THEME 6 GRID GPS 10 LOOP 40 ZOOM 20 PAUSE 2 AUTOSTART ]] | |viewerconfig = #C [[ THUMBNAIL THUMBSIZE 2 THEME 6 GRID GPS 10 LOOP 40 ZOOM 20 PAUSE 2 AUTOSTART ]] | ||
|position = center | |position = center | ||
}} | }} | ||
Dean Hickerson later greatly improved on this, | Dean Hickerson later greatly improved on this, finding a way to pull a block inwards by one diagonal space using 2 gliders, and push it out the same distance using 3 gliders. In order for the memory to be of any use there also has to be a way to read the value held. It suffices to be able to check whether the value is zero (as Conway did), or to be able to detect the transition from one to zero (as Hickerson did). | ||
Dean Hickerson's sliding block memory is used in Paul Chapman's [[URM]], and several other complex constructions such as Adam P. Goucher's [[pi calculator]] and [[Spartan | Dean Hickerson's sliding block memory is used in Paul Chapman's [[URM]], and several other complex constructions such as Adam P. Goucher's [[pi calculator]] and [[Spartan universal computer-constructor]], and David Bell's [[Collatz 5N+1 simulator]]. | ||
== | == External links == | ||
* {{LinkLexicon|lex_s.htm#slidingblockmemory}} | |||
* {{LinkCallahan|patterns/sbm/sbm.html|patternname=Sliding block memory}} | |||
[[Category:Universal computation]] | |||
Latest revision as of 05:21, 24 March 2023
A sliding block memory is a memory register whose value is stored as the position of a block. The block can be moved by means of glider collisions. See block pusher for an example.
In Conway's original formulation, as part of his proof of the existence of a universal computer in Life, two gliders were used to pull the block inwards by three diagonal spaces as shown below, and thirty gliders were used to push it out by the same amount.
| (click above to open LifeViewer) RLE: here Plaintext: here |
Dean Hickerson later greatly improved on this, finding a way to pull a block inwards by one diagonal space using 2 gliders, and push it out the same distance using 3 gliders. In order for the memory to be of any use there also has to be a way to read the value held. It suffices to be able to check whether the value is zero (as Conway did), or to be able to detect the transition from one to zero (as Hickerson did).
Dean Hickerson's sliding block memory is used in Paul Chapman's URM, and several other complex constructions such as Adam P. Goucher's pi calculator and Spartan universal computer-constructor, and David Bell's Collatz 5N+1 simulator.
External links
- Sliding block memory at the Life Lexicon
- Sliding block memory at Paul Callahan's Page of Conway's Life Miscellany