Abelian Logic Gates. (13th March 2019)

• Record Type: Journal Article
• Authors: HOLROYD, ALEXANDER E.; LEVINE, LIONEL; WINKLER, PETER
• Is Part Of: Combinatorics, probability and computing. Volume 28:Number 3(2019)
• Page Start: 388
• Page End: 422
• Publication Date: 2019-03-13
• Subjects: Primary 68Q10, -- Secondary 68Q45, -- 68Q85, -- 90B10; Combinatorial analysis -- Periodicals; Probabilities -- Periodicals; Computer science -- Mathematics -- Periodicals; 511.6
• DOI: 10.1017/S0963548318000482
• Languages: English
• ISSNs: 0963-5483

Abstract

Abstract : An abelian processor is an automaton whose output is independent of the order of its inputs. Bond and Levine have proved that a network of abelian processors performs the same computation regardless of processing order (subject only to a halting condition). We prove that any finite abelian processor can be emulated by a network of certain very simple abelian processors, which we call gates. The most fundamental gate is a toppler, which absorbs input particles until their number exceeds some given threshold, at which point it topples, emitting one particle and returning to its initial state. With the exception of an adder gate, which simply combines two streams of particles, each of our gates has only one input wire, which sends letters ('particles') from a unary alphabet. Our results can be reformulated in terms of the functions computed by processors, and one consequence is that any increasing function from ℕ k to ℕ ℓ that is the sum of a linear function and a periodic function can be expressed in terms of (possibly nested) sums of floors of quotients by integers.