Finite Automata Reduction: Difference between revisions

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Reference for Nondeterministic Finite Automata
 
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See [https://github.com/bbchallenge/bbchallenge-proofs/blob/build-latex-pdf/deciders/correctness-deciders.pdf Section 6] of bbchallenge's deciders write-up.
'''Finite Automata Reduction''' (short '''FAR''') is a co-[[CTL]] [[decider]]. It works by finding a regular language restricted to a class of Nondeterministic Finite Automata<ref>https://arxiv.org/pdf/2509.12337 Determination of the fifth Busy Beaver value</ref> containing all eventually halting configurations of a TM. If the empty tape is not in the regular language, the TM has been shown to be non-halting.
==History==
* In October 2022, Finite Automata Reduction is first introduced by Justin Blanchard,<ref>https://github.com/UncombedCoconut/bbchallenge-deciders/tree/finite-automata-reduction/decider-finite-automata-reduction</ref> later in October, Konrad Deka developes an SAT-based FAR implementation.<ref>https://github.com/colette-b/bbchallenge</ref>
* In January 2023, Finite Automata Reduction is reproduced by Tony Guilfoyle.<ref>https://github.com/TonyGuil/bbchallenge/tree/main/FAR</ref>
* In April 2023, the decider is added to the deciders write-up, becoming section 6. Later in April, it is also reproduced by Tristan Stérin.<ref>https://github.com/bbchallenge/bbchallenge-deciders/tree/main/decider-finite-automata-reduction-reproduction</ref> On the 9th of April, Finite Automata Reduction is applied on the remaining [[BB(5)]] holdouts.<ref>https://discuss.bbchallenge.org/t/decider-finite-automata-reduction/123</ref>
 
==See also==
* [https://github.com/bbchallenge/bbchallenge-proofs/blob/build-latex-pdf/deciders/correctness-deciders.pdf Section 6] of bbchallenge's deciders write-up.
* [[Meet-in-the-Middle Weighted Finite Automata Reduction (MITMWFAR)]]
 
==References==
[[Category:Deciders]]
[[Category:Deciders]]

Latest revision as of 20:53, 20 February 2026

Finite Automata Reduction (short FAR) is a co-CTL decider. It works by finding a regular language restricted to a class of Nondeterministic Finite Automata[1] containing all eventually halting configurations of a TM. If the empty tape is not in the regular language, the TM has been shown to be non-halting.

History

  • In October 2022, Finite Automata Reduction is first introduced by Justin Blanchard,[2] later in October, Konrad Deka developes an SAT-based FAR implementation.[3]
  • In January 2023, Finite Automata Reduction is reproduced by Tony Guilfoyle.[4]
  • In April 2023, the decider is added to the deciders write-up, becoming section 6. Later in April, it is also reproduced by Tristan Stérin.[5] On the 9th of April, Finite Automata Reduction is applied on the remaining BB(5) holdouts.[6]

See also

References