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Creative Commons Attribution 4.0 International license (CC BY 4.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.CCC.2022.2
URN: urn:nbn:de:0030-drops-165648
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2022/16564/
Tantau, Till
On the Satisfaction Probability of k-CNF Formulas
Abstract
The satisfaction probability σ(ϕ) := Pr_{β:vars(ϕ) → {0,1}}[β ⊧ ϕ] of a propositional formula ϕ is the likelihood that a random assignment β makes the formula true. We study the complexity of the problem kSAT-PROB_{> δ} = {ϕ is a kCNF formula ∣ σ(ϕ) > δ} for fixed k and δ. While 3SAT-PROB_{> 0} = 3SAT is NP-complete and SAT-PROB}_{> 1/2} is PP-complete, Akmal and Williams recently showed 3SAT-PROB_{> 1/2} ∈ P and 4SAT-PROB_{> 1/2} ∈ NP-complete; but the methods used to prove these striking results stay silent about, say, 4SAT-PROB_{> 3/4}, leaving the computational complexity of kSAT-PROB_{> δ} open for most k and δ. In the present paper we give a complete characterization in the form of a trichotomy: kSAT-PROB_{> δ} lies in AC⁰, is NL-complete, or is NP-complete; and given k and δ we can decide which of the three applies. The proof of the trichotomy hinges on a new order-theoretic insight: Every set of kCNF formulas contains a formula of maximal satisfaction probability. This deceptively simple result allows us to (1) kernelize kSAT-PROB_{≥ δ}, (2) show that the variables of the kernel form a strong backdoor set when the trichotomy states membership in AC⁰ or NL, and (3) prove a locality property by which for every kCNF formula ϕ we have σ(ϕ) ≥ δ iff σ(ψ) ≥ δ for every fixed-size subset ψ of ϕ’s clauses. The locality property will allow us to prove a conjecture of Akmal and Williams: The majority-of-majority satisfaction problem for kCNFS lies in P for all k.
BibTeX - Entry
@InProceedings{tantau:LIPIcs.CCC.2022.2,
author = {Tantau, Till},
title = {{On the Satisfaction Probability of k-CNF Formulas}},
booktitle = {37th Computational Complexity Conference (CCC 2022)},
pages = {2:1--2:27},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-241-9},
ISSN = {1868-8969},
year = {2022},
volume = {234},
editor = {Lovett, Shachar},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/opus/volltexte/2022/16564},
URN = {urn:nbn:de:0030-drops-165648},
doi = {10.4230/LIPIcs.CCC.2022.2},
annote = {Keywords: Satisfaction probability, majority it\{k\}-sat, kernelization, well orderings, locality}
}
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Keywords: |
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Satisfaction probability, majority it{k}-sat, kernelization, well orderings, locality |
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Collection: |
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37th Computational Complexity Conference (CCC 2022) |
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Issue Date: |
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2022 |
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Date of publication: |
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11.07.2022 |
