A Quasi-Polynomial Black-Box Algorithm for Fixed Point Evaluation

Authors André Arnold, Damian Niwiński, Paweł Parys

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Author Details

André Arnold
  • Independent Researcher, Talence, France
Damian Niwiński
  • Institute of Informatics, University of Warsaw, Poland
Paweł Parys
  • Institute of Informatics, University of Warsaw, Poland

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André Arnold, Damian Niwiński, and Paweł Parys. A Quasi-Polynomial Black-Box Algorithm for Fixed Point Evaluation. In 29th EACSL Annual Conference on Computer Science Logic (CSL 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 183, pp. 9:1-9:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


We consider nested fixed-point expressions like μ z. ν y. μ x. f(x,y,z) evaluated over a finite lattice, and ask how many queries to a function f are needed to find the value. The previous upper bounds for a monotone function f of arity d over the lattice {0,1}ⁿ were of the order n^{𝒪(d)}, whereas a lower bound of Ω(n²/(lg n)) is known in case when at least one alternation between the least (μ) and the greatest (ν) fixed point occurs in the expression. Following a recent development for parity games, we show here that a quasi-polynomial number of queries is sufficient, namely n^{lg(d/lg n)+𝒪(1)}. The algorithm is an abstract version of several algorithms proposed recently by a number of authors, which involve (implicitly or explicitly) the structure of a universal tree. We then show a quasi-polynomial lower bound for the number of queries used by the algorithms in consideration.

Subject Classification

ACM Subject Classification
  • Theory of computation → Logic and verification
  • Mu-calculus
  • Parity games
  • Quasi-polynomial time
  • Black-box algorithm


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