This paper discusses the problem of efficiently solving parity games where player Odd has to obey an additional strong transition fairness constraint on its vertices - given that a player Odd vertex v is visited infinitely often, a particular subset of the outgoing edges (called live edges) of v has to be taken infinitely often. Such games, which we call Odd-fair parity games, naturally arise from abstractions of cyber-physical systems for planning and control. In this paper, we present a new Zielonka-type algorithm for solving Odd-fair parity games. This algorithm not only shares the same worst-case time complexity as Zielonka’s algorithm for (normal) parity games but also preserves the algorithmic advantage Zielonka’s algorithm possesses over other parity solvers with exponential time complexity. We additionally introduce a formalization of Odd player winning strategies in such games, which were unexplored previous to this work. This formalization serves dual purposes: firstly, it enables us to prove our Zielonka-type algorithm; secondly, it stands as a noteworthy contribution in its own right, augmenting our understanding of additional fairness assumptions in two-player games.
@InProceedings{saglam_et_al:LIPIcs.FSTTCS.2023.34, author = {Sa\u{g}lam, Irmak and Schmuck, Anne-Kathrin}, title = {{Solving Odd-Fair Parity Games}}, booktitle = {43rd IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2023)}, pages = {34:1--34:24}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-304-1}, ISSN = {1868-8969}, year = {2023}, volume = {284}, editor = {Bouyer, Patricia and Srinivasan, Srikanth}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2023.34}, URN = {urn:nbn:de:0030-drops-194077}, doi = {10.4230/LIPIcs.FSTTCS.2023.34}, annote = {Keywords: parity games, strong transition fairness, algorithmic game theory} }
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