A Direct Reduction from Stochastic Parity Games to Simple Stochastic Games

Fuente: arXiv
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Autores principales: Berthon, Raphaël, Katoen, Joost-Pieter, Zhou, Zihan
Formato: Preprint
Publicado: 2025
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author Berthon, Raphaël
Katoen, Joost-Pieter
Zhou, Zihan
author_facet Berthon, Raphaël
Katoen, Joost-Pieter
Zhou, Zihan
contents Significant progress has been recently achieved in developing efficient solutions for simple stochastic games (SSGs), focusing on reachability objectives. While reductions from stochastic parity games (SPGs) to SSGs have been presented in the literature through the use of multiple intermediate game models, a direct and simple reduction has been notably absent. This paper introduces a novel and direct polynomial-time reduction from quantitative SPGs to quantitative SSGs. By leveraging a gadget-based transformation that effectively removes the priority function, we construct an SSG that simulates the behavior of a given SPG. We formally establish the correctness of our direct reduction. Furthermore, we demonstrate that under binary encoding this reduction is polynomial, thereby directly corroborating the known $\textbf{NP}\,\mathbf{\cap}\,\textbf{coNP}$ complexity of SPGs and providing new understanding in the relationship between parity and reachability objectives in turn-based stochastic games.
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id arxiv_https___arxiv_org_abs_2506_06223
institution arXiv
publishDate 2025
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spellingShingle A Direct Reduction from Stochastic Parity Games to Simple Stochastic Games
Berthon, Raphaël
Katoen, Joost-Pieter
Zhou, Zihan
Computer Science and Game Theory
Significant progress has been recently achieved in developing efficient solutions for simple stochastic games (SSGs), focusing on reachability objectives. While reductions from stochastic parity games (SPGs) to SSGs have been presented in the literature through the use of multiple intermediate game models, a direct and simple reduction has been notably absent. This paper introduces a novel and direct polynomial-time reduction from quantitative SPGs to quantitative SSGs. By leveraging a gadget-based transformation that effectively removes the priority function, we construct an SSG that simulates the behavior of a given SPG. We formally establish the correctness of our direct reduction. Furthermore, we demonstrate that under binary encoding this reduction is polynomial, thereby directly corroborating the known $\textbf{NP}\,\mathbf{\cap}\,\textbf{coNP}$ complexity of SPGs and providing new understanding in the relationship between parity and reachability objectives in turn-based stochastic games.
title A Direct Reduction from Stochastic Parity Games to Simple Stochastic Games
topic Computer Science and Game Theory
url https://arxiv.org/abs/2506.06223