Parity games have been broadly studied in recent years for their applications to controller synthesis and verification. In practice, partial solvers for parity games that execute in polynomial time, while incomplete, can solve most games in publicly available benchmark suites. In this paper, we combine those partial solvers with the classical recursive algorithm for parity games due to Zielonka. We also extend partial solvers to generalized parity games that are games with conjunction of parity objectives. We have implemented those algorithms and evaluated them on a large set of benchmarks proposed in the last LTL synthesis competition.

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We study the rational verification problem which consists in verifying the correctness of a system executing in an environment that is assumed to behave rationally. We consider the model of rationality in which the environment only executes behaviors that are Pareto-optimal with regards to its set of objectives, given the behaviour of the system (which is committed in advance of any interaction). When the objectives are ω-regular, we prove that the Pareto-rational verification problem is co-NP-complete and fixed-parameter tractable (FPT) in the number of objectives of the environment. When the objectives are described by LTL formulas, the problem is PSPACE-complete as the classical LTL modelchecking problem. In order to evaluate the applicability of our results in practice, we have implemented and evaluated two variations of our FPT algorithm on our running example and on randomly generated instances.

We study the framework of two-player Stackelberg games played on graphs in which Player 0 announces a strategy and Player 1 responds rationally with a strategy that is an optimal response. While it is usually assumed that Player 1 has a single objective, we consider here the new setting where he has several. In this context, after responding with his strategy, Player 1 gets a payoff in the form of a vector of Booleans corresponding to his satisfied objectives. Rationality of Player 1 is encoded by the fact that his response must produce a Pareto-optimal payoff given the strategy of Player 0. We study for several kinds of -regular objectives the Stackelberg-Pareto Synthesis problem which asks whether Player 0 can announce a strategy which satisfies his objective, whatever the rational response of Player 1. We show that this problem is fixed-parameter tractable for games in which objectives are all reachability, safety, Büchi, co-Büchi, Boolean Büchi, parity, Muller, Streett or Rabin objectives. We also show that this problem is NEXPTIME-complete except for the cases of Büchi objectives for which it is NP-complete and co-Büchi objectives for which it is in NEXPTIME and NP-hard.The problem is already NP-complete in the simple case of reachability objectives and graphs that are trees. CCS Concepts: • Theory of computation → Logic and verification; Solution concepts in game theory; • Software and its engineering → Formal methods.

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