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We present a general framework which allows to identify complex theories important in verification for which efficient reasoning methods exist. The framework we present is based on a general notion of locality. We show that locality considerations allow us to obtain parameterized decidability and complexity results for many (combinations of) theories important in verification in general and in the verification of parametric systems in particular. We give numerous examples; in particular we show that several theories of data structures studied in the verification literature are local extensions of a base theory. The general framework we use allows us to identify situations in which some of the syntactical restrictions imposed in previous papers can be relaxed.

Abstract. We introduce the reactive synthesis competition (SYNTCOMP), a long-term effort intended to stimulate and guide advances in the design and application of synthesis procedures for reactive systems. The first iteration of SYNTCOMP is based on the controller synthesis problem for finite-state systems and safety specifications. We provide an overview of this problem and existing approaches to solve it, and report on the design and results of the first SYNTCOMP. This includes the definition of the benchmark format, the collection of benchmarks, the rules of the competition, and the five synthesis tools that participated. We present and analyze the results of the competition and draw conclusions on the state of the art. Finally, we give an outlook on future directions of SYNTCOMP.

We revisit the parameterized model checking problem for token-passing systems and specifications in indexed CTL * \X. Namjoshi (1995, 2003) have shown that parameterized model checking of indexed CTL * \X in uni-directional token rings can be reduced to checking rings up to some cutoff size. Clarke et al. (2004) have shown a similar result for general topologies and indexed LTL\X, provided processes cannot choose the directions for sending or receiving the token.We unify and substantially extend these results by systematically exploring fragments of indexed CTL * \X with respect to general topologies. For each fragment we establish whether a cutoff exists, and for some concrete topologies, such as rings, cliques and stars, we infer small cutoffs.Finally, we show that the problem becomes undecidable, and thus no cutoffs exist, if processes are allowed to choose the directions in which they send or from which they receive the token.

We report on the benchmarks, participants and results of the third reactive synthesis competition (SYNTCOMP 2016). The benchmark library of SYNTCOMP 2016 has been extended to benchmarks in the new LTL-based temporal logic synthesis format (TLSF), and 2 new sets of benchmarks for the existing AIGER-based format for safety specifications. The participants of SYNTCOMP 2016 can be separated according to these two classes of specifications, and we give an overview of the 6 tools that entered the competition in the AIGER-based track, and the 3 participants that entered the TLSF-based track. We briefly describe the benchmark selection, evaluation scheme and the experimental setup of SYNTCOMP 2016. Finally, we present and analyze the results of our experimental evaluation, including a comparison to participants of previous competitions and a legacy tool. IntroductionSince the definition of the problem more than 50 years ago [16], the automatic synthesis of reactive systems from formal specifications is one of the major challenges of computer science. Research into the basic questions related to the problem has led to a large body of theoretical results, but their impact on the practice of system design has been rather limited. To increase the impact of theoretical advancements in synthesis, the reactive synthesis competition (SYNTCOMP) has been founded in 2014 [27]. The competition is designed to foster research in scalable and user-friendly implementations of synthesis techniques by establishing a standard benchmark format, maintaining a challenging public benchmark library, and providing a dedicated and independent platform for the comparison of tools under consistent experimental conditions.The venues. A design choice for the first two competitions was to focus on safety properties specified as monitor circuits in an extension of the AIGER format known from the hardware model checking competition [15,25]. SYNTCOMP 2016 introduces the first major extension of the competition: in addition to the existing competition track, we introduce a new track that is based on properties in full linear temporal logic (LTL), given in the temporal logic synthesis format (TLSF) recently introduced by Jacobs, Klein and Schirmer [29].The organization team of SYNTCOMP 2016 consisted of R. Bloem and S. Jacobs, with technical assistance from J. Kreber for the setup and execution, and from F. Klein for the integration of TLSF.The rest of this paper describes the design, benchmarks, participants, and results of SYNTCOMP 2016. We present the benchmark set for SYNTCOMP 2016 in Section 2, followed by a description of the setup, rules and execution of the competition in Section 3. In Section 4 we give an overview of the participants of SYNTCOMP 2016, focusing on changes compared to last year's participants. Finally, the experimental results are presented and analyzed in Section 5.Note that more details on the goals and design of the competition can be found in the sister paper that discusses the design of SYNTCOMP in 2016 and the future [26]. Be...

Abstract. We propose algorithms significantly extending the limits for maintaining exact representations in the verification of linear hybrid systems with large discrete state spaces. We use AND-Inverter Graphs (AIGs) extended with linear constraints (LinAIGs) as symbolic representation of the hybrid state space, and show how methods for maintaining compactness of AIGs can be lifted to support model-checking of linear hybrid systems with large discrete state spaces. This builds on a novel approach for eliminating sets of redundant constraints in such rich hybrid state representations by a suitable exploitation of the capabilities of SMT solvers, which is of independent value beyond the application context studied in this paper. We used a benchmark derived from an Airbus flap control system (containing 2 20 discrete states) to demonstrate the relevance of the approach.

We report on the design and results of the second reactive synthesis competition (SYNTCOMP 2015). We describe our extended benchmark library, with 6 completely new sets of benchmarks, and additional challenging instances for 4 of the benchmark sets that were already used in SYNTCOMP 2014. To enhance the analysis of experimental results, we introduce an extension of our benchmark format with meta-information, including a difficulty rating and a reference size for solutions. Tools are evaluated on a set of 250 benchmarks, selected to provide a good coverage of benchmarks from all classes and difficulties. We report on changes of the evaluation scheme and the experimental setup. Finally, we describe the entrants into SYNTCOMP 2015, as well as the results of our experimental evaluation. In our analysis, we emphasize progress over the tools that participated last year.Comment: In Proceedings SYNT 2015, arXiv:1602.0078

Guarded protocols were introduced in a seminal paper by Emerson and Kahlon (2000), and describe systems of processes whose transitions are enabled or disabled depending on the existence of other processes in certain local states. We study parameterized model checking and synthesis of guarded protocols, both aiming at formal correctness arguments for systems with any number of processes. Cutoff results reduce reasoning about systems with an arbitrary number of processes to systems of a determined, fixed size. Our work stems from the observation that existing cutoff results for guarded protocols i) are restricted to closed systems, and ii) are of limited use for liveness properties because reductions do not preserve fairness. We close these gaps and obtain new cutoff results for open systems with liveness properties under fairness assumptions. Furthermore, we obtain cutoffs for the detection of global and local deadlocks, which are of paramount importance in synthesis. Finally, we prove tightness or asymptotic tightness for the new cutoffs.Comment: Accepted for publication at VMCAI 2016. Extended version, revised after conference review