Game-Based Verification and Synthesis
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Downloaded from orbit.dtu.dk on: Sep 30, 2021 Game-based verification and synthesis Vester, Steen Publication date: 2016 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Vester, S. (2016). Game-based verification and synthesis. Technical University of Denmark. DTU Compute PHD-2016 No. 414 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Ph.D. Thesis Doctor of Philosophy Game-based verification and synthesis Steen Vester Kongens Lyngby, Denmark 2016 PHD-2016-414 ISSN: 0909-3192 DTU Compute Department of Applied Mathematics and Computer Science Technical University of Denmark Richard Petersens Plads Building 324 2800 Kongens Lyngby, Denmark Phone +45 4525 3031 [email protected] www.compute.dtu.dk Summary Infinite-duration games provide a convenient way to model distributed, reactive and open systems in which several entities and an uncontrollable environment interact. Here, each entitity as well as the uncontrollable environment are modelled as players. A strategy for an entity player in the model corresponds directly to a program for the corresponding entity of the system. A strategy for a player which ensures that the player wins no matter how the other players behave then corresponds to a program ensuring that the specification of the entity is satisfied no matter how the other entities and the environment behaves. Synthesis of strategies in games can thus be used for automatic generation of correct-by-construction programs from specifications. We consider verification and synthesis problems for several well-known game-based models. This includes both model-checking problems and satisfiability problems for logics capable of expressing strategic abilities of players in games with both qualitative and quantitative objectives. A number of computational complexity results for model-checking and satisfiabil- ity problems in this domain are obtained. We also show how the technique of sym- metry reduction can be extended to solve finitely-branching turn-based games more efficiently. Further, the novel concept of winning cores in parity games is introduced. We use this to develop a new polynomial-time under-approximation algorithm for solving parity games. Experimental results show that this algorithm performs better than the state-of-the-art algorithms in most benchmark games. Two new game-based modelling formalisms for distributed systems are presented. The first makes it possible to reason about systems where several identical entities interact. The second provides a game-based modelling formalism for distributed systems with continuous time and probability distributions over the duration of delays. For these new models we provide decidability and undecidability results for problems concerning computation of symmetric Nash equilibria and for deciding existence of strategies that ensure reaching a target with a high probability. ii Resumé Spil af uendelig varighed udgør bekvemme modeller for distribuerede, reaktive og åbne systemer hvori flere enheder og et ukontrollerbart miljø interagerer. Hver enkelt enhed samt det ukontrollerbare miljø modelleres som spillere. En strategi for en enhedsspiller i modellen svarer direkte til et program for den tilsvarende enhed i systemet. En strategi for en spiller, som sikrer at spilleren vinder ligegyldigt hvordan de andre spillere opfører sig, svarer så til et program der sikrer at specifikationen for enheden overholdes ligegyldigt hvordan de andre enheder og miljøet opfører sig. Syntese af strategier i spil kan således anvendes til automatisk generering af programmer fra specifikationer, der er korrekte per konstruktion. Vi betragter verifikations- og synteseproblemer for flere velkendte spilbaserede modeller. Det inkluderer både model-checking problemer og satisfiability problemer for logikker som kan udtrykke strategiske evner for spillere i spil med både kvalitative og kvantitative mål. En række beregningsmæssige kompleksitetsresultater for model-checking og satisfi- ability problemer indenfor dette felt bliver opnået. Vi viser også hvordan symmetrire- duktion kan genereliseres til turbaserede spil med endelig forgrening. Desuden intro- duceres det nye koncept vindende kerner i parity games. Dette bruges til at udvikle en ny underapproksimerende algoritme som kører i polynomiel tid. Eksperimentelle resultater viser at denne algoritme præsterer bedre end de eksisterende algoritmer for de fleste benchmark spil. To nye spilbaserede modelleringsformalismer for distribuerede systemer bliver præsenteret. Den første gør det muligt at ræsonnere om systemer hvor flere iden- tiske enheder interagerer. Den anden er en formalisme for distribuerede systemer med kontinuert tid og sandsynlighedsfordelinger over varigheden af forsinkelser. For disse nye modeller præsenterers afgørbarheds- og uafgørbarhedsresultater for proble- mer vedrørende beregning af symmetriske Nash ligevægte og eksistens af strategier som sikrer at nå en bestemt tilstand med høj sandsynlighed. iv Preface This Ph.d. thesis was prepared at the department of Applied Mathematics and Com- puter Science at the Technical University of Denmark in fulfillment of the require- ments for acquiring a Ph.d. degree. This work has been supervised by Michael Re- ichhardt Hansen, Technical University of Denmark and Valentin Goranko, Stockholm University. The thesis focuses on foundational models and techniques for game-based verifi- cation and synthesis. It presents results from the following scientific publications: • [BMV14] Patricia Bouyer, Nicolas Markey, and Steen Vester. “Nash Equilib- ria in Symmetric Games with Partial Observation”. In: Proceedings 2nd In- ternational Workshop on Strategic Reasoning (SR). Electronic Proceedings in Theoretical Computer Science. Grenoble, France, 2014, pages 49–55 • [BMV16] Patricia Bouyer, Nicolas Markey, and Steen Vester. “Nash Equilibria in Symmetric Graph Games with Partial Observation”. To appear in a special issue of Information & Computation. 2016 • [GV14] Valentin Goranko and Steen Vester. “Optimal Decision Procedures for Satisfiability in Fragments of Alternating-time Temporal Logics”. In: Advances in Modal Logic 10, invited and contributed papers from the tenth conference on Advances in Modal Logic (AiML). 2014, pages 234–253 • [HKV16] Holger Hermanns, Jan Krcál, and Steen Vester. “Distributed Synthe- sis in Continuous Time”. In: Foundations of Software Science and Computation Structures (FOSSACS) - 19th International Conference. 2016, pages 353–369 • [MV14] Nicolas Markey and Steen Vester. “Symmetry Reduction in Infinite Games with Finite Branching”. In: Proceedings of the 12th International Sym- posium on Automated Technology for Verification and Analysis (ATVA). vol- ume 8837. Lecture Notes in Computer Science. Springer, November 2014, pages 281–296 • [Ves15] Steen Vester. “On the Complexity of Model-Checking Branching and Alternating-Time Temporal Logics in One-Counter Systems”. In: Proceedings of the 13th International Symposium on Automated Technology for Verification and Analysis (ATVA). 2015, pages 361–377 vi Preface • [Ves16] Steen Vester. “Winning Cores in Parity Games”. To appear in Proceed- ings of the 31st Annual ACM/IEEE Symposium on Logic in Computer Science (LICS). 2016 All results presented in this thesis are from these papers. The presentation of the results have been adapted to this thesis, but no new results have been added. Before each chapter we write which papers the chapter is based on and summarize the changes that have been made when adapting them for the thesis. Kongens Lyngby, Denmark, April 30, 2016 Steen Vester Acknowledgements I want to thank my two supervisors Michael Reichhardt Hansen and Valentin Goranko for supporting, teaching, helping, pushing, guiding, criticizing, believing and inspiring me. I have learned a lot from you both. Not just in a strictly academic way, but in all sorts of small ways. Also, both of you have taught me very different things about life and academia. The surprisingly small overlap between the things you have taught me has taught me another thing: The supervisor role matters a lot and is a very personal thing. I can also conclude that there is not one single good way to supervise. I have enjoyed all the discussions, the visiting and the tennis playing. You have both had a large impact on me. I also want to thank my co-authors Patricia Bouyer, Holger Hermanns, Jan Krćal and Nicolas Markey for fun and interesting collaborations. I had several visits both to LSV, ENS Cachan with Patricia and Nicolas and to Saarland University with Holger and Jan. Jan also joined me for a week at DTU (during which I was half sick most of the time). I have learned a lot from all of you and appreciated working with you a lot! Next, I want to thank all my colleagues and friends in AlgoLoG at DTU for letting me