17 Search Results for "Bloem, Roderick"


Document
Optimal Strategies in Concurrent Reachability Games

Authors: Benjamin Bordais, Patricia Bouyer, and Stéphane Le Roux

Published in: LIPIcs, Volume 216, 30th EACSL Annual Conference on Computer Science Logic (CSL 2022)


Abstract
We study two-player reachability games on finite graphs. At each state the interaction between the players is concurrent and there is a stochastic Nature. Players also play stochastically. The literature tells us that 1) Player 𝖡, who wants to avoid the target state, has a positional strategy that maximizes the probability to win (uniformly from every state) and 2) from every state, for every ε > 0, Player 𝖠 has a strategy that maximizes up to ε the probability to win. Our work is two-fold. First, we present a double-fixed-point procedure that says from which state Player 𝖠 has a strategy that maximizes (exactly) the probability to win. This is computable if Nature’s probability distributions are rational. We call these states maximizable. Moreover, we show that for every ε > 0, Player 𝖠 has a positional strategy that maximizes the probability to win, exactly from maximizable states and up to ε from sub-maximizable states. Second, we consider three-state games with one main state, one target, and one bin. We characterize the local interactions at the main state that guarantee the existence of an optimal Player 𝖠 strategy. In this case there is a positional one. It turns out that in many-state games, these local interactions also guarantee the existence of a uniform optimal Player 𝖠 strategy. In a way, these games are well-behaved by design of their elementary bricks, the local interactions. It is decidable whether a local interaction has this desirable property.

Cite as

Benjamin Bordais, Patricia Bouyer, and Stéphane Le Roux. Optimal Strategies in Concurrent Reachability Games. In 30th EACSL Annual Conference on Computer Science Logic (CSL 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 216, pp. 7:1-7:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


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@InProceedings{bordais_et_al:LIPIcs.CSL.2022.7,
  author =	{Bordais, Benjamin and Bouyer, Patricia and Le Roux, St\'{e}phane},
  title =	{{Optimal Strategies in Concurrent Reachability Games}},
  booktitle =	{30th EACSL Annual Conference on Computer Science Logic (CSL 2022)},
  pages =	{7:1--7:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-218-1},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{216},
  editor =	{Manea, Florin and Simpson, Alex},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2022.7},
  URN =		{urn:nbn:de:0030-drops-157278},
  doi =		{10.4230/LIPIcs.CSL.2022.7},
  annote =	{Keywords: Concurrent reachability games, Game forms, Optimal strategies}
}
Document
History Determinism vs. Good for Gameness in Quantitative Automata

Authors: Udi Boker and Karoliina Lehtinen

Published in: LIPIcs, Volume 213, 41st IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2021)


Abstract
Automata models between determinism and nondeterminism/alternations can retain some of the algorithmic properties of deterministic automata while enjoying some of the expressiveness and succinctness of nondeterminism. We study three closely related such models - history determinism, good for gameness and determinisability by pruning - on quantitative automata. While in the Boolean setting, history determinism and good for gameness coincide, we show that this is no longer the case in the quantitative setting: good for gameness is broader than history determinism, and coincides with a relaxed version of it, defined with respect to thresholds. We further identify criteria in which history determinism, which is generally broader than determinisability by pruning, coincides with it, which we then apply to typical quantitative automata types. As a key application of good for games and history deterministic automata is synthesis, we clarify the relationship between the two notions and various quantitative synthesis problems. We show that good-for-games automata are central for "global" (classical) synthesis, while "local" (good-enough) synthesis reduces to deciding whether a nondeterministic automaton is history deterministic.

Cite as

Udi Boker and Karoliina Lehtinen. History Determinism vs. Good for Gameness in Quantitative Automata. In 41st IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 213, pp. 38:1-38:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


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@InProceedings{boker_et_al:LIPIcs.FSTTCS.2021.38,
  author =	{Boker, Udi and Lehtinen, Karoliina},
  title =	{{History Determinism vs. Good for Gameness in Quantitative Automata}},
  booktitle =	{41st IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2021)},
  pages =	{38:1--38:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-215-0},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{213},
  editor =	{Boja\'{n}czyk, Miko{\l}aj and Chekuri, Chandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2021.38},
  URN =		{urn:nbn:de:0030-drops-155495},
  doi =		{10.4230/LIPIcs.FSTTCS.2021.38},
  annote =	{Keywords: Good for games, history determinism, alternation, quantitative automata}
}
Document
Synthesis from Weighted Specifications with Partial Domains over Finite Words

Authors: Emmanuel Filiot, Christof Löding, and Sarah Winter

Published in: LIPIcs, Volume 182, 40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020)


Abstract
In this paper, we investigate the synthesis problem of terminating reactive systems from quantitative specifications. Such systems are modeled as finite transducers whose executions are represented as finite words in (I × O)^*, where I, O are finite sets of input and output symbols, respectively. A weighted specification S assigns a rational value (or -∞) to words in (I × O)^*, and we consider three kinds of objectives for synthesis, namely threshold objectives where the system’s executions are required to be above some given threshold, best-value and approximate objectives where the system is required to perform as best as it can by providing output symbols that yield the best value and ε-best value respectively w.r.t. S. We establish a landscape of decidability results for these three objectives and weighted specifications with partial domain over finite words given by deterministic weighted automata equipped with sum, discounted-sum and average measures. The resulting objectives are not regular in general and we develop an infinite game framework to solve the corresponding synthesis problems, namely the class of (weighted) critical prefix games.

Cite as

Emmanuel Filiot, Christof Löding, and Sarah Winter. Synthesis from Weighted Specifications with Partial Domains over Finite Words. In 40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 182, pp. 46:1-46:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


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@InProceedings{filiot_et_al:LIPIcs.FSTTCS.2020.46,
  author =	{Filiot, Emmanuel and L\"{o}ding, Christof and Winter, Sarah},
  title =	{{Synthesis from Weighted Specifications with Partial Domains over Finite Words}},
  booktitle =	{40th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2020)},
  pages =	{46:1--46:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-174-0},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{182},
  editor =	{Saxena, Nitin and Simon, Sunil},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2020.46},
  URN =		{urn:nbn:de:0030-drops-132874},
  doi =		{10.4230/LIPIcs.FSTTCS.2020.46},
  annote =	{Keywords: synthesis, weighted games, weighted automata on finite words}
}
Document
Invited Paper
Safe Reinforcement Learning Using Probabilistic Shields (Invited Paper)

Authors: Nils Jansen, Bettina Könighofer, Sebastian Junges, Alex Serban, and Roderick Bloem

Published in: LIPIcs, Volume 171, 31st International Conference on Concurrency Theory (CONCUR 2020)


Abstract
This paper concerns the efficient construction of a safety shield for reinforcement learning. We specifically target scenarios that incorporate uncertainty and use Markov decision processes (MDPs) as the underlying model to capture such problems. Reinforcement learning (RL) is a machine learning technique that can determine near-optimal policies in MDPs that may be unknown before exploring the model. However, during exploration, RL is prone to induce behavior that is undesirable or not allowed in safety- or mission-critical contexts. We introduce the concept of a probabilistic shield that enables RL decision-making to adhere to safety constraints with high probability. We employ formal verification to efficiently compute the probabilities of critical decisions within a safety-relevant fragment of the MDP. These results help to realize a shield that, when applied to an RL algorithm, restricts the agent from taking unsafe actions, while optimizing the performance objective. We discuss tradeoffs between sufficient progress in the exploration of the environment and ensuring safety. In our experiments, we demonstrate on the arcade game PAC-MAN and on a case study involving service robots that the learning efficiency increases as the learning needs orders of magnitude fewer episodes.

Cite as

Nils Jansen, Bettina Könighofer, Sebastian Junges, Alex Serban, and Roderick Bloem. Safe Reinforcement Learning Using Probabilistic Shields (Invited Paper). In 31st International Conference on Concurrency Theory (CONCUR 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 171, pp. 3:1-3:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2020)


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@InProceedings{jansen_et_al:LIPIcs.CONCUR.2020.3,
  author =	{Jansen, Nils and K\"{o}nighofer, Bettina and Junges, Sebastian and Serban, Alex and Bloem, Roderick},
  title =	{{Safe Reinforcement Learning Using Probabilistic Shields}},
  booktitle =	{31st International Conference on Concurrency Theory (CONCUR 2020)},
  pages =	{3:1--3:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-160-3},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{171},
  editor =	{Konnov, Igor and Kov\'{a}cs, Laura},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2020.3},
  URN =		{urn:nbn:de:0030-drops-128155},
  doi =		{10.4230/LIPIcs.CONCUR.2020.3},
  annote =	{Keywords: Safe Reinforcement Learning, Formal Verification, Safe Exploration, Model Checking, Markov Decision Process}
}
Document
Linear High-Order Deterministic Tree Transducers with Regular Look-Ahead

Authors: Paul D. Gallot, Aurélien Lemay, and Sylvain Salvati

Published in: LIPIcs, Volume 170, 45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020)


Abstract
We introduce the notion of high-order deterministic top-down tree transducers (HODT) whose outputs correspond to single-typed lambda-calculus formulas. These transducers are natural generalizations of known models of top-tree transducers such as: Deterministic Top-Down Tree Transducers, Macro Tree Transducers, Streaming Tree Transducers... We focus on the linear restriction of high order tree transducers with look-ahead (HODTR_lin), and prove this corresponds to tree to tree functional transformations defined by Monadic Second Order (MSO) logic. We give a specialized procedure for the composition of those transducers that uses a flow analysis based on coherence spaces and allows us to preserve the linearity of transducers. This procedure has a better complexity than classical algorithms for composition of other equivalent tree transducers, but raises the order of transducers. However, we also indicate that the order of a HODTR_lin can always be bounded by 3, and give a procedure that reduces the order of a HODTR_lin to 3. As those resulting HODTR_lin can then be transformed into other equivalent models, this gives an important insight on composition algorithm for other classes of transducers. Finally, we prove that those results partially translate to the case of almost linear HODTR: the class corresponds to the class of tree transformations performed by MSO with unfolding (not closed by composition), and provide a mechanism to reduce the order to 3 in this case.

Cite as

Paul D. Gallot, Aurélien Lemay, and Sylvain Salvati. Linear High-Order Deterministic Tree Transducers with Regular Look-Ahead. In 45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 170, pp. 38:1-38:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


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@InProceedings{gallot_et_al:LIPIcs.MFCS.2020.38,
  author =	{Gallot, Paul D. and Lemay, Aur\'{e}lien and Salvati, Sylvain},
  title =	{{Linear High-Order Deterministic Tree Transducers with Regular Look-Ahead}},
  booktitle =	{45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020)},
  pages =	{38:1--38:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-159-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{170},
  editor =	{Esparza, Javier and Kr\'{a}l', Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2020.38},
  URN =		{urn:nbn:de:0030-drops-127050},
  doi =		{10.4230/LIPIcs.MFCS.2020.38},
  annote =	{Keywords: Transducers, \lambda-calculus, Trees}
}
Document
A Verified and Compositional Translation of LTL to Deterministic Rabin Automata

Authors: Julian Brunner, Benedikt Seidl, and Salomon Sickert

Published in: LIPIcs, Volume 141, 10th International Conference on Interactive Theorem Proving (ITP 2019)


Abstract
We present a formalisation of the unified translation approach from linear temporal logic (LTL) to omega-automata from [Javier Esparza et al., 2018]. This approach decomposes LTL formulas into "simple" languages and allows a clear separation of concerns: first, we formalise the purely logical result yielding this decomposition; second, we develop a generic, executable, and expressive automata library providing necessary operations on automata to re-combine the "simple" languages; third, we instantiate this generic theory to obtain a construction for deterministic Rabin automata (DRA). We extract from this particular instantiation an executable tool translating LTL to DRAs. To the best of our knowledge this is the first verified translation of LTL to DRAs that is proven to be double-exponential in the worst case which asymptotically matches the known lower bound.

Cite as

Julian Brunner, Benedikt Seidl, and Salomon Sickert. A Verified and Compositional Translation of LTL to Deterministic Rabin Automata. In 10th International Conference on Interactive Theorem Proving (ITP 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 141, pp. 11:1-11:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{brunner_et_al:LIPIcs.ITP.2019.11,
  author =	{Brunner, Julian and Seidl, Benedikt and Sickert, Salomon},
  title =	{{A Verified and Compositional Translation of LTL to Deterministic Rabin Automata}},
  booktitle =	{10th International Conference on Interactive Theorem Proving (ITP 2019)},
  pages =	{11:1--11:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-122-1},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{141},
  editor =	{Harrison, John and O'Leary, John and Tolmach, Andrew},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2019.11},
  URN =		{urn:nbn:de:0030-drops-110664},
  doi =		{10.4230/LIPIcs.ITP.2019.11},
  annote =	{Keywords: Automata Theory, Automata over Infinite Words, Deterministic Automata, Linear Temporal Logic, Model Checking, Verified Algorithms}
}
Document
Long-Run Average Behavior of Vector Addition Systems with States

Authors: Krishnendu Chatterjee, Thomas A. Henzinger, and Jan Otop

Published in: LIPIcs, Volume 140, 30th International Conference on Concurrency Theory (CONCUR 2019)


Abstract
A vector addition system with states (VASS) consists of a finite set of states and counters. A configuration is a state and a value for each counter; a transition changes the state and each counter is incremented, decremented, or left unchanged. While qualitative properties such as state and configuration reachability have been studied for VASS, we consider the long-run average cost of infinite computations of VASS. The cost of a configuration is for each state, a linear combination of the counter values. In the special case of uniform cost functions, the linear combination is the same for all states. The (regular) long-run emptiness problem is, given a VASS, a cost function, and a threshold value, if there is a (lasso-shaped) computation such that the long-run average value of the cost function does not exceed the threshold. For uniform cost functions, we show that the regular long-run emptiness problem is (a) decidable in polynomial time for integer-valued VASS, and (b) decidable but nonelementarily hard for natural-valued VASS (i.e., nonnegative counters). For general cost functions, we show that the problem is (c) NP-complete for integer-valued VASS, and (d) undecidable for natural-valued VASS. Our most interesting result is for (c) integer-valued VASS with general cost functions, where we establish a connection between the regular long-run emptiness problem and quadratic Diophantine inequalities. The general (nonregular) long-run emptiness problem is equally hard as the regular problem in all cases except (c), where it remains open.

Cite as

Krishnendu Chatterjee, Thomas A. Henzinger, and Jan Otop. Long-Run Average Behavior of Vector Addition Systems with States. In 30th International Conference on Concurrency Theory (CONCUR 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 140, pp. 27:1-27:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{chatterjee_et_al:LIPIcs.CONCUR.2019.27,
  author =	{Chatterjee, Krishnendu and Henzinger, Thomas A. and Otop, Jan},
  title =	{{Long-Run Average Behavior of Vector Addition Systems with States}},
  booktitle =	{30th International Conference on Concurrency Theory (CONCUR 2019)},
  pages =	{27:1--27:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-121-4},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{140},
  editor =	{Fokkink, Wan and van Glabbeek, Rob},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2019.27},
  URN =		{urn:nbn:de:0030-drops-109293},
  doi =		{10.4230/LIPIcs.CONCUR.2019.27},
  annote =	{Keywords: vector addition systems, mean-payoff, Diophantine inequalities}
}
Document
Synthesis of Data Word Transducers

Authors: Léo Exibard, Emmanuel Filiot, and Pierre-Alain Reynier

Published in: LIPIcs, Volume 140, 30th International Conference on Concurrency Theory (CONCUR 2019)


Abstract
In reactive synthesis, the goal is to automatically generate an implementation from a specification of the reactive and non-terminating input/output behaviours of a system. Specifications are usually modelled as logical formulae or automata over infinite sequences of signals (omega-words), while implementations are represented as transducers. In the classical setting, the set of signals is assumed to be finite. In this paper, we consider data omega-words instead, i.e., words over an infinite alphabet. In this context, we study specifications and implementations respectively given as automata and transducers extended with a finite set of registers. We consider different instances, depending on whether the specification is nondeterministic, universal or deterministic, and depending on whether the number of registers of the implementation is given or not. In the unbounded setting, we show undecidability for both universal and non-deterministic specifications, while decidability is recovered in the deterministic case. In the bounded setting, undecidability still holds for non-deterministic specifications, but can be recovered by disallowing tests over input data. The generic technique we use to show the latter result allows us to reprove some known result, namely decidability of bounded synthesis for universal specifications.

Cite as

Léo Exibard, Emmanuel Filiot, and Pierre-Alain Reynier. Synthesis of Data Word Transducers. In 30th International Conference on Concurrency Theory (CONCUR 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 140, pp. 24:1-24:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{exibard_et_al:LIPIcs.CONCUR.2019.24,
  author =	{Exibard, L\'{e}o and Filiot, Emmanuel and Reynier, Pierre-Alain},
  title =	{{Synthesis of Data Word Transducers}},
  booktitle =	{30th International Conference on Concurrency Theory (CONCUR 2019)},
  pages =	{24:1--24:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-121-4},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{140},
  editor =	{Fokkink, Wan and van Glabbeek, Rob},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2019.24},
  URN =		{urn:nbn:de:0030-drops-109269},
  doi =		{10.4230/LIPIcs.CONCUR.2019.24},
  annote =	{Keywords: Register Automata, Synthesis, Data words, Transducers}
}
Document
Reconfiguration and Message Losses in Parameterized Broadcast Networks

Authors: Nathalie Bertrand, Patricia Bouyer, and Anirban Majumdar

Published in: LIPIcs, Volume 140, 30th International Conference on Concurrency Theory (CONCUR 2019)


Abstract
Broadcast networks allow one to model networks of identical nodes communicating through message broadcasts. Their parameterized verification aims at proving a property holds for any number of nodes, under any communication topology, and on all possible executions. We focus on the coverability problem which dually asks whether there exists an execution that visits a configuration exhibiting some given state of the broadcast protocol. Coverability is known to be undecidable for static networks, i.e. when the number of nodes and communication topology is fixed along executions. In contrast, it is decidable in PTIME when the communication topology may change arbitrarily along executions, that is for reconfigurable networks. Surprisingly, no lower nor upper bounds on the minimal number of nodes, or the minimal length of covering execution in reconfigurable networks, appear in the literature. In this paper we show tight bounds for cutoff and length, which happen to be linear and quadratic, respectively, in the number of states of the protocol. We also introduce an intermediary model with static communication topology and non-deterministic message losses upon sending. We show that the same tight bounds apply to lossy networks, although, reconfigurable executions may be linearly more succinct than lossy executions. Finally, we show NP-completeness for the natural optimisation problem associated with the cutoff.

Cite as

Nathalie Bertrand, Patricia Bouyer, and Anirban Majumdar. Reconfiguration and Message Losses in Parameterized Broadcast Networks. In 30th International Conference on Concurrency Theory (CONCUR 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 140, pp. 32:1-32:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{bertrand_et_al:LIPIcs.CONCUR.2019.32,
  author =	{Bertrand, Nathalie and Bouyer, Patricia and Majumdar, Anirban},
  title =	{{Reconfiguration and Message Losses in Parameterized Broadcast Networks}},
  booktitle =	{30th International Conference on Concurrency Theory (CONCUR 2019)},
  pages =	{32:1--32:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-121-4},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{140},
  editor =	{Fokkink, Wan and van Glabbeek, Rob},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2019.32},
  URN =		{urn:nbn:de:0030-drops-109345},
  doi =		{10.4230/LIPIcs.CONCUR.2019.32},
  annote =	{Keywords: model checking, parameterized verification, broadcast networks}
}
Document
Energy Mean-Payoff Games

Authors: Véronique Bruyère, Quentin Hautem, Mickael Randour, and Jean-François Raskin

Published in: LIPIcs, Volume 140, 30th International Conference on Concurrency Theory (CONCUR 2019)


Abstract
In this paper, we study one-player and two-player energy mean-payoff games. Energy mean-payoff games are games of infinite duration played on a finite graph with edges labeled by 2-dimensional weight vectors. The objective of the first player (the protagonist) is to satisfy an energy objective on the first dimension and a mean-payoff objective on the second dimension. We show that optimal strategies for the first player may require infinite memory while optimal strategies for the second player (the antagonist) do not require memory. In the one-player case (where only the first player has choices), the problem of deciding who is the winner can be solved in polynomial time while for the two-player case we show co-NP membership and we give effective constructions for the infinite-memory optimal strategies of the protagonist.

Cite as

Véronique Bruyère, Quentin Hautem, Mickael Randour, and Jean-François Raskin. Energy Mean-Payoff Games. In 30th International Conference on Concurrency Theory (CONCUR 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 140, pp. 21:1-21:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{bruyere_et_al:LIPIcs.CONCUR.2019.21,
  author =	{Bruy\`{e}re, V\'{e}ronique and Hautem, Quentin and Randour, Mickael and Raskin, Jean-Fran\c{c}ois},
  title =	{{Energy Mean-Payoff Games}},
  booktitle =	{30th International Conference on Concurrency Theory (CONCUR 2019)},
  pages =	{21:1--21:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-121-4},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{140},
  editor =	{Fokkink, Wan and van Glabbeek, Rob},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2019.21},
  URN =		{urn:nbn:de:0030-drops-109239},
  doi =		{10.4230/LIPIcs.CONCUR.2019.21},
  annote =	{Keywords: two-player zero-sum games played on graphs, energy and mean-payoff objectives, complexity study and construction of optimal strategies}
}
Document
Brave New Idea Paper
Multiverse Debugging: Non-Deterministic Debugging for Non-Deterministic Programs (Brave New Idea Paper)

Authors: Carmen Torres Lopez, Robbert Gurdeep Singh, Stefan Marr, Elisa Gonzalez Boix, and Christophe Scholliers

Published in: LIPIcs, Volume 134, 33rd European Conference on Object-Oriented Programming (ECOOP 2019)


Abstract
Many of today’s software systems are parallel or concurrent. With the rise of Node.js and more generally event-loop architectures, many systems need to handle concurrency. However, its non-deterministic behavior makes it hard to reproduce bugs. Today’s interactive debuggers unfortunately do not support developers in debugging non-deterministic issues. They only allow us to explore a single execution path. Therefore, some bugs may never be reproduced in the debugging session, because the right conditions are not triggered. As a solution, we propose multiverse debugging, a new approach for debugging non-deterministic programs that allows developers to observe all possible execution paths of a parallel program and debug it interactively. We introduce the concepts of multiverse breakpoints and stepping, which can halt a program in different execution paths, i.e. universes. We apply multiverse debugging to AmbientTalk, an actor-based language, resulting in Voyager, a multiverse debugger implemented on top of the AmbientTalk operational semantics. We provide a proof of non-interference, i.e., we prove that observing the behavior of a program by the debugger does not affect the behavior of that program and vice versa. Multiverse debugging establishes the foundation for debugging non-deterministic programs interactively, which we believe can aid the development of parallel and concurrent systems.

Cite as

Carmen Torres Lopez, Robbert Gurdeep Singh, Stefan Marr, Elisa Gonzalez Boix, and Christophe Scholliers. Multiverse Debugging: Non-Deterministic Debugging for Non-Deterministic Programs (Brave New Idea Paper). In 33rd European Conference on Object-Oriented Programming (ECOOP 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 134, pp. 27:1-27:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


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@InProceedings{torreslopez_et_al:LIPIcs.ECOOP.2019.27,
  author =	{Torres Lopez, Carmen and Gurdeep Singh, Robbert and Marr, Stefan and Gonzalez Boix, Elisa and Scholliers, Christophe},
  title =	{{Multiverse Debugging: Non-Deterministic Debugging for Non-Deterministic Programs}},
  booktitle =	{33rd European Conference on Object-Oriented Programming (ECOOP 2019)},
  pages =	{27:1--27:30},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-111-5},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{134},
  editor =	{Donaldson, Alastair F.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2019.27},
  URN =		{urn:nbn:de:0030-drops-108192},
  doi =		{10.4230/LIPIcs.ECOOP.2019.27},
  annote =	{Keywords: Debugging, Parallelism, Concurrency, Actors, Formal Semantics}
}
Document
Synthesis of Distributed Algorithms with Parameterized Threshold Guards

Authors: Marijana Lazic, Igor Konnov, Josef Widder, and Roderick Bloem

Published in: LIPIcs, Volume 95, 21st International Conference on Principles of Distributed Systems (OPODIS 2017)


Abstract
Fault-tolerant distributed algorithms are notoriously hard to get right. In this paper we introduce an automated method that helps in that process: the designer provides specifications (the problem to be solved) and a sketch of a distributed algorithm that keeps arithmetic details unspecified. Our tool then automatically fills the missing parts. Fault-tolerant distributed algorithms are typically parameterized, that is, they are designed to work for any number n of processes and any number t of faults, provided some resilience condition holds; e.g., n > 3t. In this paper we automatically synthesize distributed algorithms that work for all parameter values that satisfy the resilience condition. We focus on threshold- guarded distributed algorithms, where actions are taken only if a sufficiently large number of messages is received, e.g., more than t or n/2. Both expressions can be derived by choosing the right values for the coefficients a, b, and c, in the sketch of a threshold a·n+b·t+c. Our method takes as input a sketch of an asynchronous threshold-based fault-tolerant distributed algorithm — where the guards are missing exact coefficients—and then iteratively picks the values for the coefficients. Our approach combines recent progress in parameterized model checking of distributed algo- rithms with counterexample-guided synthesis. Besides theoretical results on termination of the synthesis procedure, we experimentally evaluate our method and show that it can synthesize sev- eral distributed algorithms from the literature, e.g., Byzantine reliable broadcast and Byzantine one-step consensus. In addition, for several new variations of safety and liveness specifications, our tool generates new distributed algorithms.

Cite as

Marijana Lazic, Igor Konnov, Josef Widder, and Roderick Bloem. Synthesis of Distributed Algorithms with Parameterized Threshold Guards. In 21st International Conference on Principles of Distributed Systems (OPODIS 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 95, pp. 32:1-32:20, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)


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@InProceedings{lazic_et_al:LIPIcs.OPODIS.2017.32,
  author =	{Lazic, Marijana and Konnov, Igor and Widder, Josef and Bloem, Roderick},
  title =	{{Synthesis of Distributed Algorithms with Parameterized Threshold Guards}},
  booktitle =	{21st International Conference on Principles of Distributed Systems (OPODIS 2017)},
  pages =	{32:1--32:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-061-3},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{95},
  editor =	{Aspnes, James and Bessani, Alysson and Felber, Pascal and Leit\~{a}o, Jo\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2017.32},
  URN =		{urn:nbn:de:0030-drops-86359},
  doi =		{10.4230/LIPIcs.OPODIS.2017.32},
  annote =	{Keywords: fault-tolerant distributed algorithms, byzantine faults, parameterized model checking, program synthesis}
}
Document
Conditionally Optimal Algorithms for Generalized Büchi Games

Authors: Krishnendu Chatterjee, Wolfgang Dvorák, Monika Henzinger, and Veronika Loitzenbauer

Published in: LIPIcs, Volume 58, 41st International Symposium on Mathematical Foundations of Computer Science (MFCS 2016)


Abstract
Games on graphs provide the appropriate framework to study several central problems in computer science, such as verification and synthesis of reactive systems. One of the most basic objectives for games on graphs is the liveness (or Büchi) objective that given a target set of vertices requires that some vertex in the target set is visited infinitely often. We study generalized Büchi objectives (i.e., conjunction of liveness objectives), and implications between two generalized Büchi objectives (known as GR(1) objectives), that arise in numerous applications in computer-aided verification. We present improved algorithms and conditional super-linear lower bounds based on widely believed assumptions about the complexity of (A1) combinatorial Boolean matrix multiplication and (A2) CNF-SAT. We consider graph games with n vertices, m edges, and generalized Büchi objectives with k conjunctions. First, we present an algorithm with running time O(k*n^2), improving the previously known O(k*n*m) and O(k^2*n^2) worst-case bounds. Our algorithm is optimal for dense graphs under (A1). Second, we show that the basic algorithm for the problem is optimal for sparse graphs when the target sets have constant size under (A2). Finally, we consider GR(1) objectives, with k_1 conjunctions in the antecedent and k_2 conjunctions in the consequent, and present an O(k_1 k_2 n^{2.5})-time algorithm, improving the previously known O(k_1*k_2*n*m)-time algorithm for m > n^{1.5}.

Cite as

Krishnendu Chatterjee, Wolfgang Dvorák, Monika Henzinger, and Veronika Loitzenbauer. Conditionally Optimal Algorithms for Generalized Büchi Games. In 41st International Symposium on Mathematical Foundations of Computer Science (MFCS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 58, pp. 25:1-25:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)


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@InProceedings{chatterjee_et_al:LIPIcs.MFCS.2016.25,
  author =	{Chatterjee, Krishnendu and Dvor\'{a}k, Wolfgang and Henzinger, Monika and Loitzenbauer, Veronika},
  title =	{{Conditionally Optimal Algorithms for Generalized B\"{u}chi Games}},
  booktitle =	{41st International Symposium on Mathematical Foundations of Computer Science (MFCS 2016)},
  pages =	{25:1--25:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-016-3},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{58},
  editor =	{Faliszewski, Piotr and Muscholl, Anca and Niedermeier, Rolf},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2016.25},
  URN =		{urn:nbn:de:0030-drops-64403},
  doi =		{10.4230/LIPIcs.MFCS.2016.25},
  annote =	{Keywords: generalized B\"{u}chi objective, GR(1) objective, conditional lower bounds, graph games, graph algorithms, computer-aided verification}
}
Document
A Coalgebraic Decision Procedure for WS1S

Authors: Dmitriy Traytel

Published in: LIPIcs, Volume 41, 24th EACSL Annual Conference on Computer Science Logic (CSL 2015)


Abstract
Weak monadic second-order logic of one successor (WS1S) is a simple and natural formalism to specify regular properties. WS1S is decidable, although the decision procedure's complexity is non-elementary. Typically, decision procedures for WS1S exploit the logic-automaton connection, i.e. they escape the simple and natural formalism by translating formulas into equally expressive regular structures such as finite automata, regular expressions, or games. In this work, we devise a coalgebraic decision procedure for WS1S that stays within the logical world by directly operating on formulas. The key operation is the derivative of a formula, modeled after Brzozowski's derivatives of regular expressions. The presented decision procedure has been formalized and proved correct in the interactive proof assistant Isabelle.

Cite as

Dmitriy Traytel. A Coalgebraic Decision Procedure for WS1S. In 24th EACSL Annual Conference on Computer Science Logic (CSL 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 41, pp. 487-503, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)


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@InProceedings{traytel:LIPIcs.CSL.2015.487,
  author =	{Traytel, Dmitriy},
  title =	{{A Coalgebraic Decision Procedure for WS1S}},
  booktitle =	{24th EACSL Annual Conference on Computer Science Logic (CSL 2015)},
  pages =	{487--503},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-90-3},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{41},
  editor =	{Kreutzer, Stephan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2015.487},
  URN =		{urn:nbn:de:0030-drops-54335},
  doi =		{10.4230/LIPIcs.CSL.2015.487},
  annote =	{Keywords: WS1S, decision procedure, coalgebra, Brzozowski derivatives, Isabelle}
}
Document
Assume-Admissible Synthesis

Authors: Romain Brenguier, Jean-François Raskin, and Ocan Sankur

Published in: LIPIcs, Volume 42, 26th International Conference on Concurrency Theory (CONCUR 2015)


Abstract
In this paper, we introduce a novel rule for synthesis of reactive systems, applicable to systems made of n components which have each their own objectives. It is based on the notion of admissible strategies. We compare our novel rule with previous rules defined in the literature, and we show that contrary to the previous proposals, our rule define sets of solutions which are rectangular. This property leads to solutions which are robust and resilient. We provide algorithms with optimal complexity and also an abstraction framework.

Cite as

Romain Brenguier, Jean-François Raskin, and Ocan Sankur. Assume-Admissible Synthesis. In 26th International Conference on Concurrency Theory (CONCUR 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 42, pp. 100-113, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)


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@InProceedings{brenguier_et_al:LIPIcs.CONCUR.2015.100,
  author =	{Brenguier, Romain and Raskin, Jean-Fran\c{c}ois and Sankur, Ocan},
  title =	{{Assume-Admissible Synthesis}},
  booktitle =	{26th International Conference on Concurrency Theory (CONCUR 2015)},
  pages =	{100--113},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-91-0},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{42},
  editor =	{Aceto, Luca and de Frutos Escrig, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2015.100},
  URN =		{urn:nbn:de:0030-drops-53711},
  doi =		{10.4230/LIPIcs.CONCUR.2015.100},
  annote =	{Keywords: Multi-player games, controller synthesis, admissibility}
}
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