14 Search Results for "David, Nicolas"

Document
DOI: 10.4230/LIPIcs.MFCS.2023.32
Isometric Path Complexity of Graphs

Authors: Dibyayan Chakraborty, Jérémie Chalopin, Florent Foucaud, and Yann Vaxès

Published in: LIPIcs, Volume 272, 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)

Abstract
A set S of isometric paths of a graph G is "v-rooted", where v is a vertex of G, if v is one of the end-vertices of all the isometric paths in S. The isometric path complexity of a graph G, denoted by ipco (G), is the minimum integer k such that there exists a vertex v ∈ V(G) satisfying the following property: the vertices of any isometric path P of G can be covered by k many v-rooted isometric paths. First, we provide an O(n² m)-time algorithm to compute the isometric path complexity of a graph with n vertices and m edges. Then we show that the isometric path complexity remains bounded for graphs in three seemingly unrelated graph classes, namely, hyperbolic graphs, (theta, prism, pyramid)-free graphs, and outerstring graphs. Hyperbolic graphs are extensively studied in Metric Graph Theory. The class of (theta, prism, pyramid)-free graphs are extensively studied in Structural Graph Theory, e.g. in the context of the Strong Perfect Graph Theorem. The class of outerstring graphs is studied in Geometric Graph Theory and Computational Geometry. Our results also show that the distance functions of these (structurally) different graph classes are more similar than previously thought. There is a direct algorithmic consequence of having small isometric path complexity. Specifically, using a result of Chakraborty et al. [ISAAC 2022], we show that if the isometric path complexity of a graph G is bounded by a constant k, then there exists a k-factor approximation algorithm for Isometric Path Cover, whose objective is to cover all vertices of a graph with a minimum number of isometric paths.
Cite as

Dibyayan Chakraborty, Jérémie Chalopin, Florent Foucaud, and Yann Vaxès. Isometric Path Complexity of Graphs. In 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 272, pp. 32:1-32:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{chakraborty_et_al:LIPIcs.MFCS.2023.32,
  author =	{Chakraborty, Dibyayan and Chalopin, J\'{e}r\'{e}mie and Foucaud, Florent and Vax\`{e}s, Yann},
  title =	{{Isometric Path Complexity of Graphs}},
  booktitle =	{48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)},
  pages =	{32:1--32:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-292-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{272},
  editor =	{Leroux, J\'{e}r\^{o}me and Lombardy, Sylvain and Peleg, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.32},
  URN =		{urn:nbn:de:0030-drops-185666},
  doi =		{10.4230/LIPIcs.MFCS.2023.32},
  annote =	{Keywords: Shortest paths, Isometric path complexity, Hyperbolic graphs, Truemper Configurations, Outerstring graphs, Isometric Path Cover}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2023.42
Recontamination Helps a Lot to Hunt a Rabbit

Authors: Thomas Dissaux, Foivos Fioravantes, Harmender Gahlawat, and Nicolas Nisse

Published in: LIPIcs, Volume 272, 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)

Abstract
The Hunters and Rabbit game is played on a graph G where the Hunter player shoots at k vertices in every round while the Rabbit player occupies an unknown vertex and, if it is not shot, must move to a neighbouring vertex after each round. The Rabbit player wins if it can ensure that its position is never shot. The Hunter player wins otherwise. The hunter number h(G) of a graph G is the minimum integer k such that the Hunter player has a winning strategy (i.e., allowing him to win whatever be the strategy of the Rabbit player). This game has been studied in several graph classes, in particular in bipartite graphs (grids, trees, hypercubes...), but the computational complexity of computing h(G) remains open in general graphs and even in more restricted graph classes such as trees. To progress further in this study, we propose a notion of monotonicity (a well-studied and useful property in classical pursuit-evasion games such as Graph Searching games) for the Hunters and Rabbit game imposing that, roughly, a vertex that has already been shot "must not host the rabbit anymore". This allows us to obtain new results in various graph classes. More precisely, let the monotone hunter number mh(G) of a graph G be the minimum integer k such that the Hunter player has a monotone winning strategy. We show that pw(G) ≤ mh(G) ≤ pw(G)+1 for any graph G with pathwidth pw(G), which implies that computing mh(G), or even approximating mh(G) up to an additive constant, is NP-hard. Then, we show that mh(G) can be computed in polynomial time in split graphs, interval graphs, cographs and trees. These results go through structural characterisations which allow us to relate the monotone hunter number with the pathwidth in some of these graph classes. In all cases, this allows us to specify the hunter number or to show that there may be an arbitrary gap between h and mh, i.e., that monotonicity does not help. In particular, we show that, for every k ≥ 3, there exists a tree T with h(T) = 2 and mh(T) = k. We conclude by proving that computing h (resp., mh) is FPT parameterised by the minimum size of a vertex cover.
Cite as

Thomas Dissaux, Foivos Fioravantes, Harmender Gahlawat, and Nicolas Nisse. Recontamination Helps a Lot to Hunt a Rabbit. In 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 272, pp. 42:1-42:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{dissaux_et_al:LIPIcs.MFCS.2023.42,
  author =	{Dissaux, Thomas and Fioravantes, Foivos and Gahlawat, Harmender and Nisse, Nicolas},
  title =	{{Recontamination Helps a Lot to Hunt a Rabbit}},
  booktitle =	{48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)},
  pages =	{42:1--42:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-292-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{272},
  editor =	{Leroux, J\'{e}r\^{o}me and Lombardy, Sylvain and Peleg, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.42},
  URN =		{urn:nbn:de:0030-drops-185763},
  doi =		{10.4230/LIPIcs.MFCS.2023.42},
  annote =	{Keywords: Hunter and Rabbit, Monotonicity, Graph Searching}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2023.88
Checking Presence Reachability Properties on Parameterized Shared-Memory Systems

Authors: Nicolas Waldburger

Published in: LIPIcs, Volume 272, 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)

Abstract
We consider the verification of distributed systems composed of an arbitrary number of asynchronous processes. Processes are identical finite-state machines that communicate by reading from and writing to a shared memory. Beyond the standard model with finitely many registers, we tackle round-based shared-memory systems with fresh registers at each round. In the latter model, both the number of processes and the number of registers are unbounded, making verification particularly challenging. The properties studied are generic presence reachability objectives, which subsume classical questions such as safety or synchronization by expressing the presence or absence of processes in some states. In the more general round-based setting, we establish that the parameterized verification of presence reachability properties is PSPACE-complete. Moreover, for the roundless model with finitely many registers, we prove that the complexity drops down to NP-complete and we provide several natural restrictions that make the problem solvable in polynomial time.
Cite as

Nicolas Waldburger. Checking Presence Reachability Properties on Parameterized Shared-Memory Systems. In 48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 272, pp. 88:1-88:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{waldburger:LIPIcs.MFCS.2023.88,
  author =	{Waldburger, Nicolas},
  title =	{{Checking Presence Reachability Properties on Parameterized Shared-Memory Systems}},
  booktitle =	{48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)},
  pages =	{88:1--88:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-292-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{272},
  editor =	{Leroux, J\'{e}r\^{o}me and Lombardy, Sylvain and Peleg, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.88},
  URN =		{urn:nbn:de:0030-drops-186225},
  doi =		{10.4230/LIPIcs.MFCS.2023.88},
  annote =	{Keywords: Verification, Parameterized models, Distributed algorithms}
}
Document
DOI: 10.4230/LIPIcs.SAND.2023.7
When Should You Wait Before Updating? - Toward a Robustness Refinement

Authors: Swan Dubois, Laurent Feuilloley, Franck Petit, and Mikaël Rabie

Published in: LIPIcs, Volume 257, 2nd Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2023)

Abstract
Consider a dynamic network and a given distributed problem. At any point in time, there might exist several solutions that are equally good with respect to the problem specification, but that are different from an algorithmic perspective, because some could be easier to update than others when the network changes. In other words, one would prefer to have a solution that is more robust to topological changes in the network; and in this direction the best scenario would be that the solution remains correct despite the dynamic of the network. In [Arnaud Casteigts et al., 2020], the authors introduced a very strong robustness criterion: they required that for any removal of edges that maintain the network connected, the solution remains valid. They focus on the maximal independent set problem, and their approach consists in characterizing the graphs in which there exists a robust solution (the existential problem), or even stronger, where any solution is robust (the universal problem). As the robustness criteria is very demanding, few graphs have a robust solution, and even fewer are such that all of their solutions are robust. In this paper, we ask the following question: Can we have robustness for a larger class of networks, if we bound the number k of edge removals allowed? To answer this question, we consider three classic problems: maximal independent set, minimal dominating set and maximal matching. For the universal problem, the answers for the three cases are surprisingly different. For minimal dominating set, the class does not depend on the number of edges removed. For maximal matching, removing only one edge defines a robust class related to perfect matchings, but for all other bounds k, the class is the same as for an arbitrary number of edge removals. Finally, for maximal independent set, there is a strict hierarchy of classes: the class for the bound k is strictly larger than the class for bound k+1. For the robustness notion of [Arnaud Casteigts et al., 2020], no characterization of the class for the existential problem is known, only a polynomial-time recognition algorithm. We show that the situation is even worse for bounded k: even for k = 1, it is NP-hard to decide whether a graph has a robust maximal independent set.
Cite as

Swan Dubois, Laurent Feuilloley, Franck Petit, and Mikaël Rabie. When Should You Wait Before Updating? - Toward a Robustness Refinement. In 2nd Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 257, pp. 7:1-7:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{dubois_et_al:LIPIcs.SAND.2023.7,
  author =	{Dubois, Swan and Feuilloley, Laurent and Petit, Franck and Rabie, Mika\"{e}l},
  title =	{{When Should You Wait Before Updating? - Toward a Robustness Refinement}},
  booktitle =	{2nd Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2023)},
  pages =	{7:1--7:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-275-4},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{257},
  editor =	{Doty, David and Spirakis, Paul},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.SAND.2023.7},
  URN =		{urn:nbn:de:0030-drops-179435},
  doi =		{10.4230/LIPIcs.SAND.2023.7},
  annote =	{Keywords: Robustness, dynamic network, temporal graphs, edge removal, connectivity, footprint, packing/covering problems, maximal independent set, maximal matching, minimum dominating set, perfect matching, NP-hardness}
}
Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2022.104
Threshold Rates of Code Ensembles: Linear Is Best

Authors: Nicolas Resch and Chen Yuan

Published in: LIPIcs, Volume 229, 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)

Abstract
In this work, we prove new results concerning the combinatorial properties of random linear codes. By applying the thresholds framework from Mosheiff et al. (FOCS 2020) we derive fine-grained results concerning the list-decodability and -recoverability of random linear codes. Firstly, we prove a lower bound on the list-size required for random linear codes over 𝔽_q ε-close to capacity to list-recover with error radius ρ and input lists of size 𝓁. We show that the list-size L must be at least {log_q binom{q,𝓁}}-R}/ε, where R is the rate of the random linear code. This is analogous to a lower bound for list-decoding that was recently obtained by Guruswami et al. (IEEE TIT 2021B). As a comparison, we also pin down the list size of random codes which is {log_q binom{q,𝓁}}/ε. This result almost closes the O({q log L}/L) gap left by Guruswami et al. (IEEE TIT 2021A). This leaves open the possibility (that we consider likely) that random linear codes perform better than the random codes for list-recoverability, which is in contrast to a recent gap shown for the case of list-recovery from erasures (Guruswami et al., IEEE TIT 2021B). Next, we consider list-decoding with constant list-sizes. Specifically, we obtain new lower bounds on the rate required for: - List-of-3 decodability of random linear codes over 𝔽₂; - List-of-2 decodability of random linear codes over 𝔽_q (for any q). This expands upon Guruswami et al. (IEEE TIT 2021A) which only studied list-of-2 decodability of random linear codes over 𝔽₂. Further, in both cases we are able to show that the rate is larger than that which is possible for uniformly random codes. A conclusion that we draw from our work is that, for many combinatorial properties of interest, random linear codes actually perform better than uniformly random codes, in contrast to the apparently standard intuition that uniformly random codes are best.
Cite as

Nicolas Resch and Chen Yuan. Threshold Rates of Code Ensembles: Linear Is Best. In 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 229, pp. 104:1-104:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{resch_et_al:LIPIcs.ICALP.2022.104,
  author =	{Resch, Nicolas and Yuan, Chen},
  title =	{{Threshold Rates of Code Ensembles: Linear Is Best}},
  booktitle =	{49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)},
  pages =	{104:1--104:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-235-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{229},
  editor =	{Boja\'{n}czyk, Miko{\l}aj and Merelli, Emanuela and Woodruff, David P.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2022.104},
  URN =		{urn:nbn:de:0030-drops-164456},
  doi =		{10.4230/LIPIcs.ICALP.2022.104},
  annote =	{Keywords: Random Linear Codes, List-Decoding, List-Recovery, Threshold Rates}
}
Document
Track B: Automata, Logic, Semantics, and Theory of Programming
DOI: 10.4230/LIPIcs.ICALP.2022.113
Parameterized Safety Verification of Round-Based Shared-Memory Systems

Authors: Nathalie Bertrand, Nicolas Markey, Ocan Sankur, and Nicolas Waldburger

Published in: LIPIcs, Volume 229, 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)

Abstract
We consider the parameterized verification problem for distributed algorithms where the goal is to develop techniques to prove the correctness of a given algorithm regardless of the number of participating processes. Motivated by an asynchronous binary consensus algorithm [James Aspnes, 2002], we consider round-based distributed algorithms communicating with shared memory. A particular challenge in these systems is that 1) the number of processes is unbounded, and, more importantly, 2) there is a fresh set of registers at each round. A verification algorithm thus needs to manage both sources of infinity. In this setting, we prove that the safety verification problem, which consists in deciding whether all possible executions avoid a given error state, is PSPACE-complete. For negative instances of the safety verification problem, we also provide exponential lower and upper bounds on the minimal number of processes needed for an error execution and on the minimal round on which the error state can be covered.
Cite as

Nathalie Bertrand, Nicolas Markey, Ocan Sankur, and Nicolas Waldburger. Parameterized Safety Verification of Round-Based Shared-Memory Systems. In 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 229, pp. 113:1-113:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bertrand_et_al:LIPIcs.ICALP.2022.113,
  author =	{Bertrand, Nathalie and Markey, Nicolas and Sankur, Ocan and Waldburger, Nicolas},
  title =	{{Parameterized Safety Verification of Round-Based Shared-Memory Systems}},
  booktitle =	{49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)},
  pages =	{113:1--113:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-235-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{229},
  editor =	{Boja\'{n}czyk, Miko{\l}aj and Merelli, Emanuela and Woodruff, David P.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2022.113},
  URN =		{urn:nbn:de:0030-drops-164541},
  doi =		{10.4230/LIPIcs.ICALP.2022.113},
  annote =	{Keywords: Verification, Parameterized models, Distributed algorithms}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2020.11
Framing Algorithms for Approximate Multicriteria Shortest Paths

Authors: Nicolas Hanusse, David Ilcinkas, and Antonin Lentz

Published in: OASIcs, Volume 85, 20th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2020)

Abstract
This paper deals with the computation of d-dimensional multicriteria shortest paths. In a weighted graph with arc weights represented by vectors, the cost of a path is the vector sum of the weights of its arcs. For a given pair consisting of a source s and a destination t, a path P dominates a path Q if and only if P’s cost is component-wise smaller than or equal to Q’s cost. The set of Pareto paths, or Pareto set, from s to t is the set of paths that are not dominated. The computation time of the Pareto paths can be prohibitive whenever the set of Pareto paths is large. We propose in this article new algorithms to compute approximated Pareto paths in any dimension. For d = 2, we exhibit the first approximation algorithm, called Frame, whose output is guaranteed to be always a subset of the Pareto set. Finally, we provide a small experimental study in order to confirm the relevance of our Frame algorithm.
Cite as

Nicolas Hanusse, David Ilcinkas, and Antonin Lentz. Framing Algorithms for Approximate Multicriteria Shortest Paths. In 20th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2020). Open Access Series in Informatics (OASIcs), Volume 85, pp. 11:1-11:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{hanusse_et_al:OASIcs.ATMOS.2020.11,
  author =	{Hanusse, Nicolas and Ilcinkas, David and Lentz, Antonin},
  title =	{{Framing Algorithms for Approximate Multicriteria Shortest Paths}},
  booktitle =	{20th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2020)},
  pages =	{11:1--11:19},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-170-2},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{85},
  editor =	{Huisman, Dennis and Zaroliagis, Christos D.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2020.11},
  URN =		{urn:nbn:de:0030-drops-131476},
  doi =		{10.4230/OASIcs.ATMOS.2020.11},
  annote =	{Keywords: Pareto set, multicriteria, shortest paths, approximation}
}
Document
Artifact
DOI: 10.4230/DARTS.6.2.18
Multiparty Session Programming with Global Protocol Combinators (Artifact)

Authors: Keigo Imai, Rumyana Neykova, Nobuko Yoshida, and Shoji Yuen

Published in: DARTS, Volume 6, Issue 2, Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
In the paper "Multiparty Session Programming with Global Protocol Combinators", we introduce a library, ocaml-mpst for programming with global combinators - a set of functions for writing and verifying multiparty protocols in OCaml. Local behaviours for all processes in a protocol are inferred at once from a global combinator. Our approach enables fully-static verification and implementation of the whole protocol, from the protocol specification to the process implementations, to happen in the same language. This artifact is the source code of ocaml-mpst, with all the examples and benchmarks discussed in the paper.
Cite as

Keigo Imai, Rumyana Neykova, Nobuko Yoshida, and Shoji Yuen. Multiparty Session Programming with Global Protocol Combinators (Artifact). In Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020). Dagstuhl Artifacts Series (DARTS), Volume 6, Issue 2, pp. 18:1-18:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@Article{imai_et_al:DARTS.6.2.18,
  author =	{Imai, Keigo and Neykova, Rumyana and Yoshida, Nobuko and Yuen, Shoji},
  title =	{{Multiparty Session Programming with Global Protocol Combinators (Artifact)}},
  pages =	{18:1--18:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2020},
  volume =	{6},
  number =	{2},
  editor =	{Imai, Keigo and Neykova, Rumyana and Yoshida, Nobuko and Yuen, Shoji},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DARTS.6.2.18},
  URN =		{urn:nbn:de:0030-drops-132159},
  doi =		{10.4230/DARTS.6.2.18},
  annote =	{Keywords: Multiparty Session Types, Communication Protocol, Concurrent and Distributed Programming, OCaml}
}
Document
DOI: 10.4230/LIPIcs.SEA.2020.18
Space and Time Trade-Off for the k Shortest Simple Paths Problem

Authors: Ali Al Zoobi, David Coudert, and Nicolas Nisse

Published in: LIPIcs, Volume 160, 18th International Symposium on Experimental Algorithms (SEA 2020)

Abstract
The k shortest simple path problem (kSSP) asks to compute a set of top-k shortest simple paths from a vertex s to a vertex t in a digraph. Yen (1971) proposed the first algorithm with the best known theoretical complexity of O(kn(m+n log n)) for a digraph with n vertices and m arcs. Since then, the problem has been widely studied from an algorithm engineering perspective, and impressive improvements have been achieved. In particular, Kurz and Mutzel (2016) proposed a sidetracks-based (SB) algorithm which is currently the fastest solution. In this work, we propose two improvements of this algorithm. We first show how to speed up the SB algorithm using dynamic updates of shortest path trees. We did experiments on some road networks of the 9th DIMAC'S challenge with up to about half a million nodes and one million arcs. Our computational results show an average speed up by a factor of 1.5 to 2 with a similar working memory consumption as SB. We then propose a second algorithm enabling to significantly reduce the working memory at the cost of an increase of the running time (up to two times slower). Our experiments on the same data set show, on average, a reduction by a factor of 1.5 to 2 of the working memory.
Cite as

Ali Al Zoobi, David Coudert, and Nicolas Nisse. Space and Time Trade-Off for the k Shortest Simple Paths Problem. In 18th International Symposium on Experimental Algorithms (SEA 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 160, pp. 18:1-18:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{alzoobi_et_al:LIPIcs.SEA.2020.18,
  author =	{Al Zoobi, Ali and Coudert, David and Nisse, Nicolas},
  title =	{{Space and Time Trade-Off for the k Shortest Simple Paths Problem}},
  booktitle =	{18th International Symposium on Experimental Algorithms (SEA 2020)},
  pages =	{18:1--18:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-148-1},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{160},
  editor =	{Faro, Simone and Cantone, Domenico},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2020.18},
  URN =		{urn:nbn:de:0030-drops-120925},
  doi =		{10.4230/LIPIcs.SEA.2020.18},
  annote =	{Keywords: k shortest simple paths, graph algorithm, space-time trade-off}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2017.14
Coverability Synthesis in Parametric Petri Nets

Authors: Nicolas David, Claude Jard, Didier Lime, and Olivier H. Roux

Published in: LIPIcs, Volume 85, 28th International Conference on Concurrency Theory (CONCUR 2017)

Abstract
We study Parametric Petri Nets (PPNs), i.e., Petri nets for which some arc weights can be parameters. In that setting, we address a problem of parameter synthesis, which consists in computing the exact set of values for the parameters such that a given marking is coverable in the instantiated net. Since the emptiness of that solution set is already undecidable for general PPNs, we address a special case where parameters are used only as input weights (preT-PPNs), and consequently for which the solution set is downward-closed. To this end, we invoke a result for the representation of upward closed set from Valk and Jantzen. To use this procedure, we show we need to decide universal coverability, that is decide if some marking is coverable for every possible values of the parameters. We therefore provide a proof of its EXPSPACE-completeness, thus settling the previously open problem of its decidability. We also propose an adaptation of this reasoning to the case of parameters used only as output weights (postT-PPNs). In this case, the condition to use this procedure can be reduced to the decidability of the existential coverability, that is decide if there exists values of the parameters making a given marking coverable. This problem is known decidable but we provide here a cleaner proof, providing its EXPSPACE-completeness, by reduction to Omega Petri Nets.
Cite as

Nicolas David, Claude Jard, Didier Lime, and Olivier H. Roux. Coverability Synthesis in Parametric Petri Nets. In 28th International Conference on Concurrency Theory (CONCUR 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 85, pp. 14:1-14:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{david_et_al:LIPIcs.CONCUR.2017.14,
  author =	{David, Nicolas and Jard, Claude and Lime, Didier and Roux, Olivier H.},
  title =	{{Coverability Synthesis in Parametric Petri Nets}},
  booktitle =	{28th International Conference on Concurrency Theory (CONCUR 2017)},
  pages =	{14:1--14:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-048-4},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{85},
  editor =	{Meyer, Roland and Nestmann, Uwe},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2017.14},
  URN =		{urn:nbn:de:0030-drops-77831},
  doi =		{10.4230/LIPIcs.CONCUR.2017.14},
  annote =	{Keywords: Petri net, Parameters, Coverability, Unboundedness, Synthesis}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2016.28
On the Expressiveness of QCTL

Authors: Amélie David, Francois Laroussinie, and Nicolas Markey

Published in: LIPIcs, Volume 59, 27th International Conference on Concurrency Theory (CONCUR 2016)

Abstract
QCTL extends the temporal logic CTL with quantification over atomic propositions. While the algorithmic questions for QCTL and its fragments with limited quantification depth are well-understood (e.g. satisfiability of QkCTL, with at most k nested blocks of quantifiers, is (k+1)-EXPTIME-complete), very few results are known about the expressiveness of this logic. We address such expressiveness questions in this paper. We first consider the distinguishing power of these logics (i.e., their ability to separate models), their relationship with behavioural equivalences, and their ability to capture the behaviours of finite Kripke structures with so-called characteristic formulas. We then consider their expressive power (i.e., their ability to express a property), showing that in terms of expressiveness the hierarchy QkCTL collapses at level 2 (in other terms, any QCTL formula can be expressed using at most two nested blocks of quantifiers).
Cite as

Amélie David, Francois Laroussinie, and Nicolas Markey. On the Expressiveness of QCTL. In 27th International Conference on Concurrency Theory (CONCUR 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 59, pp. 28:1-28:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{david_et_al:LIPIcs.CONCUR.2016.28,
  author =	{David, Am\'{e}lie and Laroussinie, Francois and Markey, Nicolas},
  title =	{{On the Expressiveness of QCTL}},
  booktitle =	{27th International Conference on Concurrency Theory (CONCUR 2016)},
  pages =	{28:1--28:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-017-0},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{59},
  editor =	{Desharnais, Jos\'{e}e and Jagadeesan, Radha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2016.28},
  URN =		{urn:nbn:de:0030-drops-61643},
  doi =		{10.4230/LIPIcs.CONCUR.2016.28},
  annote =	{Keywords: Specification, Verification, Temporal Logic, Expressiveness, Tree automata}
}
Document
Informal Presentation
DOI: 10.4230/OASIcs.SynCoP.2015.103
Discrete Parameters in Petri Nets (Informal Presentation)

Authors: Nicolas David, Claude Jard, Didier Lime, and Olivier H. Roux

Published in: OASIcs, Volume 44, 2nd International Workshop on Synthesis of Complex Parameters (SynCoP'15) (2015)

Abstract
With the aim of significantly increasing the modeling capability of Petri nets, we suggest models that involve parameters to represent the weights of arcs, or the number of tokens in places. We call these Petri nets parameterised nets or PPNs. Indeed, the introduction of parameters in models aims to improve genericity. It therefore allows the designer to leave unspecified aspects, such as those related to the modeling of the environment. This increase in modeling power usually results in greater complexity in the analysis and verification of the model. Here, we consider the property of coverability of markings. Two general questions arise: "Is there a parameter value for which the property is satisfied?" and "Does the property hold for all possible values of the parameters?". We first study the decidability of these issues, which we show to be undecidable in the general case. Therefore, we also define subclasses of parameterised networks, based on restriction of the use of parameters, depending on whether the parameters are used on places, input or output arcs of transitions or combinations of them. Those subclasses have therefore a dual interest. From a modeling point of view, restrict the use of parameters to tokens, outputs or inputs can be seen as respectively processes or synchronisation of a given number of processes. From a theoretical point of view, it is interesting to introduce those subclasses of PPN in a concern of completeness of the study. We study the relations between those subclasses and prove that, for some subclasses, certain problems become decidable, making these subclasses more usable in practice.
Cite as

Nicolas David, Claude Jard, Didier Lime, and Olivier H. Roux. Discrete Parameters in Petri Nets (Informal Presentation). In 2nd International Workshop on Synthesis of Complex Parameters (SynCoP'15). Open Access Series in Informatics (OASIcs), Volume 44, p. 103, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{david_et_al:OASIcs.SynCoP.2015.103,
  author =	{David, Nicolas and Jard, Claude and Lime, Didier and Roux, Olivier H.},
  title =	{{Discrete Parameters in Petri Nets}},
  booktitle =	{2nd International Workshop on Synthesis of Complex Parameters (SynCoP'15)},
  pages =	{103--103},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-82-8},
  ISSN =	{2190-6807},
  year =	{2015},
  volume =	{44},
  editor =	{Andr\'{e}, \'{E}tienne and Frehse, Goran},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.SynCoP.2015.103},
  URN =		{urn:nbn:de:0030-drops-56046},
  doi =		{10.4230/OASIcs.SynCoP.2015.103},
  annote =	{Keywords: Petri nets, Parameters, Coverability}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2015.311
On the Value Problem in Weighted Timed Games

Authors: Patricia Bouyer, Samy Jaziri, and Nicolas Markey

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

Abstract
A weighted timed game is a timed game with extra quantitative information representing e.g. energy consumption. Optimizing the weight for reaching a target is a natural question, which has already been investigated for ten years. Existence of optimal strategies is known to be undecidable in general, and only very restricted classes of games have been identified for which optimal weight and almost-optimal strategies can be computed. In this paper, we show that the value problem is undecidable in weighted timed games. We then introduce a large subclass of weighted timed games (for which the undecidability proof above applies), and provide an algorithm to compute arbitrary approximations of the value in such games. To the best of our knowledge, this is the first approximation scheme for an undecidable class of weighted timed games.
Cite as

Patricia Bouyer, Samy Jaziri, and Nicolas Markey. On the Value Problem in Weighted Timed Games. In 26th International Conference on Concurrency Theory (CONCUR 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 42, pp. 311-324, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{bouyer_et_al:LIPIcs.CONCUR.2015.311,
  author =	{Bouyer, Patricia and Jaziri, Samy and Markey, Nicolas},
  title =	{{On the Value Problem in Weighted Timed Games}},
  booktitle =	{26th International Conference on Concurrency Theory (CONCUR 2015)},
  pages =	{311--324},
  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-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2015.311},
  URN =		{urn:nbn:de:0030-drops-53863},
  doi =		{10.4230/LIPIcs.CONCUR.2015.311},
  annote =	{Keywords: Timed games, undecidability, approximation}
}
Document
DOI: 10.4230/DagSemProc.04491.3
Accessing Databases within Esterel

Authors: David White and Gerald Luettgen

Published in: Dagstuhl Seminar Proceedings, Volume 4491, Synchronous Programming - SYNCHRON'04 (2005)

Abstract
A current limitation of the Esterel language for reactive-systems design is its lack of support for accessing databases. This talk presents the results of a summer student project which investigated a way of integrating databases and Esterel by providing an API for database use inside Esterel. A case study, involving a warehouse storage system built using Lego Mindstorms robotics kits, demonstrates the utility of the API. This system employs an Esterel-programmed robot whose task it is to collect various items from a customer's order and assemble them in one place. To do so, the robot accesses customer-order data and floor-plan data stored in a database.
Cite as

David White and Gerald Luettgen. Accessing Databases within Esterel. In Synchronous Programming - SYNCHRON'04. Dagstuhl Seminar Proceedings, Volume 4491, pp. 1-21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2005)

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@InProceedings{white_et_al:DagSemProc.04491.3,
  author =	{White, David and Luettgen, Gerald},
  title =	{{Accessing Databases within Esterel}},
  booktitle =	{Synchronous Programming - SYNCHRON'04},
  pages =	{1--21},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2005},
  volume =	{4491},
  editor =	{Stephen A. Edwards and Nicolas Halbwachs and Reinhard v. Hanxleden and Thomas Stauner},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.04491.3},
  URN =		{urn:nbn:de:0030-drops-1619},
  doi =		{10.4230/DagSemProc.04491.3},
  annote =	{Keywords: database esterel lego mindstorms}
}
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