5 Search Results for "Iosif, Radu"

Document
DOI: 10.4230/LIPIcs.CONCUR.2023.20
Expressiveness Results for an Inductive Logic of Separated Relations

Authors: Radu Iosif and Florian Zuleger

Published in: LIPIcs, Volume 279, 34th International Conference on Concurrency Theory (CONCUR 2023)

Abstract
In this paper we study a Separation Logic of Relations (SLR) and compare its expressiveness to (Monadic) Second Order Logic [(M)SO]. SLR is based on the well-known Symbolic Heap fragment of Separation Logic, whose formulæare composed of points-to assertions, inductively defined predicates, with the separating conjunction as the only logical connective. SLR generalizes the Symbolic Heap fragment by supporting general relational atoms, instead of only points-to assertions. In this paper, we restrict ourselves to finite relational structures, and hence only consider Weak (M)SO, where quantification ranges over finite sets. Our main results are that SLR and MSO are incomparable on structures of unbounded treewidth, while SLR can be embedded in SO in general. Furthermore, MSO becomes a strict subset of SLR, when the treewidth of the models is bounded by a parameter and all vertices attached to some hyperedge belong to the interpretation of a fixed unary relation symbol. We also discuss the problem of identifying a fragment of SLR that is equivalent to MSO over models of bounded treewidth.
Cite as

Radu Iosif and Florian Zuleger. Expressiveness Results for an Inductive Logic of Separated Relations. In 34th International Conference on Concurrency Theory (CONCUR 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 279, pp. 20:1-20:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{iosif_et_al:LIPIcs.CONCUR.2023.20,
  author =	{Iosif, Radu and Zuleger, Florian},
  title =	{{Expressiveness Results for an Inductive Logic of Separated Relations}},
  booktitle =	{34th International Conference on Concurrency Theory (CONCUR 2023)},
  pages =	{20:1--20:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-299-0},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{279},
  editor =	{P\'{e}rez, Guillermo A. and Raskin, Jean-Fran\c{c}ois},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2023.20},
  URN =		{urn:nbn:de:0030-drops-190146},
  doi =		{10.4230/LIPIcs.CONCUR.2023.20},
  annote =	{Keywords: Separation Logic, Model Theory, Monadic Second Order Logic, Treewidth}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2022.24
On an Invariance Problem for Parameterized Concurrent Systems

Authors: Marius Bozga, Lucas Bueri, and Radu Iosif

Published in: LIPIcs, Volume 243, 33rd International Conference on Concurrency Theory (CONCUR 2022)

Abstract
We consider concurrent systems consisting of replicated finite-state processes that synchronize via joint interactions in a network with user-defined topology. The system is specified using a resource logic with a multiplicative connective and inductively defined predicates, reminiscent of Separation Logic [John C. Reynolds, 2002]. The problem we consider is if a given formula in this logic defines an invariant, namely whether any model of the formula, following an arbitrary firing sequence of interactions, is transformed into another model of the same formula. This property, called havoc invariance, is quintessential in proving the correctness of reconfiguration programs that change the structure of the network at runtime. We show that the havoc invariance problem is many-one reducible to the entailment problem ϕ ⊧ ψ, asking if any model of ϕ is also a model of ψ. Although, in general, havoc invariance is found to be undecidable, this reduction allows to prove that havoc invariance is in 2EXP, for a general fragment of the logic, with a 2EXP entailment problem.
Cite as

Marius Bozga, Lucas Bueri, and Radu Iosif. On an Invariance Problem for Parameterized Concurrent Systems. In 33rd International Conference on Concurrency Theory (CONCUR 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 243, pp. 24:1-24:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bozga_et_al:LIPIcs.CONCUR.2022.24,
  author =	{Bozga, Marius and Bueri, Lucas and Iosif, Radu},
  title =	{{On an Invariance Problem for Parameterized Concurrent Systems}},
  booktitle =	{33rd International Conference on Concurrency Theory (CONCUR 2022)},
  pages =	{24:1--24:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-246-4},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{243},
  editor =	{Klin, Bartek and Lasota, S{\l}awomir and Muscholl, Anca},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2022.24},
  URN =		{urn:nbn:de:0030-drops-170874},
  doi =		{10.4230/LIPIcs.CONCUR.2022.24},
  annote =	{Keywords: parameterized verification, invariant checking, resource logics, reconfigurable systems, tree automata}
}
Document
DOI: 10.4230/LIPIcs.CSL.2022.33
Revisiting Parameter Synthesis for One-Counter Automata

Authors: Guillermo A. Pérez and Ritam Raha

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

Abstract
We study the synthesis problem for one-counter automata with parameters. One-counter automata are obtained by extending classical finite-state automata with a counter whose value can range over non-negative integers and be tested for zero. The updates and tests applicable to the counter can further be made parametric by introducing a set of integer-valued variables called parameters. The synthesis problem for such automata asks whether there exists a valuation of the parameters such that all infinite runs of the automaton satisfy some ω-regular property. Lechner showed that (the complement of) the problem can be encoded in a restricted one-alternation fragment of Presburger arithmetic with divisibility. In this work (i) we argue that said fragment, called ∀∃_RPAD^+, is unfortunately undecidable. Nevertheless, by a careful re-encoding of the problem into a decidable restriction of ∀∃_RPAD^+, (ii) we prove that the synthesis problem is decidable in general and in 2NEXP for several fixed ω-regular properties. Finally, (iii) we give polynomial-space algorithms for the special cases of the problem where parameters can only be used in counter tests.
Cite as

Guillermo A. Pérez and Ritam Raha. Revisiting Parameter Synthesis for One-Counter Automata. In 30th EACSL Annual Conference on Computer Science Logic (CSL 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 216, pp. 33:1-33:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{perez_et_al:LIPIcs.CSL.2022.33,
  author =	{P\'{e}rez, Guillermo A. and Raha, Ritam},
  title =	{{Revisiting Parameter Synthesis for One-Counter Automata}},
  booktitle =	{30th EACSL Annual Conference on Computer Science Logic (CSL 2022)},
  pages =	{33:1--33:18},
  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-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2022.33},
  URN =		{urn:nbn:de:0030-drops-157534},
  doi =		{10.4230/LIPIcs.CSL.2022.33},
  annote =	{Keywords: Parametric one-counter automata, Reachability, Software Verification}
}
Document
DOI: 10.4230/LIPIcs.CSL.2021.20
Decidable Entailments in Separation Logic with Inductive Definitions: Beyond Establishment

Authors: Mnacho Echenim, Radu Iosif, and Nicolas Peltier

Published in: LIPIcs, Volume 183, 29th EACSL Annual Conference on Computer Science Logic (CSL 2021)

Abstract
We define a class of Separation Logic [Ishtiaq and O'Hearn, 2001; J.C. Reynolds, 2002] formulae, whose entailment problem given formulae ϕ, ψ₁, …, ψ_n, is every model of ϕ a model of some ψ_i? is 2-EXPTIME-complete. The formulae in this class are existentially quantified separating conjunctions involving predicate atoms, interpreted by the least sets of store-heap structures that satisfy a set of inductive rules, which is also part of the input to the entailment problem. Previous work [Iosif et al., 2013; Jens Katelaan et al., 2019; Jens Pagel and Florian Zuleger, 2020] consider established sets of rules, meaning that every existentially quantified variable in a rule must eventually be bound to an allocated location, i.e. from the domain of the heap. In particular, this guarantees that each structure has treewidth bounded by the size of the largest rule in the set. In contrast, here we show that establishment, although sufficient for decidability (alongside two other natural conditions), is not necessary, by providing a condition, called equational restrictedness, which applies syntactically to (dis-)equalities. The entailment problem is more general in this case, because equationally restricted rules define richer classes of structures, of unbounded treewidth. In this paper we show that (1) every established set of rules can be converted into an equationally restricted one and (2) the entailment problem is 2-EXPTIME-complete in the latter case, thus matching the complexity of entailments for established sets of rules [Jens Katelaan et al., 2019; Jens Pagel and Florian Zuleger, 2020].
Cite as

Mnacho Echenim, Radu Iosif, and Nicolas Peltier. Decidable Entailments in Separation Logic with Inductive Definitions: Beyond Establishment. In 29th EACSL Annual Conference on Computer Science Logic (CSL 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 183, pp. 20:1-20:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{echenim_et_al:LIPIcs.CSL.2021.20,
  author =	{Echenim, Mnacho and Iosif, Radu and Peltier, Nicolas},
  title =	{{Decidable Entailments in Separation Logic with Inductive Definitions: Beyond Establishment}},
  booktitle =	{29th EACSL Annual Conference on Computer Science Logic (CSL 2021)},
  pages =	{20:1--20:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-175-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{183},
  editor =	{Baier, Christel and Goubault-Larrecq, Jean},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2021.20},
  URN =		{urn:nbn:de:0030-drops-134546},
  doi =		{10.4230/LIPIcs.CSL.2021.20},
  annote =	{Keywords: Separation logic, Induction definitions, Inductive theorem proving, Entailments, Complexity}
}
Document
Track B: Automata, Logic, Semantics, and Theory of Programming
DOI: 10.4230/LIPIcs.ICALP.2020.123
The Strahler Number of a Parity Game

Authors: Laure Daviaud, Marcin Jurdziński, and K. S. Thejaswini

Published in: LIPIcs, Volume 168, 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)

Abstract
The Strahler number of a rooted tree is the largest height of a perfect binary tree that is its minor. The Strahler number of a parity game is proposed to be defined as the smallest Strahler number of the tree of any of its attractor decompositions. It is proved that parity games can be solved in quasi-linear space and in time that is polynomial in the number of vertices n and linear in (d/(2k))^k, where d is the number of priorities and k is the Strahler number. This complexity is quasi-polynomial because the Strahler number is at most logarithmic in the number of vertices. The proof is based on a new construction of small Strahler-universal trees. It is shown that the Strahler number of a parity game is a robust, and hence arguably natural, parameter: it coincides with its alternative version based on trees of progress measures and - remarkably - with the register number defined by Lehtinen (2018). It follows that parity games can be solved in quasi-linear space and in time that is polynomial in the number of vertices and linear in (d/(2k))^k, where k is the register number. This significantly improves the running times and space achieved for parity games of bounded register number by Lehtinen (2018) and by Parys (2020). The running time of the algorithm based on small Strahler-universal trees yields a novel trade-off k ⋅ lg(d/k) = O(log n) between the two natural parameters that measure the structural complexity of a parity game, which allows solving parity games in polynomial time. This includes as special cases the asymptotic settings of those parameters covered by the results of Calude, Jain Khoussainov, Li, and Stephan (2017), of Jurdziński and Lazić (2017), and of Lehtinen (2018), and it significantly extends the range of such settings, for example to d = 2^O(√{lg n}) and k = O(√{lg n}).
Cite as

Laure Daviaud, Marcin Jurdziński, and K. S. Thejaswini. The Strahler Number of a Parity Game. In 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 168, pp. 123:1-123:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{daviaud_et_al:LIPIcs.ICALP.2020.123,
  author =	{Daviaud, Laure and Jurdzi\'{n}ski, Marcin and Thejaswini, K. S.},
  title =	{{The Strahler Number of a Parity Game}},
  booktitle =	{47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)},
  pages =	{123:1--123:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-138-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{168},
  editor =	{Czumaj, Artur and Dawar, Anuj and Merelli, Emanuela},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2020.123},
  URN =		{urn:nbn:de:0030-drops-125304},
  doi =		{10.4230/LIPIcs.ICALP.2020.123},
  annote =	{Keywords: parity game, attractor decomposition, progress measure, universal tree, Strahler number}
}
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