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Documents authored by Vilmin, Simon

Document
DOI: 10.4230/LIPIcs.ISAAC.2025.24
Enumerating the Irreducible Closed Sets of an Acyclic Implicational Base of Bounded Degree

Authors: Oscar Defrain, Arthur Ohana, and Simon Vilmin

Published in: LIPIcs, Volume 359, 36th International Symposium on Algorithms and Computation (ISAAC 2025)

Abstract
We consider the problem of enumerating the irreducible closed sets of a closure system given by an implicational base. To date, the complexity status of this problem is widely open, and it is further known to generalize the notorious hypergraph dualization problem, even in the case of acyclic convex geometries, i.e., closure systems admitting an acyclic implicational base. This paper studies this case with a focus on the degree, which corresponds to the maximal number of implications in which an element occurs. We show that the problem is tractable for bounded values of this parameter, even when relaxed to the notions of premise- and conclusion-degree. Our algorithms rely on a sequential approach leveraging from acyclicity, combined with the solution graph traversal technique for the case of premise-degree. They are shown to perform in incremental-polynomial time. These results are complemented in the long version of this document by showing that the dual problem of constructing the implicational base can be solved in polynomial time. Finally, we argue that our running times cannot be improved to polynomial delay using the standard framework of flashlight search.
Cite as

Oscar Defrain, Arthur Ohana, and Simon Vilmin. Enumerating the Irreducible Closed Sets of an Acyclic Implicational Base of Bounded Degree. In 36th International Symposium on Algorithms and Computation (ISAAC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 359, pp. 24:1-24:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{defrain_et_al:LIPIcs.ISAAC.2025.24,
  author =	{Defrain, Oscar and Ohana, Arthur and Vilmin, Simon},
  title =	{{Enumerating the Irreducible Closed Sets of an Acyclic Implicational Base of Bounded Degree}},
  booktitle =	{36th International Symposium on Algorithms and Computation (ISAAC 2025)},
  pages =	{24:1--24:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-408-6},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{359},
  editor =	{Chen, Ho-Lin and Hon, Wing-Kai and Tsai, Meng-Tsung},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2025.24},
  URN =		{urn:nbn:de:0030-drops-249321},
  doi =		{10.4230/LIPIcs.ISAAC.2025.24},
  annote =	{Keywords: Algorithmic enumeration, closure systems, acyclic convex geometries, solution graph traversal, flashlight search, extension, hypergraph dualization}
}
Document
DOI: 10.4230/LIPIcs.WADS.2025.19
On the Enumeration of Signatures of XOR-CNF’s

Authors: Nadia Creignou, Oscar Defrain, Frédéric Olive, and Simon Vilmin

Published in: LIPIcs, Volume 349, 19th International Symposium on Algorithms and Data Structures (WADS 2025)

Abstract
Given a CNF formula φ with clauses C_1, … , C_m over a set of variables V, a truth assignment 𝐚: V → {0, 1} generates a binary sequence σ_φ(𝐚) = (C_1(𝐚), …, C_m(𝐚)), called a signature of φ, where C_i(𝐚) = 1 if clause C_i evaluates to 1 under assignment 𝐚, and C_i(𝐚) = 0 otherwise. Signatures and their associated generation problems have given rise to new yet promising research questions in algorithmic enumeration. In a recent paper, Bérczi et al. interestingly proved that generating signatures of a CNF is tractable despite the fact that verifying a solution is hard. They also showed the hardness of finding maximal signatures of an arbitrary CNF due to the intractability of satisfiability in general. Their contribution leaves open the problem of efficiently generating maximal signatures for tractable classes of CNFs, i.e., those for which satisfiability can be solved in polynomial time. Stepping into that direction, we completely characterize the complexity of generating all, minimal, and maximal signatures for XOR-CNF’s.
Cite as

Nadia Creignou, Oscar Defrain, Frédéric Olive, and Simon Vilmin. On the Enumeration of Signatures of XOR-CNF’s. In 19th International Symposium on Algorithms and Data Structures (WADS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 349, pp. 19:1-19:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{creignou_et_al:LIPIcs.WADS.2025.19,
  author =	{Creignou, Nadia and Defrain, Oscar and Olive, Fr\'{e}d\'{e}ric and Vilmin, Simon},
  title =	{{On the Enumeration of Signatures of XOR-CNF’s}},
  booktitle =	{19th International Symposium on Algorithms and Data Structures (WADS 2025)},
  pages =	{19:1--19:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-398-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{349},
  editor =	{Morin, Pat and Oh, Eunjin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.WADS.2025.19},
  URN =		{urn:nbn:de:0030-drops-242508},
  doi =		{10.4230/LIPIcs.WADS.2025.19},
  annote =	{Keywords: Algorithmic enumeration, XOR-CNF, signatures, maximal bipartite subgraphs enumeration, extension, proximity search}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2024.51
Half-Space Separation in Monophonic Convexity

Authors: Mohammed Elaroussi, Lhouari Nourine, and Simon Vilmin

Published in: LIPIcs, Volume 306, 49th International Symposium on Mathematical Foundations of Computer Science (MFCS 2024)

Abstract
We study half-space separation in the convexity of chordless paths of a graph, i.e., monophonic convexity. In this problem, one is given a graph and two (disjoint) subsets of vertices and asks whether these two sets can be separated by complementary convex sets, called half-spaces. While it is known this problem is NP-complete for geodesic convexity - the convexity of shortest paths - we show that it can be solved in polynomial time for monophonic convexity.
Cite as

Mohammed Elaroussi, Lhouari Nourine, and Simon Vilmin. Half-Space Separation in Monophonic Convexity. In 49th International Symposium on Mathematical Foundations of Computer Science (MFCS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 306, pp. 51:1-51:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{elaroussi_et_al:LIPIcs.MFCS.2024.51,
  author =	{Elaroussi, Mohammed and Nourine, Lhouari and Vilmin, Simon},
  title =	{{Half-Space Separation in Monophonic Convexity}},
  booktitle =	{49th International Symposium on Mathematical Foundations of Computer Science (MFCS 2024)},
  pages =	{51:1--51:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-335-5},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{306},
  editor =	{Kr\'{a}lovi\v{c}, Rastislav and Ku\v{c}era, Anton{\'\i}n},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2024.51},
  URN =		{urn:nbn:de:0030-drops-206070},
  doi =		{10.4230/LIPIcs.MFCS.2024.51},
  annote =	{Keywords: chordless paths, monophonic convexity, separation, half-space}
}
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