Volume

LIPIcs, Volume 63

11th International Symposium on Parameterized and Exact Computation (IPEC 2016)



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Event

IPEC 2016, August 24-26, 2016, Aarhus, Denmark

Editors

Jiong Guo
Danny Hermelin

Publication Details

  • published at: 2017-02-09
  • Publisher: Schloss-Dagstuhl - Leibniz Zentrum für Informatik
  • ISBN: 978-3-95977-023-1
  • DBLP: db/conf/iwpec/ipec2016

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Document
Complete Volume
LIPIcs, Volume 63, IPEC'16, Complete Volume

Authors: Jiong Guo and Danny Hermelin


Abstract
LIPIcs, Volume 63, IPEC'16, Complete Volume

Cite as

Jiong Guo and Danny Hermelin. LIPIcs, Volume 63, IPEC'16, Complete Volume. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@Proceedings{guo_et_al:LIPIcs.IPEC.2016,
  title =	{{LIPIcs, Volume 63, IPEC'16, Complete Volume}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016},
  URN =		{urn:nbn:de:0030-drops-69572},
  doi =		{10.4230/LIPIcs.IPEC.2016},
  annote =	{Keywords: Complexity Measures and Classes, Analysis of Algorithms and Problem Complexity, Discrete Mathematics}
}
Document
Front Matter
Front Matter, Table of Contents, Preface, Program Committee, External Reviewers, List of Authors

Authors: Jiong Guo and Danny Hermelin


Abstract
Front Matter, Table of Contents, Preface, Program Committee, External Reviewers, List of Authors

Cite as

Jiong Guo and Danny Hermelin. Front Matter, Table of Contents, Preface, Program Committee, External Reviewers, List of Authors. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 0:i-0:xiv, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{guo_et_al:LIPIcs.IPEC.2016.0,
  author =	{Guo, Jiong and Hermelin, Danny},
  title =	{{Front Matter, Table of Contents, Preface, Program Committee, External Reviewers, List of Authors}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{0:i--0:xiv},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.0},
  URN =		{urn:nbn:de:0030-drops-69180},
  doi =		{10.4230/LIPIcs.IPEC.2016.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Program Committee, External Reviewers, List of Authors}
}
Document
Invited Talk
Determinant Sums for Hamiltonicity (Invited Talk)

Authors: Andreas Björklund


Abstract
The best worst case guarantee algorithm to see if a graph has a Hamiltonian cycle, a closed tour visiting every vertex exactly once, for a long time was based on dynamic programming over all the vertex subsets of the graph. In this talk we will show some algebraic techniques that can be used to see if a graph has a Hamiltonian cycle much faster. These techniques utilize sums over determinants of matrices. In particular we will show how you can find out if an undirected graph has a Hamiltonian cycle much faster, but we will also talk about some partial results for the directed case and modular counting.

Cite as

Andreas Björklund. Determinant Sums for Hamiltonicity (Invited Talk). In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, p. 1:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{bjorklund:LIPIcs.IPEC.2016.1,
  author =	{Bj\"{o}rklund, Andreas},
  title =	{{Determinant Sums for Hamiltonicity}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.1},
  URN =		{urn:nbn:de:0030-drops-69485},
  doi =		{10.4230/LIPIcs.IPEC.2016.1},
  annote =	{Keywords: Hamiltonian cycle, exact algorithms, matrix determinant, algebraic techniques}
}
Document
Improved Algorithms and Combinatorial Bounds for Independent Feedback Vertex Set

Authors: Akanksha Agrawal, Sushmita Gupta, Saket Saurabh, and Roohani Sharma


Abstract
In this paper we study the "independent" version of the classic Feedback Vertex Set problem in the realm of parameterized algorithms and moderately exponential time algorithms. More precisely, we study the Independent Feedback Vertex Set problem, where we are given an undirected graph G on n vertices and a positive integer k, and the objective is to check if there is an independent feedback vertex set of size at most k. A set S subseteq V(G) is called an independent feedback vertex set (ifvs) if S is an independent set and G\S is a forest. In this paper we design two deterministic exact algorithms for Independent Feedback Vertex Set with running times O*(4.1481^k) and O*(1.5981^n). In fact, the algorithm with O*(1.5981^n) running time finds the smallest sized ifvs, if an ifvs exists. Both the algorithms are based on interesting measures and improve the best known algorithms for the problem in their respective domains. In particular, the algorithm with running time O*(4.1481^k) is an improvement over the previous algorithm that ran in time O*(5^k). On the other hand, the algorithm with running time O*(1.5981^n) is the first moderately exponential time algorithm that improves over the naive algorithm that enumerates all the subsets of V(G). Additionally, we show that the number of minimal ifvses in any graph on n vertices is upper bounded by 1.7485^n.

Cite as

Akanksha Agrawal, Sushmita Gupta, Saket Saurabh, and Roohani Sharma. Improved Algorithms and Combinatorial Bounds for Independent Feedback Vertex Set. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 2:1-2:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{agrawal_et_al:LIPIcs.IPEC.2016.2,
  author =	{Agrawal, Akanksha and Gupta, Sushmita and Saurabh, Saket and Sharma, Roohani},
  title =	{{Improved Algorithms and Combinatorial Bounds for Independent Feedback Vertex Set}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{2:1--2:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.2},
  URN =		{urn:nbn:de:0030-drops-69400},
  doi =		{10.4230/LIPIcs.IPEC.2016.2},
  annote =	{Keywords: independent feedback vertex set, fixed parameter tractable, exact algorithm, enumeration}
}
Document
H-Free Graphs, Independent Sets, and Subexponential-Time Algorithms

Authors: Gábor Bacsó, Dániel Marx, and Zsolt Tuza


Abstract
It is an outstanding open question in algorithmic graph theory to determine the complexity of the MAXIMUM INDEPENDENT SET problem on P_t-free graphs, that is, on graphs not containing any induced path on t vertices. So far, polynomial-time algorithms are known only for t at most 5 [Lokshtanov et al., SODA 2014, 570-581, 2014]. Here we study the existence of subexponential-time algorithms for the problem: by generalizing an earlier result of Randerath and Schiermeyer for t=5 [Discrete App. Math., 158 (2010), 1041-1044], we show that for any t at least 5, there is an algorithm for MAXIMUM INDEPENDENT SET on P_t-free graphs whose running time is subexponential in the number of vertices. SCATTERED SET is the generalization of MAXIMUM INDEPENDENT SET where the vertices of the solution are required to be at distance at least $d$ from each other. We give a complete characterization of those graphs H for which SCATTERED SET on H-free graphs can be solved in time subexponential in the size of the input (that is, in the number of vertices plus the number of edges): * If every component of H is a path, then d-SCATTERED SET on H-free graphs with n vertices and m edges can be solved in time 2^{(n+m)^{1-O(1/|V(H)|)}}, even if d is part of the input. * Otherwise, assuming ETH, there is no 2^{o(n+m)} time algorithm for d-SCATTERED SET for any fixed d at least 3 on H-free graphs with n vertices and m edges.

Cite as

Gábor Bacsó, Dániel Marx, and Zsolt Tuza. H-Free Graphs, Independent Sets, and Subexponential-Time Algorithms. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 3:1-3:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{bacso_et_al:LIPIcs.IPEC.2016.3,
  author =	{Bacs\'{o}, G\'{a}bor and Marx, D\'{a}niel and Tuza, Zsolt},
  title =	{{H-Free Graphs, Independent Sets, and Subexponential-Time Algorithms}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{3:1--3:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.3},
  URN =		{urn:nbn:de:0030-drops-69397},
  doi =		{10.4230/LIPIcs.IPEC.2016.3},
  annote =	{Keywords: independent set, scattered set, subexponential algorithms, H-free graphs}
}
Document
Parallel Multivariate Meta-Theorems

Authors: Max Bannach and Till Tantau


Abstract
Fixed-parameter tractability is based on the observation that many hard problems become tractable even on large inputs as long as certain input parameters are small. Originally, "tractable" just meant "solvable in polynomial time," but especially modern hardware raises the question of whether we can also achieve "solvable in polylogarithmic parallel time." A framework for this study of parallel fixed-parameter tractability is available and a number of isolated algorithmic results have been obtained in recent years, but one of the unifying core tools of classical FPT theory has been missing: algorithmic meta-theorems. We establish two such theorems by giving new upper bounds on the circuit depth necessary to solve the model checking problem for monadic second-order logic, once parameterized by the tree width and the formula (this is a parallel version of Courcelle's Theorem) and once by the tree depth and the formula. For our proofs we refine the analysis of earlier algorithms, especially of Bodlaender's, but also need to add new ideas, especially in the context where the parallel runtime is bounded by a function of the parameter and does not depend on the length of the input.

Cite as

Max Bannach and Till Tantau. Parallel Multivariate Meta-Theorems. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 4:1-4:17, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{bannach_et_al:LIPIcs.IPEC.2016.4,
  author =	{Bannach, Max and Tantau, Till},
  title =	{{Parallel Multivariate Meta-Theorems}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{4:1--4:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.4},
  URN =		{urn:nbn:de:0030-drops-69227},
  doi =		{10.4230/LIPIcs.IPEC.2016.4},
  annote =	{Keywords: Parallel computation, FPT, meta-theorems, tree width, tree depth}
}
Document
Finding Secluded Places of Special Interest in Graphs

Authors: René van Bevern, Till Fluschnik, George B. Mertzios, Hendrik Molter, Manuel Sorge, and Ondrej Suchý


Abstract
Finding a vertex subset in a graph that satisfies a certain property is one of the most-studied topics in algorithmic graph theory. The focus herein is often on minimizing or maximizing the size of the solution, that is, the size of the desired vertex set. In several applications, however, we also want to limit the "exposure" of the solution to the rest of the graph. This is the case, for example, when the solution represents persons that ought to deal with sensitive information or a segregated community. In this work, we thus explore the (parameterized) complexity of finding such secluded vertex subsets for a wide variety of properties that they shall fulfill. More precisely, we study the constraint that the (open or closed) neighborhood of the solution shall be bounded by a parameter and the influence of this constraint on the complexity of minimizing separators, feedback vertex sets, F-free vertex deletion sets, dominating sets, and the maximization of independent sets.

Cite as

René van Bevern, Till Fluschnik, George B. Mertzios, Hendrik Molter, Manuel Sorge, and Ondrej Suchý. Finding Secluded Places of Special Interest in Graphs. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 5:1-5:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{vanbevern_et_al:LIPIcs.IPEC.2016.5,
  author =	{van Bevern, Ren\'{e} and Fluschnik, Till and Mertzios, George B. and Molter, Hendrik and Sorge, Manuel and Such\'{y}, Ondrej},
  title =	{{Finding Secluded Places of Special Interest in Graphs}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{5:1--5:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.5},
  URN =		{urn:nbn:de:0030-drops-69380},
  doi =		{10.4230/LIPIcs.IPEC.2016.5},
  annote =	{Keywords: Neighborhood, Feedback Vertex Set, Vertex Deletion, Separator, Dominating Set}
}
Document
The Parameterized Complexity of Dependency Detection in Relational Databases

Authors: Thomas Bläsius, Tobias Friedrich, and Martin Schirneck


Abstract
We study the parameterized complexity of classical problems that arise in the profiling of relational data. Namely, we characterize the complexity of detecting unique column combinations (candidate keys), functional dependencies, and inclusion dependencies with the solution size as parameter. While the discovery of uniques and functional dependencies, respectively, turns out to be W[2]-complete, the detection of inclusion dependencies is one of the first natural problems proven to be complete for the class W[3]. As a side effect, our reductions give insights into the complexity of enumerating all minimal unique column combinations or functional dependencies.

Cite as

Thomas Bläsius, Tobias Friedrich, and Martin Schirneck. The Parameterized Complexity of Dependency Detection in Relational Databases. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 6:1-6:13, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{blasius_et_al:LIPIcs.IPEC.2016.6,
  author =	{Bl\"{a}sius, Thomas and Friedrich, Tobias and Schirneck, Martin},
  title =	{{The Parameterized Complexity of Dependency Detection in Relational Databases}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{6:1--6:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.6},
  URN =		{urn:nbn:de:0030-drops-69202},
  doi =		{10.4230/LIPIcs.IPEC.2016.6},
  annote =	{Keywords: parameterized complexity, unique column combination, functional dependency, inclusion dependency, profiling relational data}
}
Document
A Faster Parameterized Algorithm for Pseudoforest Deletion

Authors: Hans L. Bodlaender, Hirotaka Ono, and Yota Otachi


Abstract
A pseudoforest is a graph where each connected component contains at most one cycle, or alternatively, a graph that can be turned into a forest by removing at most one edge from each connected component. In this paper, we show that the following problem can be solved in O(3^k n k^{O(1)}) time: given a graph G and an integer k, can we delete at most k vertices from G such that we obtain a pseudoforest? The result improves upon an earlier result by Philip et al. [MFCS 2015] who gave a (nonlinear) 7.56^k n^{O(1)}-time algorithm both in the exponential factor depending on k as well as in the polynomial factor depending on n.

Cite as

Hans L. Bodlaender, Hirotaka Ono, and Yota Otachi. A Faster Parameterized Algorithm for Pseudoforest Deletion. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 7:1-7:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{bodlaender_et_al:LIPIcs.IPEC.2016.7,
  author =	{Bodlaender, Hans L. and Ono, Hirotaka and Otachi, Yota},
  title =	{{A Faster Parameterized Algorithm for Pseudoforest Deletion}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{7:1--7:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.7},
  URN =		{urn:nbn:de:0030-drops-69246},
  doi =		{10.4230/LIPIcs.IPEC.2016.7},
  annote =	{Keywords: pseudoforest deletion, graph class, width parameter, parameterized complexity}
}
Document
Optimal Dynamic Program for r-Domination Problems over Tree Decompositions

Authors: Glencora Borradaile and Hung Le


Abstract
There has been recent progress in showing that the exponential dependence on treewidth in dynamic programming algorithms for solving NP-hard problems is optimal under the Strong Exponential Time Hypothesis (SETH). We extend this work to r-domination problems. In r-dominating set, one wishes to find a minimum subset S of vertices such that every vertex of G is within r hops of some vertex in S. In connected r-dominating set, one additionally requires that the set induces a connected subgraph of G. We give a O((2r+1)^tw n) time algorithm for r-dominating set and a randomized O((2r+2)^tw n^{O(1)}) time algorithm for connected r-dominating set in n-vertex graphs of treewidth tw. We show that the running time dependence on r and tw is the best possible under SETH. This adds to earlier observations that a "+1" in the denominator is required for connectivity constraints.

Cite as

Glencora Borradaile and Hung Le. Optimal Dynamic Program for r-Domination Problems over Tree Decompositions. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 8:1-8:23, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{borradaile_et_al:LIPIcs.IPEC.2016.8,
  author =	{Borradaile, Glencora and Le, Hung},
  title =	{{Optimal Dynamic Program for r-Domination Problems over Tree Decompositions}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{8:1--8:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.8},
  URN =		{urn:nbn:de:0030-drops-69199},
  doi =		{10.4230/LIPIcs.IPEC.2016.8},
  annote =	{Keywords: r-dominating set, Exponential Time Hypothesis, Dynamic Programming}
}
Document
Fine-Grained Dichotomies for the Tutte Plane and Boolean #CSP

Authors: Cornelius Brand, Holger Dell, and Marc Roth


Abstract
Jaeger, Vertigan, and Welsh (1990) proved a dichotomy for the complexity of evaluating the Tutte polynomial at fixed points: The evaluation is #P-hard almost everywhere, and the remaining points admit polynomial-time algorithms. Dell, Husfeldt, and Wahlén (2010) and Husfeldt and Taslaman (2010), in combination with the results of Curticapean (2015), extended the #P-hardness results to tight lower bounds under the counting exponential time hypothesis #ETH, with the exception of the line y=1, which was left open. We complete the dichotomy theorem for the Tutte polynomial under #ETH by proving that the number of all acyclic subgraphs of a given n-vertex graph cannot be determined in time exp(o(n)) unless #ETH fails. Another dichotomy theorem we strengthen is the one of Creignou and Hermann (1996) for counting the number of satisfying assignments to a constraint satisfaction problem instance over the Boolean domain. We prove that all #P-hard cases cannot be solved in time exp(o(n)) unless #ETH fails. The main ingredient is to prove that the number of independent sets in bipartite graphs with n vertices cannot be computed in time exp(o(n)) unless #ETH fails. In order to prove our results, we use the block interpolation idea by Curticapean (2015) and transfer it to systems of linear equations that might not directly correspond to interpolation.

Cite as

Cornelius Brand, Holger Dell, and Marc Roth. Fine-Grained Dichotomies for the Tutte Plane and Boolean #CSP. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 9:1-9:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{brand_et_al:LIPIcs.IPEC.2016.9,
  author =	{Brand, Cornelius and Dell, Holger and Roth, Marc},
  title =	{{Fine-Grained Dichotomies for the Tutte Plane and Boolean #CSP}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{9:1--9:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.9},
  URN =		{urn:nbn:de:0030-drops-69426},
  doi =		{10.4230/LIPIcs.IPEC.2016.9},
  annote =	{Keywords: computational complexity, counting problems, Tutte polynomial, exponential time hypothesis, forests, independent sets}
}
Document
A Parameterized Algorithmics Framework for Degree Sequence Completion Problems in Directed Graphs

Authors: Robert Bredereck, Vincent Froese, Marcel Koseler, Marcelo Garlet Millani, André Nichterlein, and Rolf Niedermeier


Abstract
There has been intensive work on the parameterized complexity of the typically NP-hard task to edit undirected graphs into graphs fulfilling certain given vertex degree constraints. In this work, we lift the investigations to the case of directed graphs; herein, we focus on arc insertions. To this end, our general two-stage framework consists of efficiently solving a problem-specific number problem transferring its solution to a solution for the graph problem by applying flow computations. In this way, we obtain fixed-parameter tractability and polynomial kernelizability results, with the central parameter being the maximum vertex in- or outdegree of the output digraph. Although there are certain similarities with the much better studied undirected case, the flow computation used in the directed case seems not to work for the undirected case while f-factor computations as used in the undirected case seem not to work for the directed case.

Cite as

Robert Bredereck, Vincent Froese, Marcel Koseler, Marcelo Garlet Millani, André Nichterlein, and Rolf Niedermeier. A Parameterized Algorithmics Framework for Degree Sequence Completion Problems in Directed Graphs. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 10:1-10:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{bredereck_et_al:LIPIcs.IPEC.2016.10,
  author =	{Bredereck, Robert and Froese, Vincent and Koseler, Marcel and Millani, Marcelo Garlet and Nichterlein, Andr\'{e} and Niedermeier, Rolf},
  title =	{{A Parameterized Algorithmics Framework for Degree Sequence Completion Problems in Directed Graphs}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{10:1--10:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.10},
  URN =		{urn:nbn:de:0030-drops-69353},
  doi =		{10.4230/LIPIcs.IPEC.2016.10},
  annote =	{Keywords: NP-hard graph problem, graph realizability, graph modification, arc insertion, fixed-parameter tractability, kernelization}
}
Document
On the Parameterized Complexity of Biclique Cover and Partition

Authors: Sunil Chandran, Davis Issac, and Andreas Karrenbauer


Abstract
Given a bipartite graph G, we consider the decision problem called BicliqueCover for a fixed positive integer parameter k where we are asked whether the edges of G can be covered with at most k complete bipartite subgraphs (a.k.a. bicliques). In the BicliquePartition problem, we have the additional constraint that each edge should appear in exactly one of the k bicliques. These problems are both known to be NP-complete but fixed parameter tractable. However, the known FPT algorithms have a running time that is doubly exponential in k, and the best known kernel for both problems is exponential in k. We build on this kernel and improve the running time for BicliquePartition to O*(2^{2k^2+k*log(k)+k}) by exploiting a linear algebraic view on this problem. On the other hand, we show that no such improvement is possible for BicliqueCover unless the Exponential Time Hypothesis (ETH) is false by proving a doubly exponential lower bound on the running time. We achieve this by giving a reduction from 3SAT on n variables to an instance of BicliqueCover with k=O(log(n)). As a further consequence of this reduction, we show that there is no subexponential kernel for BicliqueCover unless P=NP. Finally, we point out the significance of the exponential kernel mentioned above for the design of polynomial-time approximation algorithms for the optimization versions of both problems. That is, we show that it is possible to obtain approximation factors of n/log(n) for both problems, whereas the previous best approximation factor was n/sqrt(log(n)).

Cite as

Sunil Chandran, Davis Issac, and Andreas Karrenbauer. On the Parameterized Complexity of Biclique Cover and Partition. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 11:1-11:13, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{chandran_et_al:LIPIcs.IPEC.2016.11,
  author =	{Chandran, Sunil and Issac, Davis and Karrenbauer, Andreas},
  title =	{{On the Parameterized Complexity of Biclique Cover and Partition}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{11:1--11:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.11},
  URN =		{urn:nbn:de:0030-drops-69293},
  doi =		{10.4230/LIPIcs.IPEC.2016.11},
  annote =	{Keywords: Biclique Cover/Partition, Linear algebra in finite fields, Lower bound}
}
Document
Exact Algorithms for List-Coloring of Intersecting Hypergraphs

Authors: Khaled Elbassioni


Abstract
We show that list-coloring for any intersecting hypergraph of m edges on n vertices, and lists drawn from a set of size at most k, can be checked in quasi-polynomial time (mn)^{o(k^2*log(mn))}.

Cite as

Khaled Elbassioni. Exact Algorithms for List-Coloring of Intersecting Hypergraphs. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 12:1-12:15, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{elbassioni:LIPIcs.IPEC.2016.12,
  author =	{Elbassioni, Khaled},
  title =	{{Exact Algorithms for List-Coloring of Intersecting Hypergraphs}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{12:1--12:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.12},
  URN =		{urn:nbn:de:0030-drops-69444},
  doi =		{10.4230/LIPIcs.IPEC.2016.12},
  annote =	{Keywords: Hypergraph coloring, monotone Boolean duality, list coloring, exact algorithms, quasi-polynomial time}
}
Document
Turbocharging Treewidth Heuristics

Authors: Serge Gaspers, Joachim Gudmundsson, Mitchell Jones, Julián Mestre, and Stefan Rümmele


Abstract
A widely used class of algorithms for computing tree decompositions of graphs are heuristics that compute an elimination order, i.e., a permutation of the vertex set. In this paper, we propose to turbocharge these heuristics. For a target treewidth k, suppose the heuristic has already computed a partial elimination order of width at most k, but extending it by one more vertex exceeds the target width k. At this moment of regret, we solve a subproblem which is to recompute the last c positions of the partial elimination order such that it can be extended without exceeding width k. We show that this subproblem is fixed-parameter tractable when parameterized by k and c, but it is para-NP-hard and W[1]-hard when parameterized by only k or c, respectively. Our experimental evaluation of the FPT algorithm shows that we can trade a reasonable increase of the running time for quality of the solution.

Cite as

Serge Gaspers, Joachim Gudmundsson, Mitchell Jones, Julián Mestre, and Stefan Rümmele. Turbocharging Treewidth Heuristics. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 13:1-13:13, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{gaspers_et_al:LIPIcs.IPEC.2016.13,
  author =	{Gaspers, Serge and Gudmundsson, Joachim and Jones, Mitchell and Mestre, Juli\'{a}n and R\"{u}mmele, Stefan},
  title =	{{Turbocharging Treewidth Heuristics}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{13:1--13:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.13},
  URN =		{urn:nbn:de:0030-drops-69322},
  doi =		{10.4230/LIPIcs.IPEC.2016.13},
  annote =	{Keywords: tree decomposition, heuristic, fixed-parameter tractability, local search}
}
Document
On Satisfiability Problems with a Linear Structure

Authors: Serge Gaspers, Christos H. Papadimitriou, Sigve Hortemo Sæther, and Jan Arne Telle


Abstract
It was recently shown [Sæther, Telle, and Vatshelle, JAIR 54, 2015] that satisfiability is polynomially solvable when the incidence graph is an interval bipartite graph (an interval graph turned into a bipartite graph by omitting all edges within each partite set). Here we relax this condition in several directions: First, we show an FPT algorithm parameterized by k for k-interval bigraphs, bipartite graphs which can be converted to interval bipartite graphs by adding to each node of one side at most k edges; the same result holds for the counting and the weighted maximization version of satisfiability. Second, given two linear orders, one for the variables and one for the clauses, we show how to find, in polynomial time, the smallest k such that there is a k-interval bigraph compatible with these two orders. On the negative side we prove that, barring complexity collapses, no such extensions are possible for CSPs more general than satisfiability. We also show NP-hardness of recognizing 1-interval bigraphs.

Cite as

Serge Gaspers, Christos H. Papadimitriou, Sigve Hortemo Sæther, and Jan Arne Telle. On Satisfiability Problems with a Linear Structure. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 14:1-14:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{gaspers_et_al:LIPIcs.IPEC.2016.14,
  author =	{Gaspers, Serge and Papadimitriou, Christos H. and S{\ae}ther, Sigve Hortemo and Telle, Jan Arne},
  title =	{{On Satisfiability Problems with a Linear Structure}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{14:1--14:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.14},
  URN =		{urn:nbn:de:0030-drops-69412},
  doi =		{10.4230/LIPIcs.IPEC.2016.14},
  annote =	{Keywords: Satisfiability, interval graphs, FPT algorithms}
}
Document
Cutwidth: Obstructions and Algorithmic Aspects

Authors: Archontia C. Giannopoulou, Michal Pilipczuk, Jean-Florent Raymond, Dimitrios M. Thilikos, and Marcin Wrochna


Abstract
Cutwidth is one of the classic layout parameters for graphs. It measures how well one can order the vertices of a graph in a linear manner, so that the maximum number of edges between any prefix and its complement suffix is minimized. As graphs of cutwidth at most k are closed under taking immersions, the results of Robertson and Seymour imply that there is a finite list of minimal immersion obstructions for admitting a cut layout of width at most k. We prove that every minimal immersion obstruction for cutwidth at most k has size at most 2^O(k^3*log(k)). As an interesting algorithmic byproduct, we design a new fixed-parameter algorithm for computing the cutwidth of a graph that runs in time 2^O(k^2*log(k))*n, where k is the optimum width and n is the number of vertices. While being slower by a log k-factor in the exponent than the fastest known algorithm, due to Thilikos, Bodlaender, and Serna [J. Algorithms 2005], our algorithm has the advantage of being simpler and self-contained; arguably, it explains better the combinatorics of optimum-width layouts.

Cite as

Archontia C. Giannopoulou, Michal Pilipczuk, Jean-Florent Raymond, Dimitrios M. Thilikos, and Marcin Wrochna. Cutwidth: Obstructions and Algorithmic Aspects. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 15:1-15:13, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{giannopoulou_et_al:LIPIcs.IPEC.2016.15,
  author =	{Giannopoulou, Archontia C. and Pilipczuk, Michal and Raymond, Jean-Florent and Thilikos, Dimitrios M. and Wrochna, Marcin},
  title =	{{Cutwidth: Obstructions and Algorithmic Aspects}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{15:1--15:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.15},
  URN =		{urn:nbn:de:0030-drops-69306},
  doi =		{10.4230/LIPIcs.IPEC.2016.15},
  annote =	{Keywords: cutwidth, obstructions, immersions, fixed-parameter tractability}
}
Document
Computing Graph Distances Parameterized by Treewidth and Diameter

Authors: Thore Husfeldt


Abstract
We show that the eccentricity of every vertex in an undirected graph on n vertices can be computed in time n exp O(k*log(d)), where k is the treewidth of the graph and d is the diameter. This means that the diameter and the radius of the graph can be computed in the same time. In particular, if the diameter is constant, it can be determined in time n*exp(O(k)). This result matches a recent hardness result by Abboud, Vassilevska Williams, and Wang [SODA 2016] that shows that under the Strong Exponential Time Hypothesis of Impagliazzo, Paturi, and Zane [J. Comp. Syst. Sc., 2001], for any epsilon > 0, no algorithm with running time n^{2-epsilon}*exp(o(k)) can distinguish between graphs with diameter 2 and 3.

Cite as

Thore Husfeldt. Computing Graph Distances Parameterized by Treewidth and Diameter. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 16:1-16:11, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{husfeldt:LIPIcs.IPEC.2016.16,
  author =	{Husfeldt, Thore},
  title =	{{Computing Graph Distances Parameterized by Treewidth and Diameter}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{16:1--16:11},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.16},
  URN =		{urn:nbn:de:0030-drops-69476},
  doi =		{10.4230/LIPIcs.IPEC.2016.16},
  annote =	{Keywords: Graph algorithms, diameter, treewidth, Strong Exponential Time Hypothesis}
}
Document
Lower Bounds for Protrusion Replacement by Counting Equivalence Classes

Authors: Bart M. P. Jansen and Jules J. H. M. Wulms


Abstract
Garnero et al. [SIAM J. Discrete Math. 2015, 29(4):1864-1894] recently introduced a framework based on dynamic programming to make applications of the protrusion replacement technique constructive and to obtain explicit upper bounds on the involved constants. They show that for several graph problems, for every boundary size t one can find an explicit set R_t of representatives. Any subgraph H with a boundary of size t can be replaced with a representative H' in R_t such that the effect of this replacement on the optimum can be deduced from H and H' alone. Their upper bounds on the size of the graphs in R_t grow triple-exponentially with t. In this paper we complement their results by lower bounds on the sizes of representatives, in terms of the boundary size t. For example, we show that each set of planar representatives R_t for the Independent Set problem contains a graph with Omega(2^t / sqrt{4t}) vertices. This lower bound even holds for sets that only represent the planar subgraphs of bounded pathwidth. To obtain our results we provide a lower bound on the number of equivalence classes of the canonical equivalence relation for Independent Set on t-boundaried graphs. We also find an elegant characterization of the number of equivalence classes in general graphs, in terms of the number of monotone functions of a certain kind. Our results show that the number of equivalence classes is at most 2^{2^t}, improving on earlier bounds of the form (t+1)^{2^t}.

Cite as

Bart M. P. Jansen and Jules J. H. M. Wulms. Lower Bounds for Protrusion Replacement by Counting Equivalence Classes. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 17:1-17:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{jansen_et_al:LIPIcs.IPEC.2016.17,
  author =	{Jansen, Bart M. P. and Wulms, Jules J. H. M.},
  title =	{{Lower Bounds for Protrusion Replacement by Counting Equivalence Classes}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{17:1--17:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.17},
  URN =		{urn:nbn:de:0030-drops-69275},
  doi =		{10.4230/LIPIcs.IPEC.2016.17},
  annote =	{Keywords: protrusions, boundaried graphs, independent set, equivalence classes, finite integer index}
}
Document
Treedepth Parameterized by Vertex Cover Number

Authors: Yasuaki Kobayashi and Hisao Tamaki


Abstract
To solve hard graph problems from the parameterized perspective, structural parameters have commonly been used. In particular, vertex cover number is frequently used in this context. In this paper, we study the problem of computing the treedepth of a given graph G. We show that there are an O(tau(G)^3) vertex kernel and an O(4^{tau(G)}*tau(G)*n) time fixed-parameter algorithm for this problem, where tau(G) is the size of a minimum vertex cover of G and n is the number of vertices of G.

Cite as

Yasuaki Kobayashi and Hisao Tamaki. Treedepth Parameterized by Vertex Cover Number. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 18:1-18:11, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{kobayashi_et_al:LIPIcs.IPEC.2016.18,
  author =	{Kobayashi, Yasuaki and Tamaki, Hisao},
  title =	{{Treedepth Parameterized by Vertex Cover Number}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{18:1--18:11},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.18},
  URN =		{urn:nbn:de:0030-drops-69438},
  doi =		{10.4230/LIPIcs.IPEC.2016.18},
  annote =	{Keywords: Fixed-parameter algorithm, Polynomial kernelization, Structural parameterization, Treedepth, Vertex cover}
}
Document
Dynamic Parameterized Problems

Authors: R. Krithika, Abhishek Sahu, and Prafullkumar Tale


Abstract
In this work, we study the parameterized complexity of various classical graph-theoretic problems in the dynamic framework where the input graph is being updated by a sequence of edge additions and deletions. Vertex subset problems on graphs typically deal with finding a subset of vertices having certain properties that are of interest to us. In real-world applications, the graph under consideration often changes over time and due to this dynamics, the solution at hand might lose the desired properties. The goal in the area of dynamic graph algorithms is to efficiently maintain a solution under these changes. Recomputing a new solution on the new graph is an expensive task especially when the number of modifications made to the graph is significantly smaller than the size of the graph. In the context of parameterized algorithms, two natural parameters are the size k of the symmetric difference of the edge sets of the two graphs (on n vertices) and the size r of the symmetric difference of the two solutions. We study the Dynamic Pi-Deletion problem which is the dynamic variant of the Pi-Deletion problem and show NP-hardness, fixed-parameter tractability and kernelization results. For specific cases of Dynamic Pi-Deletion such as Dynamic Vertex Cover and Dynamic Feedback Vertex Set, we describe improved FPT algorithms and give linear kernels. Specifically, we show that Dynamic Vertex Cover admits algorithms with running times 1.1740^k*n^{O(1)} (polynomial space) and 1.1277^k*n^{O(1)} (exponential space). Then, we show that Dynamic Feedback Vertex Set admits a randomized algorithm with 1.6667^k*n^{O(1)} running time. Finally, we consider Dynamic Connected Vertex Cover, Dynamic Dominating Set and Dynamic Connected Dominating Set and describe algorithms with 2^k*n^{O(1)} running time improving over the known running time bounds for these problems. Additionally, for Dynamic Dominating Set and Dynamic Connected Dominating Set, we show that this is the optimal running time (up to polynomial factors) assuming the Set Cover Conjecture.

Cite as

R. Krithika, Abhishek Sahu, and Prafullkumar Tale. Dynamic Parameterized Problems. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 19:1-19:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{krithika_et_al:LIPIcs.IPEC.2016.19,
  author =	{Krithika, R. and Sahu, Abhishek and Tale, Prafullkumar},
  title =	{{Dynamic Parameterized Problems}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{19:1--19:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.19},
  URN =		{urn:nbn:de:0030-drops-69366},
  doi =		{10.4230/LIPIcs.IPEC.2016.19},
  annote =	{Keywords: dynamic problems, fixed-parameter tractability, kernelization}
}
Document
A 2lk Kernel for l-Component Order Connectivity

Authors: Mithilesh Kumar and Daniel Lokshtanov


Abstract
In the l-Component Order Connectivity problem (l in N), we are given a graph G on n vertices, m edges and a non-negative integer k and asks whether there exists a set of vertices S subseteq V(G) such that |S| <= k and the size of the largest connected component in G-S is at most l. In this paper, we give a kernel for l-Component Order Connectivity with at most 2*l*k vertices that takes n^{O(l)} time for every constant l. On the way to obtaining our kernel, we prove a generalization of the q-Expansion Lemma to weighted graphs. This generalization may be of independent interest.

Cite as

Mithilesh Kumar and Daniel Lokshtanov. A 2lk Kernel for l-Component Order Connectivity. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 20:1-20:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{kumar_et_al:LIPIcs.IPEC.2016.20,
  author =	{Kumar, Mithilesh and Lokshtanov, Daniel},
  title =	{{A 2lk Kernel for l-Component Order Connectivity}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{20:1--20:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.20},
  URN =		{urn:nbn:de:0030-drops-69345},
  doi =		{10.4230/LIPIcs.IPEC.2016.20},
  annote =	{Keywords: Parameterized algorithms, Kernel, Component Order Connectivity, Max-min allocation, Weighted expansion}
}
Document
Structural Parameterizations of Feedback Vertex Set

Authors: Diptapriyo Majumdar


Abstract
A feedback vertex set in an undirected graph is a subset of vertices whose removal results in an acyclic graph. It is well-known that the problem of finding a minimum sized (or k sized in case of decision version of) feedback vertex set (FVS) is polynomial time solvable in (sub)-cubic graphs, in pseudo-forests (graphs where each component has at most one cycle) and mock-forests (graph where each vertex is part of at most one cycle). In general graphs, it is known that the problem is NP-Complete, and has an O*((3.619)^k) fixed-parameter algorithm and an O(k^2) kernel where k, the solution size is the parameter. We consider the parameterized and kernelization complexity of feedback vertex set where the parameter is the size of some structure of the input. In particular, we show that * FVS is fixed-parameter tractable, but is unlikely to have polynomial sized kernel when parameterized by the number of vertices of the graph whose degree is at least 4. This answers a question asked in an earlier paper. * When parameterized by k, the number of vertices, whose deletion results in a pseudo-forest, we give an O(k^6) vertices kernel improving from the previously known O(k^{10}) bound. * When parameterized by the number k of vertices, whose deletion results in a mock-d-forest, we give a kernel consisting of O(k^{3d+3}) vertices and prove a lower bound of Omega(k^{d+2}) vertices (under complexity theoretic assumptions). Mock-d-forest for a constant d is a mock-forest where each component has at most d cycles.

Cite as

Diptapriyo Majumdar. Structural Parameterizations of Feedback Vertex Set. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 21:1-21:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{majumdar:LIPIcs.IPEC.2016.21,
  author =	{Majumdar, Diptapriyo},
  title =	{{Structural Parameterizations of Feedback Vertex Set}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{21:1--21:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.21},
  URN =		{urn:nbn:de:0030-drops-69337},
  doi =		{10.4230/LIPIcs.IPEC.2016.21},
  annote =	{Keywords: Parameterized Complexity, Kernelization, Feedback Vertex Set, Structural Parameterization}
}
Document
Randomised Enumeration of Small Witnesses Using a Decision Oracle

Authors: Kitty Meeks


Abstract
Many combinatorial problems involve determining whether a universe of n elements contains a witness consisting of k elements which have some specified property. In this paper we investigate the relationship between the decision and enumeration versions of such problems: efficient methods are known for transforming a decision algorithm into a search procedure that finds a single witness, but even finding a second witness is not so straightforward in general. In this paper we show that, if the decision version of the problem belongs to FPT, there is a randomised algorithm which enumerates all witnesses in time f(k)*poly(n)*N, where N is the total number of witnesses and f is a computable function. This also gives rise to an efficient algorithm to count the total number of witnesses when this number is small.

Cite as

Kitty Meeks. Randomised Enumeration of Small Witnesses Using a Decision Oracle. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 22:1-22:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{meeks:LIPIcs.IPEC.2016.22,
  author =	{Meeks, Kitty},
  title =	{{Randomised Enumeration of Small Witnesses Using a Decision Oracle}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{22:1--22:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.22},
  URN =		{urn:nbn:de:0030-drops-69218},
  doi =		{10.4230/LIPIcs.IPEC.2016.22},
  annote =	{Keywords: enumeration algorithms, parameterized complexity, randomized algorithms, color coding}
}
Document
Backdoors for Linear Temporal Logic

Authors: Arne Meier, Sebastian Ordyniak, Ramanujan Sridharan, and Irena Schindler


Abstract
In the present paper, we introduce the backdoor set approach into the field of temporal logic for the global fragment of linear temporal logic. We study the parameterized complexity of the satisfiability problem parameterized by the size of the backdoor. We distinguish between backdoor detection and evaluation of backdoors into the fragments of Horn and Krom formulas. Here we classify the operator fragments of globally-operators for past/future/always, and the combination of them. Detection is shown to be fixed-parameter tractable (FPT) whereas the complexity of evaluation behaves differently. We show that for Krom formulas the problem is paraNP-complete. For Horn formulas, the complexity is shown to be either fixed parameter tractable or paraNP-complete depending on the considered operator fragment.

Cite as

Arne Meier, Sebastian Ordyniak, Ramanujan Sridharan, and Irena Schindler. Backdoors for Linear Temporal Logic. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 23:1-23:17, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{meier_et_al:LIPIcs.IPEC.2016.23,
  author =	{Meier, Arne and Ordyniak, Sebastian and Sridharan, Ramanujan and Schindler, Irena},
  title =	{{Backdoors for Linear Temporal Logic}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{23:1--23:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.23},
  URN =		{urn:nbn:de:0030-drops-69462},
  doi =		{10.4230/LIPIcs.IPEC.2016.23},
  annote =	{Keywords: Linear Temporal Logic, Parameterized Complexity, Backdoor Sets}
}
Document
Improved Bounds for Minimal Feedback Vertex Sets in Tournaments

Authors: Matthias Mnich and Eva-Lotta Teutrine


Abstract
We study feedback vertex sets (FVS) in tournaments, which are orientations of complete graphs. As our main result, we show that any tournament on n nodes has at most 1.5949^n minimal FVS. This significantly improves the previously best upper bound of 1.6667^n by Fomin et al. (STOC 2016). Our new upper bound almost matches the best known lower bound of 21^{n/7} approx 1.5448^n, due to Gaspers and Mnich (ESA 2010). Our proof is algorithmic, and shows that all minimal FVS of tournaments can be enumerated in time O(1.5949^n).

Cite as

Matthias Mnich and Eva-Lotta Teutrine. Improved Bounds for Minimal Feedback Vertex Sets in Tournaments. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 24:1-24:10, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{mnich_et_al:LIPIcs.IPEC.2016.24,
  author =	{Mnich, Matthias and Teutrine, Eva-Lotta},
  title =	{{Improved Bounds for Minimal Feedback Vertex Sets in Tournaments}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{24:1--24:10},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.24},
  URN =		{urn:nbn:de:0030-drops-69236},
  doi =		{10.4230/LIPIcs.IPEC.2016.24},
  annote =	{Keywords: exponential-time algorithms, feedback vertex sets, tournaments}
}
Document
Ground Reachability and Joinability in Linear Term Rewriting Systems are Fixed Parameter Tractable with Respect to Depth

Authors: Mateus de Oliveira Oliveira


Abstract
The ground term reachability problem consists in determining whether a given variable-free term t can be transformed into a given variable-free term t' by the application of rules from a term rewriting system R. The joinability problem, on the other hand, consists in determining whether there exists a variable-free term t'' which is reachable both from t and from t'. Both problems have proven to be of fundamental importance for several subfields of computer science. Nevertheless, these problems are undecidable even when restricted to linear term rewriting systems. In this work, we approach reachability and joinability in linear term rewriting systems from the perspective of parameterized complexity theory, and show that these problems are fixed parameter tractable with respect to the depth of derivations. More precisely, we consider a notion of parallel rewriting, in which an unbounded number of rules can be applied simultaneously to a term as long as these rules do not interfere with each other. A term t_1 can reach a term t_2 in depth d if t_2 can be obtained from t_1 by the application of d parallel rewriting steps. Our main result states that for some function f(R,d), and for any linear term rewriting system R, one can determine in time f(R,d)*|t_1|*|t_2| whether a ground term t_2 can be reached from a ground term t_1 in depth at most d by the application of rules from R. Additionally, one can determine in time f(R,d)^2*|t_1|*|t_2| whether there exists a ground term u, such that u can be reached from both t_1 and t_2 in depth at most d. Our algorithms improve exponentially on exhaustive search, which terminates in time 2^{|t_1|*2^{O(d)}}*|t_2|, and can be applied with regard to any linear term rewriting system, irrespective of whether the rewriting system in question is terminating or confluent.

Cite as

Mateus de Oliveira Oliveira. Ground Reachability and Joinability in Linear Term Rewriting Systems are Fixed Parameter Tractable with Respect to Depth. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 25:1-25:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{deoliveiraoliveira:LIPIcs.IPEC.2016.25,
  author =	{de Oliveira Oliveira, Mateus},
  title =	{{Ground Reachability and Joinability in Linear Term Rewriting Systems are Fixed Parameter Tractable with Respect to Depth}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{25:1--25:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.25},
  URN =		{urn:nbn:de:0030-drops-69256},
  doi =		{10.4230/LIPIcs.IPEC.2016.25},
  annote =	{Keywords: Linear Term Rewriting Systems, Ground Reachability, Ground Joinability, Fixed Parameter Tractability}
}
Document
Edge Bipartization Faster Than 2^k

Authors: Marcin Pilipczuk, Michal Pilipczuk, and Marcin Wrochna


Abstract
In the EDGE BIPARTIZATION problem one is given an undirected graph G and an integer k, and the question is whether k edges can be deleted from G so that it becomes bipartite. In 2006, Guo et al. [J. Comput. Syst. Sci., 72(8):1386-1396, 2006] proposed an algorithm solving this problem in time O(2^k m^2); today, this algorithm is a textbook example of an application of the iterative compression technique. Despite extensive progress in the understanding of the parameterized complexity of graph separation problems in the recent years, no significant improvement upon this result has been yet reported. We present an algorithm for Edge Bipartization that works in time O(1.977^k nm), which is the first algorithm with the running time dependence on the parameter better than 2^k. To this end, we combine the general iterative compression strategy of Guo et al. [J. Comput. Syst. Sci., 72(8):1386-1396, 2006], the technique proposed by Wahlström [SODA'14] of using a polynomial-time solvable relaxation in the form of a Valued Constraint Satisfaction Problem to guide a bounded-depth branching algorithm, and an involved Measure&Conquer analysis of the recursion tree.

Cite as

Marcin Pilipczuk, Michal Pilipczuk, and Marcin Wrochna. Edge Bipartization Faster Than 2^k. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 26:1-26:13, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{pilipczuk_et_al:LIPIcs.IPEC.2016.26,
  author =	{Pilipczuk, Marcin and Pilipczuk, Michal and Wrochna, Marcin},
  title =	{{Edge Bipartization Faster Than 2^k}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{26:1--26:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.26},
  URN =		{urn:nbn:de:0030-drops-69285},
  doi =		{10.4230/LIPIcs.IPEC.2016.26},
  annote =	{Keywords: edge bipartization, FPT algorithm}
}
Document
Cut and Count and Representative Sets on Branch Decompositions

Authors: Willem J. A. Pino, Hans L. Bodlaender, and Johan M. M. van Rooij


Abstract
Recently, new techniques have been introduced to speed up dynamic programming algorithms on tree decompositions for connectivity problems: the 'Cut and Count' method and a method called the rank-based approach, based on representative sets and Gaussian elimination. These methods respectively give randomised and deterministic algorithms that are single exponential in the treewidth, and polynomial, respectively linear in the number of vertices. In this paper, we adapt these methods to branch decompositions yielding algorithms, both randomised and deterministic, that are in many cases faster than when tree decompositions would be used. In particular, we obtain the currently fastest randomised algorithms for several problems on planar graphs. When the involved weights are O(n^{O(1)}), we obtain faster randomised algorithms on planar graphs for Steiner Tree, Connected Dominating Set, Feedback Vertex Set and TSP, and a faster deterministic algorithm for TSP. When considering planar graphs with arbitrary real weights, we obtain faster deterministic algorithms for all four mentioned problems.

Cite as

Willem J. A. Pino, Hans L. Bodlaender, and Johan M. M. van Rooij. Cut and Count and Representative Sets on Branch Decompositions. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 27:1-27:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{pino_et_al:LIPIcs.IPEC.2016.27,
  author =	{Pino, Willem J. A. and Bodlaender, Hans L. and van Rooij, Johan M. M.},
  title =	{{Cut and Count and Representative Sets on Branch Decompositions}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{27:1--27:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.27},
  URN =		{urn:nbn:de:0030-drops-69450},
  doi =		{10.4230/LIPIcs.IPEC.2016.27},
  annote =	{Keywords: Graph algorithms, Branchwidth, Treewidth, Dynamic Programming, Planar Graphs}
}
Document
A Fast Parameterized Algorithm for Co-Path Set

Authors: Blair D. Sullivan and Andrew van der Poel


Abstract
The k-CO-PATH SET problem asks, given a graph G and a positive integer k, whether one can delete k edges from G so that the remainder is a collection of disjoint paths. We give a linear-time, randomized fpt algorithm with complexity O^*(1.588^k) for deciding k-CO-PATH SET, significantly improving the previously best known O^*(2.17^k) of Feng, Zhou, and Wang (2015). Our main tool is a new O^*(4^{tw(G)}) algorithm for CO-PATH SET using the Cut&Count framework, where tw(G) denotes treewidth. In general graphs, we combine this with a branching algorithm which refines a 6k-kernel into reduced instances, which we prove have bounded treewidth.

Cite as

Blair D. Sullivan and Andrew van der Poel. A Fast Parameterized Algorithm for Co-Path Set. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 28:1-28:13, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{sullivan_et_al:LIPIcs.IPEC.2016.28,
  author =	{Sullivan, Blair D. and van der Poel, Andrew},
  title =	{{A Fast Parameterized Algorithm for Co-Path Set}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{28:1--28:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.28},
  URN =		{urn:nbn:de:0030-drops-69371},
  doi =		{10.4230/LIPIcs.IPEC.2016.28},
  annote =	{Keywords: co-path set, parameterized complexity, Cut\&Count, bounded treewidth}
}
Document
Clifford Algebras Meet Tree Decompositions

Authors: Michal Wlodarczyk


Abstract
We introduce the Non-commutative Subset Convolution - a convolution of functions useful when working with determinant-based algorithms. In order to compute it efficiently, we take advantage of Clifford algebras, a generalization of quaternions used mainly in the quantum field theory. We apply this tool to speed up algorithms counting subgraphs parameterized by the treewidth of a graph. We present an O^*((2^omega + 1)^{tw})-time algorithm for counting Steiner trees and an O^*((2^omega + 2)^{tw})-time algorithm for counting Hamiltonian cycles, both of which improve the previously known upper bounds. The result for Steiner Tree also translates into a deterministic algorithm for Feedback Vertex Set. All of these constitute the best known running times of deterministic algorithms for decision versions of these problems and they match the best obtained running times for pathwidth parameterization under assumption omega = 2.

Cite as

Michal Wlodarczyk. Clifford Algebras Meet Tree Decompositions. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 29:1-29:18, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{wlodarczyk:LIPIcs.IPEC.2016.29,
  author =	{Wlodarczyk, Michal},
  title =	{{Clifford Algebras Meet Tree Decompositions}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{29:1--29:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.29},
  URN =		{urn:nbn:de:0030-drops-69260},
  doi =		{10.4230/LIPIcs.IPEC.2016.29},
  annote =	{Keywords: fixed-parameter tractability, treewidth, Clifford algebra, algebra isomorphism}
}
Document
The First Parameterized Algorithms and Computational Experiments Challenge

Authors: Holger Dell, Thore Husfeldt, Bart M. P. Jansen, Petteri Kaski, Christian Komusiewicz, and Frances A. Rosamond


Abstract
In this article, the steering committee of the Parameterized Algorithms and Computational Experiments challenge (PACE) reports on the first iteration of the challenge. Where did PACE come from, how did it go, who won, and what's next?

Cite as

Holger Dell, Thore Husfeldt, Bart M. P. Jansen, Petteri Kaski, Christian Komusiewicz, and Frances A. Rosamond. The First Parameterized Algorithms and Computational Experiments Challenge. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 30:1-30:9, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)


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@InProceedings{dell_et_al:LIPIcs.IPEC.2016.30,
  author =	{Dell, Holger and Husfeldt, Thore and Jansen, Bart M. P. and Kaski, Petteri and Komusiewicz, Christian and Rosamond, Frances A.},
  title =	{{The First Parameterized Algorithms and Computational Experiments Challenge}},
  booktitle =	{11th International Symposium on Parameterized and Exact Computation (IPEC 2016)},
  pages =	{30:1--30:9},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-023-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{63},
  editor =	{Guo, Jiong and Hermelin, Danny},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2016.30},
  URN =		{urn:nbn:de:0030-drops-69310},
  doi =		{10.4230/LIPIcs.IPEC.2016.30},
  annote =	{Keywords: treewidth, feedback vertex set, contest, implementation challenge, FPT}
}

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