4 Search Results for "Linz, Simone"

Document
DOI: 10.4230/LIPIcs.WADS.2025.32
Fantastic Flips and Where to Find Them: A General Framework for Parameterized Local Search on Partitioning Problems

Authors: Niels Grüttemeier, Nils Morawietz, and Frank Sommer

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

Abstract
Parameterized local search combines classic local search heuristics with the paradigm of parameterized algorithmics. While most local search algorithms aim to improve given solutions by performing one single operation on a given solution, the parameterized approach aims to improve a solution by performing k simultaneous operations. Herein, k is a parameter called search radius for which the value can be chosen by a user. One major goal in the field of parameterized local search is to outline the trade-off between the size of k and the running time of the local search step. In this work, we introduce an abstract framework that generalizes natural parameterized local search approaches for a large class of partitioning problems: Given n items that are partitioned into b bins and a target function that evaluates the quality of the current partition, one asks whether it is possible to improve the solution by removing up to k items from their current bins and reassigning them to other bins. Among others, our framework applies for the local search versions of problems like Cluster Editing, Vector Bin Packing, and Nash Social Welfare. Motivated by a real-world application of the problem Vector Bin Packing, we introduce a parameter called number of types τ ≤ n and show that all problems fitting in our framework can be solved in τ^k ⋅ 2^𝒪(k) ⋅ |I|^𝒪(1) time, where |I| denotes the total input size. In case of Cluster Editing, the parameter τ generalizes the well-known parameter neighborhood diversity of the input graph. We complement these algorithms by showing that for all considered problems, an algorithm significantly improving over our algorithm with running time τ^k ⋅ 2^𝒪(k) ⋅ |I|^𝒪(1) would contradict the Exponential Time Hypothesis. Additionally, we show that even on very restricted instances, all considered problems are W[1]-hard when parameterized by the search radius k alone. In case of the local search version of Vector Bin Packing, we provide an even stronger W[1]-hardness result.
Cite as

Niels Grüttemeier, Nils Morawietz, and Frank Sommer. Fantastic Flips and Where to Find Them: A General Framework for Parameterized Local Search on Partitioning Problems. In 19th International Symposium on Algorithms and Data Structures (WADS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 349, pp. 32:1-32:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{gruttemeier_et_al:LIPIcs.WADS.2025.32,
  author =	{Gr\"{u}ttemeier, Niels and Morawietz, Nils and Sommer, Frank},
  title =	{{Fantastic Flips and Where to Find Them: A General Framework for Parameterized Local Search on Partitioning Problems}},
  booktitle =	{19th International Symposium on Algorithms and Data Structures (WADS 2025)},
  pages =	{32:1--32:20},
  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.2025.32},
  URN =		{urn:nbn:de:0030-drops-242631},
  doi =		{10.4230/LIPIcs.WADS.2025.32},
  annote =	{Keywords: Flip-Neighborhood, Cluster Editing, Vector Bin Packing, Vertex Cover, NP-hard problem, Max c-Cut}
}
Document
DOI: 10.4230/LIPIcs.SAT.2025.25
QRP+Gen: A Framework for Checking Q-Resolution Proofs with Generalized Axioms

Authors: Mark Peyrer and Martina Seidl

Published in: LIPIcs, Volume 341, 28th International Conference on Theory and Applications of Satisfiability Testing (SAT 2025)

Abstract
Q-resolution is a proof system for quantified Boolean formulas (QBFs) that forms the foundation for search-based QBF solvers with clause and cube learning. To derive stronger clauses and cubes, Q-resolution was extended with so-called generalized axioms. The derivation of such generalized axioms relies on solving oracles that could be, for example, SAT solvers or even QBF solvers. While the correctness of results obtained with classical QCDCL-based solving can be efficiently certified by an independent checker, until now, proof generation had to be turned off to benefit from generalized axioms. Consequently, the results obtained with reasoning under generalized axioms could not be certified independently. To overcome this restriction, we present QRP+Gen, a novel framework to automatically generate and check Q-resolution proofs that contain generalized axioms. To this end, we extended the Q-resolution format QRP such that all necessary information is included to verify the correctness of generalized axioms. Our extension allows to integrate certificates produced by any oracle which can produce automatically checkable proofs. Furthermore, we developed a proof checker that orchestrates the proof checking of the core Q-resolution proof and the proofs produced by the oracles. As a case study, we equipped the search-based QBF solver DepQBF with proof-producing oracles for the SAT-based techniques trivial truth and trivial falsity.
Cite as

Mark Peyrer and Martina Seidl. QRP+Gen: A Framework for Checking Q-Resolution Proofs with Generalized Axioms. In 28th International Conference on Theory and Applications of Satisfiability Testing (SAT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 341, pp. 25:1-25:10, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{peyrer_et_al:LIPIcs.SAT.2025.25,
  author =	{Peyrer, Mark and Seidl, Martina},
  title =	{{QRP+Gen: A Framework for Checking Q-Resolution Proofs with Generalized Axioms}},
  booktitle =	{28th International Conference on Theory and Applications of Satisfiability Testing (SAT 2025)},
  pages =	{25:1--25:10},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-381-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{341},
  editor =	{Berg, Jeremias and Nordstr\"{o}m, Jakob},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SAT.2025.25},
  URN =		{urn:nbn:de:0030-drops-237592},
  doi =		{10.4230/LIPIcs.SAT.2025.25},
  annote =	{Keywords: Automated Reasoning, Quantified Resolution Proof, Generalized Axioms}
}
Document
DOI: 10.4230/LIPIcs.CPM.2023.18
On the Complexity of Parameterized Local Search for the Maximum Parsimony Problem

Authors: Christian Komusiewicz, Simone Linz, Nils Morawietz, and Jannik Schestag

Published in: LIPIcs, Volume 259, 34th Annual Symposium on Combinatorial Pattern Matching (CPM 2023)

Abstract
Maximum Parsimony is the problem of computing a most parsimonious phylogenetic tree for a taxa set X from character data for X. A common strategy to attack this notoriously hard problem is to perform a local search over the phylogenetic tree space. Here, one is given a phylogenetic tree T and wants to find a more parsimonious tree in the neighborhood of T. We study the complexity of this problem when the neighborhood contains all trees within distance k for several classic distance functions. For the nearest neighbor interchange (NNI), subtree prune and regraft (SPR), tree bisection and reconnection (TBR), and edge contraction and refinement (ECR) distances, we show that, under the exponential time hypothesis, there are no algorithms with running time |I|^o(k) where |I| is the total input size. Hence, brute-force algorithms with running time |X|^𝒪(k) ⋅ |I| are essentially optimal. In contrast to the above distances, we observe that for the sECR-distance, where the contracted edges are constrained to form a subtree, a better solution within distance k can be found in k^𝒪(k) ⋅ |I|^𝒪(1) time.
Cite as

Christian Komusiewicz, Simone Linz, Nils Morawietz, and Jannik Schestag. On the Complexity of Parameterized Local Search for the Maximum Parsimony Problem. In 34th Annual Symposium on Combinatorial Pattern Matching (CPM 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 259, pp. 18:1-18:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{komusiewicz_et_al:LIPIcs.CPM.2023.18,
  author =	{Komusiewicz, Christian and Linz, Simone and Morawietz, Nils and Schestag, Jannik},
  title =	{{On the Complexity of Parameterized Local Search for the Maximum Parsimony Problem}},
  booktitle =	{34th Annual Symposium on Combinatorial Pattern Matching (CPM 2023)},
  pages =	{18:1--18:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-276-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{259},
  editor =	{Bulteau, Laurent and Lipt\'{a}k, Zsuzsanna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CPM.2023.18},
  URN =		{urn:nbn:de:0030-drops-179729},
  doi =		{10.4230/LIPIcs.CPM.2023.18},
  annote =	{Keywords: phylogenetic trees, parameterized complexity, tree distances, NNI, TBR}
}
Document
DOI: 10.4230/DagRep.9.10.134
Algorithms and Complexity in Phylogenetics (Dagstuhl Seminar 19443)

Authors: Magnus Bordewich, Britta Dorn, Simone Linz, and Rolf Niedermeier

Published in: Dagstuhl Reports, Volume 9, Issue 10 (2020)

Abstract
Phylogenetics is the study of ancestral relationships between species. Its central goal is the reconstruction and analysis of phylogenetic trees and networks. Even though research in phylogenetics is motivated by biological questions and applications, it heavily relies on mathematics and computer science. Dagstuhl Seminar 19443 on Algorithms and Complexity in Phylogenetics aimed at bringing together researchers from phylogenetics and theoretical computer science to enable an exchange of expertise, facilitate interactions across both research areas, and establish new collaborations. This report documents the program and outcomes of the seminar. It contains an executive summary, abstracts of talks, short summaries of working groups, and a list of open problems that were posed during the seminar.
Cite as

Magnus Bordewich, Britta Dorn, Simone Linz, and Rolf Niedermeier. Algorithms and Complexity in Phylogenetics (Dagstuhl Seminar 19443). In Dagstuhl Reports, Volume 9, Issue 10, pp. 134-151, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@Article{bordewich_et_al:DagRep.9.10.134,
  author =	{Bordewich, Magnus and Dorn, Britta and Linz, Simone and Niedermeier, Rolf},
  title =	{{Algorithms and Complexity in Phylogenetics (Dagstuhl Seminar 19443)}},
  pages =	{134--151},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2020},
  volume =	{9},
  number =	{10},
  editor =	{Bordewich, Magnus and Dorn, Britta and Linz, Simone and Niedermeier, Rolf},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.9.10.134},
  URN =		{urn:nbn:de:0030-drops-118590},
  doi =		{10.4230/DagRep.9.10.134},
  annote =	{Keywords: Approximation algorithms, Evolution, Parameterized algorithms, Phylogenetic trees and networks}
}
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