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Documents authored by Dobler, Alexander


Document
PACE Solver Description
PACE Solver Description: CRGone

Authors: Alexander Dobler

Published in: LIPIcs, Volume 321, 19th International Symposium on Parameterized and Exact Computation (IPEC 2024)


Abstract
We describe CRGone, our solver for the exact and parameterized track of the Pace Challenge 2024. It solves the problem of one-sided crossing minimization, is based on an integer linear programming (ILP) formulation with additional reduction rules, and is implemented in C++ using the ILP solver SCIP with Soplex.

Cite as

Alexander Dobler. PACE Solver Description: CRGone. In 19th International Symposium on Parameterized and Exact Computation (IPEC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 321, pp. 29:1-29:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)


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@InProceedings{dobler:LIPIcs.IPEC.2024.29,
  author =	{Dobler, Alexander},
  title =	{{PACE Solver Description: CRGone}},
  booktitle =	{19th International Symposium on Parameterized and Exact Computation (IPEC 2024)},
  pages =	{29:1--29:4},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-353-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{321},
  editor =	{Bonnet, \'{E}douard and Rz\k{a}\.{z}ewski, Pawe{\l}},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2024.29},
  URN =		{urn:nbn:de:0030-drops-222558},
  doi =		{10.4230/LIPIcs.IPEC.2024.29},
  annote =	{Keywords: Pace Challenge 2024, One-Layer Crossing Minimization, Exact Algorithm}
}
Document
Revisiting ILP Models for Exact Crossing Minimization in Storyline Drawings

Authors: Alexander Dobler, Michael Jünger, Paul J. Jünger, Julian Meffert, Petra Mutzel, and Martin Nöllenburg

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)


Abstract
Storyline drawings are a popular visualization of interactions of a set of characters over time, e.g., to show participants of scenes in a book or movie. Characters are represented as x-monotone curves that converge vertically for interactions and diverge otherwise. Combinatorially, the task of computing storyline drawings reduces to finding a sequence of permutations of the character curves for the different time points, with the primary objective being crossing minimization of the induced character trajectories. In this paper, we revisit exact integer linear programming (ILP) approaches for this NP-hard problem. By enriching previous formulations with additional problem-specific insights and new heuristics, we obtain exact solutions for an extended new benchmark set of larger and more complex instances than had been used before. Our experiments show that our enriched formulations lead to better performing algorithms when compared to state-of-the–art modelling techniques. In particular, our best algorithms are on average 2.6-3.2 times faster than the state-of-the-art and succeed in solving complex instances that could not be solved before within the given time limit. Further, we show in an ablation study that our enrichment components contribute considerably to the performance of the new ILP formulation.

Cite as

Alexander Dobler, Michael Jünger, Paul J. Jünger, Julian Meffert, Petra Mutzel, and Martin Nöllenburg. Revisiting ILP Models for Exact Crossing Minimization in Storyline Drawings. In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 31:1-31:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)


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@InProceedings{dobler_et_al:LIPIcs.GD.2024.31,
  author =	{Dobler, Alexander and J\"{u}nger, Michael and J\"{u}nger, Paul J. and Meffert, Julian and Mutzel, Petra and N\"{o}llenburg, Martin},
  title =	{{Revisiting ILP Models for Exact Crossing Minimization in Storyline Drawings}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{31:1--31:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.31},
  URN =		{urn:nbn:de:0030-drops-213159},
  doi =		{10.4230/LIPIcs.GD.2024.31},
  annote =	{Keywords: Storyline drawing, crossing minimization, integer linear programming, algorithm engineering, computational experiments}
}
Document
PACE Solver Description
PACE Solver Description: Touiouidth

Authors: Gaétan Berthe, Yoann Coudert-Osmont, Alexander Dobler, Laure Morelle, Amadeus Reinald, and Mathis Rocton

Published in: LIPIcs, Volume 285, 18th International Symposium on Parameterized and Exact Computation (IPEC 2023)


Abstract
We describe Touiouidth, a twin-width solver for the exact-track of the 2023 PACE Challenge: Twin Width. Our solver is based on a simple branch and bound algorithm with search space reductions and is implemented in C++.

Cite as

Gaétan Berthe, Yoann Coudert-Osmont, Alexander Dobler, Laure Morelle, Amadeus Reinald, and Mathis Rocton. PACE Solver Description: Touiouidth. In 18th International Symposium on Parameterized and Exact Computation (IPEC 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 285, pp. 38:1-38:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{berthe_et_al:LIPIcs.IPEC.2023.38,
  author =	{Berthe, Ga\'{e}tan and Coudert-Osmont, Yoann and Dobler, Alexander and Morelle, Laure and Reinald, Amadeus and Rocton, Mathis},
  title =	{{PACE Solver Description: Touiouidth}},
  booktitle =	{18th International Symposium on Parameterized and Exact Computation (IPEC 2023)},
  pages =	{38:1--38:4},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-305-8},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{285},
  editor =	{Misra, Neeldhara and Wahlstr\"{o}m, Magnus},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2023.38},
  URN =		{urn:nbn:de:0030-drops-194576},
  doi =		{10.4230/LIPIcs.IPEC.2023.38},
  annote =	{Keywords: Twinwidth, Pace Challenge}
}
Document
Turbocharging Heuristics for Weak Coloring Numbers

Authors: Alexander Dobler, Manuel Sorge, and Anaïs Villedieu

Published in: LIPIcs, Volume 244, 30th Annual European Symposium on Algorithms (ESA 2022)


Abstract
Bounded expansion and nowhere-dense classes of graphs capture the theoretical tractability for several important algorithmic problems. These classes of graphs can be characterized by the so-called weak coloring numbers of graphs, which generalize the well-known graph invariant degeneracy (also called k-core number). Being NP-hard, weak-coloring numbers were previously computed on real-world graphs mainly via incremental heuristics. We study whether it is feasible to augment such heuristics with exponential-time subprocedures that kick in when a desired upper bound on the weak coloring number is breached. We provide hardness and tractability results on the corresponding computational subproblems. We implemented several of the resulting algorithms and show them to be competitive with previous approaches on a previously studied set of benchmark instances containing 86 graphs with up to 183831 edges. We obtain improved weak coloring numbers for over half of the instances.

Cite as

Alexander Dobler, Manuel Sorge, and Anaïs Villedieu. Turbocharging Heuristics for Weak Coloring Numbers. In 30th Annual European Symposium on Algorithms (ESA 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 244, pp. 44:1-44:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


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@InProceedings{dobler_et_al:LIPIcs.ESA.2022.44,
  author =	{Dobler, Alexander and Sorge, Manuel and Villedieu, Ana\"{i}s},
  title =	{{Turbocharging Heuristics for Weak Coloring Numbers}},
  booktitle =	{30th Annual European Symposium on Algorithms (ESA 2022)},
  pages =	{44:1--44:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-247-1},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{244},
  editor =	{Chechik, Shiri and Navarro, Gonzalo and Rotenberg, Eva and Herman, Grzegorz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2022.44},
  URN =		{urn:nbn:de:0030-drops-169820},
  doi =		{10.4230/LIPIcs.ESA.2022.44},
  annote =	{Keywords: Structural sparsity, parameterized algorithms, parameterized complexity, fixed-parameter tractability}
}
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