13 Search Results for "Schmidt, Jens M."

Document
DOI: 10.4230/OASIcs.WCET.2024.2
The Platin Multi-Target Worst-Case Analysis Tool

Authors: Emad Jacob Maroun, Eva Dengler, Christian Dietrich, Stefan Hepp, Henriette Herzog, Benedikt Huber, Jens Knoop, Daniel Wiltsche-Prokesch, Peter Puschner, Phillip Raffeck, Martin Schoeberl, Simon Schuster, and Peter Wägemann

Published in: OASIcs, Volume 121, 22nd International Workshop on Worst-Case Execution Time Analysis (WCET 2024)

Abstract
With the increasing number of applications that require reliable runtime guarantees, the relevance of static worst-case analysis tools that can provide such guarantees increases. These analysis tools determine resource-consumption bounds of application tasks, with a model of the underlying hardware, to meet given resource budgets during runtime, such as deadlines of real-time tasks. This paper presents enhancements to the Platin worst-case analysis tool developed since its original release more than ten years ago. These novelties comprise Platin’s support for new architectures (i.e., ARMv6-M, RISC-V, and AVR) in addition to the previous backends for Patmos and ARMv7-M. Further, Platin now features system-wide analysis methods and annotation support to express system-level constraints. Besides an overview of these enhancements, we evaluate Platin’s accuracy for the two supported architecture implementations, Patmos and RISC-V.
Cite as

Emad Jacob Maroun, Eva Dengler, Christian Dietrich, Stefan Hepp, Henriette Herzog, Benedikt Huber, Jens Knoop, Daniel Wiltsche-Prokesch, Peter Puschner, Phillip Raffeck, Martin Schoeberl, Simon Schuster, and Peter Wägemann. The Platin Multi-Target Worst-Case Analysis Tool. In 22nd International Workshop on Worst-Case Execution Time Analysis (WCET 2024). Open Access Series in Informatics (OASIcs), Volume 121, pp. 2:1-2:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{maroun_et_al:OASIcs.WCET.2024.2,
  author =	{Maroun, Emad Jacob and Dengler, Eva and Dietrich, Christian and Hepp, Stefan and Herzog, Henriette and Huber, Benedikt and Knoop, Jens and Wiltsche-Prokesch, Daniel and Puschner, Peter and Raffeck, Phillip and Schoeberl, Martin and Schuster, Simon and W\"{a}gemann, Peter},
  title =	{{The Platin Multi-Target Worst-Case Analysis Tool}},
  booktitle =	{22nd International Workshop on Worst-Case Execution Time Analysis (WCET 2024)},
  pages =	{2:1--2:14},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-346-1},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{121},
  editor =	{Carle, Thomas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2024.2},
  URN =		{urn:nbn:de:0030-drops-204704},
  doi =		{10.4230/OASIcs.WCET.2024.2},
  annote =	{Keywords: worst-case resource consumption, WCET, static analysis tool}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.10
Crêpe: Clock-Reconfiguration-Aware Preemption Control in Real-Time Systems with Devices

Authors: Eva Dengler and Peter Wägemann

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
The domain of energy-constrained real-time systems that are operated on modern embedded system-on-chip (SoC) platforms brings numerous novel challenges for optimal resource minimization. These modern hardware platforms offer a heterogeneous variety of features to configure the tradeoff between temporal performance and energy efficiency, which goes beyond the state-of-the-art of existing dynamic-voltage-frequency-scaling (DVFS) scheduling schemes. The control center for configuring this tradeoff on platforms are complex clock subsystems that are intertwined with requirements of the SoC’s components (e.g., transceiver/memory/sensor devices). That is, several devices have precedence constraints with respect to specific clock sources and their settings. The challenge of dynamically adapting the various clock sources to select resource-optimal configurations becomes especially challenging in the presence of asynchronous preemptions, which are inherent to systems that use devices. In this paper, we present Crêpe, an approach to clock-reconfiguration-aware preemption control: Crêpe has an understanding of the target platform’s clock subsystem, its sleep states, and penalties to reconfigure clock sources for adapting clock frequencies. Crêpe’s hardware model is combined with an awareness of the application’s device requirements for each executed task, as well as possible interrupts that cause preemptions during runtime. Using these software/hardware constraints, Crêpe employs, in its offline phase, a mathematical formalization in order to select energy-minimal configurations while meeting given deadlines. This optimizing formalization, processed by standard mathematical solver tools, accounts for potentially occurring interrupts and the respective clock reconfigurations, which are then forwarded as alternative schedules to Crêpe’s runtime system. During runtime, the dispatcher assesses these offline-determined alternative schedules and reconfigures the clock sources for energy minimization. We developed an implementation based on a widely-used SoC platform (i.e., ESP32-C3) and an automated testbed for comprehensive energy-consumption evaluations to validate Crêpe’s claim of selecting resource-optimal settings under worst-case considerations.
Cite as

Eva Dengler and Peter Wägemann. Crêpe: Clock-Reconfiguration-Aware Preemption Control in Real-Time Systems with Devices. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 10:1-10:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dengler_et_al:LIPIcs.ECRTS.2024.10,
  author =	{Dengler, Eva and W\"{a}gemann, Peter},
  title =	{{Cr\^{e}pe: Clock-Reconfiguration-Aware Preemption Control in Real-Time Systems with Devices}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{10:1--10:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.10},
  URN =		{urn:nbn:de:0030-drops-203135},
  doi =		{10.4230/LIPIcs.ECRTS.2024.10},
  annote =	{Keywords: energy-constrained real-time systems, time/energy tradeoff, system-on-chip, energy-aware real-time scheduling, resource minimization, preemption control, worst-case energy consumption (WCEC), worst-case execution time (WCET), static whole-system analysis}
}
Document
DOI: 10.4230/DagMan.10.1.1
Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Perspectives Workshop 22282)

Authors: James P. Delgrande, Birte Glimm, Thomas Meyer, Miroslaw Truszczynski, and Frank Wolter

Published in: Dagstuhl Manifestos, Volume 10, Issue 1 (2024)

Abstract
Knowledge Representation and Reasoning is a central, longstanding, and active area of Artificial Intelligence. Over the years it has evolved significantly; more recently it has been challenged and complemented by research in areas such as machine learning and reasoning under uncertainty. In July 2022,sser a Dagstuhl Perspectives workshop was held on Knowledge Representation and Reasoning. The goal of the workshop was to describe the state of the art in the field, including its relation with other areas, its shortcomings and strengths, together with recommendations for future progress. We developed this manifesto based on the presentations, panels, working groups, and discussions that took place at the Dagstuhl Workshop. It is a declaration of our views on Knowledge Representation: its origins, goals, milestones, and current foci; its relation to other disciplines, especially to Artificial Intelligence; and on its challenges, along with key priorities for the next decade.
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James P. Delgrande, Birte Glimm, Thomas Meyer, Miroslaw Truszczynski, and Frank Wolter. Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Perspectives Workshop 22282). In Dagstuhl Manifestos, Volume 10, Issue 1, pp. 1-61, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Article{delgrande_et_al:DagMan.10.1.1,
  author =	{Delgrande, James P. and Glimm, Birte and Meyer, Thomas and Truszczynski, Miroslaw and Wolter, Frank},
  title =	{{Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Perspectives Workshop 22282)}},
  pages =	{1--61},
  journal =	{Dagstuhl Manifestos},
  ISSN =	{2193-2433},
  year =	{2024},
  volume =	{10},
  number =	{1},
  editor =	{Delgrande, James P. and Glimm, Birte and Meyer, Thomas and Truszczynski, Miroslaw and Wolter, Frank},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagMan.10.1.1},
  URN =		{urn:nbn:de:0030-drops-201403},
  doi =		{10.4230/DagMan.10.1.1},
  annote =	{Keywords: Knowledge representation and reasoning, Applications of logics, Declarative representations, Formal logic}
}
Document
DOI: 10.4230/LIPIcs.SWAT.2024.37
Toward Grünbaum’s Conjecture

Authors: Christian Ortlieb and Jens M. Schmidt

Published in: LIPIcs, Volume 294, 19th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2024)

Abstract
Given a spanning tree T of a planar graph G, the co-tree of T is the spanning tree of the dual graph G^* with edge set (E(G)-E(T))^*. Grünbaum conjectured in 1970 that every planar 3-connected graph G contains a spanning tree T such that both T and its co-tree have maximum degree at most 3. While Grünbaum’s conjecture remains open, Biedl proved that there is a spanning tree T such that T and its co-tree have maximum degree at most 5. By using new structural insights into Schnyder woods, we prove that there is a spanning tree T such that T and its co-tree have maximum degree at most 4. This tree can be computed in linear time.
Cite as

Christian Ortlieb and Jens M. Schmidt. Toward Grünbaum’s Conjecture. In 19th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 294, pp. 37:1-37:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ortlieb_et_al:LIPIcs.SWAT.2024.37,
  author =	{Ortlieb, Christian and Schmidt, Jens M.},
  title =	{{Toward Gr\"{u}nbaum’s Conjecture}},
  booktitle =	{19th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2024)},
  pages =	{37:1--37:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-318-8},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{294},
  editor =	{Bodlaender, Hans L.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SWAT.2024.37},
  URN =		{urn:nbn:de:0030-drops-200777},
  doi =		{10.4230/LIPIcs.SWAT.2024.37},
  annote =	{Keywords: Planar graph, spanning tree, maximum degree, Schnyder wood}
}
Document
Survey
DOI: 10.4230/TGDK.2.1.3
Semantic Web: Past, Present, and Future

Authors: Ansgar Scherp, Gerd Groener, Petr Škoda, Katja Hose, and Maria-Esther Vidal

Published in: TGDK, Volume 2, Issue 1 (2024): Special Issue on Trends in Graph Data and Knowledge - Part 2. Transactions on Graph Data and Knowledge, Volume 2, Issue 1

Abstract
Ever since the vision was formulated, the Semantic Web has inspired many generations of innovations. Semantic technologies have been used to share vast amounts of information on the Web, enhance them with semantics to give them meaning, and enable inference and reasoning on them. Throughout the years, semantic technologies, and in particular knowledge graphs, have been used in search engines, data integration, enterprise settings, and machine learning. In this paper, we recap the classical concepts and foundations of the Semantic Web as well as modern and recent concepts and applications, building upon these foundations. The classical topics we cover include knowledge representation, creating and validating knowledge on the Web, reasoning and linking, and distributed querying. We enhance this classical view of the so-called "Semantic Web Layer Cake" with an update of recent concepts that include provenance, security and trust, as well as a discussion of practical impacts from industry-led contributions. We conclude with an outlook on the future directions of the Semantic Web. This is a living document. If you like to contribute, please contact the first author and visit: https://github.com/ascherp/semantic-web-primer
Cite as

Ansgar Scherp, Gerd Groener, Petr Škoda, Katja Hose, and Maria-Esther Vidal. Semantic Web: Past, Present, and Future. In Special Issue on Trends in Graph Data and Knowledge - Part 2. Transactions on Graph Data and Knowledge (TGDK), Volume 2, Issue 1, pp. 3:1-3:37, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Article{scherp_et_al:TGDK.2.1.3,
  author =	{Scherp, Ansgar and Groener, Gerd and \v{S}koda, Petr and Hose, Katja and Vidal, Maria-Esther},
  title =	{{Semantic Web: Past, Present, and Future}},
  journal =	{Transactions on Graph Data and Knowledge},
  pages =	{3:1--3:37},
  ISSN =	{2942-7517},
  year =	{2024},
  volume =	{2},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/TGDK.2.1.3},
  URN =		{urn:nbn:de:0030-drops-198607},
  doi =		{10.4230/TGDK.2.1.3},
  annote =	{Keywords: Linked Open Data, Semantic Web Graphs, Knowledge Graphs}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2021.22
Local Certification of Graph Decompositions and Applications to Minor-Free Classes

Authors: Nicolas Bousquet, Laurent Feuilloley, and Théo Pierron

Published in: LIPIcs, Volume 217, 25th International Conference on Principles of Distributed Systems (OPODIS 2021)

Abstract
Local certification consists in assigning labels to the nodes of a network to certify that some given property is satisfied, in such a way that the labels can be checked locally. In the last few years, certification of graph classes received a considerable attention. The goal is to certify that a graph G belongs to a given graph class 𝒢. Such certifications with labels of size O(log n) (where n is the size of the network) exist for trees, planar graphs and graphs embedded on surfaces. Feuilloley et al. ask if this can be extended to any class of graphs defined by a finite set of forbidden minors. In this work, we develop new decomposition tools for graph certification, and apply them to show that for every small enough minor H, H-minor-free graphs can indeed be certified with labels of size O(log n). We also show matching lower bounds using a new proof technique.
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Nicolas Bousquet, Laurent Feuilloley, and Théo Pierron. Local Certification of Graph Decompositions and Applications to Minor-Free Classes. In 25th International Conference on Principles of Distributed Systems (OPODIS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 217, pp. 22:1-22:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bousquet_et_al:LIPIcs.OPODIS.2021.22,
  author =	{Bousquet, Nicolas and Feuilloley, Laurent and Pierron, Th\'{e}o},
  title =	{{Local Certification of Graph Decompositions and Applications to Minor-Free Classes}},
  booktitle =	{25th International Conference on Principles of Distributed Systems (OPODIS 2021)},
  pages =	{22:1--22:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-219-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{217},
  editor =	{Bramas, Quentin and Gramoli, Vincent and Milani, Alessia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2021.22},
  URN =		{urn:nbn:de:0030-drops-157970},
  doi =		{10.4230/LIPIcs.OPODIS.2021.22},
  annote =	{Keywords: Local certification, proof-labeling schemes, locally checkable proofs, graph decompositions, minor-free graphs}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2018.13
Computing Vertex-Disjoint Paths in Large Graphs Using MAOs

Authors: Johanna E. Preißer and Jens M. Schmidt

Published in: LIPIcs, Volume 123, 29th International Symposium on Algorithms and Computation (ISAAC 2018)

Abstract
We consider the problem of computing k in N internally vertex-disjoint paths between special vertex pairs of simple connected graphs. For general vertex pairs, the best deterministic time bound is, since 42 years, O(min{k,sqrt{n}}m) for each pair by using traditional flow-based methods. The restriction of our vertex pairs comes from the machinery of maximal adjacency orderings (MAOs). Henzinger showed for every MAO and every 1 <= k <= delta (where delta is the minimum degree of the graph) the existence of k internally vertex-disjoint paths between every pair of the last delta-k+2 vertices of this MAO. Later, Nagamochi generalized this result by using the machinery of mixed connectivity. Both results are however inherently non-constructive. We present the first algorithm that computes these k internally vertex-disjoint paths in linear time O(m), which improves the previously best time O(min{k,sqrt{n}}m). Due to the linear running time, this algorithm is suitable for large graphs. The algorithm is simple, works directly on the MAO structure, and completes a long history of purely existential proofs with a constructive method. We extend our algorithm to compute several other path systems and discuss its impact for certifying algorithms.
Cite as

Johanna E. Preißer and Jens M. Schmidt. Computing Vertex-Disjoint Paths in Large Graphs Using MAOs. In 29th International Symposium on Algorithms and Computation (ISAAC 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 123, pp. 13:1-13:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{preier_et_al:LIPIcs.ISAAC.2018.13,
  author =	{Prei{\ss}er, Johanna E. and Schmidt, Jens M.},
  title =	{{Computing Vertex-Disjoint Paths in Large Graphs Using MAOs}},
  booktitle =	{29th International Symposium on Algorithms and Computation (ISAAC 2018)},
  pages =	{13:1--13:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-094-1},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{123},
  editor =	{Hsu, Wen-Lian and Lee, Der-Tsai and Liao, Chung-Shou},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2018.13},
  URN =		{urn:nbn:de:0030-drops-99613},
  doi =		{10.4230/LIPIcs.ISAAC.2018.13},
  annote =	{Keywords: Computing Disjoint Paths, Large Graphs, Vertex-Connectivity, Linear-Time, Maximal Adjacency Ordering, Maximum Cardinality Search, Big Data, Certifying Algorithm}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2018.38
A Cut Tree Representation for Pendant Pairs

Authors: On-Hei S. Lo and Jens M. Schmidt

Published in: LIPIcs, Volume 123, 29th International Symposium on Algorithms and Computation (ISAAC 2018)

Abstract
Two vertices v and w of a graph G are called a pendant pair if the maximal number of edge-disjoint paths in G between them is precisely min{d(v),d(w)}, where d denotes the degree function. The importance of pendant pairs stems from the fact that they are the key ingredient in one of the simplest and most widely used algorithms for the minimum cut problem today. Mader showed 1974 that every simple graph with minimum degree delta contains Omega(delta^2) pendant pairs; this is the best bound known so far. We improve this result by showing that every simple graph G with minimum degree delta >= 5 or with edge-connectivity lambda >= 4 or with vertex-connectivity kappa >= 3 contains in fact Omega(delta |V|) pendant pairs. We prove that this bound is tight from several perspectives, and that Omega(delta |V|) pendant pairs can be computed efficiently, namely in linear time when a Gomory-Hu tree is given. Our method utilizes a new cut tree representation of graphs.
Cite as

On-Hei S. Lo and Jens M. Schmidt. A Cut Tree Representation for Pendant Pairs. In 29th International Symposium on Algorithms and Computation (ISAAC 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 123, pp. 38:1-38:9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{lo_et_al:LIPIcs.ISAAC.2018.38,
  author =	{Lo, On-Hei S. and Schmidt, Jens M.},
  title =	{{A Cut Tree Representation for Pendant Pairs}},
  booktitle =	{29th International Symposium on Algorithms and Computation (ISAAC 2018)},
  pages =	{38:1--38:9},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-094-1},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{123},
  editor =	{Hsu, Wen-Lian and Lee, Der-Tsai and Liao, Chung-Shou},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2018.38},
  URN =		{urn:nbn:de:0030-drops-99869},
  doi =		{10.4230/LIPIcs.ISAAC.2018.38},
  annote =	{Keywords: Pendant Pairs, Pendant Tree, Maximal Adjacency Ordering, Maximum Cardinality Search, Testing Edge-Connectivity, Gomory-Hu Tree}
}
Document
DOI: 10.4230/LIPIcs.ICALP.2018.98
Computing Tutte Paths

Authors: Andreas Schmid and Jens M. Schmidt

Published in: LIPIcs, Volume 107, 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)

Abstract
Tutte paths are one of the most successful tools for attacking problems on long cycles in planar graphs. Unfortunately, results based on them are non-constructive, as their proofs inherently use an induction on overlapping subgraphs and these overlaps prevent any attempt to bound the running time by a polynomial. For special cases however, computational results of Tutte paths are known: For 4-connected planar graphs, Tutte paths are in fact Hamiltonian paths and Chiba and Nishizeki [N. Chiba and T. Nishizeki, 1989] showed how to compute such paths in linear time. For 3-connected planar graphs, Tutte paths have a significantly more complicated structure, and it has only recently been shown that they can be computed in polynomial time [A. Schmid and J. M. Schmidt, 2015]. However, Tutte paths are defined for general 2-connected planar graphs and this is what most applications need. In this unrestricted setting, no computational results for Tutte paths are known. We give the first efficient algorithm that computes a Tutte path (in this unrestricted setting). One of the strongest existence results about such Tutte paths is due to Sanders [D. P. Sanders, 1997], which allows one to prescribe the end vertices and an intermediate edge of the desired path. Encompassing and strengthening all previous computational results on Tutte paths, we show how to compute such a special Tutte path efficiently. Our method refines both, the existence results of Thomassen [C. Thomassen, 1983] and Sanders [D. P. Sanders, 1997], and avoids that the subgraphs arising in the inductive proof intersect in more than one edge by using a novel iterative decomposition along 2-separators. Finally, we show that our algorithm runs in time O(n^2).
Cite as

Andreas Schmid and Jens M. Schmidt. Computing Tutte Paths. In 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 107, pp. 98:1-98:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{schmid_et_al:LIPIcs.ICALP.2018.98,
  author =	{Schmid, Andreas and Schmidt, Jens M.},
  title =	{{Computing Tutte Paths}},
  booktitle =	{45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)},
  pages =	{98:1--98:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-076-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{107},
  editor =	{Chatzigiannakis, Ioannis and Kaklamanis, Christos and Marx, D\'{a}niel and Sannella, Donald},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2018.98},
  URN =		{urn:nbn:de:0030-drops-91029},
  doi =		{10.4230/LIPIcs.ICALP.2018.98},
  annote =	{Keywords: Tutte Path, Tutte Cycle, 2-Connected Planar Graph, Hamiltonian Cycle}
}
Document
DOI: 10.4230/LIPIcs.ICALP.2017.75
Edge-Orders

Authors: Lena Schlipf and Jens M. Schmidt

Published in: LIPIcs, Volume 80, 44th International Colloquium on Automata, Languages, and Programming (ICALP 2017)

Abstract
Canonical orderings and their relatives such as st-numberings have been used as a key tool in algorithmic graph theory for the last decades. Recently, a unifying link behind all these orders has been shown that links them to well-known graph decompositions into parts that have a prescribed vertex-connectivity. Despite extensive interest in canonical orderings, no analogue of this unifying concept is known for edge-connectivity. In this paper, we establish such a concept named edge-orders and show how to compute (1,1)-edge-orders of 2-edge-connected graphs as well as (2,1)-edge-orders of 3-edge-connected graphs in linear time, respectively. While the former can be seen as the edge-variants of st-numberings, the latter are the edge-variants of Mondshein sequences and non-separating ear decompositions. The methods that we use for obtaining such edge-orders differ considerably in almost all details from the ones used for their vertex-counterparts, as different graph-theoretic constructions are used in the inductive proof and standard reductions from edge- to vertex-connectivity are bound to fail. As a first application, we consider the famous Edge-Independent Spanning Tree Conjecture, which asserts that every k-edge-connected graph contains k rooted spanning trees that are pairwise edge-independent. We illustrate the impact of the above edge-orders by deducing algorithms that construct 2- and 3-edge independent spanning trees of 2- and 3-edge-connected graphs, the latter of which improves the best known running time from O(n^2) to linear time.
Cite as

Lena Schlipf and Jens M. Schmidt. Edge-Orders. In 44th International Colloquium on Automata, Languages, and Programming (ICALP 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 80, pp. 75:1-75:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{schlipf_et_al:LIPIcs.ICALP.2017.75,
  author =	{Schlipf, Lena and Schmidt, Jens M.},
  title =	{{Edge-Orders}},
  booktitle =	{44th International Colloquium on Automata, Languages, and Programming (ICALP 2017)},
  pages =	{75:1--75:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-041-5},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{80},
  editor =	{Chatzigiannakis, Ioannis and Indyk, Piotr and Kuhn, Fabian and Muscholl, Anca},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2017.75},
  URN =		{urn:nbn:de:0030-drops-74078},
  doi =		{10.4230/LIPIcs.ICALP.2017.75},
  annote =	{Keywords: edge-order, st-edge-order, canonical ordering, edge-independent spanning tree, Mondshein sequence, linear time}
}
Document
DOI: 10.4230/LIPIcs.SWAT.2016.5
Linear-Time Recognition of Map Graphs with Outerplanar Witness

Authors: Matthias Mnich, Ignaz Rutter, and Jens M. Schmidt

Published in: LIPIcs, Volume 53, 15th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2016)

Abstract
Map graphs generalize planar graphs and were introduced by Chen, Grigni and Papadimitriou [STOC 1998, J.ACM 2002]. They showed that the problem of recognizing map graphs is in NP by proving the existence of a planar witness graph W. Shortly after, Thorup [FOCS 1998] published a polynomial-time recognition algorithm for map graphs. However, the run time of this algorithm is estimated to be Omega(n^{120}) for n-vertex graphs, and a full description of its details remains unpublished. We give a new and purely combinatorial algorithm that decides whether a graph G is a map graph having an outerplanar witness W. This is a step towards a first combinatorial recognition algorithm for general map graphs. The algorithm runs in time and space O(n+m). In contrast to Thorup's approach, it computes the witness graph W in the affirmative case.
Cite as

Matthias Mnich, Ignaz Rutter, and Jens M. Schmidt. Linear-Time Recognition of Map Graphs with Outerplanar Witness. In 15th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 53, pp. 5:1-5:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{mnich_et_al:LIPIcs.SWAT.2016.5,
  author =	{Mnich, Matthias and Rutter, Ignaz and Schmidt, Jens M.},
  title =	{{Linear-Time Recognition of Map Graphs with Outerplanar Witness}},
  booktitle =	{15th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2016)},
  pages =	{5:1--5:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-011-8},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{53},
  editor =	{Pagh, Rasmus},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SWAT.2016.5},
  URN =		{urn:nbn:de:0030-drops-60349},
  doi =		{10.4230/LIPIcs.SWAT.2016.5},
  annote =	{Keywords: Algorithms and data structures, map graphs, recognition, planar graphs}
}
Document
DOI: 10.4230/LIPIcs.STACS.2015.676
Computing 2-Walks in Polynomial Time

Authors: Andreas Schmid and Jens M. Schmidt

Published in: LIPIcs, Volume 30, 32nd International Symposium on Theoretical Aspects of Computer Science (STACS 2015)

Abstract
A 2-walk of a graph is a walk visiting every vertex at least once and at most twice. By generalizing decompositions of Tutte and Thomassen, Gao, Richter and Yu proved that every 3-connected planar graph contains a closed 2-walk such that all vertices visited twice are contained in 3-separators. This seminal result generalizes Tutte's theorem that every 4-connected planar graph is Hamiltonian as well as Barnette's theorem that every 3-connected planar graph has a spanning tree with maximum degree at most 3. The algorithmic challenge of finding such a closed 2-walk is to overcome big overlapping subgraphs in the decomposition, which are also inherent in Tutte's and Thomassen's decompositions. We solve this problem by extending the decomposition of Gao, Richter and Yu in such a way that all pieces, in which the graph is decomposed into, are edge-disjoint. This implies the first polynomial-time algorithm that computes the closed 2-walk mentioned above.
Cite as

Andreas Schmid and Jens M. Schmidt. Computing 2-Walks in Polynomial Time. In 32nd International Symposium on Theoretical Aspects of Computer Science (STACS 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 30, pp. 676-688, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{schmid_et_al:LIPIcs.STACS.2015.676,
  author =	{Schmid, Andreas and Schmidt, Jens M.},
  title =	{{Computing 2-Walks in Polynomial Time}},
  booktitle =	{32nd International Symposium on Theoretical Aspects of Computer Science (STACS 2015)},
  pages =	{676--688},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-78-1},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{30},
  editor =	{Mayr, Ernst W. and Ollinger, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2015.676},
  URN =		{urn:nbn:de:0030-drops-49502},
  doi =		{10.4230/LIPIcs.STACS.2015.676},
  annote =	{Keywords: algorithms and data structures, 2-walks, 3-connected planar graphs, Tutte paths, 3-trees}
}
Document
DOI: 10.4230/LIPIcs.STACS.2010.2491
Construction Sequences and Certifying 3-Connectedness

Authors: Jens M. Schmidt

Published in: LIPIcs, Volume 5, 27th International Symposium on Theoretical Aspects of Computer Science (2010)

Abstract
Given two $3$-connected graphs $G$ and $H$, a \emph{construction sequence} constructs $G$ from $H$ (e.\,g. from the $K_4$) with three basic operations, called the \emph{Barnette-Gr\"unbaum operations}. These operations are known to be able to construct all $3$-connected graphs. We extend this result by identifying every intermediate graph in the construction sequence with a subdivision in $G$ and showing under some minor assumptions that there is still a construction sequence to $G$ when we start from an \emph{arbitrary prescribed} $H$-subdivision. This leads to the first algorithm that computes a construction sequence in time $O(|V(G)|^2)$. As an application, we develop a certificate for the $3$-connectedness of graphs that can be easily computed and verified. Based on this, a certifying test on $3$-connectedness is designed.%Finding certifying algorithms is a major goal for problems where the efficient solutions known are complicated. Tutte proved that every $3$-connected graph on more than $4$ nodes has a \emph{contractible edge}. Barnette and Gr\"unbaum proved the existence of a \emph{removable edge} in the same setting. We show that the sequence of contractions and the sequence of removals from $G$ to the $K_4$ can be computed in $O(|V|^2)$ time by extending Barnette and Gr\"unbaum's theorem. As an application, we derive a certificate for the $3$-connectedness of graphs that can be easily computed and verified.
Cite as

Jens M. Schmidt. Construction Sequences and Certifying 3-Connectedness. In 27th International Symposium on Theoretical Aspects of Computer Science. Leibniz International Proceedings in Informatics (LIPIcs), Volume 5, pp. 633-644, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2010)

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@InProceedings{schmidt:LIPIcs.STACS.2010.2491,
  author =	{Schmidt, Jens M.},
  title =	{{Construction Sequences and Certifying 3-Connectedness}},
  booktitle =	{27th International Symposium on Theoretical Aspects of Computer Science},
  pages =	{633--644},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-16-3},
  ISSN =	{1868-8969},
  year =	{2010},
  volume =	{5},
  editor =	{Marion, Jean-Yves and Schwentick, Thomas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2010.2491},
  URN =		{urn:nbn:de:0030-drops-24918},
  doi =		{10.4230/LIPIcs.STACS.2010.2491},
  annote =	{Keywords: Construction sequence, 3-connected graph, nested subdivisions, inductive characterization, 3-connectedness, certifying algorithm}
}
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