7 Search Results for "Engels, Stefan"

Document
DOI: 10.4230/OASIcs.ATMOS.2025.14
Using A* for Optimal Train Routing on Moving Block Systems

Authors: Stefan Engels and Robert Wille

Published in: OASIcs, Volume 137, 25th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2025)

Abstract
Modern control systems based on Moving Block allow for shorter headways and higher capacity on existing railway infrastructure. At the same time, few algorithms for optimal routing on networks equipped with such modern control systems exist. Previous methods rely on Mixed Integer Linear Programming (MILP) and face a trade-off between model size and accuracy, especially considering comparably complex and nonlinear headway constraints as well as train dynamics. With this work, we propose a complementary approach based on A*. Under a reasonable and easy assumption on train driver behavior, we propose a solution encoding and state space that is flexible concerning the choice of search algorithm and the modeling detail. The applicability is showcased on a small benchmark set. The implementation is available open-source as part of the Munich Train Control Toolkit (MTCT) on GitHub at https://github.com/cda-tum/mtct.
Cite as

Stefan Engels and Robert Wille. Using A* for Optimal Train Routing on Moving Block Systems. In 25th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2025). Open Access Series in Informatics (OASIcs), Volume 137, pp. 14:1-14:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{engels_et_al:OASIcs.ATMOS.2025.14,
  author =	{Engels, Stefan and Wille, Robert},
  title =	{{Using A* for Optimal Train Routing on Moving Block Systems}},
  booktitle =	{25th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2025)},
  pages =	{14:1--14:18},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-404-8},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{137},
  editor =	{Sauer, Jonas and Schmidt, Marie},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2025.14},
  URN =		{urn:nbn:de:0030-drops-247701},
  doi =		{10.4230/OASIcs.ATMOS.2025.14},
  annote =	{Keywords: ETCS, Train Routing, Moving Block, A*, Munich Train Control Toolkit}
}
Artifact
Software
DOI: 10.4230/artifacts.24436
Munich Train Control Toolkit (MTCT)

Authors: Stefan Engels

Abstract
Cite as

Stefan Engels. Munich Train Control Toolkit (MTCT) (Software, Source Code). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@misc{dagstuhl-artifact-24436,
   title = {{Munich Train Control Toolkit (MTCT)}}, 
   author = {Engels, Stefan},
   note = {Software, swhId: \href{https://archive.softwareheritage.org/swh:1:dir:9eb5851e7f0b80f88dc6f09a8c9c54b58d15ee5b;origin=https://github.com/cda-tum/mtct;visit=swh:1:snp:427338aeff595fef78df193555413c97e0596701;anchor=swh:1:rev:338f866a4831e8a221e10bba88887a36af9a9df5}{\texttt{swh:1:dir:9eb5851e7f0b80f88dc6f09a8c9c54b58d15ee5b}} (visited on 2025-10-17)},
   url = {https://github.com/cda-tum/mtct},
   doi = {10.4230/artifacts.24436},
}
Document
DOI: 10.4230/LIPIcs.MFCS.2025.19
Monotone Bounded-Depth Complexity of Homomorphism Polynomials

Authors: C.S. Bhargav, Shiteng Chen, Radu Curticapean, and Prateek Dwivedi

Published in: LIPIcs, Volume 345, 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)

Abstract
For every fixed graph H, it is known that homomorphism counts from H and colorful H-subgraph counts can be determined in O(n^{t+1}) time on n-vertex input graphs G, where t is the treewidth of H. On the other hand, a running time of n^{o(t / log t)} would refute the exponential-time hypothesis. Komarath, Pandey, and Rahul (Algorithmica, 2023) studied algebraic variants of these counting problems, i.e., homomorphism and subgraph polynomials for fixed graphs H. These polynomials are weighted sums over the objects counted above, where each object is weighted by the product of variables corresponding to edges contained in the object. As shown by Komarath et al., the monotone circuit complexity of the homomorphism polynomial for H is Θ(n^{tw(H)+1}). In this paper, we characterize the power of monotone bounded-depth circuits for homomorphism and colorful subgraph polynomials. This leads us to discover a natural hierarchy of graph parameters tw_Δ(H), for fixed Δ ∈ ℕ, which capture the width of tree-decompositions for H when the underlying tree is required to have depth at most Δ. We prove that monotone circuits of product-depth Δ computing the homomorphism polynomial for H require size Θ(n^{tw_Δ(H^{†})+1}), where H^{†} is the graph obtained from H by removing all degree-1 vertices. This allows us to derive an optimal depth hierarchy theorem for monotone bounded-depth circuits through graph-theoretic arguments.
Cite as

C.S. Bhargav, Shiteng Chen, Radu Curticapean, and Prateek Dwivedi. Monotone Bounded-Depth Complexity of Homomorphism Polynomials. In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 19:1-19:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bhargav_et_al:LIPIcs.MFCS.2025.19,
  author =	{Bhargav, C.S. and Chen, Shiteng and Curticapean, Radu and Dwivedi, Prateek},
  title =	{{Monotone Bounded-Depth Complexity of Homomorphism Polynomials}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{19:1--19:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-388-1},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{345},
  editor =	{Gawrychowski, Pawe{\l} and Mazowiecki, Filip and Skrzypczak, Micha{\l}},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2025.19},
  URN =		{urn:nbn:de:0030-drops-241269},
  doi =		{10.4230/LIPIcs.MFCS.2025.19},
  annote =	{Keywords: algebraic complexity, homomorphisms, monotone circuit complexity, bounded-depth circuits, treewidth, pathwidth}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2025.73
Counting Locally Optimal Tours in the TSP

Authors: Bodo Manthey and Jesse van Rhijn

Published in: LIPIcs, Volume 345, 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)

Abstract
We show that the problem of counting 2-optimal tours in instances of the Travelling Salesperson Problem (TSP) on complete graphs is #P-complete. In addition, we show that the expected number of 2-optimal tours in random instances of the TSP on complete graphs is O(1.2098ⁿ √{n!}). Based on numerical experiments, we conjecture that the true bound is at most O(√{n!}), which is approximately the square root of the total number of tours.
Cite as

Bodo Manthey and Jesse van Rhijn. Counting Locally Optimal Tours in the TSP. In 50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 345, pp. 73:1-73:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{manthey_et_al:LIPIcs.MFCS.2025.73,
  author =	{Manthey, Bodo and van Rhijn, Jesse},
  title =	{{Counting Locally Optimal Tours in the TSP}},
  booktitle =	{50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)},
  pages =	{73:1--73:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-388-1},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{345},
  editor =	{Gawrychowski, Pawe{\l} and Mazowiecki, Filip and Skrzypczak, Micha{\l}},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2025.73},
  URN =		{urn:nbn:de:0030-drops-241807},
  doi =		{10.4230/LIPIcs.MFCS.2025.73},
  annote =	{Keywords: Travelling salesman problem, probabilistic analysis, local search, heuristics, 2-opt}
}
Document
Short Paper
DOI: 10.4230/OASIcs.ATMOS.2024.12
Towards an Optimization Pipeline for the Design of Train Control Systems with Hybrid Train Detection (Short Paper)

Authors: Stefan Engels and Robert Wille

Published in: OASIcs, Volume 123, 24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024)

Abstract
Increasing the capacity of our railway infrastructure will become more and more essential in coping with the need for sustainable transportation. This can be achieved by intelligently implementing train control systems on specific railway networks. Methods that automate and optimize parts of this planning process are of great interest. For control systems based on hybrid train detection, such optimization tasks simultaneously involve routing and block layout generation. These tasks are already complex on their own; hence, a joint consideration often becomes infeasible. This work-in-progress paper proposes an idea to tackle the corresponding complexity. To this end, we present a pipeline that allows to sequentially handle corresponding optimization tasks in a less complex fashion while generating results that remain (close to) optimal. Results from an initial case study showcase that this approach is, indeed, promising. A prototypical implementation is included in the open-source Munich Train Control Toolkit available at https://github.com/cda-tum/mtct.
Cite as

Stefan Engels and Robert Wille. Towards an Optimization Pipeline for the Design of Train Control Systems with Hybrid Train Detection (Short Paper). In 24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024). Open Access Series in Informatics (OASIcs), Volume 123, pp. 12:1-12:6, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{engels_et_al:OASIcs.ATMOS.2024.12,
  author =	{Engels, Stefan and Wille, Robert},
  title =	{{Towards an Optimization Pipeline for the Design of Train Control Systems with Hybrid Train Detection}},
  booktitle =	{24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024)},
  pages =	{12:1--12:6},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-350-8},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{123},
  editor =	{Bouman, Paul C. and Kontogiannis, Spyros C.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2024.12},
  URN =		{urn:nbn:de:0030-drops-212002},
  doi =		{10.4230/OASIcs.ATMOS.2024.12},
  annote =	{Keywords: ETCS, MILP, Design Automation, Hybrid Train Detection}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2023.6
A Symbolic Design Method for ETCS Hybrid Level 3 at Different Degrees of Accuracy

Authors: Stefan Engels, Tom Peham, and Robert Wille

Published in: OASIcs, Volume 115, 23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023)

Abstract
The European Train Control System (Hybrid) Level 3 (ETCS Hybrid Level 3) allows for introducing Virtual Subsections (VSS) into existing railway infrastructures. These VSS work similarly to blocks in conventional block signaling but do not require installation or maintenance of trackside train detection. This added flexibility can be used to adapt a given railway network’s (virtual) layout to the changing demands of new schedules. Automated methods are needed to properly use this flexibility and design such layouts on demand and avoid time-intensive manual labor. Recently, approaches inspired by design automation of electronic hardware have been proposed to address this need. But those methods - which are particularly well suited for inherently discrete problems in electronic design automation - have struggled with modeling continuous properties like train positions, time, and acceleration. This work proposes a Mixed Integer Linear Programming (MILP) formulation that, for the first time, can accurately model design problems for ETCS Hybrid Level 3 by including essential, continuous constraints, e.g., for train dynamics or braking curves. The formulation is designed to be flexible and extendable, allowing the user to include/exclude certain constraints or simplify the model as needed. By this, the user can decide whether he/she wants to quickly generate a less accurate solution or a more accurate one at the expense of higher runtimes - basically allowing him/her to trade-off accuracy and efficiency. A case study showcases the potential of the proposed approach and sketches examples to analyze which trade-offs are worthwhile and which simplifications can be safely made. The resulting tool and the benchmarks considered in this work are publicly available at https://github.com/cda-tum/mtct (as part of the Munich Train Control Toolkit, MTCT).
Cite as

Stefan Engels, Tom Peham, and Robert Wille. A Symbolic Design Method for ETCS Hybrid Level 3 at Different Degrees of Accuracy. In 23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023). Open Access Series in Informatics (OASIcs), Volume 115, pp. 6:1-6:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{engels_et_al:OASIcs.ATMOS.2023.6,
  author =	{Engels, Stefan and Peham, Tom and Wille, Robert},
  title =	{{A Symbolic Design Method for ETCS Hybrid Level 3 at Different Degrees of Accuracy}},
  booktitle =	{23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023)},
  pages =	{6:1--6:17},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-302-7},
  ISSN =	{2190-6807},
  year =	{2023},
  volume =	{115},
  editor =	{Frigioni, Daniele and Schiewe, Philine},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2023.6},
  URN =		{urn:nbn:de:0030-drops-187676},
  doi =		{10.4230/OASIcs.ATMOS.2023.6},
  annote =	{Keywords: ETCS, MILP, design automation, block signaling, virtual subsection}
}
Document
DOI: 10.4230/DagSemProc.07081.12
End-User Development Techniques for Enterprise Resource Planning Software Systems

Authors: Michael Spahn, Stefan Scheidl, and Todor Stoitsev

Published in: Dagstuhl Seminar Proceedings, Volume 7081, End-User Software Engineering (2007)

Abstract
The intent of this position paper is to present the focus of interest of our end-user development (EUD) related research at SAP Research CEC Darmstadt. As we are in an early phase of research, research topics will be presented rather than detailed results. We focus on investigating and applying EUD techniques suitable for enterprise resource planning (ERP) software systems, especially for small and medium-sized enterprises (SMEs). Our current research addresses the sub-domains of workflow management and business intelligence.
Cite as

Michael Spahn, Stefan Scheidl, and Todor Stoitsev. End-User Development Techniques for Enterprise Resource Planning Software Systems. In End-User Software Engineering. Dagstuhl Seminar Proceedings, Volume 7081, pp. 1-2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2007)

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@InProceedings{spahn_et_al:DagSemProc.07081.12,
  author =	{Spahn, Michael and Scheidl, Stefan and Stoitsev, Todor},
  title =	{{End-User Development Techniques for Enterprise Resource Planning Software Systems}},
  booktitle =	{End-User Software Engineering},
  pages =	{1--2},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2007},
  volume =	{7081},
  editor =	{Margaret H. Burnett and Gregor Engels and Brad A. Myers and Gregg Rothermel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.07081.12},
  URN =		{urn:nbn:de:0030-drops-10979},
  doi =		{10.4230/DagSemProc.07081.12},
  annote =	{Keywords: End-User Development (EUD), Enterprise Resource Planning (ERP), Workflow Management, Business Intelligence (BI)}
}
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