29 Search Results for "Borndörfer, Ralf"

Volume

OASIcs, Volume 65

18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)

ATMOS 2018, August 23-24, 2018, Helsinki, Finland

Editors: Ralf Borndörfer and Sabine Storandt

Document
DOI: 10.4230/OASIcs.ATMOS.2024.11
Solving the Electric Bus Scheduling Problem by an Integrated Flow and Set Partitioning Approach

Authors: Ralf Borndörfer, Andreas Löbel, Fabian Löbel, and Steffen Weider

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

Abstract
Attractive and cost-efficient public transport requires solving computationally difficult optimization problems from network design to crew rostering. While great progress has been made in many areas, new requirements to handle increasingly complex constraints are constantly coming up. One such challenge is a new type of resource constraints that are used to deal with the state-of-charge of battery-electric vehicles, which have limited driving ranges and need to be recharged in-service. Resource constrained vehicle scheduling problems can classically be modelled in terms of either a resource constrained (multi-commodity) flow problem or in terms of a path-based set partition problem. We demonstrate how a novel integrated version of both formulations can be leveraged to solve resource constrained vehicle scheduling with replenishment in general and the electric bus scheduling problem in particular by Lagrangian relaxation and the proximal bundle method.
Cite as

Ralf Borndörfer, Andreas Löbel, Fabian Löbel, and Steffen Weider. Solving the Electric Bus Scheduling Problem by an Integrated Flow and Set Partitioning Approach. In 24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024). Open Access Series in Informatics (OASIcs), Volume 123, pp. 11:1-11:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{borndorfer_et_al:OASIcs.ATMOS.2024.11,
  author =	{Bornd\"{o}rfer, Ralf and L\"{o}bel, Andreas and L\"{o}bel, Fabian and Weider, Steffen},
  title =	{{Solving the Electric Bus Scheduling Problem by an Integrated Flow and Set Partitioning Approach}},
  booktitle =	{24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024)},
  pages =	{11:1--11:16},
  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.2024.11},
  URN =		{urn:nbn:de:0030-drops-211992},
  doi =		{10.4230/OASIcs.ATMOS.2024.11},
  annote =	{Keywords: Electric Bus Scheduling, Electric Vehicle Scheduling, Non-linear Charging, Multi-commodity Flow, Set Partition, Lagrangian Relaxation, Proximal Bundle Method}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2024.13
A Bayesian Rolling Horizon Approach for Rolling Stock Rotation Planning with Predictive Maintenance

Authors: Felix Prause and Ralf Borndörfer

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

Abstract
We consider the rolling stock rotation planning problem with predictive maintenance (RSRP-PdM), where a timetable given by a set of trips must be operated by a fleet of vehicles. Here, the health states of the vehicles are assumed to be random variables, and their maintenance schedule should be planned based on their predicted failure probabilities. Utilizing the Bayesian update step of the Kalman filter, we develop a rolling horizon approach for RSRP-PdM, in which the predicted health state distributions are updated as new data become available. This approach reduces the uncertainty of the health states and thus improves the decision-making basis for maintenance planning. To solve the instances, we employ a local neighborhood search, which is a modification of a heuristic for RSRP-PdM, and demonstrate its effectiveness. Using this solution algorithm, the presented approach is compared with the results of common maintenance strategies on test instances derived from real-world timetables. The obtained results show the benefits of the rolling horizon approach.
Cite as

Felix Prause and Ralf Borndörfer. A Bayesian Rolling Horizon Approach for Rolling Stock Rotation Planning with Predictive Maintenance. In 24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024). Open Access Series in Informatics (OASIcs), Volume 123, pp. 13:1-13:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{prause_et_al:OASIcs.ATMOS.2024.13,
  author =	{Prause, Felix and Bornd\"{o}rfer, Ralf},
  title =	{{A Bayesian Rolling Horizon Approach for Rolling Stock Rotation Planning with Predictive Maintenance}},
  booktitle =	{24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024)},
  pages =	{13:1--13:19},
  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.2024.13},
  URN =		{urn:nbn:de:0030-drops-212013},
  doi =		{10.4230/OASIcs.ATMOS.2024.13},
  annote =	{Keywords: Rolling stock rotation planning, Predictive maintenance, Rolling horizon approach, Bayesian inference, Local neighborhood search}
}
Document
Short Paper
DOI: 10.4230/OASIcs.ATMOS.2023.3
Convergence Properties of Newton’s Method for Globally Optimal Free Flight Trajectory Optimization (Short Paper)

Authors: Ralf Borndörfer, Fabian Danecker, and Martin Weiser

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

Abstract
The algorithmic efficiency of Newton-based methods for Free Flight Trajectory Optimization is heavily influenced by the size of the domain of convergence. We provide numerical evidence that the convergence radius is much larger in practice than what the theoretical worst case bounds suggest. The algorithm can be further improved by a convergence-enhancing domain decomposition.
Cite as

Ralf Borndörfer, Fabian Danecker, and Martin Weiser. Convergence Properties of Newton’s Method for Globally Optimal Free Flight Trajectory Optimization (Short Paper). In 23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023). Open Access Series in Informatics (OASIcs), Volume 115, pp. 3:1-3:6, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{borndorfer_et_al:OASIcs.ATMOS.2023.3,
  author =	{Bornd\"{o}rfer, Ralf and Danecker, Fabian and Weiser, Martin},
  title =	{{Convergence Properties of Newton’s Method for Globally Optimal Free Flight Trajectory Optimization}},
  booktitle =	{23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023)},
  pages =	{3:1--3:6},
  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.2023.3},
  URN =		{urn:nbn:de:0030-drops-187642},
  doi =		{10.4230/OASIcs.ATMOS.2023.3},
  annote =	{Keywords: shortest path, flight planning, free flight, optimal control, global optimization, Newton’s method}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2023.13
Assignment Based Resource Constrained Path Generation for Railway Rolling Stock Optimization

Authors: Boris Grimm, Ralf Borndörfer, and Julian Bushe

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

Abstract
The fundamental task of every passenger railway operator is to offer an attractive railway timetable to the passengers while operating it as cost efficiently as possible. The available rolling stock has to be assigned to trips so that all trips are operated, operational requirements are satisfied, and the operating costs are minimum. This so-called Rolling Stock Rotation Problem (RSRP) is well studied in the literature. In this paper we consider an acyclic version of the RSRP that includes vehicle maintenance. As the latter is an important aspect, maintenance services have to be planned simultaneously to ensure the rotation’s feasibility in practice. Indeed, regular maintenance is important for the safety and reliability of the rolling stock as well as enforced by law in many countries. We present a new integer programming formulation that links a hyperflow to model vehicle compositions and their coupling decisions to a set of path variables that take care of the resource consumption of the individual vehicles. To solve the model we developed different column generation algorithms which are compared to each other as well as to the MILP flow formulation of [Ralf Borndörfer et al., 2016] on a test set of real world instances.
Cite as

Boris Grimm, Ralf Borndörfer, and Julian Bushe. Assignment Based Resource Constrained Path Generation for Railway Rolling Stock Optimization. In 23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023). Open Access Series in Informatics (OASIcs), Volume 115, pp. 13:1-13:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{grimm_et_al:OASIcs.ATMOS.2023.13,
  author =	{Grimm, Boris and Bornd\"{o}rfer, Ralf and Bushe, Julian},
  title =	{{Assignment Based Resource Constrained Path Generation for Railway Rolling Stock Optimization}},
  booktitle =	{23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023)},
  pages =	{13:1--13:15},
  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.2023.13},
  URN =		{urn:nbn:de:0030-drops-187741},
  doi =		{10.4230/OASIcs.ATMOS.2023.13},
  annote =	{Keywords: Railway Rolling Stock Optimization, Integer Programming, Column Generation}
}
Document
Short Paper
DOI: 10.4230/OASIcs.ATMOS.2023.15
Non-Linear Charge Functions for Electric Vehicle Scheduling with Dynamic Recharge Rates (Short Paper)

Authors: Fabian Löbel, Ralf Borndörfer, and Steffen Weider

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

Abstract
The ongoing electrification of logistics systems and vehicle fleets increases the complexity of associated vehicle routing or scheduling problems. Battery-powered vehicles have to be scheduled to recharge in-service, and the relationship between charging time and replenished driving range is non-linear. In order to access the powerful toolkit offered by mixed-integer and linear programming techniques, this battery behavior has to be linearized. Moreover, as electric fleets grow, power draw peaks have to be avoided to save on electricity costs or to adhere to hard grid capacity limits, such that it becomes desirable to keep recharge rates dynamic. We suggest a novel linearization approach of battery charging behavior for vehicle scheduling problems, in which the recharge rates are optimization variables and not model parameters.
Cite as

Fabian Löbel, Ralf Borndörfer, and Steffen Weider. Non-Linear Charge Functions for Electric Vehicle Scheduling with Dynamic Recharge Rates (Short Paper). In 23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023). Open Access Series in Informatics (OASIcs), Volume 115, pp. 15:1-15:6, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{lobel_et_al:OASIcs.ATMOS.2023.15,
  author =	{L\"{o}bel, Fabian and Bornd\"{o}rfer, Ralf and Weider, Steffen},
  title =	{{Non-Linear Charge Functions for Electric Vehicle Scheduling with Dynamic Recharge Rates}},
  booktitle =	{23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023)},
  pages =	{15:1--15:6},
  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.2023.15},
  URN =		{urn:nbn:de:0030-drops-187765},
  doi =		{10.4230/OASIcs.ATMOS.2023.15},
  annote =	{Keywords: Electric Vehicle Scheduling, Battery Powered Vehicles, Charging Process, Non-linear Charging, Recharge Modeling, Dynamic Recharge Rate}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2022.1
An A* Algorithm for Flight Planning Based on Idealized Vertical Profiles

Authors: Marco Blanco, Ralf Borndörfer, and Pedro Maristany de las Casas

Published in: OASIcs, Volume 106, 22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022)

Abstract
The Flight Planning Problem is to find a minimum fuel trajectory between two airports in a 3D airway network under consideration of the wind. We show that this problem is NP-hard, even in its most basic version. We then present a novel A* heuristic, whose potential function is derived from an idealized vertical profile over the remaining flight distance. This potential is, under rather general assumptions, both admissible and consistent and it can be computed efficiently. The method outperforms the state-of-the-art heuristic on real-life instances.
Cite as

Marco Blanco, Ralf Borndörfer, and Pedro Maristany de las Casas. An A* Algorithm for Flight Planning Based on Idealized Vertical Profiles. In 22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022). Open Access Series in Informatics (OASIcs), Volume 106, pp. 1:1-1:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{blanco_et_al:OASIcs.ATMOS.2022.1,
  author =	{Blanco, Marco and Bornd\"{o}rfer, Ralf and Maristany de las Casas, Pedro},
  title =	{{An A* Algorithm for Flight Planning Based on Idealized Vertical Profiles}},
  booktitle =	{22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022)},
  pages =	{1:1--1:15},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-259-4},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{106},
  editor =	{D'Emidio, Mattia and Lindner, Niels},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2022.1},
  URN =		{urn:nbn:de:0030-drops-171052},
  doi =		{10.4230/OASIcs.ATMOS.2022.1},
  annote =	{Keywords: shortest path problem, a-star algorithm, flight trajectory optimization, flight planning, heuristics}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2022.2
A Discrete-Continuous Algorithm for Globally Optimal Free Flight Trajectory Optimization

Authors: Ralf Borndörfer, Fabian Danecker, and Martin Weiser

Published in: OASIcs, Volume 106, 22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022)

Abstract
We present an efficient algorithm that finds a globally optimal solution to the 2D Free Flight Trajectory Optimization Problem (aka Zermelo Navigation Problem) up to arbitrary precision in finite time. The algorithm combines a discrete and a continuous optimization phase. In the discrete phase, a set of candidate paths that densely covers the trajectory space is created on a directed auxiliary graph. Then Yen’s algorithm provides a promising set of discrete candidate paths which subsequently undergo a locally convergent refinement stage. Provided that the auxiliary graph is sufficiently dense, the method finds a path that lies within the convex domain around the global minimizer. From this starting point, the second stage will converge rapidly to the optimum. The density of the auxiliary graph depends solely on the wind field, and not on the accuracy of the solution, such that the method inherits the superior asymptotic convergence properties of the optimal control stage.
Cite as

Ralf Borndörfer, Fabian Danecker, and Martin Weiser. A Discrete-Continuous Algorithm for Globally Optimal Free Flight Trajectory Optimization. In 22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022). Open Access Series in Informatics (OASIcs), Volume 106, pp. 2:1-2:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{borndorfer_et_al:OASIcs.ATMOS.2022.2,
  author =	{Bornd\"{o}rfer, Ralf and Danecker, Fabian and Weiser, Martin},
  title =	{{A Discrete-Continuous Algorithm for Globally Optimal Free Flight Trajectory Optimization}},
  booktitle =	{22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022)},
  pages =	{2:1--2:13},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-259-4},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{106},
  editor =	{D'Emidio, Mattia and Lindner, Niels},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2022.2},
  URN =		{urn:nbn:de:0030-drops-171068},
  doi =		{10.4230/OASIcs.ATMOS.2022.2},
  annote =	{Keywords: shortest path, flight planning, free flight, discretization error bounds, optimal control, discrete optimization, global optimization}
}
Document
Short Paper
DOI: 10.4230/OASIcs.ATMOS.2021.17
Efficient Algorithms for the Multi-Period Line Planning Problem in Public Transportation (Short Paper)

Authors: Güvenç Şahin, Amin Ahmadi Digehsara, and Ralf Borndörfer

Published in: OASIcs, Volume 96, 21st Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2021)

Abstract
In order to plan and schedule a demand-responsive public transportation system, both temporal and spatial changes in demand should be taken into account even at the line planning stage. We study the multi-period line planning problem with integrated decisions regarding dynamic allocation of vehicles among the lines. Given the NP-hard nature of the line planning problem, the multi-period version is clearly difficult to solve for large public transit networks even with advanced solvers. It becomes necessary to develop algorithms that are capable of solving even the very-large instances in reasonable time. For instances which belong to real public transit networks, we present results of a heuristic local branching algorithm and an exact approach based on constraint propagation.
Cite as

Güvenç Şahin, Amin Ahmadi Digehsara, and Ralf Borndörfer. Efficient Algorithms for the Multi-Period Line Planning Problem in Public Transportation (Short Paper). In 21st Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2021). Open Access Series in Informatics (OASIcs), Volume 96, pp. 17:1-17:6, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{sahin_et_al:OASIcs.ATMOS.2021.17,
  author =	{\c{S}ahin, G\"{u}ven\c{c} and Ahmadi Digehsara, Amin and Bornd\"{o}rfer, Ralf},
  title =	{{Efficient Algorithms for the Multi-Period Line Planning Problem in Public Transportation}},
  booktitle =	{21st Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2021)},
  pages =	{17:1--17:6},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-213-6},
  ISSN =	{2190-6807},
  year =	{2021},
  volume =	{96},
  editor =	{M\"{u}ller-Hannemann, Matthias and Perea, Federico},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2021.17},
  URN =		{urn:nbn:de:0030-drops-148863},
  doi =		{10.4230/OASIcs.ATMOS.2021.17},
  annote =	{Keywords: public transportation, line planning, multi-period planning, local branching, constraint propagation}
}
Document
APPROX
DOI: 10.4230/LIPIcs.APPROX/RANDOM.2021.27
Connected k-Partition of k-Connected Graphs and c-Claw-Free Graphs

Authors: Ralf Borndörfer, Katrin Casel, Davis Issac, Aikaterini Niklanovits, Stephan Schwartz, and Ziena Zeif

Published in: LIPIcs, Volume 207, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2021)

Abstract
A connected partition is a partition of the vertices of a graph into sets that induce connected subgraphs. Such partitions naturally occur in many application areas such as road networks, and image processing. In these settings, it is often desirable to partition into a fixed number of parts of roughly of the same size or weight. The resulting computational problem is called Balanced Connected Partition (BCP). The two classical objectives for BCP are to maximize the weight of the smallest, or minimize the weight of the largest component. We study BCP on c-claw-free graphs, the class of graphs that do not have K_{1,c} as an induced subgraph, and present efficient (c-1)-approximation algorithms for both objectives. In particular, for 3-claw-free graphs, also simply known as claw-free graphs, we obtain a 2-approximation. Due to the claw-freeness of line graphs, this also implies a 2-approximation for the edge-partition version of BCP in general graphs. A harder connected partition problem arises from demanding a connected partition into k parts that have (possibly) heterogeneous target weights w₁,…,w_k. In the 1970s Győri and Lovász showed that if G is k-connected and the target weights sum to the total size of G, such a partition exists. However, to this day no polynomial algorithm to compute such partitions exists for k > 4. Towards finding such a partition T₁,…, T_k in k-connected graphs for general k, we show how to efficiently compute connected partitions that at least approximately meet the target weights, subject to the mild assumption that each w_i is greater than the weight of the heaviest vertex. In particular, we give a 3-approximation for both the lower and the upper bounded version i.e. we guarantee that each T_i has weight at least (w_i)/3 or that each T_i has weight most 3w_i, respectively. Also, we present a both-side bounded version that produces a connected partition where each T_i has size at least (w_i)/3 and at most max({r,3}) w_i, where r ≥ 1 is the ratio between the largest and smallest value in w₁, … , w_k. In particular for the balanced version, i.e. w₁ = w₂ = , … , = w_k, this gives a partition with 1/3w_i ≤ w(T_i) ≤ 3w_i.
Cite as

Ralf Borndörfer, Katrin Casel, Davis Issac, Aikaterini Niklanovits, Stephan Schwartz, and Ziena Zeif. Connected k-Partition of k-Connected Graphs and c-Claw-Free Graphs. In Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 207, pp. 27:1-27:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{borndorfer_et_al:LIPIcs.APPROX/RANDOM.2021.27,
  author =	{Bornd\"{o}rfer, Ralf and Casel, Katrin and Issac, Davis and Niklanovits, Aikaterini and Schwartz, Stephan and Zeif, Ziena},
  title =	{{Connected k-Partition of k-Connected Graphs and c-Claw-Free Graphs}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2021)},
  pages =	{27:1--27:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-207-5},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{207},
  editor =	{Wootters, Mary and Sanit\`{a}, Laura},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX/RANDOM.2021.27},
  URN =		{urn:nbn:de:0030-drops-147200},
  doi =		{10.4230/LIPIcs.APPROX/RANDOM.2021.27},
  annote =	{Keywords: connected partition, Gy\H{o}ri-Lov\'{a}sz, balanced partition, approximation algorithms}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2019.1
A Cut Separation Approach for the Rolling Stock Rotation Problem with Vehicle Maintenance

Authors: Boris Grimm, Ralf Borndörfer, Markus Reuther, and Thomas Schlechte

Published in: OASIcs, Volume 75, 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)

Abstract
For providing railway services the company’s railway rolling stock is one if not the most important ingredient. It decides about the number of passenger or cargo trips the company can offer, about the quality a passenger experiences the train ride and it is often related to the image of the company itself. Thus, it is highly desired to have the available rolling stock in the best shape possible. Moreover, in many countries, as Germany where our industrial partner DB Fernverkehr AG (DBF) is located, laws enforce regular vehicle inspections to ensure the safety of the passengers. This leads to rolling stock optimization problems with complex rules for vehicle maintenance. This problem is well studied in the literature for example see [Maróti and Kroon, 2005; Gábor Maróti and Leo G. Kroon, 2007], or [Cordeau et al., 2001] for applications including vehicle maintenance. The contribution of this paper is a new algorithmic approach to solve the Rolling Stock Rotation Problem for the ICE high speed train fleet of DBF with included vehicle maintenance. It is based on a relaxation of a mixed integer linear programming model with an iterative cut generation to enforce the feasibility of a solution of the relaxation in the solution space of the original problem. The resulting mixed integer linear programming model is based on a hypergraph approach presented in [Ralf Borndörfer et al., 2015]. The new approach is tested on real world instances modeling different scenarios for the ICE high speed train network in Germany and compared to the approaches of [Reuther, 2017] that are in operation at DB Fernverkehr AG. The approach shows a significant reduction of the run time to produce solutions with comparable or even better objective function values.
Cite as

Boris Grimm, Ralf Borndörfer, Markus Reuther, and Thomas Schlechte. A Cut Separation Approach for the Rolling Stock Rotation Problem with Vehicle Maintenance. In 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019). Open Access Series in Informatics (OASIcs), Volume 75, pp. 1:1-1:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{grimm_et_al:OASIcs.ATMOS.2019.1,
  author =	{Grimm, Boris and Bornd\"{o}rfer, Ralf and Reuther, Markus and Schlechte, Thomas},
  title =	{{A Cut Separation Approach for the Rolling Stock Rotation Problem with Vehicle Maintenance}},
  booktitle =	{19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)},
  pages =	{1:1--1:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-128-3},
  ISSN =	{2190-6807},
  year =	{2019},
  volume =	{75},
  editor =	{Cacchiani, Valentina and Marchetti-Spaccamela, Alberto},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2019.1},
  URN =		{urn:nbn:de:0030-drops-114136},
  doi =		{10.4230/OASIcs.ATMOS.2019.1},
  annote =	{Keywords: Railway Operations Research, Integer Programming, Infeasible Path Cuts, Cut Separation, Rolling Stock Rotation Problem}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2019.2
New Perspectives on PESP: T-Partitions and Separators

Authors: Niels Lindner and Christian Liebchen

Published in: OASIcs, Volume 75, 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)

Abstract
In the planning process of public transportation companies, designing the timetable is among the core planning steps. In particular in the case of periodic (or cyclic) services, the Periodic Event Scheduling Problem (PESP) is well-established to compute high-quality periodic timetables. We are considering algorithms for computing good solutions and dual bounds for the very basic PESP with no additional extra features as add-ons. The first of these algorithms generalizes several primal heuristics that have been proposed, such as single-node cuts and the modulo network simplex algorithm. We consider partitions of the graph, and identify so-called delay cuts as a structure that allows to generalize several previous heuristics. In particular, when no more improving delay cut can be found, we already know that the other heuristics could not improve either. This heuristic already had been proven to be useful in computational experiments [Ralf Borndörfer et al., 2019], and we locate it in the more general concept of what we denote T-partitions. With the second of these algorithms we propose to turn a strategy, that has been discussed in the past, upside-down: Instead of gluing together the network line-by-line in a bottom-up way, we develop a divide-and-conquer-like top-down approach to separate the initial problem into two easier subproblems such that the information loss along their cutset edges is as small as possible. We are aware that there may be PESP instances that do not fit well the separator setting. Yet, on the RxLy-instances of PESPlib in our experimental computations, we come up with good primal solutions and dual bounds. In particular, on the largest instance (R4L4), this new separator approach, which applies a state-of-the-art solver as subroutine, is able to come up with better dual bounds than purely applying this state-of-the-art solver in the very same time.
Cite as

Niels Lindner and Christian Liebchen. New Perspectives on PESP: T-Partitions and Separators. In 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019). Open Access Series in Informatics (OASIcs), Volume 75, pp. 2:1-2:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{lindner_et_al:OASIcs.ATMOS.2019.2,
  author =	{Lindner, Niels and Liebchen, Christian},
  title =	{{New Perspectives on PESP: T-Partitions and Separators}},
  booktitle =	{19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)},
  pages =	{2:1--2:18},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-128-3},
  ISSN =	{2190-6807},
  year =	{2019},
  volume =	{75},
  editor =	{Cacchiani, Valentina and Marchetti-Spaccamela, Alberto},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2019.2},
  URN =		{urn:nbn:de:0030-drops-114144},
  doi =		{10.4230/OASIcs.ATMOS.2019.2},
  annote =	{Keywords: Periodic Event Scheduling Problem, Periodic Timetabling, Graph Partitioning, Graph Separators, Balanced Cuts}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2019.12
A Graph- and Monoid-Based Framework for Price-Sensitive Routing in Local Public Transportation Networks

Authors: Ricardo Euler and Ralf Borndörfer

Published in: OASIcs, Volume 75, 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)

Abstract
We present a novel framework to mathematically describe the fare systems of local public transit companies. The model allows the computation of a provably cheapest itinerary even if prices depend on a number of parameters and non-linear conditions. Our approach is based on a ticket graph model to represent tickets and their relation to each other. Transitions between tickets are modeled via transition functions over partially ordered monoids and a set of symbols representing special properties of fares (e.g. surcharges). Shortest path algorithms rely on the subpath optimality property. This property is usually lost when dealing with complicated fare systems. We restore it by relaxing domination rules for tickets depending on the structure of the ticket graph. An exemplary model for the fare system of Mitteldeutsche Verkehrsbetriebe (MDV) is provided. By integrating our framework in the multi-criteria RAPTOR algorithm we provide a price-sensitive algorithm for the earliest arrival problem and assess its performance on data obtained from MDV. We discuss three preprocessing techniques that improve run times enough to make the algorithm applicable for real-time queries.
Cite as

Ricardo Euler and Ralf Borndörfer. A Graph- and Monoid-Based Framework for Price-Sensitive Routing in Local Public Transportation Networks. In 19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019). Open Access Series in Informatics (OASIcs), Volume 75, pp. 12:1-12:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{euler_et_al:OASIcs.ATMOS.2019.12,
  author =	{Euler, Ricardo and Bornd\"{o}rfer, Ralf},
  title =	{{A Graph- and Monoid-Based Framework for Price-Sensitive Routing in Local Public Transportation Networks}},
  booktitle =	{19th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2019)},
  pages =	{12:1--12:15},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-128-3},
  ISSN =	{2190-6807},
  year =	{2019},
  volume =	{75},
  editor =	{Cacchiani, Valentina and Marchetti-Spaccamela, Alberto},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2019.12},
  URN =		{urn:nbn:de:0030-drops-114243},
  doi =		{10.4230/OASIcs.ATMOS.2019.12},
  annote =	{Keywords: shortest path, public transit, optimization, price-sensitive, raptor, fare, operations research}
}
Document
Complete Volume
DOI: 10.4230/OASIcs.ATMOS.2018
OASIcs, Volume 65, ATMOS'18, Complete Volume

Authors: Ralf Borndörfer and Sabine Storandt

Published in: OASIcs, Volume 65, 18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)

Abstract
OASIcs, Volume 65, ATMOS'18, Complete Volume
Cite as

18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018). Open Access Series in Informatics (OASIcs), Volume 65, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@Proceedings{borndorfer_et_al:OASIcs.ATMOS.2018,
  title =	{{OASIcs, Volume 65, ATMOS'18, Complete Volume}},
  booktitle =	{18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-096-5},
  ISSN =	{2190-6807},
  year =	{2018},
  volume =	{65},
  editor =	{Bornd\"{o}rfer, Ralf and Storandt, Sabine},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2018},
  URN =		{urn:nbn:de:0030-drops-97272},
  doi =		{10.4230/OASIcs.ATMOS.2018},
  annote =	{Keywords: Theory of computation, Design and analysis of algorithms, Mathematics of computing, Discrete mathematics, Mathematics of computing, Combinatorics}
}
Document
Front Matter
DOI: 10.4230/OASIcs.ATMOS.2018.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Ralf Borndörfer and Sabine Storandt

Published in: OASIcs, Volume 65, 18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018). Open Access Series in Informatics (OASIcs), Volume 65, pp. 0:i-0:x, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{borndorfer_et_al:OASIcs.ATMOS.2018.0,
  author =	{Bornd\"{o}rfer, Ralf and Storandt, Sabine},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)},
  pages =	{0:i--0:x},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-096-5},
  ISSN =	{2190-6807},
  year =	{2018},
  volume =	{65},
  editor =	{Bornd\"{o}rfer, Ralf and Storandt, Sabine},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2018.0},
  URN =		{urn:nbn:de:0030-drops-97050},
  doi =		{10.4230/OASIcs.ATMOS.2018.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
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