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Documents authored by Bortoletto, Enrico

Document
DOI: 10.4230/OASIcs.ATMOS.2024.4
Periodic Event Scheduling with Flexible Infrastructure Assignment

Authors: Enrico Bortoletto, Rolf Nelson van Lieshout, Berenike Masing, and Niels Lindner

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

Abstract
We present novel extensions of the Periodic Event Scheduling Problem (PESP) that integrate the assignment of activities to infrastructure elements. An application of this is railway timetabling, as station and platform capacities are limited and need to be taken into account. We show that an assignment of activities to platforms can always be made periodic, and that it can be beneficial to allow larger periods for the assignment than for the timetable. We present mixed-integer programming formulations for the general problem, as well as for the practically relevant case when multiple platforms can be considered equivalent, for which we present a bipartite matching approach. We finally test and compare these models on real-world instances.
Cite as

Enrico Bortoletto, Rolf Nelson van Lieshout, Berenike Masing, and Niels Lindner. Periodic Event Scheduling with Flexible Infrastructure Assignment. In 24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024). Open Access Series in Informatics (OASIcs), Volume 123, pp. 4:1-4:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bortoletto_et_al:OASIcs.ATMOS.2024.4,
  author =	{Bortoletto, Enrico and van Lieshout, Rolf Nelson and Masing, Berenike and Lindner, Niels},
  title =	{{Periodic Event Scheduling with Flexible Infrastructure Assignment}},
  booktitle =	{24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024)},
  pages =	{4:1--4:18},
  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.2024.4},
  URN =		{urn:nbn:de:0030-drops-211929},
  doi =		{10.4230/OASIcs.ATMOS.2024.4},
  annote =	{Keywords: Periodic Event Scheduling, Periodic Timetabling, Railway Timetabling, Matchings, Infrastructure Assignments, Platform Assignments, Station Capacities}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2023.7
Periodic Timetabling with Cyclic Order Constraints

Authors: Enrico Bortoletto, Niels Lindner, and Berenike Masing

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

Abstract
Periodic timetabling for highly utilized railway networks is a demanding challenge. We formulate an infrastructure-aware extension of the Periodic Event Scheduling Problem (PESP) by requiring that not only events, but also activities using the same infrastructure must be separated by a minimum headway time. This extended problem can be modeled as a mixed-integer program by adding constraints on the sum of periodic tensions along certain cycles, so that it shares some structural properties with standard PESP. We further refine this problem by fixing cyclic orders at each infrastructure element. Although the computational complexity remains unchanged, the mixed-integer programming model then becomes much smaller. Furthermore, we also discuss how to find a minimal subset of infrastructure elements whose cyclic order already prescribes the order for the remaining parts of the network, and how cyclic order information can be modeled in a mixed-integer programming context. In practice, we evaluate the impact of cyclic orders on a real-world instance on the S-Bahn Berlin network, which turns out to be computationally fruitful.
Cite as

Enrico Bortoletto, Niels Lindner, and Berenike Masing. Periodic Timetabling with Cyclic Order Constraints. In 23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023). Open Access Series in Informatics (OASIcs), Volume 115, pp. 7:1-7:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{bortoletto_et_al:OASIcs.ATMOS.2023.7,
  author =	{Bortoletto, Enrico and Lindner, Niels and Masing, Berenike},
  title =	{{Periodic Timetabling with Cyclic Order Constraints}},
  booktitle =	{23rd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2023)},
  pages =	{7:1--7:18},
  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.2023.7},
  URN =		{urn:nbn:de:0030-drops-187689},
  doi =		{10.4230/OASIcs.ATMOS.2023.7},
  annote =	{Keywords: Periodic Timetabling, Railway Timetabling, Periodic Event Scheduling Problem, Cyclic Orders, Mixed-Integer Programming}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2022.3
Tropical Neighbourhood Search: A New Heuristic for Periodic Timetabling

Authors: Enrico Bortoletto, Niels Lindner, and Berenike Masing

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

Abstract
Periodic timetabling is a central aspect of both the long-term organization and the day-to-day operations of a public transportation system. The Periodic Event Scheduling Problem (PESP), the combinatorial optimization problem that forms the mathematical basis of periodic timetabling, is an extremely hard problem, for which optimal solutions are hardly ever found in practice. The most prominent solving strategies today are based on mixed-integer programming, and there is a concurrent PESP solver employing a wide range of heuristics [Borndörfer et al., 2020]. We present tropical neighborhood search (tns), a novel PESP heuristic. The method is based on the relations between periodic timetabling and tropical geometry [Bortoletto et al., 2022]. We implement tns into the concurrent solver, and test it on instances of the benchmarking library PESPlib. The inclusion of tns turns out to be quite beneficial to the solver: tns is able to escape local optima for the modulo network simplex algorithm, and the overall share of improvement coming from tns is substantial compared to the other methods available in the solver. Finally, we provide better primal bounds for five PESPlib instances.
Cite as

Enrico Bortoletto, Niels Lindner, and Berenike Masing. Tropical Neighbourhood Search: A New Heuristic for Periodic Timetabling. In 22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022). Open Access Series in Informatics (OASIcs), Volume 106, pp. 3:1-3:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bortoletto_et_al:OASIcs.ATMOS.2022.3,
  author =	{Bortoletto, Enrico and Lindner, Niels and Masing, Berenike},
  title =	{{Tropical Neighbourhood Search: A New Heuristic for Periodic Timetabling}},
  booktitle =	{22nd Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2022)},
  pages =	{3:1--3:19},
  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.2022.3},
  URN =		{urn:nbn:de:0030-drops-171075},
  doi =		{10.4230/OASIcs.ATMOS.2022.3},
  annote =	{Keywords: Periodic Timetabling, Tropical Geometry, Neighborhood Search, Mixed-Integer Programming}
}
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