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Documents authored by van Rhijn, Jesse

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
DOI: 10.4230/LIPIcs.ISAAC.2024.48
Complexity of Local Search for Euclidean Clustering Problems

Authors: Bodo Manthey, Nils Morawietz, Jesse van Rhijn, and Frank Sommer

Published in: LIPIcs, Volume 322, 35th International Symposium on Algorithms and Computation (ISAAC 2024)

Abstract
We show that the simplest local search heuristics for two natural Euclidean clustering problems are PLS-hard. First, we show that the Hartigan-Wong method, which is essentially the Flip heuristic, for k-Means clustering is PLS-hard, even when k = 2. Second, we show the same result for the Flip heuristic for Max Cut, even when the edge weights are given by the (squared) Euclidean distances between the points in some set 𝒳 ⊆ R^d; a problem which is equivalent to Min Sum 2-Clustering.
Cite as

Bodo Manthey, Nils Morawietz, Jesse van Rhijn, and Frank Sommer. Complexity of Local Search for Euclidean Clustering Problems. In 35th International Symposium on Algorithms and Computation (ISAAC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 322, pp. 48:1-48:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{manthey_et_al:LIPIcs.ISAAC.2024.48,
  author =	{Manthey, Bodo and Morawietz, Nils and van Rhijn, Jesse and Sommer, Frank},
  title =	{{Complexity of Local Search for Euclidean Clustering Problems}},
  booktitle =	{35th International Symposium on Algorithms and Computation (ISAAC 2024)},
  pages =	{48:1--48:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-354-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{322},
  editor =	{Mestre, Juli\'{a}n and Wirth, Anthony},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2024.48},
  URN =		{urn:nbn:de:0030-drops-221755},
  doi =		{10.4230/LIPIcs.ISAAC.2024.48},
  annote =	{Keywords: Local search, PLS-complete, max cut, k-means, partitioning problem, flip-neighborhood}
}
Document
DOI: 10.4230/LIPIcs.STACS.2024.52
Worst-Case and Smoothed Analysis of the Hartigan-Wong Method for k-Means Clustering

Authors: Bodo Manthey and Jesse van Rhijn

Published in: LIPIcs, Volume 289, 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)

Abstract
We analyze the running time of the Hartigan-Wong method, an old algorithm for the k-means clustering problem. First, we construct an instance on the line on which the method can take 2^{Ω(n)} steps to converge, demonstrating that the Hartigan-Wong method has exponential worst-case running time even when k-means is easy to solve. As this is in contrast to the empirical performance of the algorithm, we also analyze the running time in the framework of smoothed analysis. In particular, given an instance of n points in d dimensions, we prove that the expected number of iterations needed for the Hartigan-Wong method to terminate is bounded by k^{12kd}⋅ poly(n, k, d, 1/σ) when the points in the instance are perturbed by independent d-dimensional Gaussian random variables of mean 0 and standard deviation σ.
Cite as

Bodo Manthey and Jesse van Rhijn. Worst-Case and Smoothed Analysis of the Hartigan-Wong Method for k-Means Clustering. In 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 289, pp. 52:1-52:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{manthey_et_al:LIPIcs.STACS.2024.52,
  author =	{Manthey, Bodo and van Rhijn, Jesse},
  title =	{{Worst-Case and Smoothed Analysis of the Hartigan-Wong Method for k-Means Clustering}},
  booktitle =	{41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)},
  pages =	{52:1--52:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-311-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{289},
  editor =	{Beyersdorff, Olaf and Kant\'{e}, Mamadou Moustapha and Kupferman, Orna and Lokshtanov, Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2024.52},
  URN =		{urn:nbn:de:0030-drops-197628},
  doi =		{10.4230/LIPIcs.STACS.2024.52},
  annote =	{Keywords: k-means clustering, smoothed analysis, probabilistic analysis, local search, heuristics}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2023.52
Improved Smoothed Analysis of 2-Opt for the Euclidean TSP

Authors: Bodo Manthey and Jesse van Rhijn

Published in: LIPIcs, Volume 283, 34th International Symposium on Algorithms and Computation (ISAAC 2023)

Abstract
The 2-opt heuristic is a simple local search heuristic for the Travelling Salesperson Problem (TSP). Although it usually performs well in practice, its worst-case running time is poor. Attempts to reconcile this difference have used smoothed analysis, in which adversarial instances are perturbed probabilistically. We are interested in the classical model of smoothed analysis for the Euclidean TSP, in which the perturbations are Gaussian. This model was previously used by Manthey & Veenstra, who obtained smoothed complexity bounds polynomial in n, the dimension d, and the perturbation strength σ^{-1}. However, their analysis only works for d ≥ 4. The only previous analysis for d ≤ 3 was performed by Englert, Röglin & Vöcking, who used a different perturbation model which can be translated to Gaussian perturbations. Their model yields bounds polynomial in n and σ^{-d}, and super-exponential in d. As the fact that no direct analysis exists for Gaussian perturbations that yields polynomial bounds for all d is somewhat unsatisfactory, we perform this missing analysis. Along the way, we improve all existing smoothed complexity bounds for Euclidean 2-opt with Gaussian perturbations.
Cite as

Bodo Manthey and Jesse van Rhijn. Improved Smoothed Analysis of 2-Opt for the Euclidean TSP. In 34th International Symposium on Algorithms and Computation (ISAAC 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 283, pp. 52:1-52:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{manthey_et_al:LIPIcs.ISAAC.2023.52,
  author =	{Manthey, Bodo and van Rhijn, Jesse},
  title =	{{Improved Smoothed Analysis of 2-Opt for the Euclidean TSP}},
  booktitle =	{34th International Symposium on Algorithms and Computation (ISAAC 2023)},
  pages =	{52:1--52:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-289-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{283},
  editor =	{Iwata, Satoru and Kakimura, Naonori},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2023.52},
  URN =		{urn:nbn:de:0030-drops-193549},
  doi =		{10.4230/LIPIcs.ISAAC.2023.52},
  annote =	{Keywords: Travelling salesman problem, smoothed analysis, probabilistic analysis, local search, heuristics, 2-opt}
}
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