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OP-01093 Open

Planar Euclidean maximum traveling salesman problem

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Given a finite set of points in the plane, the maximum traveling salesman problem asks for a tour through all the points whose total Euclidean length is as large as possible.

Barvinok gave a polynomial-time approximation scheme. Barvinok, Johnson, Woeginger and Woodroofe solved the problem exactly for polyhedral norms in fixed dimension, in time $O(n^{f-2}\log n)$ when the unit ball has $f$ facets. Fekete showed that it takes $O(n)$ time for rectilinear distances in the plane but is NP-hard for Euclidean distances in three dimensions and on the sphere, and conjectured that the planar Euclidean case is NP-hard. The problem is not known to be in NP: a polynomial-time algorithm would need some handle on comparing sums of square roots.

Problem. For a finite point set in the plane, is computing a longest Euclidean tour NP-hard, or can it be done in polynomial time?

Source: Origin uncertain; earliest known mention Barvinok (1996), who gave a PTAS; see Fekete (1999) and Barvinok, Fekete, Johnson, Tamir, Woeginger and Woodroofe (2003); Problem 49 of The Open Problems Project (Demaine, Mitchell and O'Rourke).

Imported from topp.openproblem.net.

Classification

Primary
MG — Metric Geometry
Secondary
CO, OC
Keywords
Euclidean distances, maximum traveling salesman problem, The Open Problems Project

References

@article{barvinok1996,
  author  = {Barvinok, Alexander I.},
  title   = {Two Algorithmic Results for the {TSP}},
  journal = {Math. Oper. Res.},
  volume  = {21},
  year    = {1996},
  pages   = {65--84}
}

@inproceedings{barvinok1998,
  author    = {Barvinok, Alexander and Johnson, David S. and Woeginger, Gerhard J. and Woodroofe, Russell},
  title     = {The maximum traveling salesman problem under polyhedral norms},
  booktitle = {Sixth Conference on Integer Programming and Combinatorial Optimization (IPCO '98)},
  series    = {Springer LNCS},
  volume    = {1412},
  year      = {1998},
  pages     = {195--201}
}

@inproceedings{fekete1999,
  author    = {Fekete, S. P.},
  title     = {Simplicity and hardness of the Maximum Traveling Salesman Problem under geometric distances},
  booktitle = {Proc. 10th ACM-SIAM Sympos. Discrete Algorithms (SODA '99)},
  year      = {1999},
  pages     = {337--345}
}

@article{barvinok2003,
  author  = {Barvinok, A. and Fekete, S. P. and Johnson, D. S. and Tamir, A. and Woeginger, G. J. and Woodroofe, R.},
  title   = {The geometric maximum {T}raveling {S}alesman problem},
  journal = {Journal of the ACM},
  volume  = {50},
  number  = {5},
  year    = {2003},
  pages   = {641--664}
}

Citing this problem

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OP-01093, "Planar Euclidean maximum traveling salesman problem", clopen.solutions.