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arXiv · 2106.10097

The Graphical Traveling Salesperson Problem has no Integer Programming Formulation in the Original Space

Matthias Walter
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Abstract

The Graphical Traveling Salesperson Problem (GTSP) is the problem of assigning, for a given weighted graph, a nonnegative number $x_e$ each edge $e$ such that the induced multi-subgraph is of minimum weight among those that are spanning, connected and Eulerian. Naturally, known mixed-integer programming formulations use integer variables $x_e$ in addition to others. Denis Naddef posed the challenge of finding a (reasonably simple) mixed-integer programming formulation that has integrality constraints only on these edge variables. Recently, Carr and Simonetti (IPCO 2021) showed that such a formulation cannot consist of polynomial-time certifyiable inequality classes unless $\mathsf{NP}=\mathsf{coNP}$. In this note we establish a more rigorous result, namely that no such MIP formulation exists at all.

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Matthias Walter. 2021-06-18. The Graphical Traveling Salesperson Problem has no Integer Programming Formulation in the Original Space. https://arxiv.org/abs/2106.10097

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