An improved approximation algorithm for ATSP

12/02/2019

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by   Vera Traub, et al.

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We revisit the constant-factor approximation algorithm for the asymmetric traveling salesman problem by Svensson, Tarnawski, and Végh. We improve on each part of this algorithm. We avoid the reduction to irreducible instances and thus obtain a simpler and much better reduction to vertebrate pairs. We also show that a slight variant of their algorithm for vertebrate pairs has a much smaller approximation ratio. Overall we improve the approximation ratio from 506 to 22+ϵ for any ϵ > 0. This also improves the upper bound on the integrality ratio from 319 to 22.