An improved approximation algorithm for TSP in the half integral case

We design a 1.49993-approximation algorithm for the metric traveling salesperson problem (TSP) for instances in which an optimal solution to the subtour linear programming relaxation is half-integral. These instances received significant attention over the last decade due to a conjecture of Schalekamp, Williamson and van Zuylen stating that half-integral LP solutions have the largest integrality gap over all fractional solutions. So, if the conjecture of Schalekamp et al. holds true, our result shows that the integrality gap of the subtour polytope is bounded away from 3/2.

Authors

• Anna R. Karlin
• Nathan Klein
• Shayan Oveis Gharan

Keywords

• Approximation Algorithms
• Cactus Representation
• Max Entropy
• Randomized Rounding
• Strongly Rayleigh
• Traveling Salesman Problem