A Deterministic Better-than-3/2 Approximation Algorithm for Metric TSP

We show that the max entropy algorithm can be derandomized (with respect to a particular objective function) to give a deterministic $$3/2-\epsilon $$ approximation algorithm for metric TSP for some $$\epsilon > 10^{-36}$$ . To obtain our result, we apply the method of conditional expectation to an objective function constructed in prior work which was used to certify that the expected cost of the algorithm is at most $$3/2-\epsilon $$ times the cost of an optimal solution to the subtour elimination LP. The proof in this work involves showing that the expected value of this objective function can be computed in polynomial time (at all stages of the algorithm’s execution).