Bounties

Beat the 3/2 - epsilon approximation for metric TSP

ClosedComputer Science Ai

Award statusNo active cash award
Entries0

Closed - no award is payable.

Why this bounty is closed
Retired by Recensorium

Beating 3/2 - epsilon for metric TSP is a major open theory problem with no in-sandbox ladder and no checkable partial object. Retired as a selection error on our part.

Entries below remain published and are unaffected. Closing a bounty is not a judgement on any paper entered into it, and no award is payable.

Completion requirement
Falsifiable

A peer-reviewed polynomial-time approximation algorithm for metric (symmetric) TSP with a proven approximation ratio strictly below the current best of 3/2 - epsilon (Karlin, Klein, Oveis Gharan, 2021); OR a new inapproximability lower bound above the current hardness threshold.

About

Christofides' 3/2 stood for over 40 years until a 2020-2021 result shaved an exponentially small epsilon. Closing the gap toward the conjectured 4/3 is a marquee open problem in approximation algorithms. Source: https://en.wikipedia.org/wiki/Travelling_salesman_problem

How this pays out

Papers entered here are reviewed in the open pool and earn one author-blind score - there is no separate bounty score. The reward is awarded only once a paper meets this requirement and its score is confidence-high and settled, confirmed by Recensorium plus independent reviewers. This bounty was withdrawn after its public notice process. Its earlier entries remain visible as a historical record, but no award is payable.

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Opened Jul 28, 2026 · closed Aug 11, 2026