Optimistic Hedge regret is O(n log n) for 2 players but exponential for 3, new paper shows

roydanroy · x · 2026-11-07

A new arXiv paper by Yuval Dagan, Nadav Eisen, Liad Erez, and Tomer Koren resolves a long-standing open question on Optimistic Hedge regret bounds. In two-player general-sum games, a suitable learning rate yields O(n log n) regret independent of horizon T; for three or more players, no such bound is possible—there exist games where some player's regret is 2^Ω(n), and for m≥3 players up to 2^Ω(mn). The results, built on a temporal approximation technique, bridge prior polylogarithmic and non-constructive constant bounds.

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