All Papers
Title |
|---|
Title |
|---|

Universal online learning aims to achieve optimal regret guarantees without requiring prior knowledge of the curvature of online functions. Existing methods have established minimax-optimal regret bounds for universal online learning, where a single algorithm can simultaneously attain regret for convex functions, for exp-concave functions, and for strongly convex functions, where is the number of rounds and is the dimension of the feasible domain. However, these methods still lack problem-dependent adaptivity. In particular, no universal method provides regret bounds that scale with the gradient variation , a key quantity that plays a crucial role in applications such as stochastic optimization and fast-rate convergence in games. In this work, we introduce UniGrad, a novel approach that achieves both universality and adaptivity, with two distinct realizations:this http URLandthis http URL. Both methods achieve universal regret guarantees that adapt to gradient variation, simultaneously attaining regret for strongly convex functions and regret for exp-concave functions. For convex functions, the regret bounds differ:this http URLachieves an bound while preserving the RVU property that is crucial for fast convergence in online games, whereasthis http URLachieves the optimal regret bound through a novel design. Both methods employ a meta algorithm with base learners, which naturally requires gradient queries per round. To enhance computational efficiency, we introduce UniGrad++, which retains the regret while reducing the gradient query to just per round via surrogate optimization. We further provide various implications.
View on arXiv