Black-Box Reductions for Parameter-free Online Learning in Banach Spaces
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Abstract (arXiv)
We introduce several new black-box reductions that significantly improve the design of adaptive and parameter-free online learning algorithms by simplifying analysis, improving regret guarantees, and sometimes even improving runtime. We reduce parameter-free online learning to online exp-concave optimization, we reduce optimization in a Banach space to one-dimensional optimization, and we reduce optimization over a constrained domain to unconstrained optimization. All of our reductions run as fast as online gradient descent. We use our new techniques to improve upon the previously best regret bounds for parameter-free learning, and do so for arbitrary norms.
Key facts. Cited by 124 papers in the map (data through 7 Oct 2026). First posted on arXiv 17 Feb 2018.
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Citing papers per year: 2021: 15; 2022: 24; 2023: 24; 2024: 15; 2025: 23; 2026: 23.
124 papers.
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- 2023Prodigy: An Expeditiously Adaptive Parameter-Free Learnercited by 129
- 2023DoG is SGD's Best Friend: A Parameter-Free Dynamic Step Size Schedulecited by 85
- 2021Adaptivity and Non-stationarity: Problem-dependent Dynamic Regret for Online Convex Optimizationcited by 66
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- 2021Parameter-free Stochastic Optimization of Variationally Coherent Functionscited by 27
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50 most cited of 124 All 124 (JSON)
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50 newest of 124 All 124 (JSON)
- 2025Reasoning without Regretcited by 0
- 2025Reasoning without Regret14 Apr 2025
- 2023Prodigy: An Expeditiously Adaptive Parameter-Free Learnercited by 129
- 2023DoG is SGD's Best Friend: A Parameter-Free Dynamic Step Size Schedulecited by 85
- 2021Adaptivity and Non-stationarity: Problem-dependent Dynamic Regret for Online Convex Optimizationcited by 66
- 2021Impossible Tuning Made Possible: A New Expert Algorithm and Its Applicationscited by 52
- 2022Making SGD Parameter-Freecited by 50
- 2022Parameter-free Mirror Descentcited by 45
- 2021Tight Concentrations and Confidence Sequences from the Regret of Universal Portfoliocited by 42
- 2023Optimal Stochastic Non-smooth Non-convex Optimization through Online-to-Non-convex Conversioncited by 42
- 2023Optimal Linear Decay Learning Rate Schedules and Further Refinementscited by 41
- 2023SGD with AdaGrad Stepsizes: Full Adaptivity with High Probability to Unknown Parameters, Unbounded Gradients and Affine Variancecited by 30
- 2023Parameter-Agnostic Optimization under Relaxed Smoothnesscited by 29
- 2021Parameter-free Stochastic Optimization of Variationally Coherent Functionscited by 27
12 most cited of 123 All 123 (JSON)
- 2026On the Relation Between Interval Regret and Dynamic Regret28 Sep 2026
- 2026The Price of Peeking: Anytime-Valid Leakage Detection on ML-KEM EM Traces27 Sep 2026
- 2026Rank Confidence Sequences:Anytime-valid Leaderboards26 Sep 2026
- 2026From Switching to Dynamic Regret: A Simple Reduction via Unbiased Random Sequences17 Sep 2026
- 2026From Approachability Residuals to Anytime-Valid Evidence: The Online Convex Geometry of Testing by Betting10 Aug 2026
- 2026Data-Dependent Regret and Polyak Corrections for Constrained Online Convex Optimization28 Jul 2026
- 2026Clipping the Price of Adaptivity at the Tail21 Jun 2026
- 2026Zero-order Parameter-free Optimization for LMO-based Methods: Novel Approach for Efficient Fine-tuning12 Jun 2026
- 2026Policy Regret for Embedding Model Routing: Contextual Bandits with Low-Rank Experts12 Jun 2026
- 2026Noise-Adaptive High-Probability Regret Bounds for Online Convex Optimization6 Jun 2026
- 2026Online Learning with Gradient-Variation Interval Regret2 Jun 2026
- 2026Distance-Aware Muon: Adaptive Step Scaling for Normalized Optimization18 May 2026
12 newest of 123 All 123 (JSON)