lil' UCB : An Optimal Exploration Algorithm for Multi-Armed Bandits
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Abstract (arXiv)
The paper proposes a novel upper confidence bound (UCB) procedure for identifying the arm with the largest mean in a multi-armed bandit game in the fixed confidence setting using a small number of total samples. The procedure cannot be improved in the sense that the number of samples required to identify the best arm is within a constant factor of a lower bound based on the law of the iterated logarithm (LIL). Inspired by the LIL, we construct our confidence bounds to explicitly account for the infinite time horizon of the algorithm. In addition, by using a novel stopping time for the algorithm we avoid a union bound over the arms that has been observed in other UCB-type algorithms. We prove that the algorithm is optimal up to constants and also show through simulations that it provides superior performance with respect to the state-of-the-art.
Key facts. Cited by 148 papers in the map (data through 7 Oct 2026). First posted on arXiv 27 Dec 2013.
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Citing papers per year: 2021: 26; 2022: 29; 2023: 28; 2024: 20; 2025: 22; 2026: 23.
148 papers.
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- 2022Anytime-valid off-policy inference for contextual banditscited by 37
- 2022Top Two Algorithms Revisitedcited by 34
- 2025FOCUS: Efficient Keyframe Selection for Long Video Understandingcited by 30
- 2021Best Arm Identification with Safety Constraintscited by 25
- 2022Revisiting Simple Regret: Fast Rates for Returning a Good Armcited by 25
- 2021Online certification of preference-based fairness for personalized recommender systemscited by 22
- 2021Near-optimal inference in adaptive linear regressioncited by 20
- 2021Exploiting Heterogeneity in Robust Federated Best-Arm Identificationcited by 20
- 2021Efficient Pure Exploration for Combinatorial Bandits with Semi-Bandit Feedbackcited by 19
- 2022Near-Optimal Collaborative Learning in Banditscited by 18
- 2021Martingale Methods for Sequential Estimation of Convex Functionals and Divergencescited by 17
- 2022Optimistic PAC Reinforcement Learning: the Instance-Dependent Viewcited by 17
38 more
- 2021Bandits with many optimal armscited by 16
- 2022Almost Optimal Variance-Constrained Best Arm Identificationcited by 16
- 2022Active Learning with Safety Constraintscited by 16
- 2024On Speeding Up Language Model Evaluationcited by 14
- 2021Pure Exploration in Kernel and Neural Banditscited by 13
- 2021Achieving the Pareto Frontier of Regret Minimization and Best Arm Identification in Multi-Armed Banditscited by 13
- 2023Adaptive Algorithms for Relaxed Pareto Set Identificationcited by 13
- 2023Bandit Pareto Set Identification: the Fixed Budget Settingcited by 13
- 2025Sample Complexity and Representation Ability of Test-time Scaling Paradigmscited by 12
- 2022Exploiting Correlation to Achieve Faster Learning Rates in Low-Rank Preference Banditscited by 11
- 2022Almost Cost-Free Communication in Federated Best Arm Identificationcited by 11
- 2022Non-Asymptotic Analysis of a UCB-based Top Two Algorithmcited by 11
- 2021Understanding the Origin of Information-Seeking Exploration in Probabilistic Objectives for Controlcited by 10
- 2024Model Assessment and Selection under Temporal Distribution Shiftcited by 10
- 2021Variance-Dependent Best Arm Identificationcited by 9
- 2022Combinatorial Pure Exploration of Causal Banditscited by 9
- 2023Practical Bandits: An Industry Perspectivecited by 9
- 2023Tight Regret Bounds for Single-pass Streaming Multi-armed Banditscited by 9
- 2024Online Experimental Design With Estimation-Regret Trade-off Under Network Interferencecited by 9
- 2021The Role of Contextual Information in Best Arm Identificationcited by 8
- 2021Learning from an Exploring Demonstrator: Optimal Reward Estimation for Banditscited by 8
- 2021A unified framework for bandit multiple testingcited by 8
- 2021Best-Arm Identification in Correlated Multi-Armed Banditscited by 8
- 2021Comparing Sequential Forecasterscited by 8
- 2022Federated Best Arm Identification with Heterogeneous Clientscited by 8
- 2023Optimal Batched Best Arm Identificationcited by 8
- 2024Optimal Multi-Fidelity Best-Arm Identificationcited by 8
- 2025Strategic Scaling of Test-Time Compute: A Bandit Learning Approachcited by 8
- 2021A Non-asymptotic Approach to Best-Arm Identification for Gaussian Banditscited by 7
- 2021Bandit Quickest Changepoint Detectioncited by 7
- 2023Huber-Robust Confidence Sequencescited by 7
- 2024Query-Efficient Correlation Clustering with Noisy Oraclecited by 7
- 2024Tighter Confidence Bounds for Sequential Kernel Regressioncited by 7
- 2024Taming False Positives in Out-of-Distribution Detection with Human Feedbackcited by 7
- 2026Best Arm Identification with LLM Judges and Limited Humancited by 7
- 2021Mean-based Best Arm Identification in Stochastic Bandits under Reward Contaminationcited by 6
- 2022Parallel Best Arm Identification in Heterogeneous Environmentscited by 6
- 2023Semi-parametric inference based on adaptively collected datacited by 6
50 most cited of 148 All 148 (JSON)
- 2026Sharp Non-Asymptotic Analysis of the Penalized Challenger in β-EB-TCI for Bernoulli Bandits1 Oct 2026
- 2026Same Winners, Different Success Rates: Evaluating How LLM Agents Recover from Failures28 Sep 2026
- 2026Gap Entropy and Almost Instance-Wise Optimal Best-Arm Identification12 Sep 2026
- 2026A positive resolution of the gap-entropy conjecture9 Sep 2026
- 2026The Price of Decentralization in Top-K Arm Identification22 Aug 2026
- 2026The Cost of Adaptivity: Matching Lower Bounds Across Learning Problems9 Aug 2026
- 2026Cost-Aware Multi-Objective Bandits: Theory and Application to Budgeted LLM Configuration Evaluation5 Aug 2026
- 2026When May a Model Replace the Experiment? Audits, Licenses, and the Price of Trust in Surrogate-Driven Design2 Aug 2026
- 2026Offline-to-Online Creative Optimization with Generative Models and Adaptive Testing26 Jul 2026
- 2026Information-Directed Sampling for Causal Bandits17 Jul 2026
- 2026Best-Arm Identification with Generative Proxy8 Jul 2026
- 2026Probably Correct Optimal Stable Matching under Two-Sided Uncertainty6 Jul 2026
38 more
- 2026Two-Fidelity Best-Action Identification for Stochastic Minimax Tree1 Jun 2026
- 2026An Interactive Paradigm for Deep Research22 May 2026
- 2026Many Needles in a Haystack: Active Hit Discovery for Perturbation Experiments11 May 2026
- 2026Enabling Unsupervised Training of Deep EEG Denoisers With Intelligent Partitioning7 May 2026
- 2026Order-Optimal Sequential 1-Bit Mean Estimation in General Tail Regimes9 Apr 2026
- 2026Multi-Drafter Speculative Decoding with Alignment Feedback7 Apr 2026
- 2026Best-Arm Identification with Noisy Actuation2 Apr 2026
- 2026Learning with a Budget: Identifying the Best Arm with Resource Constraints27 Feb 2026
- 2026Fixed Budget is No Harder Than Fixed Confidence in Best-Arm Identification up to Logarithmic Factors3 Feb 2026
- 2026Best Arm Identification with LLM Judges and Limited Human29 Jan 2026
- 2026Exact Minimum-Volume Confidence Set Intersection for Multinomial Outcomes26 Jan 2026
- 2025Conformal bandits: bringing statistical validity and reward efficiency under weak arm separability10 Dec 2025
- 2025UCB for Large-Scale Pure Exploration: Beyond Sub-Gaussianity27 Nov 2025
- 2025Constrained Best Arm Identification with Tests for Feasibility12 Nov 2025
- 2025Beyond the Lower Bound: Bridging Regret Minimization and Best Arm Identification in Lexicographic Bandits8 Nov 2025
- 2025FOCUS: Efficient Keyframe Selection for Long Video Understanding31 Oct 2025
- 2025Limitations on Accurate, Trusted, Human-level Reasoning25 Sep 2025
- 2025Threshold-Based Optimal Arm Selection in Monotonic Bandits: Regret Lower Bounds and Algorithms2 Sep 2025
- 2025FraPPE: Fast and Efficient Preference-based Pure Exploration22 Aug 2025
- 2025Fixed-Confidence Multiple Change Point Identification under Bandit Feedback11 Jul 2025
- 2025Bandit Pareto Set Identification in a Multi-Output Linear Model6 Jul 2025
- 2025Strategic Scaling of Test-Time Compute: A Bandit Learning Approach15 Jun 2025
- 2025Constrained Pareto Set Identification with Bandit Feedback9 Jun 2025
- 2025Near Optimal Non-asymptotic Sample Complexity of 1-Identification8 Jun 2025
- 2025Sample Complexity and Representation Ability of Test-time Scaling Paradigms5 Jun 2025
- 2025Balancing Performance and Costs in Best Arm Identification26 May 2025
- 2025Optimal Best-Arm Identification under Fixed Confidence with Multiple Optima21 May 2025
- 2025ASAT: Adaptive Scoring and Thresholding with Human Feedback for Robust Out-of-Distribution Detection5 May 2025
- 2025On the Problem of Best Arm Retention16 Apr 2025
- 2025A characterization of sample adaptivity in UCB data6 Mar 2025
- 2025From Individual Experience to Collective Evidence: A Reporting-Based Framework for Identifying Systemic Harms12 Feb 2025
- 2025The Batch Complexity of Bandit Pure Exploration3 Feb 2025
- 2025Breaking the log(1/Delta2) Barrier: Better Batched Best Arm Identification with Adaptive Grids29 Jan 2025
- 2024Online Experimental Design With Estimation-Regret Trade-off Under Network Interference4 Dec 2024
- 2024Preference-based Pure Exploration4 Dec 2024
- 2024Fixing the Loose Brake: Exponential-Tailed Stopping Time in Best Arm Identification4 Nov 2024
- 2024Optimal Streaming Algorithms for Multi-Armed Bandits23 Oct 2024
- 2024Best Arm Identification with Minimal Regret27 Sep 2024
50 newest of 148 All 148 (JSON)
- 2021Pure Exploration with Structured Preference Feedbackcited by 1
- 2023Pure Exploration under Mediators' Feedbackcited by 1
- 2023Pure Exploration under Mediators' Feedback29 Aug 2023
- 2021Pure Exploration with Structured Preference Feedback12 Apr 2021
- 2022Anytime-valid off-policy inference for contextual banditscited by 37
- 2022Top Two Algorithms Revisitedcited by 34
- 2021Best Arm Identification with Safety Constraintscited by 25
- 2022Revisiting Simple Regret: Fast Rates for Returning a Good Armcited by 25
- 2021Online certification of preference-based fairness for personalized recommender systemscited by 22
- 2021Near-optimal inference in adaptive linear regressioncited by 20
- 2021Exploiting Heterogeneity in Robust Federated Best-Arm Identificationcited by 20
- 2021Efficient Pure Exploration for Combinatorial Bandits with Semi-Bandit Feedbackcited by 19
- 2022Near-Optimal Collaborative Learning in Banditscited by 18
- 2021Martingale Methods for Sequential Estimation of Convex Functionals and Divergencescited by 17
- 2022Optimistic PAC Reinforcement Learning: the Instance-Dependent Viewcited by 17
- 2021Bandits with many optimal armscited by 16
12 most cited of 140 All 140 (JSON)
- 2026Sharp Non-Asymptotic Analysis of the Penalized Challenger in β-EB-TCI for Bernoulli Bandits1 Oct 2026
- 2026Gap Entropy and Almost Instance-Wise Optimal Best-Arm Identification12 Sep 2026
- 2026A positive resolution of the gap-entropy conjecture9 Sep 2026
- 2026The Price of Decentralization in Top-K Arm Identification22 Aug 2026
- 2026The Cost of Adaptivity: Matching Lower Bounds Across Learning Problems9 Aug 2026
- 2026Cost-Aware Multi-Objective Bandits: Theory and Application to Budgeted LLM Configuration Evaluation5 Aug 2026
- 2026When May a Model Replace the Experiment? Audits, Licenses, and the Price of Trust in Surrogate-Driven Design2 Aug 2026
- 2026Information-Directed Sampling for Causal Bandits17 Jul 2026
- 2026Best-Arm Identification with Generative Proxy8 Jul 2026
- 2026Probably Correct Optimal Stable Matching under Two-Sided Uncertainty6 Jul 2026
- 2026Two-Fidelity Best-Action Identification for Stochastic Minimax Tree1 Jun 2026
- 2026An Interactive Paradigm for Deep Research22 May 2026
12 newest of 140 All 140 (JSON)