The Batch Complexity of Bandit Pure Exploration

Published: 17 Jul 2025, Last Modified: 06 Sept 2025EWRL 2025 PosterEveryoneRevisionsBibTeXCC BY 4.0
Keywords: Bandits, Best arm identification, batched
Abstract: In a fixed-confidence pure exploration problem in stochastic multi-armed bandits, an algorithm iteratively samples arms and should stop as early as possible and return the correct answer to a query about the arms distributions. We are interested in batched methods, which change their sampling behaviour only a few times, between batches of observations. We give an instance-dependent lower bound on the number of batches used by any sample efficient algorithm for any pure exploration task. We then give a general batched algorithm and prove upper bounds on its expected sample complexity and batch complexity.
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Submission Number: 35
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