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We study dynamic regret minimization in unconstrained adversarial linear bandit problems. In this setting, a learner must minimize the cumulative loss relative to an arbitrary sequence of comparators…

Machine Learning · Computer Science 2026-03-30 Alberto Rumi , Andrew Jacobsen , Nicolò Cesa-Bianchi , Fabio Vitale

We study online learning with bandit feedback (i.e. learner has access to only zeroth-order oracle) where cost/reward functions $\f_t$ admit a "pseudo-1d" structure, i.e. $\f_t(\w) = \loss_t(\pred_t(\w))$ where the output of $\pred_t$ is…

Machine Learning · Computer Science 2021-02-16 Aadirupa Saha , Nagarajan Natarajan , Praneeth Netrapalli , Prateek Jain

We propose the first regret-based approach to the Graphical Bilinear Bandits problem, where $n$ agents in a graph play a stochastic bilinear bandit game with each of their neighbors. This setting reveals a combinatorial NP-hard problem that…

Machine Learning · Computer Science 2022-10-13 Geovani Rizk , Igor Colin , Albert Thomas , Rida Laraki , Yann Chevaleyre

We give an oracle-based algorithm for the adversarial contextual bandit problem, where either contexts are drawn i.i.d. or the sequence of contexts is known a priori, but where the losses are picked adversarially. Our algorithm is…

Machine Learning · Computer Science 2016-06-02 Vasilis Syrgkanis , Haipeng Luo , Akshay Krishnamurthy , Robert E. Schapire

We study agents communicating over an underlying network by exchanging messages, in order to optimize their individual regret in a common nonstochastic multi-armed bandit problem. We derive regret minimization algorithms that guarantee for…

Machine Learning · Computer Science 2019-11-19 Yogev Bar-On , Yishay Mansour

In this study, we propose a new method for constructing UCB-type algorithms for stochastic multi-armed bandits based on general convex optimization methods with an inexact oracle. We derive the regret bounds corresponding to the convergence…

Machine Learning · Computer Science 2024-02-13 Yuriy Dorn , Aleksandr Katrutsa , Ilgam Latypov , Andrey Pudovikov

We present a new anytime algorithm that achieves near-optimal regret for any instance of finite stochastic partial monitoring. In particular, the new algorithm achieves the minimax regret, within logarithmic factors, for both "easy" and…

Machine Learning · Computer Science 2012-07-03 Gabor Bartok , Navid Zolghadr , Csaba Szepesvari

We study the linear contextual bandit problem with finite action sets. When the problem dimension is $d$, the time horizon is $T$, and there are $n \leq 2^{d/2}$ candidate actions per time period, we (1) show that the minimax expected…

Machine Learning · Statistics 2020-08-20 Yingkai Li , Yining Wang , Yuan Zhou

We study the problem of non-stationary dueling bandits and provide the first adaptive dynamic regret algorithm for this problem. The only two existing attempts in this line of work fall short across multiple dimensions, including…

Machine Learning · Computer Science 2022-10-27 Thomas Kleine Buening , Aadirupa Saha

We derive near-optimal per-action regret bounds for sleeping bandits, in which both the sets of available arms and their losses in every round are chosen by an adversary. In a setting with $K$ total arms and at most $A$ available arms in…

Machine Learning · Computer Science 2024-05-31 Quan Nguyen , Nishant A. Mehta

We present an efficient second-order algorithm with $\tilde{O}(\frac{1}{\eta}\sqrt{T})$ regret for the bandit online multiclass problem. The regret bound holds simultaneously with respect to a family of loss functions parameterized by…

Machine Learning · Computer Science 2018-01-19 Alina Beygelzimer , Francesco Orabona , Chicheng Zhang

We study the multi-armed bandit problem with adversarially chosen delays in the Best-of-Both-Worlds (BoBW) framework, which aims to achieve near-optimal performance in both stochastic and adversarial environments. While prior work has made…

Machine Learning · Computer Science 2025-10-21 Ofir Schlisselberg , Tal Lancewicki , Peter Auer , Yishay Mansour

We introduce a new algorithm for online linear-quadratic control in a known system subject to adversarial disturbances. Existing regret bounds for this setting scale as $\sqrt{T}$ unless strong stochastic assumptions are imposed on the…

Machine Learning · Computer Science 2020-06-24 Dylan J. Foster , Max Simchowitz

We study distributed adversarial bandits, where $N$ agents cooperate to minimize the global average loss while observing only their own local losses. We show that the minimax regret for this problem is…

Machine Learning · Computer Science 2026-02-09 Hao Qiu , Mengxiao Zhang , Nicolò Cesa-Bianchi

We introduce the problem of regret minimization in Adversarial Dueling Bandits. As in classic Dueling Bandits, the learner has to repeatedly choose a pair of items and observe only a relative binary `win-loss' feedback for this pair, but…

Machine Learning · Computer Science 2020-10-29 Aadirupa Saha , Tomer Koren , Yishay Mansour

In this paper, we investigate the existence of online learning algorithms with bandit feedback that simultaneously guarantee $O(1)$ regret compared to a given comparator strategy, and $\tilde{O}(\sqrt{T})$ regret compared to any fixed…

Machine Learning · Computer Science 2025-06-05 Adrian Müller , Jon Schneider , Stratis Skoulakis , Luca Viano , Volkan Cevher

I introduce and analyse an anytime version of the Optimally Confident UCB (OCUCB) algorithm designed for minimising the cumulative regret in finite-armed stochastic bandits with subgaussian noise. The new algorithm is simple, intuitive (in…

Machine Learning · Computer Science 2016-05-09 Tor Lattimore

The Competing Bandits framework is a recently emerging area that integrates multi-armed bandits in online learning with stable matching in game theory. While conventional models assume that all players and arms are constantly available, in…

Machine Learning · Computer Science 2026-03-23 Shinnosuke Uba , Yutaro Yamaguchi

We consider linear stochastic bandits where the set of actions is an ellipsoid. We provide the first known minimax optimal algorithm for this problem. We first derive a novel information-theoretic lower bound on the regret of any algorithm,…

Machine Learning · Statistics 2025-02-25 Raymond Zhang , Hedi Hadiji , Richard Combes

We introduce a simple and efficient algorithm for unconstrained zeroth-order stochastic convex bandits and prove its regret is at most $(1 + r/d)[d^{1.5} \sqrt{n} + d^3] polylog(n, d, r)$ where $n$ is the horizon, $d$ the dimension and $r$…

Machine Learning · Computer Science 2023-02-13 Tor Lattimore , András György