Bayesian Design Principles for Frequentist Sequential Learning
This work addresses the challenge of making Bayesian-type algorithms prior-free and applicable to adversarial settings in sequential learning, offering a systematic approach that is incremental in unifying existing methods.
The paper tackles the problem of optimizing frequentist regret in sequential learning by developing a general theory that derives efficient bandit and reinforcement learning algorithms from Bayesian principles, resulting in a novel algorithm for multi-armed bandits that achieves best-of-all-worlds empirical performance across stochastic, adversarial, and non-stationary environments.
We develop a general theory to optimize the frequentist regret for sequential learning problems, where efficient bandit and reinforcement learning algorithms can be derived from unified Bayesian principles. We propose a novel optimization approach to generate "algorithmic beliefs" at each round, and use Bayesian posteriors to make decisions. The optimization objective to create "algorithmic beliefs," which we term "Algorithmic Information Ratio," represents an intrinsic complexity measure that effectively characterizes the frequentist regret of any algorithm. To the best of our knowledge, this is the first systematical approach to make Bayesian-type algorithms prior-free and applicable to adversarial settings, in a generic and optimal manner. Moreover, the algorithms are simple and often efficient to implement. As a major application, we present a novel algorithm for multi-armed bandits that achieves the "best-of-all-worlds" empirical performance in the stochastic, adversarial, and non-stationary environments. And we illustrate how these principles can be used in linear bandits, bandit convex optimization, and reinforcement learning.