Reproduce “Prudent-Banker: No Extra Fees for Baseline Safety in Adversarial Bandits With and Without Delays” on OpenResearch

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About this paper

Ting Hu, Luanda Cai, Emmanouil-Vasileios Vlatakis-Gkaragkounis

The PRUDENT-BANKER algorithm tackles adversarial multi-armed bandits with arbitrary feedback delays, providing worst-case regret bounds of O(sqrt(T) + sqrt(D)) against the optimal arm while simultaneously ensuring O(1) regret relative to a pre-defined safe baseline. This dual objective is met through a novel delay-calibrated phase transition mechanism that accounts for unobserved feedback.

Key insights

  • It is possible to simultaneously achieve minimax-optimal worst-case regret and nearly constant regret against an exploratory safe baseline even under arbitrary feedback delays, providing the first affirmative resolution to the SOLID problem.
  • The inherent information deficit from delayed feedback can be managed by augmenting restart conditions with a delay-dependent slack term, enabling accurate certification of baseline suboptimality.
  • The component of adversarial regret proportional to sqrt(delta^{-1}D) is a fundamental "price of safety" in delayed bandit settings, as confirmed by theoretical lower bounds.

Summary by alphaXiv.

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