Poster
Conservative Contextual Bandits: Beyond Linear Representations
Rohan Deb · Mohammad Ghavamzadeh · Arindam Banerjee
Hall 3 + Hall 2B #447
[
Abstract
]
Wed 23 Apr 7 p.m. PDT
— 9:30 p.m. PDT
Abstract:
Conservative Contextual Bandits (CCBs) address safety in sequential decision making by requiring that an agent's policy, along with minimizing regret, also satisfies a safety constraint: the performance is not worse than a baseline policy (e.g., the policy that the company has in production) by more than (1+α) factor. Prior work developed UCB-stylealgorithms for this problem in the multi-armed (Wu et al., 2016) and contextuallinear (Kazerouni et al., 2017) settings.However, in practice the cost of the armsis often a non-linear function, and therefore existing UCB algorithms are ineffective in such settings. In this paper, we consider CCBs beyond the linear case and develop two algorithms C-SquareCB and C-FastCB, using Inverse Gap Weighting (IGW) based exploration and an online regression oracle. We show that the safety constraint is satisfied in high probability and that the regret for C-SquareCB is sub-linear in horizon T, while the the regret for C-FastCB is first-order and is sub-linear in L∗, the cumulative loss of the optimal policy. Subsequently, we use a neural network for function approximation and online gradient descent as the regression oracle to provide ˜O(√KT+K/α) and ˜O(√KL∗+K(1+1/α)) regret bounds respectively. Finally, we demonstrate the efficacy of our algorithms on real world data, and show that they significantly outperform the existing baseline while maintaining the performance guarantee.
Live content is unavailable. Log in and register to view live content