2020

Doubly Robust Off-Policy Value and Gradient Estimation for Deterministic Policies

Kallus, Nathan, Uehara, Masatoshi

Understand

Offline reinforcement learning, wherein one uses off-policy data logged by a fixed behavior policy to evaluate and learn new policies, is crucial in applications where experimentation is limited such as medicine.

  • We study the estimation of policy value and gradient of a deterministic policy from off-policy data when actions are continuous.
  • Targeting deterministic policies, for which action is a deterministic function of state, is crucial since optimal policies are always deterministic (up to ties).
  • In this setting, standard importance sampling and doubly robust estimators for policy value and gradient fail because the density ratio does not exist.

Reading the bibliography…