Active Imitation Learning via Reduction to I.I.D. Active Learning
This work addresses the challenge of high expert effort in imitation learning for AI and robotics, offering a practical reduction in query complexity.
The paper tackles the problem of reducing expert effort in imitation learning by querying actions at selected states instead of observing full trajectories, and shows that active imitation learning can require substantially fewer queries than passive methods.
In standard passive imitation learning, the goal is to learn a target policy by passively observing full execution trajectories of it. Unfortunately, generating such trajectories can require substantial expert effort and be impractical in some cases. In this paper, we consider active imitation learning with the goal of reducing this effort by querying the expert about the desired action at individual states, which are selected based on answers to past queries and the learner's interactions with an environment simulator. We introduce a new approach based on reducing active imitation learning to i.i.d. active learning, which can leverage progress in the i.i.d. setting. Our first contribution, is to analyze reductions for both non-stationary and stationary policies, showing that the label complexity (number of queries) of active imitation learning can be substantially less than passive learning. Our second contribution, is to introduce a practical algorithm inspired by the reductions, which is shown to be highly effective in four test domains compared to a number of alternatives.