Leveraging Value-awareness for Online and Offline Model-based Reinforcement Learning

Abstract

Model-based Reinforcement Learning (RL) lies at the intersection of planning and learning for sequential decision making. Value-awareness in model learning has recently emerged as a means to imbue task or reward information into the objective of model learn- ing, in order for the model to leverage specificity of a task. While finding success in theory as being superior to maximum likelihood estimation in the context of (online) model-based RL, value-awareness has remained impractical for most non-trivial tasks.

This thesis aims to bridge the gap in theory and practice by applying the principle of value-awareness to two settings – the online RL setting and offline RL setting. First, within online RL, this thesis revisits value-aware model learning from the perspective of minimizing performance difference, obtaining a novel value-aware model learning objec- tive as a direct upper bound of it. Then, this thesis investigates and remedies the issue of stale value estimates that has so far been holding back the practicality of value-aware model learning. Using the proposed remedy, performance improvements are presented over maximum-likelihood based baselines and existing value-aware objectives, in several continuous control tasks, while also enabling existing value-aware objectives to become performant.

In the offline RL context, this thesis takes a step back from model learning and ap- plies value-awareness towards better data augmentation. Such data augmentation, when applied to model-based offline RL algorithms, allows for leveraging unseen states with low epistemic uncertainty that have previously not been reachable within the assumptions and limitations of model-based offline RL. Value-aware state augmentations are found to enable better performance on offline RL benchmarks compared to existing baselines and non-value-aware alternatives.