Strengths, Weaknesses, and Combinations of Model-based and Model-free Reinforcement Learning

  • Author / Creator
    Asadi Atui, Kavosh
  • Reinforcement learning algorithms are conventionally divided into two approaches: a model-based approach that builds a model of the environment and then computes a value function from the model, and a model-free approach that directly estimates the value function. The first contribution of this thesis is to demonstrate that, with similar computational resources, neither approach dominates the other. Explicitly, the model-based approach achieves a better performance with fewer environmental interactions, while the model-free approach reaches a more accurate solution asymptotically by using a larger representation or eligibility traces. The strengths offered by each approach are important for a reinforcement learning agent and, therefore, it is desirable to search for a combination of the two approaches and get the strengths of both. The main contribution of this thesis is to propose a new architecture in which a model-based algorithm forms an initial value function estimate and a model-free algorithm adds on to and improves the initial value function estimate. Experiments show that our architecture, called the Cascade Architecture, preserves the data efficiency of the model-based algorithm. Moreover, we prove that the Cascade Architecture converges to the original model-free solution and thus prevents any imperfect model from impairing the asymptotic performance. These results strengthen the case for combining model-based and model-free reinforcement learning.

  • Subjects / Keywords
  • Graduation date
    Spring 2016
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.