Improving reinforcement learning by using sequence trees

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Girgin S., POLAT F., Alhajj R.

MACHINE LEARNING, vol.81, no.3, pp.283-331, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 81 Issue: 3
  • Publication Date: 2010
  • Doi Number: 10.1007/s10994-010-5182-y
  • Journal Name: MACHINE LEARNING
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.283-331
  • Keywords: Reinforcement learning, Options, Conditionally terminating sequences, Temporal abstractions, Semi-Markov decision processes, SOCCER, ABSTRACTION
  • Middle East Technical University Affiliated: Yes


This paper proposes a novel approach to discover options in the form of stochastic conditionally terminating sequences; it shows how such sequences can be integrated into the reinforcement learning framework to improve the learning performance. The method utilizes stored histories of possible optimal policies and constructs a specialized tree structure during the learning process. The constructed tree facilitates the process of identifying frequently used action sequences together with states that are visited during the execution of such sequences. The tree is constantly updated and used to implicitly run corresponding options. The effectiveness of the method is demonstrated empirically by conducting extensive experiments on various domains with different properties.