Letters: On the bias of batch Bellman residual minimisation

  • Authors:
  • Daniel Schneegass

  • Affiliations:
  • Siemens AG, Corporate Technology, Information and Communications, Learning Systems, Otto-Hahn-Ring 6, D-81739 Munich, Germany and University of Luebeck, Institute for Neuro- and Bioinformatics, Ra ...

  • Venue:
  • Neurocomputing
  • Year:
  • 2009

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Abstract

This letter addresses the problem of Bellman residual minimisation in reinforcement learning for the model-free batch case. We prove the simple, but not necessarily obvious result, that no unbiased estimate of the Bellman residual exists for a single trajectory of observations. We further pick up the recent suggestion of Antos et al. [Learning near-optimal policies with Bellman-residual minimisation based fitted policy iteration and a single sample path, in: COLT, 2006, pp. 574-588] for approximative Bellman residual minimisation and discuss its properties concerning consistency, biasedness, and optimality. We finally give a suggestion to improve the optimality.