A stochastic memoizer for sequence data

  • Authors:
  • Frank Wood;Cédric Archambeau;Jan Gasthaus;Lancelot James;Yee Whye Teh

  • Affiliations:
  • University College London, London, UK;University College London, London, UK;University College London, London, UK;Hong Kong University of Science and Technology, Kowloon, Hong Kong;University College London, London, UK

  • Venue:
  • ICML '09 Proceedings of the 26th Annual International Conference on Machine Learning
  • Year:
  • 2009

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Abstract

We propose an unbounded-depth, hierarchical, Bayesian nonparametric model for discrete sequence data. This model can be estimated from a single training sequence, yet shares statistical strength between subsequent symbol predictive distributions in such a way that predictive performance generalizes well. The model builds on a specific parameterization of an unbounded-depth hierarchical Pitman-Yor process. We introduce analytic marginalization steps (using coagulation operators) to reduce this model to one that can be represented in time and space linear in the length of the training sequence. We show how to perform inference in such a model without truncation approximation and introduce fragmentation operators necessary to do predictive inference. We demonstrate the sequence memoizer by using it as a language model, achieving state-of-the-art results.