A lower bound for learning distributions generated by probabilistic automata

  • Authors:
  • Borja Balle;Jorge Castro;Ricard Gavaldà

  • Affiliations:
  • Universitat Politècnica de Catalunya, Barcelona;Universitat Politècnica de Catalunya, Barcelona;Universitat Politècnica de Catalunya, Barcelona

  • Venue:
  • ALT'10 Proceedings of the 21st international conference on Algorithmic learning theory
  • Year:
  • 2010

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Abstract

Known algorithms for learning PDFA can only be shown to run in time polynomial in the so-called distinguishability µ of the target machine, besides the number of states and the usual accuracy and confidence parameters. We show that the dependence on µ is necessary for every algorithm whose structure resembles existing ones. As a technical tool, a new variant of Statistical Queries termed L∞-queries is defined. We show how these queries can be simulated from samples and observe that known PAC algorithms for learning PDFA can be rewritten to access its target using L∞-queries and standard Statistical Queries. Finally, we show a lower bound: every algorithm to learn PDFA using queries with a resonable tolerance needs a number of queries larger than (1/µ)c for every c