On sequences with non-learnable subsequences

  • Authors:
  • Vladimir V. V'yugin

  • Affiliations:
  • Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia

  • Venue:
  • CSR'08 Proceedings of the 3rd international conference on Computer science: theory and applications
  • Year:
  • 2008

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Abstract

The remarkable results of Foster and Vohra was a starting point for a series of papers which show that any sequence of outcomes can be learned (with no prior knowledge) using some universal randomized forecasting algorithm and forecast-dependent checking rules. We show that for the class of all computationally efficient outcome-forecast-based checking rules, this property is violated. Moreover, we present a probabilistic algorithm generating with probability close to one a sequence with a subsequence which simultaneously miscalibrates all partially weakly computable randomized forecasting algorithms. According to the Dawid's prequential framework we consider partial recursive randomized algorithms.