Optimum follow the leader algorithm

  • Authors:
  • Dima Kuzmin;Manfred K. Warmuth

  • Affiliations:
  • University of California, Santa Cruz;University of California, Santa Cruz

  • Venue:
  • COLT'05 Proceedings of the 18th annual conference on Learning Theory
  • Year:
  • 2005

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Abstract

Consider the following setting for an on-line algorithm (introduced in [FS97]) that learns from a set of experts: In trial t the algorithm chooses an expert with probability p$^{t}_{i}$ . At the end of the trial a loss vector Lt∈[0,R]n for the n experts is received and an expected loss of ∑ip$^{t}_{i}$L$^{t}_{i}$ is incurred. A simple algorithm for this setting is the Hedge algorithm which uses the probabilities $p^{t}_{i} \sim exp^{-\eta L^{L*, R and n, then the total expected loss of the Hedge/WMR algorithm is at most $$L_{*} + \sqrt{\bf 2}\sqrt{L_{*}R{\rm log} n} + O({\rm log} n)$$ The factor of $\sqrt{\bf 2}$ is in some sense optimal [Vov97].