The α-EM algorithm: surrogate likelihood maximization using α-logarithmic information measures

  • Authors:
  • Y. Matsuyama

  • Affiliations:
  • Dept. of Comput. Sci., Waseda Univ., Tokyo, Japan

  • Venue:
  • IEEE Transactions on Information Theory
  • Year:
  • 2006

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Abstract

A new likelihood maximization algorithm called the α-EM algorithm (α-expectation-maximization algorithm) is presented. This algorithm outperforms the traditional or logarithmic EM algorithm in terms of convergence speed for an appropriate range of the design parameter α. The log-EM algorithm is a special case corresponding to α=-1. The main idea behind the α-EM algorithm is to search for an effective surrogate function or a minorizer for the maximization of the observed data's likelihood ratio. The surrogate function adopted in this paper is based upon the α-logarithm which is related to the convex divergence. The convergence speed of the α-EM algorithm is theoretically analyzed through α-dependent update matrices and illustrated by numerical simulations. Finally, general guidelines for using the α-logarithmic methods are given. The choice of alternative surrogate functions is also discussed.