A random-sampling-based algorithm for learning intersections of halfspaces

  • Authors:
  • Santosh S. Vempala

  • Affiliations:
  • Georgia Tech, Atlanta, GA

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 2010

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Abstract

We give an algorithm to learn an intersection of k halfspaces in Rn whose normals span an l-dimensional subspace. For any input distribution with a logconcave density such that the bounding hyperplanes of the k halfspaces pass through its mean, the algorithm (&epsis;,δ)-learns with time and sample complexity bounded by (nkl/&epsis;)O(l) log 1/&epsis; δ. The hypothesis found is an intersection of O(k log (1/&epsis;)) halfspaces. This improves on Blum and Kannan's algorithm for the uniform distribution over a ball, in the time and sample complexity (previously doubly exponential) and in the generality of the input distribution.