Lower bounds on the VC dimension of smoothly parameterized function classes

  • Authors:
  • Wee Sun Lee;Peter L. Bartlett;Robert C. Williamson

  • Affiliations:
  • -;-;-

  • Venue:
  • Neural Computation
  • Year:
  • 1995

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Abstract

We examine the relationship between the VC dimension and thenumber of parameters of a threshold smoothly parameterized functionclass. We show that the VC dimension of such a function class is atleast k if there exists a k-dimensionaldifferentiable manifold in the parameter space such that eachmember of the manifold corresponds to a different decisionboundary. Using this result, we are able to obtain lower bounds onthe VC dimension proportional to the number of parameters forseveral thresholded function classes including two-layer neuralnetworks with certain smooth activation functions and radial basisfunctions with a gaussian basis. These lower bounds hold even ifthe magnitudes of the parameters are restricted to be arbitrarilysmall. In Valiant's probably approximately correct learningframework, this implies that the number of examples necessary forlearning these function classes is at least linear in the number ofparameters.