k-Means Has Polynomial Smoothed Complexity

  • Authors:
  • David Arthur;Bodo Manthey;Heiko Röglin

  • Affiliations:
  • -;-;-

  • Venue:
  • FOCS '09 Proceedings of the 2009 50th Annual IEEE Symposium on Foundations of Computer Science
  • Year:
  • 2009

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Abstract

The k-means method is one of the most widely used clustering algorithms, drawing its popularity from its speed in practice. Recently, however, it was shown to have exponential worst-case running time. In order to close the gap between practical performance and theoretical analysis, the k-means method has been studied in the model of smoothed analysis. But even the smoothed analyses so far are unsatisfactory as the bounds are still super-polynomial in the number n of data points. In this paper, we settle the smoothed running time of the k-means method. We show that the smoothed number of iterations is bounded by a polynomial in n and 1/sigma, where sigma is the standard deviation of the Gaussian perturbations. This means that if an arbitrary input data set is randomly perturbed, then the k-means method will run in expected polynomial time on that input set.