Scalable k-means++

  • Authors:
  • Bahman Bahmani;Benjamin Moseley;Andrea Vattani;Ravi Kumar;Sergei Vassilvitskii

  • Affiliations:
  • Stanford University, Stanford, CA;University of Illinois, Urbana, IL;University of California, San Diego, CA;Yahoo! Research, Sunnyvale, CA;Yahoo! Research, New York, NY

  • Venue:
  • Proceedings of the VLDB Endowment
  • Year:
  • 2012

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Abstract

Over half a century old and showing no signs of aging, k-means remains one of the most popular data processing algorithms. As is well-known, a proper initialization of k-means is crucial for obtaining a good final solution. The recently proposed k-means++ initialization algorithm achieves this, obtaining an initial set of centers that is provably close to the optimum solution. A major downside of the k-means++ is its inherent sequential nature, which limits its applicability to massive data: one must make k passes over the data to find a good initial set of centers. In this work we show how to drastically reduce the number of passes needed to obtain, in parallel, a good initialization. This is unlike prevailing efforts on parallelizing k-means that have mostly focused on the post-initialization phases of k-means. We prove that our proposed initialization algorithm k-means|| obtains a nearly optimal solution after a logarithmic number of passes, and then show that in practice a constant number of passes suffices. Experimental evaluation on real-world large-scale data demonstrates that k-means|| outperforms k-means++ in both sequential and parallel settings.