Bi-criteria linear-time approximations for generalized k-mean/median/center

Dan Feldman, Amos Fiat, Micha Sharir, Danny Segev

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


We consider the problem of approximating a set P of n points in R d by a collection of j-dimensional flats, andextensions thereof, under the standard median / mean / centermeasures, in which we wish to minimize, respectively, the sum of thedistances from each point of P to its nearest flat, the sum of thesquares of these distances, or the maximal such distance.Such problems cannot be approximated unless P=NP but do allowbi-criteria approximations where one allows some leeway in both the numberof flats and the quality of the objective function.We give a very simple bi-criteria approximation algorithm, which producesat most α(k,j,n) = (k j log n) O(j) flats, which exceeds the optimalobjective value for any k j-dimensional flats by a factor of nomore than Β(j)= 2O(j). Given this bi-criteria approximation, wecan use it to reduce the approximation factor arbitrarily, at the costof increasing the number of flats. Our algorithm hasmany advantages over previous work, in that it is muchmore widely applicable (wider set of objective functions and classes ofclusters) and much more efficient - reducing the running time bound from O(nPoly(k,j)) to nd (jk)O(j).Our algorithm is randomized and successful with probability 1/2(easily boosted to probabilities arbitrary close to 1).

Original languageEnglish
Title of host publicationProceedings of the Twenty-third Annual Symposium on Computational Geometry, SCG'07
Number of pages8
StatePublished - 2007
Externally publishedYes
Event23rd Annual Symposium on Computational Geometry, SCG'07 - Gyeongju, Korea, Republic of
Duration: 6 Jun 20078 Jun 2007

Publication series

NameProceedings of the Annual Symposium on Computational Geometry


Conference23rd Annual Symposium on Computational Geometry, SCG'07
Country/TerritoryKorea, Republic of


  • Approximation
  • Bi-criteria approximation
  • Geometric optimization
  • K-center
  • K-mean
  • K-median

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Geometry and Topology
  • Computational Mathematics


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