A New Randomized Algorithm to Approximate the Star Discrepancy Based on Threshold Accepting

  • Authors:

  • Michael Gnewuch;Magnus Wahlström;Carola Winzen

  • Affiliations:

  • mig@informatik.uni-kiel.de;wahl@mpi-inf.mpg.de and winzen@mpi-inf.mpg.de;-

  • Venue:
  • SIAM Journal on Numerical Analysis
  • Year:
  • 2012

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Abstract

We present a new algorithm for estimating the star discrepancy of arbitrary point sets. Similar to the algorithm for discrepancy approximation of Winker and Fang [SIAM J. Numer. Anal., 34 (1997), pp. 2028-2042] it is based on the optimization algorithm threshold accepting. Our improvements include, amongst others, a nonuniform sampling strategy, which is more suited for higher-dimensional inputs and additionally takes into account the topological characteristics of given point sets, and rounding steps which transform axis-parallel boxes, on which the discrepancy is to be tested, into critical test boxes. These critical test boxes provably yield higher discrepancy values and contain the box that exhibits the maximum value of the local discrepancy. We provide comprehensive experiments to test the new algorithm. Our randomized algorithm computes the exact discrepancy frequently in all cases where this can be checked (i.e., where the exact discrepancy of the point set can be computed in feasible time). Most importantly, in higher dimensions the new method behaves clearly better than all previously known methods.