On the Complexities of the Optimal Rounding Problems of Sequences and Matrices

  • Authors:
  • Tetsuo Asano;Tomomi Matsui;Takeshi Tokuyama

  • Affiliations:
  • -;-;-

  • Venue:
  • SWAT '00 Proceedings of the 7th Scandinavian Workshop on Algorithm Theory
  • Year:
  • 2000

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Abstract

In this paper, we discuss the problem of computing an optimal rounding of a real sequence (resp. matrix) into an integral sequence (resp. matrix). Our criterion of the optimality is to minimize the weighted l∞ distance Dist∞F, w (A, B) between an input sequence (resp. matrix) A and the output B. The distance is dependent on a family F of intervals (resp. rectangular regions) for the sequence rounding (resp. matrix rounding) and positive valued weight function w on the family. We give efficient polynomial time algorithms for the sequence-rounding problem, one for the weighted l∞ distance, and the other for any weight function w, for any family F of intervals. We give an algorithm that computes a matrix rounding with an error at most 1:75 with respect to the unweighted l∞ distance associated with the family W2 of all 2 × 2 square regions, whereas we prove that it is NP-hard to compute an approximate solution to the matrix-rounding problem with an approximate ratio smaller than 2 for the same distance.