All-Norm Approximation Algorithms

  • Authors:
  • Yossi Azar;Leah Epstein;Yossi Richter;Gerhard J. Woeginger

  • Affiliations:
  • -;-;-;-

  • Venue:
  • SWAT '02 Proceedings of the 8th Scandinavian Workshop on Algorithm Theory
  • Year:
  • 2002

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Abstract

A major drawback in optimization problems and in particular in scheduling problems is that for every measure there may be a different optimal solution. In many cases the various measures are different lp norms. We address this problem by introducing the concept of an All-norm 驴approximation algorithm, which supplies one solution that guarantees 驴approximation to all lp norms simultaneously. Specifically, we consider the problem of scheduling in the restricted assignment model, where there are m machines and n jobs, each is associated with a subset of the machines and shouldb e assignedto one of them. Previous work considered approximation algorithms for each norm separately. Lenstra et al. [12] showeda 2-approximation algorithm for the problem with respect to the l驴 norm. For any fixed lp norm the previously known approximation algorithm has a performance of 驴(p). We provide an all-norm 2-approximation polynomial algorithm for the restricted assignment problem. On the other hand, we show that for any given lp norm (p 1) there is no PTAS unless P=NP by showing an APX-hardness result. We also show for any given lp norm a FPTAS for any fixedn umber of machines.