Optimal on-line algorithms for the uniform machine scheduling problem with ordinal data

  • Authors:
  • Zhiyi Tan;Yong He;Leah Epstein

  • Affiliations:
  • Department of Mathematics, State Key Lab of CAD and CG, Zhejiang University, Hangzhou 310027, PR China;Department of Mathematics, State Key Lab of CAD and CG, Zhejiang University, Hangzhou 310027, PR China;School of Computer Science, The Interdisciplinary Center, P.O. Box 167, 46150 Herzliya, Israel

  • Venue:
  • Information and Computation
  • Year:
  • 2005

Quantified Score

Hi-index 0.00

Visualization

Abstract

In this paper, we consider an ordinal on-line scheduling problem. A sequence of n independent jobs has to be assigned non-preemptively to two uniformly related machines. We study two objectives which are maximizing the minimum machine completion time, and minimizing the lp, norm of the completion times. It is assumed that the values of the processing times of jobs are unknown at the time of assignment. However it is known in advance that the processing times of arriving jobs are sorted in a non-increasing order. We are asked to construct an assignment of all jobs to the machines at time zero, by utilizing only ordinal data rather than actual magnitudes of jobs. For the problem of maximizing the minimum completion time we first present a comprehensive lower bound on the competitive ratio, which is a piecewise function of machine speed ratio s. Then, we propose an algorithm which is optimal for any s ≥ 1. For minimizing the lp norm, we study the case of identical machines (s = 1) and present tight bounds as a function of p.