Preemptive and Non-preemptive On-line Algorithms for Scheduling with Rejection on Two Uniform Machines

  • Authors:

  • G. Dósa;Y. He

  • Affiliations:

  • Department of Mathematics, University of Veszprém, 8201, Veszprém, Hungary;Department of Mathematics and State Key Lab of CAD & CG, Zhejiang University, 310027, Hangzhou, P. R. China

  • Venue:
  • Computing
  • Year:
  • 2006

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Abstract

In this paper, we consider the problem of on-line scheduling a job sequence on two uniform machines. A job can be either rejected, in which case we pay its penalty, or scheduled on machines, in which case it contributes its processing time to the makspan of the constructed schedule. The objective is to minimize the sum of the makespan of the schedule for all accepted jobs and the penalties of all rejected jobs. Both preemptive and non-preemptive versions are considered. For the preemptive version, we present an optimal on-line algorithm with a competitive ratio ** for any s≥1, where s is the machine speed ratio. For the non-preemptive version, we present an improved lower bound. Moreover, as an optimal algorithm for s≥1.6180 is known, we present a modified version of the known algorithm, and show that it becomes optimal for any 1.3852≤ss