Approximation in Preemptive Stochastic Online Scheduling

  • Nicole Megow
  • Tjark Vredeveld
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4168)


We present a first constant performance guarantee for preemptive stochastic scheduling to minimize the sum of weighted completion times. For scheduling jobs with release dates on identical parallel machines we derive a policy with a guaranteed performance ratio of 2 which matches the currently best known result for the corresponding deterministic online problem.

Our policy applies to the recently introduced stochastic online scheduling model in which jobs arrive online over time. In contrast to the previously considered nonpreemptive setting, our preemptive policy extensively utilizes information on processing time distributions other than the first (and second) moments. In order to derive our result we introduce a new nontrivial lower bound on the expected value of an unknown optimal policy that we derive from an optimal policy for the basic problem on a single machine without release dates. This problem is known to be solved optimally by a Gittins index priority rule. This priority index also inspires the design of our policy.


Schedule Problem Optimal Policy Release Date Parallel Machine Single Machine 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • Nicole Megow
    • 1
  • Tjark Vredeveld
    • 2
  1. 1.Technische Universität Berlin, Institut für MathematikBerlinGermany
  2. 2.Department of Quantitative EconomicsMaastricht UniversityMD MaastrichtThe Netherlands

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