Competitive analysis of scheduling algorithms for aggregated links

  • Authors:
  • Wojciech Jawor;Marek Chrobak;Christoph Dürr

  • Affiliations:
  • Department of Computer Science, University of California, Riverside;Department of Computer Science, University of California, Riverside;Laboratoire d'Informatique de l'Ecole Polytechnique, CNRS, France

  • Venue:
  • LATIN'06 Proceedings of the 7th Latin American conference on Theoretical Informatics
  • Year:
  • 2006

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Abstract

We study an online job scheduling problem arising in networks with aggregated links. The goal is to schedule n jobs, divided into k disjoint chains, on m identical machines, without preemption, so that the jobs within each chain complete in the order of release times and the maximum flow time is minimized. We present a deterministic online algorithm Block with competitive ratio O$(\sqrt{n/m})$, and show a matching lower bound, even for randomized algorithms. The performance bound for Block we derive in the paper is, in fact, more subtle than a simple competitive analysis, and it shows that in overload conditions (when many jobs are released in a short amount of time), Block's performance is close to the optimum. We also show efficient offline algorithms to minimize maximum flow time and makespan in our model for k = 1, and prove that minimizing the maximum flow time and makespan for k,m ≥ 2 is ${\mathcal NP}$-hard.