Unrelated parallel machine scheduling with resource dependent processing times

  • Authors:
  • Alexander Grigoriev;Maxim Sviridenko;Marc Uetz

  • Affiliations:
  • Maastricht University, Quantitative Economics, Maastricht, The Netherlands;IBM T. J. Watson Research Center, Yorktown Heights, NY;Maastricht University, Quantitative Economics, Maastricht, The Netherlands

  • Venue:
  • IPCO'05 Proceedings of the 11th international conference on Integer Programming and Combinatorial Optimization
  • Year:
  • 2005

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Abstract

We consider unrelated parallel machine scheduling problems with the objective to minimize the schedule makespan. In addition to its machine-dependence, the processing time of any job is also dependent on the usage of a scarce renewable resource. An amount of k units of that resource, e.g. workers, can be distributed over the jobs in process, and the more of that resource is allocated to a job, the smaller its processing time. The model generalizes the classical unrelated machine scheduling problem, adding a resource-time tradeoff. It is also a natural variant of a generalized assignment problem studied previously by Shmoys and Tardos, the difference lying in the fact the resource is renewable and not a total budget constraint. We use a two-phased LP rounding technique to assign resources to jobs and jobs to machines. Combined with Graham's list scheduling, we thus prove the existence of a $(4+2\sqrt{2})$-approximation algorithm. We show how our approach can be adapted to scheduling problems with dedicated machines as well, with an improvement of the performance bound to $(3+2\sqrt{2})$. Moreover, we derive a lower bound of 2 for the employed LP-based analysis, and we prove a (3/2)-inapproximability result.