Improved Approximation Schemes for Scheduling Unrelated Parallel Machines

  • Authors:
  • Klaus Jansen;Lorant Porkolab

  • Affiliations:
  • -;-

  • Venue:
  • Mathematics of Operations Research
  • Year:
  • 2001

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Abstract

We consider the problem of schedulingn independent jobs onm unrelated parallel machines where each job has to be processed by exactly one machine, processing jobj on machinei requiresp ijtime units, and the objective is to minimize the makespan, i.e., the maximum job completion time. Focusing on the case whenm is fixed, we present for both preemptive and nonpreemptive variants of the problem fully polynomial approximation schemes whose running times depend only linearly onn. We also study an extension of the problem where processing jobj on machinei incurs a cost ofc ij , and thus there are two optimization criteria: makespan and cost. We show that, for any fixedm, there is a fully polynomial approximation scheme that, given valuesT andC, computes for any fixed e > 0 a schedule in0( n) time with makespan at most (1 + e) T and cost at most (1 + e) C, if there exists a schedule of makespanT and costC.