A primal-dual approximation algorithm for min-sum single-machine scheduling problems

  • Authors:
  • Maurice Cheung;David B. Shmoys

  • Affiliations:
  • School of Operations Research & Information Engineering, Cornell University, Ithaca NY;School of Operations Research & Info. Engineering & Computer Science Dept., Cornell University, Ithaca NY

  • Venue:
  • APPROX'11/RANDOM'11 Proceedings of the 14th international workshop and 15th international conference on Approximation, randomization, and combinatorial optimization: algorithms and techniques
  • Year:
  • 2011

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Abstract

We consider the following single-machine scheduling problem, which is often denoted 1||Σfj: we are given n jobs to be scheduled on a single machine, where each job j has an integral processing time pj, and there is a nondecreasing, nonnegative cost function fj (Cj) that specifies the cost of finishing j at time Cj; the objective is to minimize n Σj=1n fj (Cj). Bansal & Pruhs recently gave the first constant approximation algorithm and we improve on their 16-approximation algorithm, by giving a primal-dual pseudo-polynomial-time algorithm that finds a solution of cost at most twice the optimal cost, and then show how this can be extended to yield, for any ε 0, a (2 + ε)-approximation algorithm for this problem. Furthermore, we generalize this result to allow the machine's speed to vary over time arbitrarily, for which no previous constant-factor approximation algorithm was known.