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APPROX

2009

Springer

2009

Springer

Abstract. Scheduling jobs on unrelated parallel machines so as to minimize the makespan is one of the basic, well-studied problems in the area of machine scheduling. In the ﬁrst part of the paper we prove that the power of preemption, i.e., the ratio between the makespan of an optimal nonpreemptive and an optimal preemptive schedule, is exactly 4. This result is a deﬁnite answer to an important basic open problem in scheduling. The proof of the lower bound is based on a clever iterative construction while the rounding technique we use to prove the upper bound is an adaptation of Shmoys and Tardos’ rounding for the generalized assignment problem. In the second part of the paper we apply this adaptation to the more general setting in which orders, consisting of several jobs, have to be processed on unrelated parallel machines so as to minimize the sum of weighted completion times of the orders. We obtain the ﬁrst constant factor approximation algorithms for the preemptive and non...

Related Content

Added |
25 May 2010 |

Updated |
25 May 2010 |

Type |
Conference |

Year |
2009 |

Where |
APPROX |

Authors |
José R. Correa, Martin Skutella, José Verschae |

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