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The power of reordering for online minimum makespan scheduling
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Englert, Matthias, Özmen, Deniz and Westermann, Matthias (2014) The power of reordering for online minimum makespan scheduling. SIAM Journal on Computing, Volume 43 (Number 3). pp. 1220-1237. doi:10.1137/130919738
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Official URL: http://dx.doi.org/10.1137/130919738
Abstract
In the classic minimum makespan scheduling problem, we are given an input sequence of jobs with processing times. A scheduling algorithm has to assign the jobs to m parallel machines. The objective is to minimize the makespan, which is the time it takes until all jobs are processed. In this paper, we consider online scheduling algorithms without preemption. However, we do not require that each arriving job has to be assigned immediately to one of the machines. A reordering buffer with limited storage capacity can be used to reorder the input sequence in a restricted fashion so as to schedule the jobs with a smaller makespan. This is a natural extension of lookahead. We present an extensive study of the power and limits of online reordering for minimum makespan scheduling. As a main result, we give, for $m$ identical machines, tight and, in comparison to the problem without reordering, much improved bounds on the competitive ratio for minimum makespan scheduling with reordering buffers. Depending on m, the achieved competitive ratio lies between 4/3 and 1.4659. This optimal ratio is achieved with a buffer of size Theta(m). We show that larger buffer sizes do not result in an additional advantage and that a buffer of size Omega(m) is necessary to achieve this competitive ratio. Further, we present several algorithms for different buffer sizes. For m uniformly related machines, we give a scheduling algorithm that achieves a competitive ratio of 2 with a reordering buffer of size m. Considering that the best known competitive ratio for uniformly related machines without reordering is 5.828, this result further emphasizes the power of online reordering.
| Item Type: | Journal Article | ||||||||
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| Subjects: | Q Science > QA Mathematics > QA76 Electronic computers. Computer science. Computer software | ||||||||
| Divisions: | Faculty of Science > Computer Science | ||||||||
| Library of Congress Subject Headings (LCSH): | Computer scheduling -- Mathematical models | ||||||||
| Journal or Publication Title: | SIAM Journal on Computing | ||||||||
| Publisher: | Society for Industrial and Applied Mathematics | ||||||||
| ISSN: | 1095-7111 | ||||||||
| Official Date: | 27 May 2014 | ||||||||
| Dates: |
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| Volume: | Volume 43 | ||||||||
| Number: | Number 3 | ||||||||
| Number of Pages: | 18 | ||||||||
| Page Range: | pp. 1220-1237 | ||||||||
| DOI: | 10.1137/130919738 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Access rights to Published version: | Restricted or Subscription Access | ||||||||
| Funder: | Deutsche Forschungsgemeinschaft (DFG), University of Warwick. Centre for Discrete Mathematics and Its Applications, Engineering and Physical Sciences Research Council (EPSRC) | ||||||||
| Grant number: | WE 2842/1 (DFG), EP/D063191/1 (EPSRC) | ||||||||
| Embodied As: | 1 |
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