Scheduling jobs with communication delays: Using infeasible solutions for approximation
 Rolf H. Möhring,
 Markus W. Schäffter,
 Andreas S. Schulz
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Abstract
In the last few years, multiprocessor scheduling with interprocessor communication delays has received increasing attention. This is due to the more realistic constraints in modeling parallel processor systems.
Most research in this vein is concerned with the makespan criterion. We contribute to this work by presenting a new and simple (2−1/m)approximation algorithm for scheduling to minimize the makespan on identical parallel processors subject to seriesparallel precedence constraints and both unit processing times and communication delays. This meets the best known performance guarantee for the same problem but without communication delays. For the same problem but with (nontrivial) release dates, arbitrary precedence constraints, arbitrary processing times and “locally small” communication delays we obtain a simple 7/3approximation algorithm compared with the involved (7/3−4/3m)approximation algorithm by Hanen and Munier for the case with identical release dates.
Another quite important goal in realworld scheduling is to optimize average performance. Very recently, there have been significant developments in computing nearly optimal schedules for several classic processor scheduling models to minimize the average weighted completion time. In this paper, we study for the first time scheduling with communication delays to minimize the average weighted completion time. Specifically, based on an LP relaxation we give the first constantfactor polynomialtime approximation algorithm for scheduling identical parallel processors subject to release dates and locally small communication delays. Moreover, the optimal LP value provides a lower bound on the optimum with the same worstcase performance guarantee.
The common underlying idea of our algorithms is to compute first a schedule that regards all constraints except for the processor restrictions. This schedule is then used to construct a provable good feasible schedule for a given number of processors and as a tool in the analysis of our algorithms. Complementing our approximation results, we also show that minimizing the makespan on an unrestricted number of identical parallel processors subject to seriesparallel precedence constraints, unittime jobs, and zeroone communication delays is NPhard.
 Title
 Scheduling jobs with communication delays: Using infeasible solutions for approximation
 Book Title
 Algorithms — ESA '96
 Book Subtitle
 Fourth Annual European Symposium Barcelona, Spain, September 25–27, 1996 Proceedings
 Pages
 pp 7690
 Copyright
 1996
 DOI
 10.1007/3540616802_48
 Print ISBN
 9783540616801
 Online ISBN
 9783540706670
 Series Title
 Lecture Notes in Computer Science
 Series Volume
 1136
 Series ISSN
 03029743
 Publisher
 Springer Berlin Heidelberg
 Copyright Holder
 SpringerVerlag
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 Authors

 Rolf H. Möhring ^{(1)}
 Markus W. Schäffter ^{(1)}
 Andreas S. Schulz ^{(1)}
 Author Affiliations

 1. Fachbereich Mathematik, Technische Universität Berlin, Sekr. MA 61, Straße des 17. Juni 136, 10623, Berlin, Germany
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