Abstract
We consider the well-known problem of schedulingn independent tasks nonpre-emptively onm identical processors with the aim of minimizing the makespan. Coffman, Garey and Johnson [1] described an algorithm, MULTIFIT, based on techniques from binpacking, with better worst performance than the LPT algorithm and proved that it satisfies a bound of 1.22. It has been claimed by Friesen [2] that this bound can be improved upon to 1.2. However, we found his proof, in particular his lemma 4.9, difficult to understand. Yue, Kellerer and Yu [3] have presented the bound 1.2 in a simpler way. In this paper, we prove first that the bound cannot exceed 13/11 and then prove that it is exactly 13/11.
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References
E.G. Coffman, M.R. Garey and D.S. Johnson, An application of bin-packing to multiprocessor scheduling, SIAM J. Comput. 7(1978)1–17.
D.K. Friesen, Tighter bounds for the MULTIFIT processor scheduling algorithm, SIAM J. Comput. 13(1984)179–181.
M. Yue, H. Kellerer and Z. Yu, A simple proof of the inequalityR M (MF(k))≤1.2+1/2k in multiprocessor scheduling, Report No. 124, Institut für Mathematik, Technische Universität Graz (1988), pp. 1–10.
E.G. Coffman, Jr., etal., Approximation algorithms for bin-packing—an updated survey, in:Algorithm Design and Computer System Design, ed. G. Ausiello et al., CISM Courses and Lectures 284 (Springer, Vienna), pp. 49–106.
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This work was done while the author was visiting the Institut für Operations Research, Universität Bonn. The author expresses his thanks to the Institut for the support given to him in the preparation and completion of the work.
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Yue, M. On the exact upper bound for the multifit processor scheduling algorithm. Ann Oper Res 24, 233–259 (1990). https://doi.org/10.1007/BF02216826
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DOI: https://doi.org/10.1007/BF02216826