Best-Possible Online Algorithms for Single Machine Scheduling to Minimize the Maximum Weighted Completion Time

2018 ◽  
Vol 35 (06) ◽  
pp. 1850048
Author(s):  
Xing Chai ◽  
Lingfa Lu ◽  
Wenhua Li ◽  
Liqi Zhang

In this paper, we consider the online single machine scheduling problem to minimize the maximum weighted completion time of the jobs. For the preemptive problem, we show that the LW (Largest Weight first) rule yields an optimal schedule. For the non-preemptive problem, Li [Li, W (2015). A best possible online algorithm for the parallel-machine scheduling to minimize the maximum weighted completion time. Asia-Pacific Journal of Operational Research, 32(4), 1550030 (10 pages)] presented a lower bound 2, and then provided an online algorithm with a competitive ratio of 3. In this paper, we present two online algorithms with the best-possible competitive ratio of [Formula: see text] for the non-preemptive problem.

2017 ◽  
Vol 34 (05) ◽  
pp. 1750022
Author(s):  
Lingfa Lu ◽  
Liqi Zhang

In this paper, we consider the online single machine scheduling problem to minimize the maximum starting time of the jobs. For the non-preemptive model, we show that there is no determined or randomized online algorithm with a bounded competitive ratio. For the preemption-resume model, we show that the well-known SRPT rule yields an optimal schedule. For the preemption-restart model, we show that any determined online algorithm has a competitive ratio of at least 2 and present an online algorithm with the best-possible competitive ratio of 2.


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