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Mathematical Problems in Engineering
Volume 2013, Article ID 343287, 7 pages
Research Article

WSPT's Competitive Performance for Minimizing the Total Weighted Flow Time: From Single to Parallel Machines

1Department of Automation, Xiamen University, Xiamen, China
2Center for Cloud Computing and Big Data, Xiamen University, Xiamen, China

Received 9 June 2013; Accepted 5 September 2013

Academic Editor: Dane Quinn

Copyright © 2013 Jiping Tao and Tundong Liu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We consider the classical online scheduling problem over single and parallel machines with the objective of minimizing total weighted flow time. We employ an intuitive and systematic analysis method and show that the weighted shortest processing time (WSPT) is an optimal online algorithm with the competitive ratio of for the case of single machine, and it is ( )-competitive for the case of parallel machines , where P is the ratio of the longest to the shortest processing time.