Operations Research Transactions ›› 2022, Vol. 26 ›› Issue (3): 57-74.doi: 10.15960/j.cnki.issn.1007-6093.2022.03.005

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Maximum matching based approximation algorithms for precedence constrained scheduling problems

An ZHANG1, Yong CHEN1, Guangting CHEN2, Zhanwen CHEN1, Qiaojun SHU1, Guohui LIN3,*()   

  1. 1. Department of Mathematics, Hangzhou Dianzi University. Zhejiang, Hangzhou 310018, China
    2. Zhejiang University of Water Resources and Electric Power. Zhejiang, Hangzhou 310018, China
    3. Department of Computing Science, University of Alberta. Edmonton, T6G 2E8 Alberta, Canada
  • Received:2022-01-08 Online:2022-09-15 Published:2022-09-07
  • Contact: Guohui LIN E-mail:guohui@ualberta.ca
  • About author:LIN Guohui, E-mail: guohui@ualberta.ca

Abstract:

We investigate the problem to schedule a set of precedence constrained jobs of unit size on an open-shop or on a flow-shop to minimize the makespan. The precedence constraints among the jobs are presented as a directed acyclic graph called the precedence graph. When the number of machines in the shop is part of the input, both problems are strongly NP-hard on general precedence graphs, but were proven polynomial-time solvable for some special precedence graphs such as intrees. In this paper, we characterize improved lower bounds on the minimum makespan in terms of the number of agreeable pairings among certain jobs and propose approximation algorithms based on a maximum matching among these jobs, so that every agreeable pair of jobs can be processed on different machines simultaneously. For open-shop with an arbitrary precedence graph and for flow-shop with a spine precedence graph, both achieved approximation ratios are $2 - \frac 2m$, where $m$ is the number of machines in the shop.

Key words: job precedence, open-shop, flow-shop, maximum matching, approximation algorithm

CLC Number: