The three-machine flowshop scheduling problem to minimize total completion time is studied where setup times are treated as separate from processing times. Setup and processing times of all jobs on all machines are unknown variables before the actual occurrence of these times. The lower and upper bounds for setup and processing times of each job on each machine is the only information that is available. In such a scheduling environment, there may not exist a unique schedule that remains optimal for all possible realizations of setup and processing times. Therefore, it is desired to obtain a set of dominating schedules (which dominate all other schedules) if possible. The objective for such a scheduling environment is to reduce the size of dominating schedule set. We obtain global and local dominance relations for a three-machine flowshop scheduling problem. Furthermore, we illustrate the use of dominance relations by numerical examples and conduct computational experiments on randomly generated problems to measure the effectiveness of the developed dominance relations. The computational experiments show that the developed dominance relations are quite helpful in reducing the size of dominating schedules.
1. Allahverdi, A., Two-machine flowshop scheduling problem to minimize total completion time with bounded setup and processing times, International Journal of Production Economics 103 (2006), 386–400.
2. Allahverdi, A., Minimizing mean flowtime in a two-machine flowshop with sequence independent setup times, Computers & Operations Research 27 (2000), 111–127.
3. Allahverdi, A., and Al-Anzi, F., A branch-and-bound algorithm for three-machine flowshop scheduling problem to minimize total completion time with separate setup times, European Journal of Operational Research 169 (2006), 767–780.
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