Search

Many dominance relations have been established in the literature for scheduling problems where they are mainly used in implicit enumeration techniques to further reduce the search space for finding an optimal solution. In this paper, we propose a novel method for discovering dominance relations for scheduling problems. We discover dominance relations by using an evolutionary algorithm. The proposed method of empirically discovering dominance relations can be used for any scheduling problem. After the description of the method, we apply it to a specific scheduling problem. The specific problem is the multimedia data objects scheduling problem for WWW applications which can be modelled as the two-machine flowshop problem of minimizing maximum lateness with separate setup times. The performances of the dominance relations obtained by the proposed method as well as the existing four dominance relations in literature are analysed. The results of the computational experiments show that the proposed method is quite efficient. [ABSTRACT FROM AUTHOR]

The problem of scheduling on a multi-stage parallel-processor architecture in computer centres is addressed with the objective of minimizing average completion time of a set of requests. The problem is modelled as a flexible flowshop problem for which few heuristics exist in the flowshop scheduling literature. A new three-phase heuristic is proposed in this paper. An extensive computational experiment has been conducted to compare the performance of the existing heuristics and the proposed heuristic. The results indicate that the proposed heuristic significantly outperforms the existing ones. More specifically, the overall average error of the best existing heuristic is about five times that of the proposed heuristic while the overall average CPU time of the proposed heuristic is about half of the best existing one. More importantly, as the number of requests increases, the CPU time of the proposed heuristic decreases considerably (compared to the best existing heuristic) while the ratio of the error (of the best existing to the proposed heuristic) of about five times remains almost the same. [ABSTRACT FROM AUTHOR]