Development and analysis of cost-based dispatching rules for job shop scheduling

Most dispatching rules for job shop scheduling assume that the cost of holding per unit time is the same for all jobs. Likewise, it is assumed that the cost of tardiness per unit time is the same for all jobs. In other words, it is implied that the holding cost of a job is directly proportional to its flowtime, and the tardiness cost of a job is directly proportional to its positive lateness. These assumptions may not hold good in all situations. Some attempts were made to overcome this deficiency, and a couple of dispatching rules were proposed by considering different weights or penalties for different jobs. However, these dispatching rules assume that the holding and tardiness costs per unit time of a given job are the same, even though these costs may differ from job to job in practice. In this study, we propose dispatching rules by explicitly considering different weights and penalties for flowtime and tardiness of a job. Many measures of performance related to weighted flowtime and weighted tardiness of jobs are considered, and the results of simulation are presented.