Efficient dispatching rules for scheduling in a job shop

We consider in this article the development of new and efficient dispatching rules with respect to the objectives of minimizing mean flowtime, maximum flowtime, variance of flowtime, proportion of tardy jobs, mean tardiness, maximum tardiness and variance of tardiness. We present five new dispatching rules for scheduling in a job shop. Some of these rules make use of the process time and work-content in the queue of the next operation on a job, by following a simple additive approach, in addition to the arrival time and dynamic slack of a job. An extensive and rigorous simulation study has been carried out to evaluate the performance of the proposed dispatching rules against those rules such as the SPT, WINQ, FIFO and COVERT, and the best existing rule. It has been observed that the proposed rules are not only simple in structure, but also quite efficient in minimizing several measures of performance. The important aspects of the results of experimental investigation are also discussed in detail.