PRIORITY UPDATE INTERVALS AND ANOMALIES IN DYNAMIC RATIO TYPE JOB SHOP SCHEDULING RULES

Dynamic priority dispatching rules in job shops require the computation of all job priorities in a work center queue every time a machine in the work center becomes idle. This is extremely costly. Alternative priority update procedures are studied and comparative results in terms of performance measures and costs are reported. Ease of implementation of the various procedures in a real world job shop environment is discussed. A second problem related to an anomaly in ratio type dynamic priority rules is also studied; a simple modification to remove the anomaly is suggested and the performances of the ″old″ and ″modified″ procedures are compared.