Improving the performance of the ATC dispatch rule by using workload data to determine the lookahead parameter value

The apparent tardiness cost heuristic is one of the best performing dispatch rules for the weighted tardiness scheduling problem. This heuristic uses a lookahead parameter that has previously been set at a fixed value. We propose two different approaches for determining an appropriate value for this parameter. In the first approach, a function is used to map several instance statistics into an adequate value. The second method uses the characteristics of the current workload to determine an appropriate value each time a scheduling decision is to be made. The computational results show that the new procedures outperform the fixed value approach over a wide range of test instances and workload characteristics. The new versions are therefore suited for application in scheduling systems, since they are capable of adjusting themselves to changes in the workload, and provide important savings over the current fixed value implementations.