Abstract
Twofold Look-Ahead Search is proposed as a general-purpose technique based on the human problem solving process, utilizing the superior calculation ability of computers. In the search process, nodes are expanded in a tree using two look-ahead features : a local look-ahead which foresees states in the near future with high accuracy, and a global look-ahead which provides a rough evaluation of goal states. This method is applied to job shop scheduling, and the schedules generated are compared with those of dispatching rules and an optimization method. Results showed the proposed method to have high performance, giving nearly optimal solutions and being much superior to the dispatching rules. In addition, the effectiveness of the twofold look-ahead approach in the search process is also confirmed through comparisons of several variations of the proposed method.
