Considering a dynamic single machine problem in which operations cannot be split, the authors first develop a decision theory based heuristic called DT-TD (Decision Theory-Tactically Delayed) of computational complexity O(n2). Using a simple look-ahead procedure, it produces tactically delayed (TD) schedules. The authors then develop a branch-and-bound (BB) algorithm (which uses DT-TD to obtain the initial upper bound) to obtain the optimum schedule. The optimum schedules are examined to identify conditions where TD schedules are necessary. Results based on 540 test problems suggest that TD schedules are important, for job shop scheduling under the range of conditions examined, when due dates are arbitrary and utilization is low. Additional test results indicate that the difference between the optimum schedule and the optimum non-delay schedule could be substantial. Finally, the performance of the DT-TD heuristic is analyzed by comparing its solution to the optimum solution obtained using the BB algorithm. The results indicate that the DT-TD heuristic is effective.
