Robustness of the minimum makespan schedules in a job shop

A measure of robustness for the minimum makespan schedules in a job shop has been proposed. In general, more than one optimal solution exists for makespan minimization problems. It is important to select the best one based on a secondary criterion. The paper focuses on the uncertainty of processing times, and proposes a sensitivity measure for the delay of completion times by one time unit. Based on this sensitivity the robustness of the schedule is defined as being the maximum value. A branch and bound approach to obtaining the most robust schedule among minimum makespan schedules has been developed. Both the most and least robust schedules are obtained and the differences of the robustness are presented for 10 test problems