A combinatorial Benders decomposition algorithm for parallel machine scheduling with working-time restrictions

This paper addresses a parallel machine scheduling problem with restrictions on employees’ working-times and break times. Tasks must be processed by employees nonpreemptively on unrelated parallel machines with different thresholds that specify for each employee the maximum total and consecutive working-time, and the minimum break time. The objective is to minimize the weighted sum of the makespan, the machine depreciation costs, and the labor costs. To solve this problem, a mixed integer linear programming model is formulated, and two different decomposition-based exact algorithms are implemented as well as a list scheduling (LS)-based heuristic method. Extensive computational experiments are performed on randomly generated instances, and the results demonstrate the efficiency of our proposed combinatorial Benders decomposition approach.