Two-stage flowshop scheduling with a common second-stage machine
Computers and Operations Research
The strong NP-hardness of two-stage flowshop scheduling with a common second-stage machine
Computers and Operations Research
Parallel machine selection and job scheduling to minimize machine cost and job tardiness
Computers and Operations Research
A Genetic Algorithm for Hybrid Flow-shop Scheduling with Multiprocessor Tasks
Journal of Scheduling
Computers and Operations Research
Scheduling unrelated parallel machines with optional machines and jobs selection
Computers and Operations Research
Minimizing flow-time on a single machine with integer batch sizes
Operations Research Letters
Batching in single operation manufacturing systems
Operations Research Letters
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We study practical scheduling problems with a major decision referring to the number of machines to be used. We focus on a two-stage flexible flowshop, where each job is processed on the first (critical) machine, and then continues to one of the second-stage parallel machines. Jobs are assumed to have identical processing times, and are processed in batches. A setup time is required when starting a new batch. We consider two objective functions: minimum makespan and minimum flowtime. In both cases, a closed form expression for the optimal number of machines to be used is introduced, and a unique and unusual sequence of decreasing batch sizes is shown to be optimal.