The objective is to find a schedule which minimizes the maximum completion time or makespan. The problem is NP-hard in the strong sense, even when there are two machines at the first stage. Several lower bounds are derived and are tested in a branch and bound algorithm. Also, constructive heuristics are presented, and a descent algorithm is proposed. Extensive computational tests with up to 250 jobs, and up to 10 machines in the first stage, indicate that some of the heuristics consistently generate optimal or near-optimal solutions.
E is a set of edges.
We study a problem of cyclic no-wait scheduling of identical parts on m sequential machines. A number of robots are used to transport the parts from one machine to another. Given a set of tasks to be assigned to a group of agents and the cost of performing each task by each agent, the model allocates tasks to agents to minimize the total cost subject to the availability of a single resource type. The single resource is consumed by the agents when performing these tasks. In this paper, we add the impact of time to the model assuming that each task has a due date, and inventory cost as well as shortage cost is incurred when a task is finished ahead or after its due date, respectively.