Scheduling
In this chapter we discuss scheduling problems and how methods from computational intelligence can be applied to them. We start with general considerations on scheduling problems and discuss variants and some simple solution concepts. After that some stan
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Scheduling
Abstract In this chapter we discuss scheduling problems and how methods from computational intelligence can be applied to them. We start with general considerations on scheduling problems and discuss variants and some simple solution concepts. After that some standard scheduling problems are discussed in more detail followed by a discussion of further scheduling problems relevant to logistics and supply chain management. After that we discus solution approaches from the field of computational intelligence with emphasis on encoding issues, especially in the context of using evolutionary algorithms. The paper ends with a discussion of the importance and success of using respective solution approaches especially from the area of metaheuristics.
5.1
Introduction
The production problems discussed in the previous chapter, deal with planning tasks on a rather rough level. The planning is done for a number of periods such as days, weeks, or months, and it is only planned what should be produced in what amount. The question of how the production is done, i.e. which particular resources are used, is mainly left out. Also the specific times of production activities such as hours and minutes are not considered. When dealing with the planning on a fine time scale it is more important to make sure that the plans are consistent and feasible. For instance, the planning of the resources must respect their given availability and capacities over time. Also, the employees’ working hours, absences, break times, and other required idle times must be considered in the same way as their capacities, e.g. being able to only process one item at a time. Working hours may also apply to machines e.g. because of maintenance breaks or defined servicing periods. Moreover, already planned or dispatched activities influence the availability of the respective resources over time. The detailed planning of jobs, tasks or activities which require specific resources is denoted as scheduling. Instead of resources, the expression “machines” is frequently used in the scheduling terminology irrespective of whether genuine machines are © Springer International Publishing Switzerland 2017 T. Hanne, R. Dornberger, Computational Intelligence in Logistics and Supply Chain Management, International Series in Operations Research & Management Science 244, DOI 10.1007/978-3-319-40722-7_5
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5 Scheduling
involved or not. The result of the planning process, the schedule, is a plan which includes the assignment of the jobs to resources and the specific times when the jobs are to be executed. In some cases it is sufficient to assign the jobs to a pool of resources (without the need to specify an individual resource) or to specify the sequence of jobs to be executed on a resource is adequate for their later execution. However, the basic idea is that jobs are planned on a detailed level which can be used for their final execution. Scheduling problems arise in many different areas. Apart from the planning of production, logistics processes and other
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