CHAPTER VI - RESOURCE CONSTRAINED SCHEDULING METHODS

Abstract

This chapter reviews resource constrained scheduling methods. The problem of scheduling activities under limited resources and precedence constraints is a relatively common one that has received considerable attention in the literature. This problem belongs to a class of problems for which currently optimal solution can be found only for unrealistically small problems of marginal practical value. For larger problems, a number of heuristic algorithms are available. There is considerable conflicting evidence regarding the relative merit of the heuristics used in these algorithms, and there are few, if any, guidelines available regarding the choice of a heuristic algorithm. The chapter presents a general flowchart of a scheduling algorithm utilizing dispatching rules or urgency factors. The basic premise of this algorithm is the requirement that all activities are to start as early as possible. When several activities are competing for a limited amount of resources, activities are selected one by one to start in accordance with some priority or urgency scheme. There are two approaches to the calculation of these urgency factors: (1) they may either be calculated prior to the scheduling process—static scheduling—or (2) they may be recalculated throughout the scheduling process as delays of activities cause a change in actual slack and finish times—dynamic scheduling.