In this paper, the focus of discussion is resource constrained project scheduling where
there is a single renewable resource to consider. Such projects occur frequently in
practice: such as use of labour in construction projects, or constraints on number of
programmers to carry out a software project. Usually the manpower needs are estimated
in units such as work-hours or work-days. The multi-mode consists essentially of how
many people can be employed to finish an activity. For example, if it takes 72 workhours
to finish an activity, one mode may be with 6 workers, who will finish the work in
12 hours. However if 10 workers take up the project, it may take 8 hours. There may be
minimum and maximum limits on the number of workers to be assigned. Thus the main
concern is with the work content Wi for each activity i, and if rim and dim are the resource
requirements and durations for some particular mode m, rim dim ³ Wi : only efficient
modes are considered, where higher resource requirements result in lower durations of
activities. No pre-emption is allowed. This problem is also called the discrete
time/resource trade-off problem. The beam search technique is applied to generate a
makespan minimising schedule for such projects