Metaheuristics for some discrete-continuous project scheduling problems to maximize the net present value

In this paper a discrete-continuous project scheduling problem with discounted cash flows is considered. Each activity of the project requires for its processing discrete resources and an amount of a continuous, renewable resource. Processing rate of an activity is an increasing function of the amount of the continuous resource allotted to this activity at a time. A positive cash flow is associated with the completion of each activity. The objective is the maximization of the net present value (NPV). A heuristic procedure for allocating the continuous resource is presented. Three local search metaheuristics: simulated annealing (SA), tabu search (TS), and genetic algorithm (GA) are proposed for the defined problem, and compared a basis of a computational experiment. Some conclusions and directions for future research are given.