A Hybrid Method for the Multi-Mode Resource-Constrained Project Scheduling Problem with Strip Packing like Resource Constraints

This paper presents an improved hybrid algorithm for the multi-mode resource-constrained project scheduling problem with strip packing like resource constraints. In the proposed primary-secondary criteria algorithm, a resource-constrained project is characterized by its "best" schedule, where best means a makespan minimal resource-constrained schedule with dedicated resource demand servicing for which the resource profiles approach the ideal rectangular shape as much as possible. In the traditional resource-constrained project scheduling the activities are not necessarily assigned to the same resource units over their processing times, so an "optimal" solution may be far from the reality, because the machine (workforce) changing always needs extra time and cost. In the improved model the activities are assigned to dedicated resource units over their processing times. The applied resource leveling-smoothing procedure, preferring the continuous work, tries to minimize the number of starting-restarting events of dedicated resource units on the set of resource-feasible activity movements fixing the makespan, the modes, and the scheduling order. To illustrate the essence and viability of the proposed approach, we present detailed computational results for a medium size project instance.