Resource-constrained project scheduling: A critical activity reordering heuristic

In this paper, we present a new metaheuristic algorithm for the resource-constrained project-scheduling problem. The procedure is a non-standard implementation of fundamental concepts of tabu search without explicitly using memory structures embedded in a population-based framework. The procedure makes use of a fan search strategy to intensify the search, whereas a strategic oscillation mechanism loosely related to the forward/backward technique provides the necessary diversification. Our implementation employs the topological order (TO) representation of schedules. To explore the TO vector space we introduce three types of moves, two of them based on the concept of relative criticality, and a third one based on multi-pass sampling ideas. The strategic utilisation of probabilities for move construction is another distinguishing feature of our approach. Extensive computational testing with more than 2000 problem instances shows the merit of the proposed solution method.