Constructive heuristics for selecting and scheduling alternative subgraphs in resource-constrained projects

Abstract

In this paper, we investigate two constructive heuristics based on existing and newly developed priority rules (PRs) for the resource-constrained project scheduling problem with alternative subgraphs (RCPSP-AS). The RCPSP-AS deals with scheduling the selected activities from work packages that can be executed in different ways, resulting in a selection and a scheduling subproblem. The inclusion of alternatives in the project structure implies that even moderate-sized projects become very large, motivating the use of PR-based approaches. In the existing literature, many PRs were already developed for the scheduling subproblem, however, no studies have focused on specific PRs for the selection subproblem. Therefore, we examine the performance of previously developed PRs for the RCPSP-AS and observe that employing a unique PR for each subproblem decreases the project makespan. Based on this knowledge, we develop two constructive heuristics based on well-suited PRs. In the first constructive heuristic, distinct PRs are selected based on the project properties, while several schedules according to different PRs are generated in the second constructive heuristic. Our experiments show that project managers should consider the project properties and select the appropriate selection PRs accordingly in order to minimise the project makespan in the RCPSP-AS.