An exact algorithm for the flexible multilevel project scheduling problem

•A novel algorithm is proposed to flexible multilevel project scheduling problems.•It extends traditional multilevel scheduling to handle flexible project portfolios.•A matrix-based model is proposed to model flexible multilevel projects. Single project scheduling has received far more attention than have schedules of project portfolios or multi-projects. This lack of scheduling techniques is especially true for flexible portfolios, such as agile, hybrid and extreme project portfolios, which require flexible project structures. While multilevel project scheduling algorithms already exist for deterministic multilevel project structures, they are not able to handle flexible structures. This short paper wants to fill this gap. A matrix-based multilevel multimode project scheduling (M4PSP) algorithm is proposed to schedule flexible multilevel projects.