The trade-off between stability and makespan in resource-constrained project scheduling

During the last decade, considerable research efforts in the project scheduling literature have concentrated on resource-constrained project scheduling under uncertainty. Most of this research focuses on protecting the project due date against disruptions during execution. Few efforts have been made to protect the starting times of intermediate activities. In this paper, we develop a heuristic algorithm for minimizing a stability cost function (weighted sum of deviations between planned and realized activity starting times). The algorithm basically proposes a clever way to scatter time buffers throughout the baseline schedule. We provide an extensive simulation experiment to investigate the trade-off between quality robustness (measured in terms of project duration) and solution robustness (stability). We address the issue whether to concentrate safety time in so-called project and feeding buffers in order to protect the planned project completion time or to scatter safety time throughout the baseline schedule in order to enhance stability.