Multi-project scheduling under mode duration uncertainties

Official URL: http://192.168.1.20/record=b1378244 (Table of Contents)

In this study, we investigate the multi-mode multi-project resource constrained project scheduling problem under uncertainty. We assume a multi-objective setting with 2 objectives : minimizing multi-project makespan and minimizing total sum of absolute deviations of scheduled starting times of activities from their earliest starting times found through simulation. We develop two multi-objective genetic algorithm (MOGA) solution approaches. The first one, called decomposition MOGA, decomposes the problem into two-stages and the other one, called holistic MOGA, combines all activities of each project into one big network and does not require that activities of a project are scheduled consecutively as a benchmark. Decomposition MOGA starts with an initial step of a 2-stage decomposition where each project is reduced to a single macro-activity by systematicaly using artificial budget values and expected project durations. Generated macro-activities may have one or more processing modes called macro-modes. Deterministic macromodes are transformed into random variables by generating disruption cases via simulation. For fitness computation of each MOGA two similar 2-stage heuristics are developed. In both heuristics, a minimum target makespan of overall projects is determined. In the second stage minimum total sum of absolute deviations model is solved in order to find solution robust starting times of activities for each project. The objective value of this model is taken as the second objective of the MOGA's. Computational studies measuring performance of the two proposed solution approaches are performed for different datasets in different parameter settings. When non-dominated solutions of each approach are combined to a final population, overall results show that a larger ratio of these solutions are genetared by decomposition MOGA. Additionally, required computational effort for decompositon MOGA is much less than holistic approach as expected.