Scheduling in resource-constrained multiple projects to minimise the weighted tardiness and weighted earliness of projects

Determination of a schedule to complete projects exactly on their assigned due-dates is considered a major objective for many researchers and practicing managers. In some situations, projects that are completed before their due-dates are not handed over to the project owner or customer, but held with the organisation that executes the project, while the projects that are completed after their due-dates are considered tardy and result in loss of customer goodwill and penalty. The current study, therefore, addresses the problem of scheduling resource-constrained multiple projects with the consideration of projects having different relative earliness and relative tardiness costs. In the first phase of the study, relative costs (or weights) for tardiness of projects is considered, and the scheduling rules are presented in order to minimise the weighted tardiness of projects. In the second phase of the study, the objective considered is the minimisation of the sum of weighted earliness and weighted tardiness of projects, and the scheduling rules are presented by incorporating the relative costs of earliness and tardiness of projects. Computational studies have been conducted separately for both phases of the current study; the performance of the scheduling rules has been observed independently and the results of the computational study have been reported.