Abstract
This paper addresses a decision problem related to simultaneously scheduling the tasks in a project and assigning the staff to these tasks, taking into account that a task can be performed only by employees with certain skills, and that the length of each task depends on the number of employees assigned. This type of problems usually appears in service companies, where both tasks scheduling and staff assignment are closely related. An integer programming model for the problem is proposed, together with some extensions to cope with different situations. Additionally, the advantages of the controllable processing times approach are compared with the fixed processing times. Due to the complexity of the integrated model, a simple GRASP algorithm is implemented in order to obtain good, approximate solutions in short computation times.
Highlights
The lead time required to carry out a project—project makespan—has turned to be one of the main sources of competitive advantage for companies
The project scheduling and staff assignment (PSSA)-controllable processing times (CPT) model is implemented using the software Gurobi Optimizer 4.51 and ILOG CPLEX 12.4 and the greedy randomized adaptive search procedure (GRASP) heuristic is coded in C#
The integer programming problem presented in this paper was solved by the software Gurobi Optimizer 4.5 for instances based on the sets j30 and j60 of the PSPLIB classical instances [50], which are a reference test beds for project scheduling
Summary
The lead time required to carry out a project—project makespan—has turned to be one of the main sources of competitive advantage for companies (see, e.g., [1, 2]). Staff assignment is essential in a project [6] and it can be defined as the allocation of company workers to different tasks. It is essential that a particular employee is available at that time; otherwise the realization of such task should be postponed until the employee becomes available and, staff assignment directly influences task schedule. Due to the importance of the scheduling and the assignment in a project environment and since both are very related, it is critical to address both problems in an integrated manner. The majority of scheduling problems in the literature consider fixed processing times [11] and most of the rest assume that processing times depend linearly on the amount of resources assigned [12]. As lead times strongly depend on the processing times of the task, and since the processing time of a task depends on the number of employees assigned to this task, in this paper we explicitly take into account this relationship
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
