a model to solve project scheduling and staff assignment problems

the allocation of human resources to project activities in order to schedule them is one of the closest states to the actual conditions of scheduling problems. but regarding the fact that this problem belongs to the class of np-hard problems; so far the exact methods have only been able to solve the small size problems. in this study, the renewable resources are humans in a way that every staff with multiple skills is only able to satisfy one of activities’ skill requirements at a specific time. in this paper, defining the efficiency degrees for the staff, a mathematical programming model is presented for simultaneous solving of the two problems. since this problem belongs to np-hard problems, a meta-heuristic differential evolution algorithm is developed for solving real-world cases. the results prove the efficiency of the algorithm in simultaneous solving of project scheduling and human resources allocation problems.