Most practical scheduling applications involve some uncertainty about the arriving times and lengths of jobs. Stochastic online is a well-established model capturing this. Here arrivals occur online, while processing are random. For this model, Gupta, Moseley, Uetz, Xie recently devised an efficient policy for non-preemptive on unrelated machines with objective to minimize expected total weight...

Total weighted tardiness is a measure of customer satisfaction. Minimizing it represents satisfying the general requirement of on-time delivery. In this research, we consider an ant colony optimization (ACO) algorithm to solve the problem of scheduling unrelated parallel machines to minimize total weighted tardiness. The problem is NP-hard in the strong sense. Computational results show that th...