Integrating Mixed Integer Programming and Local Search : A Case Study on Job-Shop Scheduling Problems

Recent work on solving job-shop scheduling problems with earliness and tardiness costs has led to several hybrid algorithms that are more effective than any one method alone. In particular, these hybrid methods have been found to be more effective than pure mixed integer programming (MIP) approaches. This paper takes a fresh look at MIP formulations in light of several new MIP strategies for producing better feasible solutions. We find that a new MIP approach that is a hybrid method in spirit only, since it only exploits MIP methods but is inspired by concepts from local search, produces highly favorable results. We also identify two key factors that explain the variation of performance of a previous hybrid method on two different