A Hybrid Algorithm for the Unrelated Parallel Machine Scheduling Problem

This work proposes a hybrid algorithm for the unrelated parallel machine scheduling problem with sequence-dependent setup times, aiming to minimize the makespan. The proposed algorithm, named Enhanced Smart General Variable Neighborhood Search (e-SGVNS), combines heuristic and exact optimization strategies to explore the solution space of the problem. The exact strategy works like a local search and consists of applying a mathematical programming formulation based on the time-dependent traveling salesman problem to obtain the optimal solution to the sequencing problem on each machine. In turn, the heuristic strategy explores neighborhoods based on swap and insertion moves. The computational results, performed in benchmark instances from literature, showed that e-SGVNS is competitive when compared to state-of-the-art algorithms.