Surrogate gradient algorithm for Lagrangian relaxation
Journal of Optimization Theory and Applications - Special issue in honor of Yu-Chi Ho
Tabu search for total tardiness minimization in flowshop scheduling problems
Computers and Operations Research
New bundle methods for solving Lagrangian relaxation dual problems
Journal of Optimization Theory and Applications
Computers and Operations Research
Computers and Operations Research
Modeling realistic hybrid flexible flowshop scheduling problems
Computers and Operations Research
Computers and Operations Research
Scheduling with an outsourcing option on both manufacturer and subcontractors
Computers and Operations Research
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In this paper, we address a new Lagrangian relaxation (LR) method for solving the hybrid flowshop scheduling problem to minimize the total weighted tardiness. For the conventional LR, the problem relaxing machine capacity constraints can be decomposed into individual job-level subproblems which can be solved by dynamic programming. The Lagrangian dual problem is solved by the subgradient method. In this paper, a Lagrangian relaxation with cut generation is proposed to improve the Lagrangian bounds for the conventional LR. The lower bound is strengthened by imposing additional constraints for the relaxed problem. The state space reductions for dynamic programming for subproblems are also incorporated. Computational results demonstrate that the proposed method outperforms the conventional LR method without significantly increasing the total computing time.