Minimizing the sum of the job completion times in the two-machine flow shop by Lagrangian relaxation
Annals of Operations Research
Stronger Lagrangian bounds by use of slack variables: applications to machine scheduling problems
Mathematical Programming: Series A and B
Exact, Approximate, and Guaranteed Accuracy Algorithms for the Flow-Shop Problem n/2/F/ F
Journal of the ACM (JACM)
A matheuristic approach for the total completion time two-machines permutation flow shop problem
EvoCOP'11 Proceedings of the 11th European conference on Evolutionary computation in combinatorial optimization
An assignment-based lower bound for a class of two-machine flow shop problems
Computers and Operations Research
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For the $$\mathcal{NP}$$-hard problem of scheduling n jobs in a two-machine flow shop so as to minimize the total completion time, we present two equivalent lower bounds that are computable in polynomial time. We formulate the problem by the use of positional completion time variables, which results in two integer linear programming formulations with O(n 2) variables and O(n) constraints. Solving the linear programming relaxation renders a very strong lower bound with an average relative gap of only 0.8% for instances with more than 30 jobs. We further show that relaxing the formulation in terms of positional completion times by applying Lagrangean relaxation yields the same bound, no matter which set of constraints we relax.