Exact makespan minimization of unrelated parallel machines

We study methods for the exact solution of the unrelated parallel machine problem with makespan minimization, generally denoted as $R||C_\text{max}$. Our original application arises from the automotive assembly process where tasks needs to be distributed among several robots. This involves the solut...

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Bibliographic Details
Main Authors: Åblad, Edvin, Strömberg, Ann-Brith, Spensieri, Domenico
Format: Article
Language:English
Published: Université de Montpellier 2021-05-01
Series:Open Journal of Mathematical Optimization
Subjects:
Online Access:https://ojmo.centre-mersenne.org/articles/10.5802/ojmo.4/
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Summary:We study methods for the exact solution of the unrelated parallel machine problem with makespan minimization, generally denoted as $R||C_\text{max}$. Our original application arises from the automotive assembly process where tasks needs to be distributed among several robots. This involves the solutions of several $R||C_\text{max}$ instances, which proved hard for a MILP solver since the makespan objective induces weak LP relaxation bounds. To improve these bounds and to enable the solution of larger instances, we propose a branch–and–bound method based on a Lagrangian relaxation of the assignment constraints. For this relaxation we derive a criterion for variable fixing and prove the zero duality gap property for the case of two parallel machines. Our computational studies indicate that the proposed algorithm is competitive with state-of-the-art methods on different types of instances. Moreover, the impact of each proposed feature is analysed.
ISSN:2777-5860