A note on exact algorithms for the identical parallel machine scheduling problem

A recently published paper by Mokotoff presents an exact algorithm for the classical P//Cmax scheduling problem, evaluating its average performance through computational experiments on a series of randomly generated test problems. It is shown that, on the same types of instances, an exact algorithm proposed 10 years ago by the authors of the present note outperforms the new algorithm by some orders of magnitud

Logic based Benders' decomposition for orthogonal stock cutting problems

We consider the problem of packing a set of rectangular items into a strip of fixed width, without overlapping, using minimum height. Items must be packed with their edges parallel to those of the strip, but rotation by 90\ub0 is allowed. The problem is usually solved through branch-and-bound algorithms. We propose an alternative method, based on Benders' decomposition. The master problem is solved through a new ILP model based on the arc flow formulation, while constraint programming is used to solve the slave problem. The resulting method is hybridized with a state-of-the-art branch-and-bound algorithm. Computational experiments on classical benchmarks from the literature show the effectiveness of the proposed approach. We additionally show that the algorithm can be successfully used to solve relevant related problems, like rectangle packing and pallet loading

Heuristic algorithms and scatter search for the cardinality constrained P//Cmax problem

We consider the generalization of the classical P//Cmax problem (assign n jobs to m identical parallel processors by minimizing the makespan) arising when the number of jobs that can be assigned to each processor cannot exceed a given integer k. The problem is strongly NP-hard for any fixed k > 2. We briefly survey lower and upper bounds from the literature. We introduce greedy heuristics, local search and a scatter search approach. The effectiveness of these approaches is evaluated through extensive computational comparison with a depth-first branch-and-bound algorithm that includes new lower bounds and dominance criteri

Two-dimensional packing problems in telecommunications

We present the transcript of the IFORS distinguished lecture delivered by the author on invitation of SOBRAPO and IFORS. The lecture concerned the development of an interdisciplinary research motivated by an application in mobile telecommunication systems, a project jointly developed by four research teams. The presentation follows the typical steps of a classical operations research study, and aims at reviewing the main theoretical and practical results that were obtained

Editorial: Sweet sixteen

This is the traditional triennial note used by the editors to give the readers of 4OR information on the state of the journal and its future. In the 3years that have passed since the last editorial note (Liberti et al. in Q J Oper 13:1–13, 2015), three volumes (each containing four issues) of the journal have been published: vol. 13 (2015), vol. 14 (2016), and vol. 15 (2017)