Navegando por Autor "Gendron, Bernard"

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Strong bounds for resource constrained project scheduling : preprocessing and cutting planes.
(2020) Araujo, Janniele Aparecida Soares; Santos, Haroldo Gambini; Gendron, Bernard; Jena, Sanjay Dominik; Brito, Samuel Souza; Souza, Danilo Santos
Resource Constrained Project Scheduling Problems (RCPSPs) without preemption are well-known N Phard combinatorial optimization problems. A feasible RCPSP solution consists of a time-ordered schedule of jobs with corresponding execution modes, respecting precedence and resources constraints. In this paper, we propose a cutting plane algorithm to separate five different cut families, as well as a new preprocessing routine to strengthen resource-related constraints. New lifted versions of the well-known precedence and cover inequalities are employed. At each iteration, a dense conflict graph is built considering feasibility and optimality conditions to separate cliques, odd-holes and strengthened Chvátal-Gomory cuts. The proposed strategies considerably improve the linear relaxation bounds, allowing a state-of-theart mixed-integer linear programming solver to find provably optimal solutions for 754 previously open instances of different variants of the RCPSPs, which was not possible using the original linear programming formulations.