Two-machine chain-reentrant ow shop with the no-wait constraint

This paper addresses the chain-reentrant flow shop scheduling problem with two machines and n non-preemptive jobs in the presence of the no-wait constraint; we assume that each job passes from the first machine to the second and returns back to the first machine. The objective is to minimise the makespan. The general problem is NP-hard in the strong sense. Based on a dynamic programming algorithm, we prove that the problem is polynomially solvable when the execution order of the jobs through the machines is a fixed permutation. For the resolution of the general problem, we propose a linear mathematical model, local search heuristics, a simulated annealing metaheuristic and lower bounds with numerical experiments. [Received: 8 February 2019; Revised: 19 June 2019; Revised: 26 August 2019; Revised: 8 October 2019; Revised: 9 November 2019; Accepted: 11 November 2019]