In this article, we present a study that compares variants of two ACO algorithms designed to tackle a biobjective permutation flowshop scheduling problem where the makespan and the total tardiness are the objectives considered. These two algorithms use respectively one and two pheromone matrices. The analysis of the results gives indications on the choices to adopt when designing an ACO approac...

We study a 2-machine flowshop in which all processing times are independently and identically distributed, with values known to the scheduler. We are able to describe in detail the expected behavior of the flowshop under optimal and under heuristic schedules. Our results suggest that minimizing makespan might be a superfluous objective: Scheduling the jobs randomly requires less information and...

The flowshop problem (FSP) is one of the most thoroughly studied scheduling problems. In the FSP, a set N = {1, . . . , n} of n independent jobs has to be processed on a set M = {1, . . . ,m} of m machines. Every job j, j ∈ N , requires a given fixed, non-negative processing time pij on every machine i, i ∈ M . In a flowshop, all n jobs are to be processed on the m machines in the same order, t...

Flowshop scheduling is a very active research area. This problem still attracts a considerable amount of interest despite the sheer amount of available results. Total flowtime minimization of a flowshop has been actively studied and many effective algorithms have been proposed in the last few years. New best solutions have been found for common benchmarks at a rapid pace. However, these improve...

The general flowshop scheduling problem is a production problem where a set of n jobs have to be processed with identical flow pattern on m machines. In permutation flowshops the sequence of jobs is the same on all machines. A significant research effort has been devoted for sequencing jobs in a flowshop minimizing the makespan. This paper describes the application of a Constructive Genetic Alg...