Jean-Louis Bouquard

New Single Machine and Job-Shop Scheduling Problems with Availability Constraints

In this paper we deal with variants of traditional cases of unavailability constraints in scheduling problems. In the literature, two main approaches are usually found. In the first one, operations can be interrupted by unavailability periods and in the second one, operations cannot be interrupted. The context we consider is more general; some operations can be interrupted, the others cannot. Moreover, we assume that information can be related to operations as well as to unavailability periods. Consequently an unavailability period can make possible or not the interruption of an operation. As an application to this new problem, the single machine problem with heads and tails and the job-shop scheduling problem are tackled. All combinations of possible cases are studied and after a review of the state-of-the-art, branch-and-bound algorithms are proposed to solve these problems. Finally, computational experiments are conducted and discussed.

Enumeration of Pareto Optima for a Flowshop Scheduling Problem with Two Criteria

We consider a two-machine flowshop-scheduling problem with an unknown common due date where the objective is minimization of both the number of tardy jobs and the unknown common due date. We show that the problem is NP-hard in the ordinary sense and present a pseudopolynomial dynamic program for its solution. Then, we propose an exact e-constraint approach based on the optimal solution of a related single-machine problem. For this latter problem a compact ILP formulation is explored: a powerful variable-fixing technique is presented and several logic cuts are considered. Computational results indicate that, with the proposed approach, the pareto optima can be computed, in reasonable time, for instances with up to 500 jobs.

Application of an optimization problem in max-plus algebra to scheduling problems

The problem tackled in this paper deals with products of a finite number of triangular matrices in Max-Plus algebra, and more precisely with an optimization problem related to the product order. We propose a polynomial time optimization algorithm for 2 × 2 matrices products. We show that the problem under consideration generalizes numerous scheduling problems, like single machine problems or two-machine flow shop problems. Then, we show that for 3 × 3 matrices, the problem is NP-hard and we propose a branch-and-bound algorithm, lower bounds and upper bounds to solve it. We show that an important number of results in the literature can be obtained by solving the presented problem, which is a generalization of single machine problems, two- and three-machine flow shop scheduling problems. The branch-and-bound algorithm is tested in the general case and for a particular case and some computational experiments are presented and discussed.

Two-machine flow shop scheduling problems with no-wait jobs

In this paper we provide a fairly complete complexity classification of various versions of the two-machine permutation flow shop scheduling problem to minimize the makespan in which some of the jobs have to be processed with no-wait in process. For some version, we offer a fully polynomial-time approximation scheme and a 43-approximation algorithm.

Two-machine flow shop scheduling problems with minimal and maximal delays

Abstract.In this paper, we show lower bounds and upper bounds for the F2/max delay/Cmax problem. These bounds allow us to build a branch-and-bound procedure. Computational experiments reveal that these bounds and the associated branch-and-bound procedure are efficient.

The e-OCEA project: towards an internet decision system for scheduling problems

This paper deals with an Internet decision support system for scheduling problems. This system, called e-OCEA, is being developed at the Laboratory of Computer Sciences of the University of Tours. It provides a user with tools to help create an effective algorithm to solve a scheduling problem. From the modelisation of the problem to the visualization of a computed schedule, the e-OCEA system offers software that can be used either by operations researchers or industrial engineers. In this paper, we present the current state of this system and provide future directions.

Genetic branch-and-bound or exact genetic algorithm?

Production resettings is a vital element of production flexibilityand optimizing the setup tasks scheduling within a productionchannel is required to improve production rate. This paper deals with aNP-Hard production resetting optimization problem based on an industrialcase. In this paper we present how to hybrid a Branch-and-Bound method for this problem with a genetic algorithm. The idea is to use thegenetic algorithm to improve the upper bound and thus speeding up theBranch-and-Bound while the genetic algorithm uses the content of theBranch-and-Bound stack to reduce its search space. Both methods arerunning in parallel and are therefore collaborating together.

Matheuristic algorithms for minimizing total tardiness in the m-machine flow-shop scheduling problem

We consider in this paper the m-machine permutation flow-shop problem with total tardiness minimization. We propose several matheuristic algorithms, which are an hybridization of a local search and an exact resolution method. The matheuristics are compared to a genetic algorithm. Computational experiments are performed on benchmark instances and the results show the good performances of the matheuristic algorithms. Finally, some future research directions are given.

An Unrelated Parallel Machines Model For Production Resetting Optimization

Efficient production resettings are necessary to achieve production flexibility. For this reason, most modern companies are trying to reduce the setup time required to switch the production from one product type to another. One way to minimize these times is to schedule correctly the various tasks involved during a production resetting: changing tools, modifying each machine settings, etc. In this paper, we present how this problem can be identified to an unrelated parallel machine problem with release dates and delivery times where the resources are operators. We show that the data structure allow to simplify the problem into an assignment problem even when we take into consideration the availability constraints of the operators. Moreover, we describe a branch-and-bound algorithm that we have used to solve this problem

Dimensioning an inbound call center using constraint programming

One of the critical problems in the call center industries is the staffing problem, since they must face variable demands and because staff costs represent a major part of the costs of these industries. From a modeling point of view, a call center is generally modeled as a M / M / N system, also called the Erlang-C model. In [Koole and Mandelbaum, 2001], the authors present a survey of the state-of-the-art about possible models of a call center.