Nicolas Dupin

• PhD, Operations Research
• Maître de Conférences (Assoc. Professor) at University of Angers

The discrete unit commitment problem with min‐stop ramping constraints optimizes the daily production of thermal power plants, subject to an operational reactivity of thermal units in a 30‐minute delay. Previously, mixed integer programming (MIP) formulations aimed at an exact optimization approach. This paper derives matheuristics to face the shor...

This paper deals with the long-term Military Flight and Maintenance Planning problem. In order to solve this problem efficiently, we propose a new solution approach based on a new Mixed Integer Program and the use of both valid cuts generated on the basis of initial conditions and learned cuts based on the prediction of certain characteristics of o...

Planning the maintenance of nuclear power plants is a complex optimization problem, involving a joint optimization of maintenance dates, fuel constraints and power production decisions. This paper investigates Mixed Integer Linear Programming (MILP) matheuristics for this problem, to tackle large size instances used in operations with a time scope...

This paper investigates the Electric Autonomous Dial-A-Ride Problem (E-ADARP), which consists in designing a set of minimum-cost routes that accommodates all customer requests for a fleet of Electric Autonomous Vehicles (EAVs). Problem-specific features of the E-ADARP include: (i) the employment of EAVs and a partial recharging policy; (ii) the wei...

In this paper, p-dispersion problems are studied to select $p\geqslant 2$ representative points from a large 2D Pareto Front (PF), solution of bi-objective optimization. Four standard p-dispersion variants are considered. A novel variant, Max-Sum-Neighbor p-dispersion, is introduced for the specific case of a 2D PF. Firstly, $2$-dispersion and $3$-...

If DSATUR heuristic was proven efficient for many instances of the vertex coloring problem, this paper aims to analyze inefficiency causes of DSATUR heuristic, extending DSATUR with matheuristic operators. Using an Integer Linear Programming formulation allows to have larger local greedy optimization in DSATUR construction scheme. Matheuristics all...

Le problème d’ordonnancement linéaire (LOP, Linear Ordering Problem) consiste à former une permutation d’un ensemble de N items, définissant un classement le plus représentatif issu de préférences entre couples d’items [5]. Le LOP s’applique en théorie du choix social, mais également en bio-informatique, median de permutations pour des requêtes de...

A well-known bottleneck of Min-Sum-of-Square Clustering (MSSC, the celebrated k-means problem) is to tackle the presence of outliers. In this paper, we propose a Partial clustering variant termed PMSSC which considers a fixed number of outliers to remove. We solve PMSSC by Integer Programming formulations and complexity results extending the ones f...

A known bottleneck of Min-Sum-of-Square Clustering (MSSC, also denoted k-means problem) is to tackle the perturbation implied by outliers. This paper proposes a partial clustering variant, denoted PMSSC, considering a fixed number of outliers to remove. Integer Programming formulations are proposed. Complexity results extending the ones from MSSC a...

This article studies the linear ordering problem, with applications in social choice theory and databases for biological datasets. Integer Linear Programming (ILP) formulations are available for linear ordering and some extensions. ILP reformulations are proposed, showing relations with the Asymmetric Travel Salesman Problem. If a strictly tighter...

This paper investigates the Electric Autonomous Dial-A-Ride Problem (E-ADARP), which consists in designing a set of minimum-cost routes that accommodates all customer requests for a fleet of Electric Autonomous Vehicles (EAVs). Problem-specific features of the E-ADARP include: (i) the employment of EAVs and a partial recharging policy; (ii) the wei...

The Electric Autonomous Dial-A-Ride Problem (E-ADARP) consists in scheduling a fleet of electric autonomous vehicles to provide ride-sharing services for customers that specify their origins and destinations. The E-ADARP differs from typical DARP in two aspects: (i) a weighted-sum objective that minimizes both total travel time and total excess use...

K-medoids clustering is solvable by dynamic programming in O(N 3) time for a 2D Pareto Front (PF). A key element is a interval clustering optimality. This paper proves this property holds also for local minima for k-medoids. It allows to enumerate the local minima of k-medoids with the same complexity than the computation of global optima for k=2 o...

This article studies the linear ordering problem, with applications in social choice theory and databases for biological datasets. Integer Linear Programming (ILP) formulations are available for the linear ordering problem and some extensions. ILP reformulations are proposed , showing relations with the Asymmetric Travel Salesman Problem. If a stri...

Cet exposé fait suite à l'appel de partage de bonnes pratiques : "ceux qui ont souffert (en thèse) en utilisant des outils/langages mal adaptés pour la RO sont invités à présenter leur expériences et surtout leurs solutions". Pour ma part, j'ai été très satisfait d'utiliser OPL, le modeleur de Cplex, sur des problèmes d'optimisation industriels. Je...

In this article, we address a class of non convex, integer, non linear mathematical programs using dynamic programming. The mathematical program considered, whose properties are studied in this article, may be used to model the optimal liquidation problem of a single asset portfolio, held in a very large quantity, in a low volatility and perfect me...

This paper considers a variant of the Vehicle Routing Problem with Time Windows, with site dependencies, multiple depots and outsourcing costs. This problem is the basis for many technician routing problems. Having both site-dependency and time window constraints lresults in difficulties in finding feasible solutions and induces highly constrained...

Having N points in a planar Pareto Front (2D PF), k-means and k-medoids are solvable in O(N3) time by dynamic programming algorithms. Standard local search approaches, PAM and Lloyd’s heuristics, are investigated in the 2D PF case to solve faster large instances. Specific initialization strategies related to 2D PF cases are implemented with the gen...

Dans la lignée des discussions sur le lien entre algorithmes de RO et questions d'implémentation, nous souhaitons partager des retours d'expérience sur ce sujet en enseignement. Nous avons expérimenté par la RO un apprentissage décloisonné d'algorithmes et de bonnes pra-tiques de programmation. Nous nous étions rendus compte que les étudiants de L3...

With many efficient solutions for a multi-objective optimization problem, this paper aims to cluster the Pareto Front in a given number of clusters K and to detect isolated points. K-center problems and variants are investigated with a unified formulation considering the discrete and continuous versions, partial K-center problems, and their min-sum...

This paper studies the hybridization of Mixed Integer Programming (MIP) with dual heuristics and machine learning techniques, to provide dual bounds for a large scale optimization problem from an industrial application. The case study is the EURO/ROADEF Challenge 2010, to optimize the refueling and maintenance planning of nuclear power plants. Seve...

Having many best compromise solutions for bi-objective optimization problems, this paper studies p-dispersion problems to select $p\geqslant 2$ representative points in the Pareto Front(PF). Four standard variants of p-dispersion are considered. A novel variant, denoted Max-Sum-Neighbor p-dispersion, is introduced for the specific case of a 2d PF....

The Military Flight and Maintenance Planning (MFMP) Problem assigns missions and schedules maintenance operations (checks) for military aircraft. It has been studied in short, medium and long-term planning horizons ([1, 2, 5, 4]) and it has been proved NP-Hard in its long-term variant by [3]. The present model is an alternative formulation to that...

Having many non dominated solutions in bi-objective optimization problems, this paper aims to cluster the Pareto front using Euclidean distances. The p-center problems, both in the discrete and continuous versions, become solvable with a dynamic programming algorithm. Having N points, the complexity of clustering is (resp. ) time and O(N) memory sp...

We present the Flight and Maintenance Planning (FMP) problem in its military variant and applied to long term planning. The problem has been previously studied for short- and medium-term horizons only. We compare its similarities and differences with previous work and prove its complexity. We generate scenarios inspired by the French Air Force flee...

The k-medoids problem is a discrete sum-of-square clustering problem, which is known to be more robust to outliers than k-means clustering. As an optimization problem, k-medoids is NP-hard. This paper examines k-medoids clustering in the case of a two-dimensional Pareto front, as generated by bi-objective optimization approaches. A characterization...

The discrete unit commitment problem with min-stop ramping constraints optimizes the daily production of thermal power plants (coal, gas, fuel units). For this problem, compact Integer Linear Programming (ILP) formulations have been designed to solve exactly small instances and heuristically real-size instances. This paper investigates whether Dant...

This paper is motivated by real-life applications of multi-objective optimization. Many efficient solutions may exist considering the Pareto optimality. The problem is here to select only a few good compromise solutions K from N >> K non dominated solutions. This selection aims to maximize the representativity of these K solutions among the N initi...

This paper is motivated by real-life applications of bi-objective optimization. Having many non dominated solutions, one wishes to cluster the Pareto front using Euclidian distances. The p-center problems, both in the discrete and continuous versions, are proven solvable in polynomial time with a common dynamic programming algorithm. Having $N$ poi...

The discrete unit commitment problem with min-stop ramping constraints optimizes the daily production of thermal power plants. For this problem, compact Integer Linear Programming (ILP) formulations have been designed to solve exactly small instances and heuristically real-size instances. This paper investigates whether Dantzig-Wolfe reformulation...

Nous considérons une variante du problème site-dependent VRPTW introduit précédemment. Des interventions doivent être réalisées par des techniciens ayant les niveaux de qualifications requis sur des fenêtres de temps imposées, ou non planifiées au prix d'une forte pénalisation. Une fois le nombre maximal d'interventions planifié, la longueur des to...

The discrete unit commitment problem with min-stop ramping constraints optimizes the daily production of thermal power plants. For this problem, compact Integer Linear Programming (ILP) formulations have been designed to solve exactly small instances and heuristically real-size instances. This paper investigates whether Dantzig-Wolfe reformulation...

Scheduling the maintenances of nuclear power plants is a complex optimization problem, formulated in 2-stage stochastic programming for the EURO/ROADEF 2010 challenge. The first level optimizes the maintenance dates and refueling decisions. The second level optimizes the production to fulfill the power demands and to ensure feasibility and costs of...

This paper is motivated by a real life application of multi-objective optimization without preference. Having many incomparable solutions with Pareto optimality, the motivation is to select a small number of representative solutions for decision makers. The k-means clustering is investigated in this paper for the 2-dimensional case using the specif...

A specific Flight and Maintenance Planning problem is presented. In this problem, preventive maintenance operations are scheduled for military aircraft along with the assignment of regular missions. The quality of the solutions is measured via a bi-objective function that smooths both maintenance operations and aircraft unavailability among time pe...

This paper is motivated by a real life application of multi-objective optimization without preference. Having many non-dominated solutions with Pareto dominance, the problem is to select and present a small number of representative solutions to decision makers. The p-median and p-center clustering problems are investigated in this paper for the 2-d...

This paper considers a simplified Technician Routing and Scheduling Problem with skill constraints, where a Column Generation (CG) heuristic was shown effective. This work proposes new CG schemes to stabilize the CG process and thus to accelerate the CG heuristics. Solving CG subproblems with matheuristics allows to diversify the column generation....

The EURO/ROADEF 2010 Challenge aimed to schedule the maintenance and refueling operations of French nuclear power plants, ranking the approaches in competition for the quality of primal solutions. This paper justifies the high quality of the best solutions computing dual bounds with dual heuristics. A first step designs several Mixed Integer Progra...

The EURO/ROADEF 2010 Challenge aimed to schedule the maintenance and refueling operations of French nuclear power plants, ranking the approaches in competition for the quality of primal solutions. This paper justifies the high quality of the best solutions computing dual bounds with dual heuristics. A first step designs several Mixed Integer Progra...

The discrete unit commitment problem with min-stop ramping constraints optimizes the daily production of thermal power plants, subject to an operational reactivity of thermal units in a 30 minutes delay. Previously, Mixed Integer Programming (MIP) formulations aimed at an exact optimization approach. This paper derives matheuristics to face the sho...

Pour gérer le parc de ses aéronefs militaires, l'Armée de l'Air fait face à un problème d'optimisation conjointe des dates de maintenances et des affectations en missions. Les affectations en missions nécessitent de respecter de standards requis pour participer à une mission, et les contraintes d'immobilisations im-pliquées par les maintenances et...

This paper considers a variant of the multiple depot Vehicle Routing Problem with Time Windows where skill constraints define the places that vehicles can visit. A difficulty faced here is that the special set of instances are highly constrained, due to tight skill and time window constraints. This induced a matheuristic approach, combining advanta...

This paper elaborates compact MIP formulations for a discrete unit commitment problem with minimum stop and ramping constraints. The variables can be defined in two different ways. Both MIP formulations are tightened with clique cuts and local constraints. The projection of constraints from one variable structure to the other allows to compare and...

L'Armée de l'Air française est actuellement engagée sur de nombreux théâtres d'opérations, ce qui sollicite tout particulièrement les avions de combat. Une planification optimisée des activ-ités aériennes et des opérations de maintenance est indispensable pour atteindre les objectifs opérationnels en respectant les contraintes réglementaires, finan...

To examine the Project Management aspects of the French Air Defense Program SCCOA, a Model-Based System Engineering approach using the NATO Architecture Framework (NAF) is appropriate to ensure the System of Systems consistency. Two limitations of the NAF are addressed: incorporating temporality and incorporating decision support tools. The first i...

Scheduling the maintenances of nuclear power plants is a complex industrial problem, formulated as a 2-stage stochastic problem for the EURO/ROADEF 2010 challenge with uncertainty on demands, production costs and capabilities. The first stage optimization concerns the maintenance dates and refueling decisions, whereas the second level concerns unit...

The discrete unit commitment problem with min-stop ramp-ing constraints applies for thermal units. To face the operational time limit for resolution, this article derives efficient matheuristics from MIP formulations previously obtained. Constructive matheuristics defines variable fixing and relax-and-fix strategies. To improve known feasible solut...

This paper addresses the scheduling problem of nuclear power plant outages for maintenance and refuelling, defined for the Challenge EURO/ROADEF 2010. Dual matheuristics compute dual bounds using Mixed Integer Programming (MIP) formulations. A first step designs a MIP formulation for the problem relaxing only 2 types of constraints, declaring binar...

La programmation linéaire en nombre entiers est un outil puissant pour modéliser des processus industriels. Le développement d’outils logiciels et de bibliothèques adossées aux langages de programmation les plus populaires a démocratisé des outils de calcul performants. Cependant, un facteur limitatif demeure, la taille des problèmes et les temps d...

Mixed Integer Linear Programming (MILP) is a very popular and useful framework to model industrial optimization problems. This success is due to the facility to model complex optimization problems, with numerous sets of constraints and variables, including discrete variables. The work can be focused on modeling, with a black box generic resolution...

Mots-clés : application industrielle de la RO, challenge EURO/ROADEF 2010, PLNE. Le challenge EURO/ROADEF 2010, proposé par EDF, avait pour but d'optimiser les arrêts de rechargements et de maintenances des réacteurs nucléaires, selon un formalisme de program-mation stochastique. En temps contraint, l'impact d'hypothèses simplificatrices ou certain...

L’électricité en France est majoritairement produite par les réacteurs nucléaires, qui doivent être arrêtés périodiquement pour le rechargement du combustible, et divers travaux de maintenance. L’arrêt d’un réacteur peut conduire à lui substituer d’autres types d’unités au coût de production plus élevé. La planification des arrêts des réacteurs nuc...

Prix Jeune Chercheur de la ROADEF Mots-clés : Unit Commitment Problem, gestion de production d'´ electricité du parc thermique, modélisation PLNE, renforcement de contraintes, coupes de cliques.

Prix Jeune Chercheur de la ROADEF Mots-clés : Unit Commitment Problem, gestion de production d’´ electricité du parc thermique, modélisation PLNE, renforcement de contraintes, coupes de cliques.

Cette étude est motivée par le placement de plages de travaux sur des voies ferrovières. Il s'agira ici d'adapter les horaires des trains pour permettre l'établissement de plages horaires de travaux. On se place sur le cas d’un tronçon traversé par deux voies en sens inverses, entre deux points d’où il est possible d’effectuer des bifurcations pou...