12 research outputs found
The pickup and delivery traveling salesman problem with handling costs
This paper introduces the pickup and delivery traveling salesman problem with handling costs (PDTSPH). In the PDTSPH, a single vehicle has to transport loads from origins to destinations. Loading and unloading of the vehicle is operated in a last-in-first-out (LIFO) fashion. However, if a load must be unloaded that was not loaded last, additional handling operations are allowed to unload and reload other loads that block access. Since the additional handling operations take time and effort, penalty costs are associated with them. The aim of the PDTSPH is to find a feasible route such that the total costs, consisting of travel costs and penalty costs, are minimized. We show that the PDTSPH is a generalization of the pickup and delivery traveling salesman problem (PDTSP) and the pickup and delivery traveling salesman problem with LIFO loading (PDTSPL). We propose a large neighborhood search (LNS) heuristic to solve the problem. We compare our LNS heuristic against best known solutions on 163 benchmark instances for the PDTSP and 42 benchmark instances for the PDTSPL. We provide new best known solutions on 52 instances for the PDTSP and on 15 instances for the PDTSPL, besides finding the optimal or best known solution on 102 instances for the PDTSP and on 23 instances for the PDTSPL. The LNS finds optimal or near-optimal solutions on instances for the PDTSPH. Results show that PDTSPH solutions provide large reductions in handling compared to PDTSP solutions, increasing the travel distance by only a small percentage
Le problĂšme de tournĂ©es de vĂ©hicules avec cueillettes, livraisons, fenĂȘtres de temps et contraintes de manutention
RĂSUMĂ : Les problĂšmes de tournĂ©es de vĂ©hicules avec cueillettes et livraisons consistent Ă trouver des
tournĂ©es rĂ©alisables minimisant le nombre de vĂ©hicules utilisĂ©s et la distante totale parcourue, et permettant de complĂ©ter toutes les requĂȘtes. Une requĂȘte est dĂ©finie par un point de cueillette et un point de livraison, et une quantitĂ© de marchandise Ă transporter du point de cueillette au point de livraison. Ce faisant, une tournĂ©e est dite rĂ©alisable si la charge du vĂ©hicule ne dĂ©passe pas sa capacitĂ© et si, pour chaque requĂȘte, on visite le point de cueillette avant le point de livraison avec le mĂȘme vĂ©hicule. Dans la derniĂšre dĂ©cennie, la communautĂ© de recherche opĂ©rationnelle sâest attaquĂ©e Ă des problĂšmes de plus en plus complexes qui tiennent compte de contraintes opĂ©rationnelles difficiles Ă traiter. Cette thĂšse sâinsĂšre dans cette tendance. Cette thĂšse propose des modĂšles et des algorithmes pour rĂ©soudre deux variantes du problĂšme de tournĂ©es de vĂ©hicules avec cueillettes et livraisons : le problĂšme de tournĂ©es de vĂ©hicules avec cueillettes, livraisons, fenĂȘtres de temps et contrainte de chargement dernier entrĂ© premier sorti (last-in-first-out â LIFO) (pickup and delivery problem with time Windows and LIFO loading â PDPTWL) et le problĂšme de tournĂ©es de vĂ©hicules avec fenĂȘtres de temps et plusieurs piles (pickup and delivery problem with time windows and multiple stacks
â PDPTWMS). Dans le PDPTWL, la contrainte de chargement dernier entrĂ© premier sorti stipule quâaucune manutention non nĂ©cessaire nâest faite lors de la livraison dâun item : un item peut seulement ĂȘtre livrĂ© sâil est situĂ© sur le dessus de la pile. Dans le PDPTWMS, chaque vĂ©hicule contient plusieurs piles qui sont gĂ©rĂ©es selon une politique de chargement dernier entrĂ© premier sorti.
Afin de résoudre le PDPTWL, trois algorithmes de génération de colonnes avec plans coupants et un algorithme heuristique sont proposés. Le premier algorithme de génération de colonnes incorpore la contrainte de chargement dans le problÚme maßtre, alors que le second
lâincorpore dans le sous-problĂšme. Pour ce faire, un algorithme dâĂ©tiquetage et un critĂšre de dominance spĂ©cialisĂ©s sont proposĂ©s. Le troisiĂšme algorithme de gĂ©nĂ©ration de colonnes est une combinaison des deux premiers algorithmes. Des inĂ©galitĂ©s valides connues sont adaptĂ©es pour le PDPTWL. Des instances ayant jusquâĂ 75 requĂȘtes sont rĂ©solues par ces trois algorithmes exacts en une heure de temps de calcul. Lâalgorithme heuristique, quant Ă lui, permet de traiter plus rapidement des instances de plus grande taille. Dâabord, un ensemble de solutions initiales est construit avec un algorithme
glouton. Puis, pour chaque solution, un algorithme de recherche locale est utilisé afin de diminuer en priorité le nombre de véhicules et ensuite la distance totale parcourue. Puis, deux stratégies sont utilisées pour créer des solutions enfants. La premiÚre choisit aléatoirement des
tournĂ©es de lâensemble de solutions alors que la deuxiĂšme utilise un opĂ©rateur de croisement. Pour les deux stratĂ©gies, un algorithme de recherche locale est ensuite utilisĂ©. Finalement, les enfants sont ajoutĂ©s Ă lâensemble de solutions et les meilleurs survivants sont conservĂ©s.
Lâensemble de solutions est gĂ©rĂ© afin de garder uniquement les solutions variĂ©es de meilleure qualitĂ© par rapport au coĂ»t total. Des instances ayant jusquâĂ 300 requĂȘtes sont rĂ©solues par cette heuristique en deux heures de temps de calcul. Afin de rĂ©soudre le PDPTWMS, deux algorithmes de gĂ©nĂ©ration de colonnes avec plans coupants sont proposĂ©s. Le premier algorithme de gĂ©nĂ©ration de colonnes incorpore la contrainte de chargement avec plusieurs piles dans le sous-problĂšme. Pour ce faire, un algorithme dâĂ©tiquetage
et un critÚre de dominance spécialisés sont proposés. Le deuxiÚme algorithme incorpore partiellement la contrainte de chargement avec plusieurs piles dans le sous-problÚme et
ajoute, au besoin, des contraintes au problĂšme maĂźtre lorsque la solution trouvĂ©e ne respecte pas la contrainte de chargement avec plusieurs piles. Des instances avec une, deux et trois piles et ayant jusquâĂ 75 requĂȘtes sont rĂ©solues par ces deux algorithmes exacts en deux heures de temps de calcul.----------ABSTRACT : In the pickup and delivery problem, vehicles based at a depot are used to satisfy a set of requests which consists of transporting goods (or items) from a specific pickup location to a
specific delivery location. We consider an unlimited fleet of identical vehicles with multiple homogeneous compartments of limited capacity. A vehicle route is feasible if the load in each compartment of the vehicle does not exceed its capacity and each completed request is first picked up at its pickup location and then delivered at its corresponding delivery location. The pickup and delivery problem consists of determining a set of least-cost feasible routes in which the number of vehicles is first minimized. In the last decade, the operations research
community has tackled more complex problems that consider real-life constraints. This thesis follows this trend.
This thesis proposes models and algorithms for two variants of the pickup and delivery problem: the pickup and delivery problem with time windows and last-in-first-out (LIFO)
loading constraints (PDPTWL) and the pickup and delivery problem with time windows and multiple stacks (PDPTWMS). In the first problem, the LIFO loading rule ensures that no
handling is required prior to unloading an item from a vehicle: an item can only be delivered if it is the last one in the stack. In the second problem, each vehicle contains multiple stacks that are operated in a LIFO fashion. To solve the PDPTWL, three exact branch-price-and-cut algorithms and one metaheuristic algorithm are developed. The first branch-price-and-cut algorithm incorporates the LIFO constraints in the master problem. The second branch-price-and-cut algorithm handles the
LIFO constraints directly in the shortest path pricing problem and applies a dynamic programming algorithm relying on an ad hoc dominance criterion. The third branch-price-andcut algorithm is a hybrid between the first two. Known valid inequalities are adapted to the PDPTWL. Instances with up to 75 requests are solved within one hour of computational time. The metaheuristic is capable of handling larger instances much faster. First, a set of initial solutions is generated with a greedy randomized adaptive search procedure. For each of these solutions, local search is applied in order to first decrease the total number of vehicles and then the total traveled distance. Two different strategies are used to create offspring. The first selects vehicle routes from the solution pool. The second selects two parents to create
an offspring with a crossover operator. For both strategies, local search is then performed on the child solution. Finally, the offspring is added to the population and the best survivors are kept. The population is managed so as to maintain good quality solutions with respect
to total cost and population diversity. Instances with up to 300 requests are solved within two hours of computational time. To solve the PDPTWMS, two exact branch-price-and-cut algorithms are proposed. The first
branch-price-and-cut algorithm handles the multiple stacks policy in the shortest path pricing problem and applies a dynamic programming algorithm relying on an ad hoc dominance
criterion. The second branch-price-and-cut algorithm incorporates the multiple stacks Policy partly in the shortest path pricing problem and adds additional inequalities to the master problem when infeasible LIFO multiple stacks are encountered. Instances with one, two and
three stacks involving up to 75 requests are solved within two hours of computational time
Constrained Task Assignment and Scheduling on Networks of Arbitrary Topology.
This dissertation develops a framework to address centralized and distributed constrained task assignment and task scheduling problems. This framework is used to prove properties of these problems that can be exploited, develop effective solution algorithms, and to prove important properties such as correctness, completeness and optimality.
The centralized task assignment and task scheduling problem treated here is expressed as a vehicle routing problem with the goal of optimizing mission time subject to mission constraints on task precedence and agent capability. The algorithm developed to solve this problem is able to coordinate vehicle (agent) timing for task completion. This class of problems is NP-hard and analytical guarantees on solution quality are often unavailable. This dissertation develops a technique for determining solution quality that can be used on a large class of problems and does not rely on traditional analytical guarantees.
For distributed problems several agents must communicate to collectively solve a distributed task assignment and task scheduling problem. The distributed task assignment and task scheduling algorithms developed here allow for the optimization of constrained military missions in situations where the communication network may be incomplete and only locally known. Two problems are developed. The distributed task assignment problem incorporates communication constraints that must be satisfied; this is the Communication-Constrained Distributed Assignment Problem. A novel distributed assignment algorithm, the Stochastic Bidding Algorithm, solves this problem. The algorithm is correct, probabilistically complete, and has linear average-case time complexity.
The distributed task scheduling problem addressed here is to minimize mission time subject to arbitrary predicate mission constraints; this is the Minimum-time Arbitrarily-constrained Distributed Scheduling Problem. The Optimal Distributed Non-sequential Backtracking Algorithm solves this problem. The algorithm is correct, complete, outputs time optimal schedules, and has low average-case time complexity.
Separation of the task assignment and task scheduling problems is exploited here to ameliorate the effects of an incomplete communication network. The mission-modeling conditions that allow this and the benefits gained are discussed in detail. It is shown that the distributed task assignment and task scheduling algorithms developed here can operate concurrently and maintain their correctness, completeness, and optimality properties.Ph.D.Aerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91527/1/jpjack_1.pd
Approches générales de résolution pour les problÚmes multi-attributs de tournées de véhicules et confection d'horaires
ThÚse réalisée en cotutelle entre l'Université de Montréal et l'Université de Technologie de TroyesLe problÚme de tournées de véhicules (VRP) implique de planifier les itinéraires d'une flotte de véhicules afin de desservir un ensemble de clients à moindre coût. Ce problÚme d'optimisation combinatoire NP-difficile apparait dans de nombreux domaines d'application, notamment en logistique, télécommunications, robotique ou gestion de crise dans des contextes militaires et humanitaires. Ces applications amÚnent différents contraintes, objectifs et décisions supplémentaires ; des "attributs" qui viennent compléter les formulations classiques du problÚme. Les nombreux VRP Multi-Attributs (MAVRP) qui s'ensuivent sont le support d'une littérature considérable, mais qui manque de méthodes généralistes capables de traiter efficacement un éventail significatif de variantes. Par ailleurs, la résolution de problÚmes "riches", combinant de nombreux attributs, pose d'importantes difficultés méthodologiques.
Cette thĂšse contribue Ă relever ces dĂ©fis par le biais d'analyses structurelles des problĂšmes, de dĂ©veloppements de stratĂ©gies mĂ©taheuristiques, et de mĂ©thodes unifiĂ©es. Nous prĂ©sentons tout d'abord une Ă©tude transversale des concepts Ă succĂšs de 64 mĂ©ta-heuristiques pour 15 MAVRP afin d'en cerner les "stratĂ©gies gagnantes". Puis, nous analysons les problĂšmes et algorithmes d'ajustement d'horaires en prĂ©sence d'une sĂ©quence de tĂąches fixĂ©e, appelĂ©s problĂšmes de "timing". Ces mĂ©thodes, dĂ©veloppĂ©es indĂ©pendamment dans diffĂ©rents domaines de recherche liĂ©s au transport, ordonnancement, allocation de ressource et mĂȘme rĂ©gression isotonique, sont unifiĂ©s dans une revue multidisciplinaire.
Un algorithme gĂ©nĂ©tique hybride efficace est ensuite proposĂ©, combinant l'exploration large des mĂ©thodes Ă©volutionnaires, les capacitĂ©s d'amĂ©lioration agressive des mĂ©taheuristiques Ă voisinage, et une Ă©valuation bi-critĂšre des solutions considĂ©rant coĂ»t et contribution Ă la diversitĂ© de la population. Les meilleures solutions connues de la littĂ©rature sont retrouvĂ©es ou amĂ©liorĂ©es pour le VRP classique ainsi que des variantes avec multiples dĂ©pĂŽts et pĂ©riodes. La mĂ©thode est Ă©tendue aux VRP avec contraintes de fenĂȘtres de temps, durĂ©e de route, et horaires de conducteurs. Ces applications mettent en jeu de nouvelles mĂ©thodes d'Ă©valuation efficaces de contraintes temporelles relaxĂ©es, des phases de dĂ©composition, et des recherches arborescentes pour l'insertion des pauses des conducteurs. Un algorithme de gestion implicite du placement des dĂ©pĂŽts au cours de recherches locales, par programmation dynamique, est aussi proposĂ©. Des Ă©tudes expĂ©rimentales approfondies dĂ©montrent la contribution notable des nouvelles stratĂ©gies au sein de plusieurs cadres mĂ©ta-heuristiques.
Afin de traiter la variété des attributs, un cadre de résolution heuristique modulaire est présenté ainsi qu'un algorithme génétique hybride unifié (UHGS). Les attributs sont gérés par des composants élémentaires adaptatifs. Des expérimentations sur 26 variantes du VRP et 39 groupes d'instances démontrent la performance remarquable de UHGS qui, avec une unique implémentation et paramétrage, égalise ou surpasse les nombreux algorithmes dédiés, issus de plus de 180 articles, révélant ainsi que la généralité ne s'obtient pas forcément aux dépends de l'efficacité pour cette classe de problÚmes. Enfin, pour traiter les problÚmes riches, UHGS est étendu au sein d'un cadre de résolution parallÚle coopératif à base de décomposition, d'intégration de solutions partielles, et de recherche guidée.
L'ensemble de ces travaux permet de jeter un nouveau regard sur les MAVRP et les problÚmes de timing, leur résolution par des méthodes méta-heuristiques, ainsi que les méthodes généralistes pour l'optimisation combinatoire.The Vehicle Routing Problem (VRP) involves designing least cost delivery routes to service a geographically-dispersed set of customers while taking into account vehicle-capacity constraints. This NP-hard combinatorial optimization problem is linked with multiple applications in logistics, telecommunications, robotics, crisis management in military and humanitarian frameworks, among others. Practical routing applications are usually quite distinct from the academic cases, encompassing additional sets of specific constraints, objectives and decisions which breed further new problem variants. The resulting "Multi-Attribute" Vehicle Routing Problems (MAVRP) are the support of a vast literature which, however, lacks unified methods capable of addressing multiple MAVRP. In addition, some "rich" VRPs, i.e. those that involve several attributes, may be difficult to address because of the wide array of combined and possibly antagonistic decisions they require.
This thesis contributes to address these challenges by means of problem structure analysis, new metaheuristics and unified method developments. The "winning strategies" of 64 state-of-the-art algorithms for 15 different MAVRP are scrutinized in a unifying review. Another analysis is targeted on "timing" problems and algorithms for adjusting the execution dates of a given sequence of tasks. Such methods, independently studied in different research domains related to routing, scheduling, resource allocation, and even isotonic regression are here surveyed in a multidisciplinary review.
A Hybrid Genetic Search with Advanced Diversity Control (HGSADC) is then introduced, which combines the exploration breadth of population-based evolutionary search, the aggressive-improvement capabilities of neighborhood-based metaheuristics, and a bi-criteria evaluation of solutions based on cost and diversity measures. Results of remarkable quality are achieved on classic benchmark instances of the capacitated VRP, the multi-depot VRP, and the periodic VRP. Further extensions of the method to VRP variants with constraints on time windows, limited route duration, and truck drivers' statutory pauses are also proposed.
New route and neighborhood evaluation procedures are introduced to manage penalized infeasible solutions w.r.t. to time-window and duration constraints. Tree-search procedures are used for drivers' rest scheduling, as well as advanced search limitation strategies, memories and decomposition phases. A dynamic programming-based neighborhood search is introduced to optimally select the depot, vehicle type, and first customer visited in the route during local searches. The notable contribution of these new methodological elements is assessed within two different metaheuristic frameworks.
To further advance general-purpose MAVRP methods, we introduce a new component-based heuristic resolution framework and a Unified Hybrid Genetic Search (UHGS), which relies on modular self-adaptive components for addressing problem specifics. Computational experiments demonstrate the groundbreaking performance of UHGS. With a single implementation, unique parameter setting and termination criterion, this algorithm matches or outperforms all current problem-tailored methods from more than 180 articles, on 26 vehicle routing variants and 39 benchmark sets. To address rich problems, UHGS was included in a new parallel cooperative solution framework called "Integrative Cooperative Search (ICS)", based on problem decompositions, partial solutions integration, and global search guidance.
This compendium of results provides a novel view on a wide range of MAVRP and timing problems, on efficient heuristic searches, and on general-purpose solution methods for combinatorial optimization problems
A Polyhedral Study of Mixed 0-1 Set
We consider a variant of the well-known single node fixed charge network flow set with constant capacities. This set arises from the relaxation of more general mixed integer sets such as lot-sizing problems with multiple suppliers. We provide a complete polyhedral characterization of the convex hull of the given set