A hybrid GRASP-VNS for Ship Routing and Scheduling Problem with Discretized Time Windows

This paper addresses the Ship Routing and Scheduling Problem with Discretized Time Windows. Being one of the most relevant and challenging problems faced by decision makers from shipping companies, this tramp shipping problem lies in determining the set of contracts that should be served by each ship and the time windows that ships should use to serve each contract, with the aim of minimizing total costs. The use of discretized time windows allows for the consideration of a broad variety of features and practical constraints in a simple way. In order to solve this problem we propose a hybridazation of a Greedy Randomized Adaptive Search Procedure and a Variable Neighborhood Search, which improves previous heuristics results found in literature and requires very short computational time. Moreover, this algorithm is able to achieve the optimal results for many instances, demonstrating its good performance

A Greedy Randomized Adaptive Search With Probabilistic Learning for solving the Uncapacitated Plant Cycle Location Problem

In this paper, we address the Uncapacitated Plant Cycle Location Problem. It is a location-routing problem aimed at determining a subset of locations to set up plants dedicated to serving customers. We propose a mathematical formulation to model the problem. The high computational burden required by the formulation when tackling large scenarios encourages us to develop a Greedy Randomized Adaptive Search Procedure with Probabilistic Learning Model. Its rationale is to divide the problem into two interconnected sub-problems. The computational results indicate the high performance of our proposal in terms of the quality of reported solutions and computational time. Specifically, we have overcome the best approach from the literature on a wide range of scenarios.</p

Decentralized Cooperative Metaheuristic for the Dynamic Berth Allocation Problem

The increasing demand of maritime transport and the great competition among port terminals force their managers to reduce costs by exploiting its resources accurately. In this environment, the Berth Allocation Problem, which aims to allocate and schedule incoming vessels along the quay, plays a relevant role in improving the overall terminal productivity. In order to address this problem, we propose Decentralized Cooperative Metaheuristic (DCM), which is a population-based approach that exploits the concepts of communication and grouping. In DCM, the individuals are organized into groups, where each individual shares information with its group partners. This grouping strategy allows to diversify as well as intensify the search in some regions by means of information shared among the individuals of each group. Moreover, the constrained relation for sharing information among individuals through the proposed grouping strategy allows to reduce computational resources in comparison to the `all to all' communication strategy. The computational experiments for this problem reveal that DCM reports high-quality solutions and identifies promising regions within the search space in short computational times

Automatización de los procesos de corrección y autoevaluación de prácticas en asignaturas con contenidos de programación mediante herramientas TIC

La programación informática se ha convertido en los últimos años en una herramienta transversal en múltiples áreas de conocimiento. A través de la programación el estu- diante crea programas que presentan un comportamiento deseado en un contexto práctico concreto. Sin embargo, el proceso de escritura de programación le demanda al estudiante habitualmente de conocimientos de múltiples áreas, dominio de lenguajes de programación, algoritmos de propósito específico y lógica formal, entre otros. Actualmente, la Universidad de La Laguna incluye la programación en múltiples titulaciones oficiales. En estas titulaciones el estudiante se enfrenta a la realización de múltiples prácticas de laboratorio donde tiene que demostrar sus conocimientos relativos a programación para la resolución de algún problema planteado por el profesorado dentro del contexto de la asignatura que imparte. El proceso de corrección de las prácticas involucra un análisis exhaustivo por parte del profesorado de las propuestas de programación realizadas por el alumnado. Esto habitualmente implica la corrección de un número elevado de propuestas durante las sesiones prácticas, lo cual da lugar a que el nivel de detalle en la evaluación sea inevitablemente inferior al deseado. Consecuentemente, se da lugar a que algunos alumnos presenten insatisfacción con las calificaciones ob- tenidas así como extenuación por parte del profesorado ante la carga de trabajo concentrada en las sesiones prácticas. En este trabajo se plantea el diseño, implementación y validación de una herra- mienta software que automatiza los procesos de corrección a la vez que facilita la autoevaluación por parte del alumnado durante el desarrollo de las prácticas.In recent years, computer programming has become a transversal tool in multiple areas of knowledge. The student creates programs that present a desired behavior in a given practical context through the programming. However, the writing process demands the student usually of knowledge about multiple areas, domaining program- ming languages, algorithms of specific purpose, and formal logic, among others. Nowadays, the Universidad de La Laguna includes computer programming in multiple official degrees. In these degrees the student faces the performance of multiple laboratory practices where he has to demonstrate his knowledge related to computer programming for solving a problem proposed by the teacher within the context of the subject he teaches. The process of correcting the practices involves a thorough analysis by the teachers of the programming proposals made by the students. This usually involves asses- sing a large number of proposals during the practice sessions, which results in the level of detail in the evaluation being inevitably lower than desired. Consequently, some students are dissatisfied with the grades obtained as well as exhaustion by the teachers in the face of the workload concentrated in the practical sessions. In this paper, the design, implementation, and validation of a software tool that automates the assessment processes while facilitating self-assessment by students during the development of practices is described

Repositorio interactivo para facilitar el aprendizaje de algoritmos heurísticos aplicados a problemas de optimización

La algoritmia es una de las ramas de aprendizaje principales en la formación de un Graduado en Ingeniería Informática, ya que permite abordar la resolución de un gran número de problemas de forma automatizada. Las (meta)heurísticas son técnicas aproximadas destinadas a resolver problemas de optimización mediante una demanda de recursos computacionales reducida. Esto hace que puedan resolver problemas de gran complejidad. En el presente trabajo se expone el repositorio creado con el fin de explicar el con- junto de algoritmos heurísticos de mayor utilización en la resolución de diferentes tipos de problemas, los cuales son impartidos frecuentemente en las asignaturas que componen el Grado de Ingeniería Informática. Con la idea de complementar la comprensión de los algoritmos, el repositorio incluye un conjunto de problemas de optimización altamente estudiados en la literatura, de tal forma que el alumno pueda comprender el comportamiento de los algoritmos disponibles sobre problemas de distintas características. Además de una explicación detallada de tanto los algoritmos heurísticos como de los problemas de optimización, se incluyen ejemplos interactivos de funcionamiento, sobre los cuales se puede realizar un análisis de resultados así como una compa- rativa entre los mismos. Con ello se pretende fomentar la interacción del alumno en el aprendizaje, mediante la ejecución paso a paso de los diferentes ejemplos de algoritmos a través de un software específico, consiguiendo que el alumno compren- da en profundidad los distintos algoritmos, sus características y sus posibles usos.Algorithmics is one of the main branches of learning in the studies of a Graduate on Computer Engineering, because it allows to address the resolution of a huge amount of problems on an automated way. (Meta)heuristics are approximate techniques aimed at solving optimization problems by means of a reduce number of compu- tational resources. This allows they can solve high complex optimization problems. The present work exposes the repository created with the goal to explain the set of heuristic algorithms with more use in the resolution of different types of pro- blems, and that are frequently taugh in the subjects that compose the Grade on Computer Engineering. With the idea of complement the understanding of the algorithms, the repository includes a set of optimization problems highly studied in the literature, in such a way that the student can learn the behaviour of the available algorithms in pro- blems with different characteristics. In addition to a detailed explanation of the heuristic algorithms as well the optimization problems, a set interactive examples of execution are included, on which an analysis of results can be carried out as well as a comparison between them. The idea is to encourage the interaction of the student in learning, through a step-by-step execution of different algorithm examples using a specific software, getting the student to un- derstand in depth the different algorithms, their characteristics and their possible uses

Intelligent Heuristic Techniques for the Optimization of the Transshipment and Storage Operations at Maritime Container Terminals

This paper summarizes the main contributions of the Ph.D. thesis of Christopher Exp\'osito-Izquierdo. This thesis seeks to develop a wide set of intelligent heuristic and meta-heuristic algorithms aimed at solving some of the most highlighted optimization problems associated with the transshipment and storage of containers at conventional maritime container terminals. Under the premise that no optimization technique can have a better performance than any other technique under all possible assumptions, the main point of interest in the domain of maritime logistics is to propose optimization techniques superior in terms of effectiveness and computational efficiency to previous proposals found in the scientific literature when solving individual optimization problems under realistic scenarios. Simultaneously, these optimization techniques should be enough competitive to be potentially implemented in practice. }

A Two-Level Solution Approach to Solve the Clustered Capacitated Vehicle Routing Problem

International audienceThe Clustered Capacitated Vehicle Routing Problem (CCVRP) aims to determine the routes of a fleet of capacitated vehicles to fulfill the service demands of customers organized into clusters. The optimization criterion is to minimize the total travel cost of the routes. The main constraint is that all the customers belonging to the same cluster have to be served by the same vehicle consecutively. In this work, a mathematical formulation for the CCVRP is developed. Since the problem is NP-hard, an approximate Two-Level solution approach is proposed. It is based upon breaking the problem down into two routing problems. The first one aims to determine routes targeted at visiting the clusters. A metaheuristic algorithm is considered to address this sub-problem. Furthermore, the second one is aimed at finding a visiting order of the customers belonging to each cluster. Exact and approximate methods are proposed to tackle this sub-problem. The computational results indicate the high performance of our approach over a wide range of real-size problem instances. In this regard, a cluster generation to define problem instances is presented

Modeling and Solving the Clustered Capacitated Vehicle Routing Problem

ISBN 978-3-86818-049-7International audienc

Tournées de véhicules avec contraintes de clustering

International audienceDe nombreuses applications de la logistique imposent que les clients à livrer soient regroupés en sous-ensembles (clusters) ce qui facilite la livraison ou tout travail amont ou aval de traitement des clients. On est alors face à un problème de " Clustered CVRP ". Le problème est celui du CVRP avec la contrainte supplémentaire que chaque cluster doit être visité intégralement par un même véhicule (ce véhicule peut visiter plusieurs clusters). Notre approche divise le problème en deux parties (stratégique et opérationnelle). Dans l'étape stratégique, on décide de l'ordre de visite des clusters et des affectations de ces clusters aux véhicules. Cette étape est réalisée à partir d'un algorithme de la littérature (Record-To-Record Travel Algorithm). Dans la partie opérationnelle, on indique dans quel ordre les clients seront visités à l'intérieur de chaque cluster. Ce sous-problème est le Shortest Hamiltonian Path Problem (NP-Difficile) qui est abordé à l'aide de plusieurs approches (MILP, Algorithmes de Christophides et de Lin-Kernighan). Les deux étapes sont itérées au sein d'une approche de type multi-start avec des phases d'intensification et de shaking. Les tests numériques montrent la validité de cette approche

Optimization Model and Heuristic Approach for Blocks Retrieval Processes in Warehouses

In this paper we introduce a planning problem termed as Q-Blocks Relocation Problem, which pursues to retrieve a subset of blocks located in a warehouse by minimizing the number of relocation movements. We formalize the problem by means of a Mixed Integer Linear Programming model. However, the high computational burden required by the model encourages us to develop a heuristic algorithm for tackling it. The rationale behind the proposed heuristic is both to retrieve the requested blocks as soon as possible while reducing the number of blocks placed above another one with a higher priority. The computational results indicate that the heuristic reports near-optimal solutions for realistic instances by short computational times, which makes it attractive to be applied by management systems