A memetic ant colony optimization algorithm for the dynamic travelling salesman problem

Copyright @ Springer-Verlag 2010.Ant colony optimization (ACO) has been successfully applied for combinatorial optimization problems, e.g., the travelling salesman problem (TSP), under stationary environments. In this paper, we consider the dynamic TSP (DTSP), where cities are replaced by new ones during the execution of the algorithm. Under such environments, traditional ACO algorithms face a serious challenge: once they converge, they cannot adapt efficiently to environmental changes. To improve the performance of ACO on the DTSP, we investigate a hybridized ACO with local search (LS), called Memetic ACO (M-ACO) algorithm, which is based on the population-based ACO (P-ACO) framework and an adaptive inver-over operator, to solve the DTSP. Moreover, to address premature convergence, we introduce random immigrants to the population of M-ACO when identical ants are stored. The simulation experiments on a series of dynamic environments generated from a set of benchmark TSP instances show that LS is beneficial for ACO algorithms when applied on the DTSP, since it achieves better performance than other traditional ACO and P-ACO algorithms.This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/01 and Grant EP/E060722/02

Memory-based immigrants for ant colony optimization in changing environments

Copyright @ 2011 SpringerAnt colony optimization (ACO) algorithms have proved that they can adapt to dynamic optimization problems (DOPs) when they are enhanced to maintain diversity. DOPs are important due to their similarities to many real-world applications. Several approaches have been integrated with ACO to improve their performance in DOPs, where memory-based approaches and immigrants schemes have shown good results on different variations of the dynamic travelling salesman problem (DTSP). In this paper, we consider a novel variation of DTSP where traffic jams occur in a cyclic pattern. This means that old environments will re-appear in the future. A hybrid method that combines memory and immigrants schemes is proposed into ACO to address this kind of DTSPs. The memory-based approach is useful to directly move the population to promising areas in the new environment by using solutions stored in the memory. The immigrants scheme is useful to maintain the diversity within the population. The experimental results based on different test cases of the DTSP show that the memory based immigrants scheme enhances the performance of ACO in cyclic dynamic environments.This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/2

Interactive and non-interactive hybrid immigrants schemes for ant algorithms in dynamic environments

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Dynamic optimization problems (DOPs) have been a major challenge for ant colony optimization (ACO) algorithms. The integration of ACO algorithms with immigrants schemes showed promising results on different DOPs. Each type of immigrants scheme aims to address a DOP with specific characteristics. For example, random and elitism-based immigrants perform well on severely and slightly changing environments, respectively. In this paper, two hybrid immigrants, i.e., non-interactive and interactive, schemes are proposed to combine the merits of the aforementioned immigrants schemes. The experiments on a series of dynamic travelling salesman problems showed that the hybridization of immigrants further improves the performance of ACO algorithms

An immune system based genetic algorithm using permutation-based dualism for dynamic traveling salesman problems

Copyright @ Springer-Verlag Berlin Heidelberg 2009.In recent years, optimization in dynamic environments has attracted a growing interest from the genetic algorithm community due to the importance and practicability in real world applications. This paper proposes a new genetic algorithm, based on the inspiration from biological immune systems, to address dynamic traveling salesman problems. Within the proposed algorithm, a permutation-based dualism is introduced in the course of clone process to promote the population diversity. In addition, a memory-based vaccination scheme is presented to further improve its tracking ability in dynamic environments. The experimental results show that the proposed diversification and memory enhancement methods can greatly improve the adaptability of genetic algorithms for dynamic traveling salesman problems.This work was supported by the Key Program of National Natural Science Foundation (NNSF) of China under Grant No. 70431003 and Grant No. 70671020, the Science Fund for Creative Research Group of NNSF of China under GrantNo. 60521003, the National Science and Technology Support Plan of China under Grant No. 2006BAH02A09 and the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant No. EP/E060722/1

A survey of swarm intelligence for dynamic optimization: algorithms and applications

Swarm intelligence (SI) algorithms, including ant colony optimization, particle swarm optimization, bee-inspired algorithms, bacterial foraging optimization, firefly algorithms, fish swarm optimization and many more, have been proven to be good methods to address difficult optimization problems under stationary environments. Most SI algorithms have been developed to address stationary optimization problems and hence, they can converge on the (near-) optimum solution efficiently. However, many real-world problems have a dynamic environment that changes over time. For such dynamic optimization problems (DOPs), it is difficult for a conventional SI algorithm to track the changing optimum once the algorithm has converged on a solution. In the last two decades, there has been a growing interest of addressing DOPs using SI algorithms due to their adaptation capabilities. This paper presents a broad review on SI dynamic optimization (SIDO) focused on several classes of problems, such as discrete, continuous, constrained, multi-objective and classification problems, and real-world applications. In addition, this paper focuses on the enhancement strategies integrated in SI algorithms to address dynamic changes, the performance measurements and benchmark generators used in SIDO. Finally, some considerations about future directions in the subject are given

Analysis of the characteristics and applications associated to the dynamic vehicle routing problem - DVRP

El Problema del Ruteo Dinámico de Vehículos - DVRP, permite analizar sistemas con la inclusión de una variable de carácter dinámico, ajustando el ruteo en función de nuevas restricciones y comportamientos a nivel de desarrollo de dimensiones temporales y desarrollo constructivo con información en tiempo real. Este problema se ha clasificado en diferentes sistemas, de acuerdo a su aplicabilidad y algoritmos de solución, además del efecto del dinamismo presente. Sin embargo, no todas las características y diferencias frente al ruteo estocástico clásico, han sido mencionadas y resaltadas, debido a su reciente desarrollo, así como la limitada investigación desarrollada. Por tal motivo el presente artículo, plantea la realización de un análisis de las principales características y aplicaciones asociadas a los problemas de ruteo dinámico de vehículos., a través de una revisión bibliográfica con el propósito de brindar información acerca de las características principales, fortalezas respecto al problema clásico y sus aplicaciones para solución. La metodología empleada, incluye una investigación cualitativa, basada en la búsqueda sistemática en bases de datos acerca del DVRP, en últimos cuatro años (2011-2014). Se concluye que el problema de ruteo dinámico de vehículos, permite establecer y analizar sistemas de ruteo, con la inclusión de una variable de carácter dinámico, permitiendo la aplicación y ajuste de heurísticas y metaheurísticas, permitiendo abarcar nuevos sistemas de análisis a nivel logístico. De la misma manera se evidencia que existe un comportamiento variable con tendencia a la baja, en referencia al número de publicaciones relacionadas con el tema, reflejando, un potencial de investigación y desarrollo inexplorado en referencia a la aplicación y ajuste de la temáticaThe Dynamic Vehicle Routing Problem- DVRP allows analyzing systems with the inclusion of a dynamic variable, adjusting the routing in function of new restrictions and behaviors at the development level of temporal dimensions and constructive development with real-time information. This problem has been classified into different systems, according to their applicability and solution algorithms, besides the current dynamic effect. However, not all features and differences compared to classical stochastic routing have been mentioned and highlighted because of their recent development, as well as limited research developed. Therefore, the present article proposes to carry out an analysis about the main features and applications associated with the dynamic routing vehicle problem, through a literature review with the purpose of providing information about the main characteristics, strengths compared to the classical problem and its applications to solution. The methodology includes a qualitative research based on a systematic search in databases about DVRP in last four years (2011-2014). As main conclusion, is related that the DVRP allows establishing and analyzing routing systems, with the inclusion of a variable dynamic, allowing the application and set of heuristics and metaheuristics, allowing embrace new analysis systems in a logistical level. Likewise, it is evident that there is a variable behavior downtrend, referring to the number of publications related to the theme, reflecting unexplored potential in research and development in reference to the application and setting the them

Ant Colony Optimization With Local Search for Dynamic Traveling Salesman Problems

For a dynamic traveling salesman problem (DTSP), the weights (or traveling times) between two cities (or nodes) may be subject to changes. Ant colony optimization (ACO) algorithms have proved to be powerful methods to tackle such problems due to their adaptation capabilities. It has been shown that the integration of local search operators can significantly improve the performance of ACO. In this paper, a memetic ACO algorithm, where a local search operator (called unstring and string) is integrated into ACO, is proposed to address DTSPs. The best solution from ACO is passed to the local search operator, which removes and inserts cities in such a way that improves the solution quality. The proposed memetic ACO algorithm is designed to address both symmetric and asymmetric DTSPs. The experimental results show the efficiency of the proposed memetic algorithm for addressing DTSPs in comparison with other state-of-the-art algorithms

Evolutionary Computation for Dynamic Optimization Problems

This is an invited tutorial on "Evolutionary Computation for Dynamic Optimization Problems", which was given at the 2015 Genetic and Evolutionary Computation Conference (GECCO 2015).Many real-world optimization problems are subject to dynamic environments, where changes may occur over time regarding optimization objectives, decision variables, and/or constraint conditions. Such dynamic optimization problems (DOPs) are challenging problems for researchers and practitioners in decision-making due to their nature of difficulty. Yet, they are important problems that decision-makers in many domains need to face and solve. Evolutionary computation (EC) is a class of stochastic optimization methods that mimic principles from natural evolution to solve optimization and search problems. EC methods are good tools to address DOPs due to their inspiration from natural and biological evolution, which has always been subject to changing environments. EC for DOPs has attracted a lot of research effort during the last twenty years with some promising results. However, this research area is still quite young and far away from well-understood. This tutorial aims to summarise the research area of EC for DOPs and attract potential young researchers into the important research area. It will provide an introduction to the research area of EC for DOPs and carry out an in-depth description of the state-of-the-art of research in the field regarding the following five aspects: benchmark problems and generators, performance measures, algorithmic approaches, theoretical studies, and applications. Some future research issues and directions regarding EC for DOPs will also be presented. The purpose is to (i) provide clear definition and classification of DOPs; (ii) review current approaches and provide detailed explanations on how they work; (iii) review the strengths and weaknesses of each approach; (iv) discuss the current assumptions and coverage of existing research on EC for DOPs; and (v) identify current gaps, challenges, and opportunities in EC for DOPs