Competitive co-evolutionary algorithms can solve function optimization problems

Competitive co-evolutionary algorithms (CCEAs) have many advantages, but their range of applications has been crucially limited. This study provides a simple, non-problem-specific framework to extend that range. The framework has two co-evolving populations, one of candidate solutions and one of criteria, in which these populations competitively co-evolve with each other. The framework aims to avoid candidate solutions getting stuck in a local optimum by changing the fitness landscape dynamically. Moreover, the framework has a mechanism which will establish and maintain a proper arms race. We have conducted experiments on two function optimization problems, the 1-dimensional function maximization problem and the Rastrigin function minimization problem, in order to investigate the basic properties of the framework. The results of the experiments showed that a CCEA achieves a performance which is comparable to that of a GA.     

Coevolution and the Red Queen effect shape virtual plants

According to the Red Queen hypothesis a population of individuals may be improving some trait even though fitness remains constant. We have tested this hypothesis using a population of virtual plants. The plants have to compete with each other for virtual sunlight. Plants are modeled using Lindenmayer systems and rendered with OpenGL. Reproductive success of a plant depends on the amount of virtual light received as well as on the structural complexity of the plant. We experiment with two different modes of evaluation. In one experiment, plants are evaluated in isolation, while in other experiments plants are evaluated using coevolution. When using coevolution plants have to compete with each other for sunlight inside the same environment. Coevolution produces much thinner and taller plants in comparison to bush-like plants which are obtained when plants are evaluated in isolation. The presence of other individuals leads to an evolutionary arms race. Because plants are evaluated inside the same environment, the leaves of one plant may be shadowed by other plants. In an attempt to gain more sunlight, plants grow higher and higher. The Red Queen effect was observed when individuals of a single population were coevolving. Communicated by: Una-May O'Reilly     

A Tournament-Based Competitive Coevolutionary Algorithm

For an efficient competitive coevolutionary algorithm, it is important that competing populations be capable of maintaining a coevolutionary balance and hence, continuing evolutionary arms race to increase the levels of complexity. We propose a competitive coevolutionary algorithm that combines the strategies of neighborhood-based evolution, entry fee exchange tournament competition (EFE-TC) and localized elitism. An emphasis is placed on analyzing the effects of these strategies on the performance of competitive coevolutionary algorithms. We have tested the proposed algorithm with two adversarial problems: sorting network and Nim game problems that have different characteristics. The experimental results show that the interacting effects of the strategies appear to promote a balanced evolution between host and parasite populations, which naturally leads them to keep on evolutionary arms race. Consequently, the proposed algorithm provides good quality solutions with a little computation time.     

Environmental effects on the coevolution of pursuit and evasion strategies

The game of tag is frequently used in the study of pursuit and evasion strategies that are discovered through competitive coevolution. The aim of coevolution is to create an arms race where opposing populations cyclically evolve in incremental improvements, driving the system towards better strategies. A coevolutionary simulation of the game of tag involving two populations of agents; pursuers and evaders, is developed to investigate the effects of a boundary and two obstacles. The evolution of strategies through Chemical Genetic Programming optimizes the mapping of genotypic strings to phenotypic trees. Four experiments were conducted, distinguished by speed differentials and environmental conditions. Designing experiments to evaluate the efficacy of emergent strategies often reveal necessary steps needed for coevolutionary progress. The experiments that excluded obstacles and boundaries provided design pointers to ensure coevolutionary progress as well as a deeper understanding of strategies that emerged when obstacles and boundaries were added. In the latter, we found that an awareness of the environment and the pursuer was not critical in an evader’s strategy to survive, instead heading to the edge of the boundary or behind an obstacle in a bid to ‘throw-off or hide from the pursuer’ or simply turn in circles was often sufficient, thereby revealing possible suboptimal strategies that were environment specific. We also observed that a condition for coevolutionary progress was that the problem complexity must be surmountable by at least one population; that is, some pursuer must be able to tag an opponent. Due to the use of amino-acid building blocks in our Chemical Genetic Program, our simulations were able to achieve significant complexity in a short period of time.

求解动态优化问题的多种群竞争差分进化算法

针对动态优化问题（DOP）的求解,提出结合多种群方法和竞争策略的差分进化算法（DECS）。首先,将一个种群作为侦测种群,通过监测种群中所有个体的评价值和种群维度来判断环境是否发生变化。其次,将余下多个种群作为搜索种群,独立搜索环境中的最优值。在搜索过程中,引入排除规则,避免多个搜索种群聚集在同一个局部最优的邻域。在迭代若干代后对各搜索种群执行竞争操作,保留评估值最优个体所在的种群并对该种群的下一代个体生成采用量子个体生成机制,而对其他搜索种群重新初始化。最后,利用7个测试函数的49个动态变化问题对DECS进行验证,并将实验结果与人工免疫算法（Dopt-aiNet）、复位粒子群优化（rPSO）算法、改进差分进化（MDE）算法进行比较。实验结果表明,在49个问题上,DECS有34个问题的平均离线误差期望小于Dopt-aiNet算法,所有问题的平均离线误差期望都小于rPSO算法和MDE算法,因此DECS对DOP求解动态优化问题是可行的。     

Toward a Monopoly Botnet Market

ABSTRACT

Economics play an increasingly important role in fighting cyber crimes. While the arms race against botnet problems has achieved limited success, we propose an approach attacking botnets through affecting a botnet market structure. The characteristics of the present underground botnet market suggest that it functions effectively as perfectly competitive. Competitive markets are usually efficient. We argue that less competition in the botnet market is actually preferred. Our economic analysis suggests that monopoly reduces the overall market output of botnets. Using a model of market structure evolution, we identify key forces that affect the botnet market structure and propose possible ways such as defaming botnet entrants to reduce competition, which ultimately reduce the size and output of the botnet market. The analysis provides useful insight to botnet defenders as a guidance on an efficient allocation of defending resources by attacking more on new entrants to the botnet market relative to the existing botmasters.     

Exploring Coevolutionary Relations by Alterations in Fitness Function: Experiments with Simulated Robots

This paper focuses on various coevolutionary robotic experiments where all parameters except for the fitness function remain the same. Initially an attempt to categorize coevolutionary experiments is made and subsequently three experiments of competitive coevolution (hunt, battle and mating) are presented. The experiment concerning implicit competition of two species (mating) is given special attention as it shows emergence of compromise and collaboration through a competitive environment. The co-evolution progress monitoring is evaluated through fitness graphs, CIAO and Hamming maps and the results are interpreted for each experimental setup. The paper concludes that despite the alteration of fitness functions, several evasion–pursuit elements emerge. Furthermore, conciliatory strategies can emerge in implicit competitional cases.     

An augmented EDA with dynamic diversity control and local neighborhood search for coevolution of optimal negotiation strategies

In this paper, we present an estimation of distribution algorithm (EDA) augmented with enhanced dynamic diversity controlling and local improvement methods to solve competitive coevolution problems for agent-based automated negotiations. Since optimal negotiation strategies ensure that interacting agents negotiate optimally, finding such strategies—particularly, for the agents having incomplete information about their opponents—is an important and challenging issue to support agent-based automated negotiation systems. To address this issue, we consider the problem of finding optimal negotiation strategies for a bilateral negotiation between self-interested agents with incomplete information through an EDA-based coevolution mechanism. Due to the competitive nature of the agents, EDAs should be able to deal with competitive coevolution based on two asymmetric populations each consisting of self-interested agents. However, finding optimal negotiation solutions via coevolutionary learning using conventional EDAs is difficult because the EDAs suffer from premature convergence and their search capability deteriorates during coevolution. To solve these problems, even though we have previously devised the dynamic diversity controlling EDA (D²C-EDA), which is mainly characterized by a diversification and refinement (DR) procedure, D²C-EDA suffers from the population reinitialization problem that leads to a computational overhead. To reduce the computational overhead and to achieve further improvements in terms of solution accuracy, we have devised an improved D²C-EDA (ID²C-EDA) by adopting an enhanced DR procedure and a local neighborhood search (LNS) method. Favorable empirical results support the effectiveness of the proposed ID²C-EDA compared to conventional and the other proposed EDAs. Furthermore, ID²C-EDA finds solutions very close to the optimum.     

协同演化算法研究进展

协同演化算法(coevolutionary algorithms,CEA)是当前国际上计算智能研究的一个热点,它运用生物协同演化的思想,是针对演化算法的不足而兴起的,通过构造两个或多个种群,建立它们之间的竞争或合作关系,多个种群通过相互作用来提高各自性能,适应复杂系统的动态演化环境,以达到种群优化的目的.介绍了协同演化算法的研究状况以及目前的研究进展,概述了它的基本算法、主要特点、理论与技术,同时介绍了一些主要的应用领域,指出了协同演化算法的研究方向.     

Coevolution of Fitness Predictors

We present an algorithm that coevolves fitness predictors, optimized for the solution population, which reduce fitness evaluation cost and frequency, while maintaining evolutionary progress. Fitness predictors differ from fitness models in that they may or may not represent the objective fitness, opening opportunities to adapt selection pressures and diversify solutions. The use of coevolution addresses three fundamental challenges faced in past fitness approximation research: 1) the model learning investment; 2) the level of approximation of the model; and 3) the loss of accuracy. We discuss applications of this approach and demonstrate its impact on the symbolic regression problem. We show that coevolved predictors scale favorably with problem complexity on a series of randomly generated test problems. Finally, we present additional empirical results that demonstrate that fitness prediction can also reduce solution bloat and find solutions more reliably.      

A computational evolutionary approach to evolving game strategy and cooperation

This paper describes an approach to the co-evolution of competing virtual creatures. Pairs of individuals enter one-on-one contests in which they contend to establish contact with a common resource. The individuals are subjected to competitive fitness functions. In each tournament one type of organism implements a game rule based on a set of basic cognitive capabilities. The second type of contestant genetically determines its game strategy. Interesting strategy patterns are identified when this evolutionary process is simulated on populations of competing individuals. These experiments show how cooperation emerges in order to improve both individual and collective game performances.     

Cooperative and penalized competitive learning with application to kernel-based clustering

Competitive learning approaches with individual penalization or cooperation mechanisms have the attractive ability of automatic cluster number selection in unsupervised data clustering. In this paper, we further study these two mechanisms and propose a novel learning algorithm called Cooperative and Penalized Competitive Learning (CPCL), which implements the cooperation and penalization mechanisms simultaneously in a single competitive learning process. The integration of these two different kinds of competition mechanisms enables the CPCL to locate the cluster centers more quickly and be insensitive to the number of seed points and their initial positions. Additionally, to handle nonlinearly separable clusters, we further introduce the proposed competition mechanism into kernel clustering framework. Correspondingly, a new kernel-based competitive learning algorithm which can conduct nonlinear partition without knowing the true cluster number is presented. The promising experimental results on real data sets demonstrate the superiority of the proposed methods.     

基于改进集成学习分类的代理辅助进化算法

当使用代理辅助进化算法求解昂贵高维多目标优化问题时,代理模型通常用于近似昂贵的适应度函数.然而,随着目标数的增加,近似误差将逐渐累积,计算量也会急剧增加.对此,提出一种基于改进集成学习分类的代理辅助进化算法,使用一种改进的装袋集成学习分类器作为代理模型.首先,从被昂贵的适应度评价的个体中选择一组分类边界,将所有个体分成两类;其次,利用这些带有分类标签的个体训练分类器,以对候选个体的类别进行预测;最后,选择有前途的个体进行昂贵适应度评价.实验结果表明,算法中所提出的代理模型可有效提高基于分类的代理辅助进化算法求解昂贵高维多目标优化问题的能力,且与目前流行的代理辅助进化算法相比,基于改进集成学习分类的代理辅助进化算法更具竞争力.     

应用协同进化的图像矢量量化码书设计方法

为了减小LBG算法对初始码书的依赖性,提高跳出局部最优的能力,提出了一种基于协同进化的矢量量化码书设计方法（Coevolution Based LBG,CLBG）。该算法根据码书在同其他码书竞争中的表现来衡量码书的适应度。实验结果表明：CLBG有效地减小了算法对初始码书的依赖性,所得码书性能超过了其他典型的改进码书设计方法。     

Rank-density-based multiobjective genetic algorithm and benchmark test function study

Concerns the use of evolutionary algorithms (EA) in solving multiobjective optimization problems (MOP). We propose the use of a rank-density-based genetic algorithm (RDGA) that synergistically integrates selected features from existing algorithms in a unique way. A new ranking method, automatic accumulated ranking strategy, and a "forbidden region" concept are introduced, completed by a revised adaptive cell density evaluation scheme and a rank-density-based fitness assignment technique. In addition, four types of MOP features, such as discontinuous and concave Pareto front, local optimality, high-dimensional decision space and high-dimensional objective space are exploited and the corresponding MOP test functions are designed. By examining the selected performance indicators, RDGA is found to be statistically competitive with four state-of-the-art algorithms in terms of keeping the diversity of the individuals along the tradeoff surface, tending to extend the Pareto front to new areas and finding a well-approximated Pareto optimal front.     

动态种群划分量子遗传算法求解几何约束

几何约束问题的约束方程组可转化为优化模型,因此约束求解问题可以转化为优化问题。针对传统量子遗传算法个体间信息交换不足,易使算法陷入局部最优的缺点,提出了动态种群划分量子遗传算法（dynamic population divided quantum genetic algorithm,DPDQGA）,并将其应用于几何约束求解中。该算法种群中的个体按照一定规则自发地进行信息交换。在每一代进化的开始阶段,分别对两个初始种群中的个体计算个体适应度。将两个种群合并,使用联赛选择的方法为种群中的个体打分,并按照得分对种群进行排序。最后将合并的种群重新划分为两个子种群。实验表明,基于动态种群划分的量子遗传算法求解几何约束问题具有更好的求解精度和求解速率。     

Classification as clustering: a Pareto cooperative-competitive GP approach

Intuitively population based algorithms such as genetic programming provide a natural environment for supporting solutions that learn to decompose the overall task between multiple individuals, or a team. This work presents a framework for evolving teams without recourse to prespecifying the number of cooperating individuals. To do so, each individual evolves a mapping to a distribution of outcomes that, following clustering, establishes the parameterization of a (Gaussian) local membership function. This gives individuals the opportunity to represent subsets of tasks, where the overall task is that of classification under the supervised learning domain. Thus, rather than each team member representing an entire class, individuals are free to identify unique subsets of the overall classification task. The framework is supported by techniques from evolutionary multiobjective optimization (EMO) and Pareto competitive coevolution. EMO establishes the basis for encouraging individuals to provide accurate yet nonoverlaping behaviors; whereas competitive coevolution provides the mechanism for scaling to potentially large unbalanced datasets. Benchmarking is performed against recent examples of nonlinear SVM classifiers over 12 UCI datasets with between 150 and 200,000 training instances. Solutions from the proposed coevolutionary multiobjective GP framework appear to provide a good balance between classification performance and model complexity, especially as the dataset instance count increases.     

协同进化在遗传算法中的应用述评

生态系统中协同进化的含义是几个生存能力相关联的种群的同时进化,在遗传算法中应用协同进化的实质是改变了个体适应度的计算方法:经典遗传算法中个体的适应度由它的染色体所决定,协同进化中个体的适应度却是由个体在协同关系中的表现决定.根据个体之间的适应度关联方式的不同,协同进化在遗传算法中应用可以分为两种:竞争协同进化算法、合作协同进化算法.竞争协同进化算法中的个体适应度由个体在竞争中的表现决定;合作协同进化算法中的个体适应度决定于个体在合作中的表现.对这两种方法的实质以及主要思想进行了述评.     

Competitive information systems in Australian retail banking

Competitive information systems may provide sustainable competitive advantage to a firm through the use of information technology and systems. Current research suggests generalizations about their nature, based only on a limited range of apparently successful systems from different industries and periods. However, the approach in this study is to look at one industry, and so at a set of comparable businesses and competitive information systems. The Australian banking industry, an industry in transmission from oligopoly to competition, is used as the basis for a study of competitive information system, using an industry-wide framework. Competitive information systems appear as a more complex phenomenon than is generally proposed and their use in a competitive industry seems to be characterized more by a number of small interactive moves than one sustainable competitive breakthrough.     

基于粒子群优化和遗传算法的协同聚类算法

为充分发挥粒子群优化算法和遗传算法各自的优势,提出一种新的基于粒子群和遗传算法的协同进化算法,并将其应用于聚类分析。通过构建2个相互竞争的种群,采用相对适应度度量方法,在一个纯自举的过程中产生最优竞争个体。在现实世界数据集上的仿真实验表明,该算法在收敛精度方面优于基于遗传算法的聚类方法和基本粒子群优化聚类算法。