D. Dumitrescu

Multimodal Optimization by Means of a Topological Species Conservation Algorithm

Any evolutionary technique for multimodal optimization must answer two crucial questions in order to guarantee some success on a given task: How to most unboundedly distinguish between the different attraction basins and how to most accurately safeguard the consequently discovered solutions. This paper thus aims to present a novel technique that integrates the conservation of the best successive local individuals (as in the species conserving genetic algorithm) with a topological subpopulations separation (as in the multinational genetic algorithm) instead of the common but problematic radius-triggered manner. A special treatment for offspring integration, a more rigorous control on the allowed number and uniqueness of the resulting seeds, and a more efficient fitness evaluations budget management further augment a previously suggested naïve combination of the two algorithms. Experiments have been performed on a series of benchmark test functions, including a problem from engineering design. Comparison is primarily conducted to show the significant performance difference to the naïve combination; also the related radius-dependent conserving algorithm is subsequently addressed. Additionally, three more multimodal evolutionary methods, being either conceptually close, competitive as radius-based strategies, or recent state-of-the-art are also taken into account. We detect a clear advantage of three of the six algorithms that, in the case of our method, probably comes from the proper topological separation into subpopulations according to the existing attraction basins, independent of their locations in the function landscape. Additionally, an investigation of the parameter independence of the method as compared to the radius-compelled algorithms is systematically accomplished.

A collaborative model for tracking optima in dynamic environments

A new hybrid approach to optimization in dynamic environments called collaborative evolutionary-swarm optimization (CESO) is presented. CESO is a simple method for tracking moving optima in a dynamic environment by combining the search abilities of an evolutionary algorithm for multimodal optimization and a particle swarm optimization algorithm. A collaborative mechanism is designed for the two methods. Numerical experiments indicate CESO to be an efficient method for the selected test problems compared with other evolutionary approaches.

Evolutionary swarm cooperative optimization in dynamic environments

A hybrid approach called Evolutionary Swarm Cooperative Algorithm (ESCA) based on the collaboration between a particle swarm optimization algorithm and an evolutionary algorithm is presented. ESCA is designed to deal with moving optima of optimization problems in dynamic environments. ESCA uses three populations of individuals: two EA populations and one Particle Swarm Population. The EA populations evolve by the rules of an evolutionary multimodal optimization algorithm being used to maintain the diversity of the search. The particle swarm confers precision to the search process. The efficiency of ESCA is evaluated by means of numerical experiments.

Community detection in complex networks using collaborative evolutionary algorithms

Scientific researchers from computer science, communication and as well from sociology and epidemiology reveal a strong interest in the study of networks. One important feature studied in complex network is the community structure. A new evolutionary technique for community detection in complex networks is proposed in this paper. The new algorithm is based on an information sharing mechanism between the individuals of a population. A real-world network is considered for numerical experiments.

Generators of fuzzy dynamical systems

Abstract In some previous papers (Dumitrescu, 1983, 1993, 1995) an ergodic theory for fuzzy dynamical systems has been proposed. The entropy of a fuzzy dynamical system has been defined. It has proven (Dumitrescu and Barbu, 1985; Dumitrescu, 1995) that this entropy is an isomorphism invariant. In this paper we define the generators of a fuzzy dynamical system. Using this notion a fuzzy version of Kolmogorov—Sinai theorem (Kolmogorov, 1958; Sinai, 1959) is given.

Disburdening the species conservation evolutionary algorithm of arguing with radii

The present paper investigates the hybridization of two well-known multimodal optimization methods, i.e. species conservation and multinational algorithms. The topological species conservation algorithm embraces the vision of the existence of subpopulations around seeds (the best local individuals) and the preservation of these dominating individuals from one generation to another, but detects multimodality by means of the hill-valley mechanism employed by multinational algorithms. The aim is to inherit the strengths of both parent techniques and at the same time overcome their flaws. The species conservation algorithm efficiently keeps track of several good search space regions at once, but is difficult to parametrize without prior problem knowledge. Conversely, the multinational algorithms use many functionevaluations to establish subpopulations, but do not depend onprovided radius parameter values. Experiments with all threealgorithms are made on a wide range of test problems in order toinvestigate their advantages and shortcomings.

Concerning the potential of evolutionary support vector machines

Within the present paper, we put forward a novel hybridization between support vector machines and evolutionary algorithms. Evolutionary support vector machines consider the classification task as in support vector machines but use an evolutionary algorithm to solve the optimization problem of determining the decision function. They can explicitly acquire the coefficients of the separating hyperplane, which is often not possible within the classical technique. More important, evolutionary support vector machines obtain the coefficients directly from the evolutionary algorithm and can refer them at any point during a run. In addition, they do not require properties of positive (semi-)definition for kernels within nonlinear learning. The concept can be furthermore extended to handle large amounts of data, a problem frequently occurring e.g. in spam mail detection, one of our test cases. An adapted chunking technique is therefore alternatively used. In addition to two different representations, a crowding variant of the evolutionary algorithm is tested in order to investigate whether the performance of the algorithm is maintained; its global search capabilities would be important for the prospected coevolution of non-standard kernels. Evolutionary support vector machines are validated on four real-world classification tasks; obtained results show the promise of this new approach.

Generative relations for evolutionary equilibria detection

A general technique for detecting equilibria in finite non cooperative games is proposed. Fundamental idea is that every equilibrium is characterized by a binary relation on the game strategies. This relation - called generative relation -- induces an appropriate domination concept. Game equilibrium is described as the set of non dominated strategies with respect to the generative relation. Slight generalizations of some well known equilibrium concepts are proposed. A population of strategies is evolved according to a domination-based ranking in oder to produce better and better equilibrium approximations. Eventually the process converges towards the game equilibrium. The proposed technique opens an way for qualitative approach of game equilibria. In order to illustrate the proposed evolutionary technique different equilibria for different continuous games are studied. Numerical experiments indicate the potential of the proposed concepts and technique.

A new collaborative evolutionary-swarm optimization technique

A new hybrid approach to optimization in dynamical environments called Collaborative Evolutionary-Swarm Optimization (CESO) is presented. CESO tracks moving optima in a dynamical environment by combining the search abilities of an evolutionary algorithm for multimodal optimization and a particle swarm optimization algorithm. A collaborative mechanism between the two methods is proposed by which the diversity provided by the multimodal technique is transmitted to the particle swarm in order to prevent its premature convergence. Numerical experiments indicate CESO as an efficient method compared with other evolutionary approaches.

Support vector machine learning with an evolutionary engine

The paper presents a novel evolutionary technique constructed as an alternative of the standard support vector machines architecture. The approach adopts the learning strategy of the latter but aims to simplify and generalize its training, by offering a transparent substitute to the initial black-box. Contrary to the canonical technique, the evolutionary approach can at all times explicitly acquire the coefficients of the decision function, without any further constraints. Moreover, in order to converge, the evolutionary method does not require the positive (semi-)definition properties for kernels within nonlinear learning. Several potential structures, enhancements and additions are proposed, tested and confirmed using available benchmarking test problems. Computational results show the validity of the new approach in terms of runtime, prediction accuracy and flexibility.