Nature Computation with Self-Adaptive Dynamic Control Strategy of Population Size

提出了一种种群规模自适应动态控制策略,实现了种群规模根据进化过程自适应的动态变化.该策略的实现不依赖于算法进化操作的具体步骤,因而适用于各种基于种群优化的自然计算方法.首先给出了动态控制策略的框架;然后,在此框架下,充分利用动态种群规模反馈的有用信息,提出了基于Logistic模型的增加/删除数目自适应变化的方法,设计了自适应地兼顾有效性和多样性的增加算子和基于多样性的删除算子.将该策略应用到两种不同的自然计算方法中,采用经典测试函数和新型CEC05测试函数验证其性能,实验结果均表明,结合了所提出的种群规模自适应动态控制策略的新算法,比原算法在求解精度和收敛速度上均有明显的提升.     

自适应学习集成优化算法及矩阵特征值求解

为了增强数值优化算法的高效性和鲁棒性,提出一种基于自适应学习的集成算法(self-adaptivelearning-based ensemble algorithm,SALBEA).在SALBEA中,采用贪婪繁殖算子、进化搜索策略学习算子、X进化算子、种群多样性维持算子改进算法进化结构.此外,SALBEA通过引入概率选择模型和自适应学习机制集成了4种有效的进化搜索策略.首先,为了评估所提算法的性能,采用26个测试函数进行算法对比测试,实验结果表明SALBEA比同类算法具有更好的高效性和鲁棒性.最终,将SALBEA用于求解矩阵特征值这一数值计算问题,结果表明该算法求解精度较高,具有较好的应用前景.     

基于年龄动力学模型的自适应种群演化算法

本文针对演化算法中的自适应动态种群问题,探讨了年龄动力学模型,给出了简化的模型框架,提出了基于该模型的自适应种群演化算法,实现了对进化种群规模的动态控制 。实验表明,该算法比固定种群规模的经典算法具有更好的性能。     

基于标准差的自适应激素调节遗传算法

基于生物内分泌系统的激素调节原理,提出了一种新的自适应遗传算法。该算法以内分泌激素调节的H ill函数下降形式为基础,设计了自适应交叉算子和自适应变异算子,使交叉率和变异率在遗传算法迭代过程中,能够根据函数适应度值的标准差进行自适应调节,使得整个进化过程中将种群多样性维持在合理水平,从而保证算法的正常进化。4种测试函数及三维人脑图像分割的实验结果显示,提出的自适应遗传算法可较好地保持种群多样性并克服早熟现象,性能优于其他3种自适应遗传算法及传统遗传算法。     

基于自适应变异算子的差分进化算法

针对差分演化算法易于早熟、收敛速度慢和收敛精度低等问题,提出一种基于自适应变异算子的差分进化算法。给出个体向量粒子及维度层定义,并提出了基于维度层加权的异维维度选择策略,首次将加权异维学习策略引入差分演化算法中,有效地提高了种群的多样性;根据种群聚集度的思想,提出一种基于种群聚集度自适应的变异算子,该算子能依据种群个体当前的种群聚集度自适应地调整DE/best/1变异算子和加权异维学习变异算子的变异权重,加快算法收敛速度、提高其收敛精度。通过在20个典型的测试函数上进行测试,与7种具有代表性的算法相比,结果表明提出的算法在求解精度和收敛速度上具有很大优势,并显示出了非常好的鲁棒性。     

一种并行免疫进化策略算法研究

基于克隆选择原理，提出一种自适应并行免疫进化策略．在算法中根据抗体抗原亲和度将初始抗体种群分为两个子群，相应地提出了精英克隆算子和超变异算子．通过精英克隆算子提高算法局部搜索能力，同时利用超变异算子维持种群多样性，通过这两个功能互补算子的并行操作实现种群进化．仿真表明，自适应并行免疫进化策略搜索效率高，能有效抑制早熟收敛现象，可用于解决复杂机器学习问题．     

自适应激素调节遗传算法

基于生物内分泌系统的激素调节原理,提出了一种新的自适应遗传算法。该算法以内分泌激素调节的Hill函数下降形式为基础,设计了自适应交叉算子和自适应变异算子,使交叉率和变异率在遗传算法迭代过程中,能够根据各代种群多样性的变化进行自适应调节,在整个进化过程中将种群多样性维持在合理水平。4种测试函数及三维人脑图像分割的实验结果显示,提出的自适应遗传算法可较好地保持种群多样性并克服早熟现象,性能优于其他两种自适应遗传算法及传统遗传算法。     

基于自适应邻域策略的改进型MOEA/D算法

为避免传统MOEA/D算法使用固定领域规模易造成种群进化效率降低的情况,提出一种基于自适应邻域策略的改进算法。设计一种能够反映子问题进化幅度和种群进化状态的判断机制。针对进化过程中的收敛性和分布性需求,提出基于进化状态判断的自适应邻域策略,从而根据种群和子问题的进化状态设定不同的邻域规模。使用WFG系列测试函数进行实验,结果表明,该算法能有效平衡进化过程中种群的收敛性与分布性,提高解集的整体性能。     

多空间协同进化的自然计算方法

在自然计算方法中,种群规模大,计算复杂度高;种群规模小,容易陷入局部最优.本文提出多空间协同进化(Multispace Coevolution,简称MSC)的自然计算方法,该方法适用于各种基于种群进化的优化算法,不依赖于算法进化的具体步骤,具有普适性.在传统的生物种群进化的基础上,将大种群分解为个数有限的小种群,部分小种群组成进化空间,另一部分构成指导空间,两个空间拥有不同的功能,指导空间通过特定的信息传递方式将经验概括信息传递到进化空间,从而使整个种群协同进化.将该策略分别应用到粒子群优化算法(PSO)和遗传算法(GA)中,并与标准粒子群算法、遗传算法以及目前主流的针对大规模问题进行优化的7个算法对比,在高维测试函数中,结果表明,寻优性能方面新的种群进化算法相比其他算法提高80%左右,具有普适性.     

基于自适应差分进化的常压塔轻质油产量多目标优化

常压塔轻质油产量最大化是提高企业效益的重要途径之一.为了适应市场需求和价格变化,生产高需求与高价值的轻质油产品,提出一种基于自适应差分进化的常压塔轻质油产量多目标优化算法.该算法采用惩罚边界交叉法的分解方法,在种群变异阶段引入择优学习算子来改进传统变异算子随机选取个体或者单纯选取最好个体的随机性和盲目性,利用自适应策略逐渐改变交叉变异算子.将改进算法应用于3种测试函数和实际炼油厂常压塔轻质油产量优化,结果表明所提出的算法在测试函数上具有明显优势,并能有效提高常压塔轻质油产量,验证了所提算法的有效性.     

Enhancing the performance of biogeography-based optimization using polyphyletic migration operator and orthogonal learning

Biogeography-based optimization (BBO) is a powerful population-based algorithm inspired by biogeography and has been extensively applied to many science and engineering problems. However, its direct-copying-based migration and random mutation operators make BBO possess local exploitation ability but lack global exploration ability. To remedy the defect and enhance the performance of BBO, an enhanced BBO variant, called POLBBO, is developed in this paper. In POLBBO, a proposed efficient operator named polyphyletic migration operator can formally utilize as many as four individuals’ features to construct a new solution vector. This operator cannot only generate new features from more promising areas in the search space, but also effectively increase the population diversity. On the other hand, an orthogonal learning (OL) strategy based on orthogonal experimental design is employed. The OL strategy can quickly discover more useful information from the search experiences and efficiently utilize the information to construct a more promising solution, and thereby provide a systematic and elaborate reasoning method to guide the search directions of POLBBO. The proposed POLBBO is verified on a set of 24 benchmark functions with diverse complexities, and is compared with the basic BBO, five state-of-the-art BBO variants, five existing OL-based algorithms, and nine other evolutionary algorithms. The experimental results and comparisons demonstrate that the polyphyletic migration operator and the OL strategy can work together well and enhance the performance of BBO significantly in terms of the quality of the final solutions and the convergence rate.     

A directional mutation operator for differential evolution algorithms

Differential evolution (DE) is widely studied in the past decade. In its mutation operator, the random variations are derived from the difference of two randomly selected different individuals. Difference vector plays an important role in evolution. It is observed that the best fitness found so far by DE cannot be improved in every generation. In this article, a directional mutation operator is proposed. It attempts to recognize good variation directions and increase the number of generations having fitness improvement. The idea is to construct a pool of difference vectors calculated when fitness is improved at a generation. The difference vector pool will guide the mutation search in the next generation once only. The directional mutation operator can be applied into any DE mutation strategy. The purpose is to speed up the convergence of DE and improve its performance. The proposed method is evaluated experimentally on CEC 2005 test set with dimension 30 and on CEC 2008 test set with dimensions 100 and 1000. It is demonstrated that the proposed method can result in a larger number of generations having fitness improvement than classic DE. It is combined with eleven DE algorithms as examples of how to combine with other algorithms. After its incorporation, the performance of most of these DE algorithms is significantly improved. Moreover, simulation results show that the directional mutation operator is helpful for balancing the exploration and exploitation capacity of the tested DE algorithms. Furthermore, the directional mutation operator modifications can save computational time compared to the original algorithms. The proposed approach is compared with the proximity based mutation operator as both are claimed to be applicable to any DE mutation strategy. The directional mutation operator is shown to be better than the proximity based mutation operator on the five variants in the DE family. Finally, the applications of two real world engineering optimization problems verify the usefulness of the proposed method.     

A new effective operator for the hybrid algorithm for solving global optimisation problems

Hybrid algorithms have been recently used to solve complex single-objective optimisation problems. The ultimate goal is to find an optimised global solution by using these algorithms. Based on the existing algorithms (HP_CRO, PSO, RCCRO), this study proposes a new hybrid algorithm called MPC (Mean-PSO-CRO), which utilises a new Mean-Search Operator. By employing this new operator, the proposed algorithm improves the search ability on areas of the solution space that the other operators of previous algorithms do not explore. Specifically, the Mean-Search Operator helps find the better solutions in comparison with other algorithms. Moreover, the authors have proposed two parameters for balancing local and global search and between various types of local search, as well. In addition, three versions of this operator, which use different constraints, are introduced. The experimental results on 23 benchmark functions, which are used in previous works, show that our framework can find better optimal or close-to-optimal solutions with faster convergence speed for most of the benchmark functions, especially the high-dimensional functions. Thus, the proposed algorithm is more effective in solving single-objective optimisation problems than the other existing algorithms.     

Parallel discovery of network motifs

Many natural structures can be naturally represented by complex networks. Discovering network motifs, which are overrepresented patterns of inter-connections, is a computationally hard task related to graph isomorphism. Sequential methods are hindered by an exponential execution time growth when we increase the size of motifs and networks. In this article we study the opportunities for parallelism in existing methods and propose new parallel strategies that adapt and extend one of the most efficient serial methods known from the Fanmod tool. We propose both a master–worker strategy and one with distributed control, in which we employ a randomized receiver initiated methodology capable of providing dynamic load balancing during the whole computation process. Our strategies are capable of dealing both with exact and approximate network motif discovery. We implement and apply our algorithms to a set of representative networks and examine their scalability up to 128 processing cores. We obtain almost linear speedups, showcasing the efficiency of our proposed approach and are able to reach motif sizes that were not previously achievable using conventional serial algorithms.     

Image Segmentation with Depth Information via Simplified Variational Level Set Formulation

Image segmentation with depth information can be modeled as a minimization problem with Nitzberg–Mumford–Shiota functional, which can be transformed into a tractable variational level set formulation. However, such formulation leads to a series of complicated high-order nonlinear partial differential equations which are difficult to solve efficiently. In this paper, we first propose an equivalently reduced variational level set formulation without using curvatures by taking level set functions as signed distance functions. Then, an alternating direction method of multipliers (ADMM) based on this simplified variational level set formulation is designed by introducing some auxiliary variables, Lagrange multipliers via using alternating optimization strategy. With the proposed ADMM method, the minimization problem for this simplified variational level set formulation is transformed into a series of sub-problems, which can be solved easily via using the Gauss–Seidel iterations, fast Fourier transform and soft thresholding formulas. The level set functions are treated as signed distance functions during computation process via implementing a simple algebraic projection method, which avoids the traditional re-initialization process for conventional variational level set methods. Extensive experiments have been conducted on both synthetic and real images, which validate the proposed approach, and show advantages of the proposed ADMM projection over algorithms based on traditional gradient descent method in terms of computational efficiency.     

基于广义差别矩阵的核和属性约简算法

属性约简是粗糙集理论的重要研究内容.为此引入广义差别矩阵,提出基于广义差别矩阵的核和属性约简算法.该框架可有效避免连续属性值离散化,且有利于与其他机器学习方法相结合.理论分析表明,所提出的算法是有效而可行的.     

Efficient Rearrangement Algorithms for Shape Optimization on Elliptic Eigenvalue Problems

In this paper, several efficient rearrangement algorithms are proposed to find the optimal shape and topology for elliptic eigenvalue problems with inhomogeneous structures. The goal is to solve minimization and maximization of the k-th eigenvalue and maximization of spectrum ratios of the second order elliptic differential operator. Physically, these problems are motivated by the frequency control based on density distribution of vibrating membranes. The methods proposed are based on Rayleigh quotient formulation of eigenvalues and rearrangement algorithms which can handle topology changes automatically. Due to the efficient rearrangement strategy, the new proposed methods are more efficient than classical level set approaches based on shape and/or topological derivatives. Numerous numerical examples are provided to demonstrate the robustness and efficiency of new approach.     

自适应熵的投影聚类算法

受“维度效应”的影响,许多传统聚类方法运用于高维数据时往往聚类效果不佳。近年来投影聚类方法获得广泛关注,其中软子空间聚类法更是得到了广泛的研究和应用。然而,现有的投影子空间聚类算法大多数均要求用户预先设置一些重要参数,且未能考虑簇类投影子空间的优化问题,从而降低了算法的聚类性能。为此,定义了一种新的优化目标函数,在最小化簇内紧凑度的同时,优化每个簇所在的子空间。通过数学推导得到了新的特征权重计算方法,并提出了一种自适应的“均值型投影聚类算法。该算法在聚类过程中,依靠数据集自身的相关信息及推导获得的公式动态地计算各优化参数。实验结果表明,新算法通过对投影子空间的优化改善了聚类质量,其性能较已有投影聚类算法有了明显提升。     

基于矩的数字图像多边形逼近方法

提出了两种基于矩的数字图像的多边形逼近方法。通过比较原始图形和近似图形之间几体矩或Legendre矩的偏差的大小,选择一个最佳的近似结果,进一步可以得到一个顶点数递减的近似多边形序列。与现存的方法比较,这种方法有效地避免了逼近这结果依赖于起始点的选取的缺陷。     

一种新的求解函数优化问题的快速演化算法

提出一种新的求解函数优化的快速演化算法;新算法的特征是引入一种基于高斯变异和Cauchy变异的混合自适应变异算子,并作为算法的唯一遗传算子;提出多父体变异的群体爬山搜索策略;采用随机排序选择策略,克服了经典算法易于陷入局部最优解的常见弊病;新算法具有保持群体的多样性、全概率收敛、淘汰压力小、子空间搜索、快速收敛、评价次数少等特性;通过7个标准测试函数测试结果表明,新算法在所有的测试函数中体现出很好的性能,具有稳定、高效和快速等特点.