基于多变异个体的多目标差分进化改进算法

针对多目标差分进化算法在高维函数下收敛速度慢和易早熟的问题,提出一种基于多变异个体的多目标差分进化改进算法。通过在多目标差分进化算法的个体变异及交叉操作中,引入多个变异个体,使得在高维多目标函数情况下,多目标差分进化算法种群可以更好地保持多样性,减少种群陷入局部最优解的可能性,从而提高该算法在高维多目标优化问题环境下,最优值解的搜索速度及全局最优值解的查找能力。实验结果表明,在高维多目标环境下,与标准多目标差分进化算法相比,该算法可以更快速地找到多个目标函数组的非劣最优值解集。     

面向多峰优化问题的双层协同差分进化算法

多峰优化问题是一类存在多个全局最优解的复杂优化问题,不仅要求算法找到尽可能多的最优解,而且要求算法尽可能提高所找到的最优解的精度.演化计算方法是求解这类问题的重要手段.但是传统演化计算方法面临多样性和收敛性两个方面的挑战.针对这两个方面的挑战,提出了一种通过探索层和精炼层协同演化的双层协同差分进化算法.在探索层中,每个...     

融合Sin混沌和分段权值的阿基米德优化算法

针对阿基米德优化算法（Archimedes optimization algorithm,AOA）存在全局搜索能力弱、收敛精度低,易陷入局部最优等问题,提出融合Sin混沌和分段权值的阿基米德优化算法（SAOA）。采用无限折叠迭代的Sin混沌反向学习策略初始化种群,提高初始阶段解的质量,为全局搜索多样性奠定基础;引入算数交叉算子,将当前个体向与全局最优个体进行交叉,引导种群向最优解区域寻优,提高全局搜索能力;引入分段权值策略,平衡算法的全局勘探与局部开发能力,降低算法陷入局部最优的概率;通过对8个测试函数和部分CEC2014函数进行仿真实验及Wilcoxon秩和检验来评估改进算法的寻优性能,实验结果表明改进算法在搜索精度、收敛速度和稳定性等方面均有较大提升。另外,引入优化机械设计案例进行测试分析,进一步验证SAOA在工程优化问题上的可行性和适用性。     

多元优化算法及其收敛性分析

提出了一种搜索个体分工明确、协同合作的群智能优化算法,并从理论上证明了其收敛性. 由于搜索个体(搜索元)具有分工不同的多元化特点,所以我们称该算法为多元优化算法(Multivariant optimization algorithm, MOA).多元优化算法中, 全局搜索元和局部搜索元基于数据表高效的记录和分享信息以协同合作对解空间进行搜索. 在一次迭代中,全局搜索元搜索整个解空间以寻找潜在解区域,然后具有不同种群大小的局部搜索元组对潜力不同的历史潜在解区域以及新发现的潜在解区域进行不同粒度的搜索. 搜索元找到的较优解按照一定的规则保存在由队列和堆栈组成的结构体中以实现历史信息的高效记忆和共享. 结构体中保存的候选解在迭代过程中不断更新逐渐接近最优解,最终找到优化问题的多个全局最优解以及局部次优解.基于马尔科夫过程的理论分析表明:多元优化算法以概率1 收敛于全局最优解.为了评估多元优化算法的收敛性,本文利用多元优化算法以及其他五个常用的优化算法对十三个二维及十维标准测试函数进行了寻优测试. 实验结果表明,多元优化算法在收敛成功率和收敛精度方面优于其他参与比较的算法.     

全局优化的蝴蝶优化算法

针对基本蝴蝶优化算法中存在的易陷入局部最优值、收敛速度慢等问题,提出一种全局优化的蝴蝶算法,引入limit阈值来限定蝴蝶优化算法陷入局部最优解的次数,从而改变算法易陷入早熟的问题,结合单纯形策略优化迭代后期位置较差的蝴蝶使种群能够较快地找到全局最优解;将正弦余弦算法作为局部算子融入BOA中,改善迭代后期种群多样性下降的缺陷,加快算法跳出局部最优。在仿真模拟实验中与多个算法进行对比,结果表明改进算法的寻优性能更好。     

基于空间交配遗传算法的收敛性分析

基于空间交配遗传算法(GASM)采用空间交配遗传算子,有效克服早熟收敛问题,但缺少相关理论分析。文中采用马尔可夫链分析基于空间交配遗传算法的收敛性。证明采用最优个体保留机制的GASM,可收敛到全局最优解。同时证明在没有变异算子的情况下,GASM以概率1收敛到全局最优解。通过4个测试问题(其中3个为多峰值复杂问题)的对比实验,结果表明,GASM在求解多峰值复杂问题时,比采用最优个体保留机制的经典遗传算法,具有更好的收敛性。同时也与快速蜂群优化算法进行比较实验。     

基于SAA-SSA-BPNN的网络安全态势评估模型

针对目前网络安全态势评估模型准确性和收敛性有待提高的问题,提出一种基于SAA-SSA-BPNN的网络安全态势评估模型。该模型利用模拟退火算法（SAA）可以一定概率接受劣解并有大概率跳出局部极值达到全局最优解的特性来优化麻雀搜索算法,利用优化后的麻雀搜索算法（SSA）具有良好稳定性和收敛速度快且不易陷入局部最优的特点对BP神经网络（BPNN）进行改进,找到最佳适应度个体并获取最优权值和阈值,将其作为初始值赋给BP神经网络,将预处理后的指标数据输入改进后的BP神经网络模型对其进行训练,利用训练好的模型对网络系统所遭受威胁的程度进行评估。对比实验结果表明,该评估模型比其他基于改进BP神经网络的态势评估模型准确性更高,收敛速度更快。     

最优粒子增强探索粒子群算法

针对粒子群优化算法（Particle Swarm Optimization,PSO）存在收敛速度慢、寻优精度低和早熟收敛的问题,提出一种最优粒子增强探索粒子群算法（Optimal particle Enhanced Exploration Particle Swarm Optimization,OEEPSO）。OEEPSO将最优粒子在空间中的位置信息以二维一组划分,按4种方式计算每二维的适应值,选择适应值最小的方式更新对应维度的速度值和位置值。该策略加强了对最优粒子周围区域的探索,使粒子群能更快地向全局最优解靠近,提高了算法的收敛速度和求解精度。当算法陷入局部最优时,根据群体历史最优解的适应值,动态调整各粒子的速度值和位置值,使算法最终收敛到全局最优解。实验结果表明,OEEPSO具有收敛速度快、求解精度高的特点。     

基于IFI与FUA的Pareto遗传算法

在适应值快速辨识算法和基于聚类排挤的外部种群快速替换算法的基础上,提出了搜索Pareto最优解集的快速遗传算法。在该算法中,IFI算法实现个体适应值的快速辨识,FUA维持种群多样度和Pareto最优解集的均匀分布性。采用FPGA算法对多种多目标0/1背包问题进行仿真优化,FPGA算法能够以较少的计算成本搜索到高精度、分布均匀、高质量的Pareto非劣解集,收敛速度和收敛准确性均优于强度Pareto进化算法(SPEA)。     

求解TSP问题的改进混合蛙跳算法

针对TSP问题的特点,设计了一种求解TSP问题的改进的混合蛙跳算法。该算法改进了子种群青蛙个体优化的方式,而不仅是对最坏个体进行优化,这种方式可以有效提高算法的收敛速度。提出了青蛙个体翻转时依赖于全局最优解的“导优”概率和依赖于子种群局部最优解的“导次优”概率,进一步提高了算法寻找最优解的能力。在多个TSPLIB上的实验结果表明,该算法是可行有效的。     

A space search optimization algorithm with accelerated convergence strategies

Evolutionary algorithms (EAs), which have been widely used to solve various scientific and engineering optimization problems, are essentially stochastic search algorithms operating in the overall solution space. However, such random search mechanism may lead to some disadvantages such as a long computing time and premature convergence. In this study, we propose a space search optimization algorithm (SSOA) with accelerated convergence strategies to alleviate the drawbacks of the purely random search mechanism. The overall framework of the SSOA involves three main search mechanisms: local space search, global space search, and opposition-based search. The local space search that aims to form new solutions approaching the local optimum is realized based on the concept of augmented simplex method, which exhibits significant search abilities realized in some local space. The global space search is completed by Cauchy searching, where the approach itself is based on the Cauchy mutation. This operation can help the method avoid of being trapped in local optima and in this way alleviate premature convergence. An opposition-based search is exploited to accelerate the convergence of space search. This operator can effectively reduce a substantial computational overhead encountered in evolutionary algorithms (EAs). With the use of them SSOA realizes an effective search process. To evaluate the performance of the method, the proposed SSOA is contrasted with a method of differential evolution (DE), which is a well-known space concept-based evolutionary algorithm. When tested against benchmark functions, the SSOA exhibits a competitive performance vis-a-vis performance of some other competitive schemes of differential evolution in terms of accuracy and speed of convergence, especially in case of high-dimensional continuous optimization problems.     

Modified differential evolution approach for optimization of planar parallel manipulators force capabilities

The global optimization problem is not easy to solve and is still an open challenge for researchers since an analytical optimal solution is difficult to obtain even for relatively simple application problems. Conventional deterministic numerical algorithms tend to stop the search in local minimum nearest to the input starting point, mainly when the optimization problem presents nonlinear, non-convex and non-differential functions, multimodal and nonlinear. Nowadays, the use of evolutionary algorithms (EAs) to solve optimization problems is a common practice due to their competitive performance on complex search spaces. EAs are well known for their ability to deal with nonlinear and complex optimization problems. The primary advantage of EAs over other numerical methods is that they just require the objective function values, while properties such as differentiability and continuity are not necessary. In this context, the differential evolution (DE), a paradigm of the evolutionary computation, has been widely used for solving numerical global optimization problems in continuous search space. DE is a powerful population-based stochastic direct search method. DE simulates natural evolution combined with a mechanism to generate multiple search directions based on the distribution of solutions in the current population. Among DE advantages are its simple structure, ease of use, speed, and robustness, which allows its application on several continuous nonlinear optimization problems. However, the performance of DE greatly depends on its control parameters, such as crossover rate, mutation factor, and population size and it often suffers from being trapped in local optima. Conventionally, users have to determine the parameters for problem at hand empirically. Recently, several adaptive variants of DE have been proposed. In this paper, a modified differential evolution (MDE) approach using generation-varying control parameters (mutation factor and crossover rate) is proposed and evaluated. The proposed MDE presents an efficient strategy to improve the search performance in preventing of premature convergence to local minima. The efficiency and feasibility of the proposed MDE approach is demonstrated on a force optimization problem in Robotics, where the force capabilities of a planar 3-RRR parallel manipulator are evaluated considering actuation limits and different assembly modes. Furthermore, some comparison results of MDE approach with classical DE to the mentioned force optimization problem are presented and discussed.     

一种新的混合量子进化算法

量子进化算法(QEA)用于多峰函数优化时,容易陷入局部最优.本文提出一种新的混合量子进化算法,通过双编码机制(经典二进制编码和量子概率编码),以及经典交叉和量子概率编码更新策略,实现了经典遗传算法与量子进化算法的有机结合,在发挥经典遗传算法全局优化能力的同时,利用量子概率搜索提高了算法的局部搜索能力.通过一组典型函数优化实验对该算法的性能进行了考察,并与QEA进行了比较.结果表明,本文算法在解的质量和收敛速度上都要优于QEA.     

Multimodal optimization by artificial weed colonies enhanced with localized group search optimizers

Multimodal optimization aims at finding multiple global and local optima (as opposed to a single solution) of a function, so that the user can have a better knowledge about different optimal solutions in the search space and as and when needed, the current solution may be switched to another suitable one while still maintaining the optimal system performance. Evolutionary Algorithms (EAs) due to their population-based approach are able to detect multiple solutions within a population in a single simulation run and have a clear advantage over the classical optimization techniques, which need multiple restarts and multiple runs in the hope that a different solution may be discovered every run, with no guarantee however. This article proposes a hybrid two-stage optimization technique that firstly employs Invasive Weed Optimization (IWO), an ecologically inspired algorithm to find the promising Euclidean sub-regions surrounding multiple global and local optima. IWO is run for 80% of the total budget of function evaluations (FEs), and consecutively the search is intensified by using a modified Group Search Optimizer (GSO), in each detected sub-region. GSO, invoked in each sub-region discovered with IWO, is continued for 20% of the total budget of FEs. Both IWO and GSO have been modified from their original forms to meet the demands of the multimodal problems used in this work. Performance of the proposed algorithm is compared with a number of state-of-the-art multimodal optimization algorithms over a benchmark-suite comprising of 21 basic multimodal problems and 7 composite multimodal problems. A practical multimodal optimization problem concerning the design of dielectric composites has also been used to test the performance of the algorithm. Experimental results suggest that the proposed technique is able to provide better and more consistent performance over the existing well-known multimodal algorithms for majority of the test problems without incurring any serious computational burden.     

A robust stochastic genetic algorithm (StGA) for global numerical optimization

Many real-life problems can be formulated as numerical optimization of certain objective functions. However, often an objective function possesses numerous local optima, which could trap an algorithm from moving toward the desired global solution. Evolutionary algorithms (EAs) have emerged to enable global optimization; however, at the present stage, EAs are basically limited to solving small-scale problems due to the constraint of computational efficiency. To improve the search efficiency, this paper presents a stochastic genetic algorithm (StGA). A novel stochastic coding strategy is employed so that the search space is dynamically divided into regions using a stochastic method and explored region-by-region. In each region, a number of children are produced through random sampling, and the best child is chosen to represent the region. The variance values are decreased if at least one of five generated children results in improved fitness, otherwise, the variance values are increased. Experiments on 20 test functions of diverse complexities show that the StGA is able to find the near-optimal solution in all cases. Compared with several other algorithms, StGA achieves not only an improved accuracy, but also a considerable reduction of the computational effort. On average, the computational cost required by StGA is about one order less than the other algorithms. The StGA is also shown to be able to solve large-scale problems.     

A Novel Multiobjective Fireworks Algorithm and Its Applications to Imbalanced Distance Minimization Problems

Recently, multimodal multiobjective optimization problems (MMOPs) have received increasing attention. Their goal is to find a Pareto front and as many equivalent Pareto optimal solutions as possible. Although some evolutionary algorithms for them have been proposed, they mainly focus on the convergence rate in the decision space while ignoring solutions diversity. In this paper, we propose a new multiobjective fireworks algorithm for them, which is able to balance exploitation and exploration in the decision space. We first extend a latest single-objective fireworks algorithm to handle MMOPs. Then we make improvements by incorporating an adaptive strategy and special archive guidance into it, where special archives are established for each firework, and two strategies (i.e., explosion and random strategies) are adaptively selected to update the positions of sparks generated by fireworks with the guidance of special archives. Finally, we compare the proposed algorithm with eight state-of-the-art multimodal multiobjective algorithms on all 22 MMOPs from CEC2019 and several imbalanced distance minimization problems. Experimental results show that the proposed algorithm is superior to compared algorithms in solving them. Also, its runtime is less than its peers’.      

多选择背包问题的元胞萤火虫算法

为有效求解多选择背包问题,基于元胞自动机的原理和萤火虫算法,提出一种求解多选择背包问题的元胞萤火虫算法。将元胞及其邻居引入到算法中来保持种群的多样性,利用元胞的演化规则进行局部优化,避免算法陷入局部极值。通过对典型多选择背包问题的仿真实验和其他算法的比较,表明该算法可行有效,有良好的全局优化能力。     

求解背包问题的演化算法

背包问题(Knapsack Problem, KP)是一类著名的组合优化问题,也是一类NP难问题,它包括0-1背包问题、有界背包问题、多维背包问题、多背包问题、多选择背包问题、二次背包问题、动态背包问题和折扣背包问题等多种形式,在众多领域有着广泛的应用.演化算法(EAs)是一类有效的快速近似求解KP的算法.本文对近十余年来利用EAs求解KP的研究情况进行一个较为详细的总结,它一方面讨论了利用EAs求解各种KP问题时个体的编码方法与处理不可行解的有效方法,另一方面为今后进一步利用最新提出的EAs求解KP问题提供一个可借鉴的思路.     

一种多粒子群协同进化算法

为进一步提高多粒子群协同进化算法的寻优精度, 并有效改善粒子群易陷入局部极值及收敛速度慢的问题, 结合遗传算法较强的全局搜索能力和极值优化算法的局部搜索能力, 提出了一种改进的多粒子群协同进化算法. 对粒子群优化算法提出改进策略, 并在种群进化过程中, 利用遗传算法增加粒子的多样性及优良性, 经过一定次数的迭代, 利用极值优化算法加快收敛速度. 实验结果表明该算法具有较好的性能, 能够摆脱陷入局部极值点的问题, 并具有较快的收敛速度.     

Deriving operating policies for multi-objective reservoir systems: Application of Self-Learning Genetic Algorithm

Optimal multi-reservoir operation is a multi-objective problem in nature and some of its objectives are nonlinear, non-convex and multi-modal functions. There are a few areas of application of mathematical optimization models with a richer or more diverse history than in reservoir systems optimization. However, actual implementations remain limited or have not been sustained.Genetic Algorithms (GAs) are probabilistic search algorithms that are capable of solving a variety of complex multi-objective optimization problems, which may include non-linear, non-convex and multi-modal functions. GA is a population based global search method that can escape from local optima traps and find the global optima. However GAs have some drawbacks such as inaccuracy of the intensification process near the optimal set.In this paper, a new model called Self-Learning Genetic Algorithm (SLGA) is presented, which is an improved version of the SOM-Based Multi-Objective GA (SBMOGA) presented by Hakimi-Asiabar et al. (2009) [45]. The proposed model is used to derive optimal operating policies for a three-objective multi-reservoir system. SLGA is a new hybrid algorithm which uses Self-Organizing Map (SOM) and Variable Neighborhood Search (VNS) algorithms to add a memory to the GA and improve its local search accuracy. SOM is a neural network which is capable of learning and can improve the efficiency of data processing algorithms. The VNS algorithm can enhance the local search efficiency in the Evolutionary Algorithms (EAs).To evaluate the applicability and efficiency of the proposed methodology, it is used for developing optimal operating policies for the Karoon-Dez multi-reservoir system, which includes one-fifth of Iran's surface water resources. The objective functions of the problem are supplying water demands, generating hydropower energy and controlling water quality in downstream river.