CN116306919A - Large-Scale Multi-objective Combinatorial Optimization Method Based on Problem Recombination and Its Application - Google Patents

Large-Scale Multi-objective Combinatorial Optimization Method Based on Problem Recombination and Its Application Download PDF

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CN116306919A
CN116306919A CN202310233019.XA CN202310233019A CN116306919A CN 116306919 A CN116306919 A CN 116306919A CN 202310233019 A CN202310233019 A CN 202310233019A CN 116306919 A CN116306919 A CN 116306919A
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丁炜超
祝梦杨
时昌银
周贤芳
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Abstract

The invention relates to a large-scale multi-objective combination optimization method based on problem recombination and application thereof, wherein the method comprises the following steps: randomly initializing a population; based on a decision variable clustering technology, dividing decision variables into convergence variables and diversity variables; adopting directional cross variation facing convergence, and combining a convergence environment selection mechanism to select an optimal individual as a new parent population; when the population encounters selection pressure, problem reconstruction is carried out, and large-scale multi-objective optimization is converted into single-objective optimization; adopting diversity-oriented directional cross variation and combining a diversity environment selection mechanism to select a population as a new parent population; and after the termination condition is met, outputting the parent population as an optimal solution set of the optimization target. Compared with the prior art, the complementary search strategy and the problem reconstruction strategy provided by the invention can solve the problem of large-scale multi-objective optimization, respectively process the problems of convergence and diversity in different optimization stages, and avoid the situation of sinking into local optimum.

Description

基于问题重组的大规模多目标组合优化方法及应用Large-Scale Multi-objective Combinatorial Optimization Method Based on Problem Recombination and Its Application

技术领域technical field

本发明涉及多目标演化计算领域,尤其是涉及一种基于问题重组的大规模多目标组合进化优化方法。The invention relates to the field of multi-objective evolutionary calculation, in particular to a large-scale multi-objective combined evolutionary optimization method based on problem reorganization.

背景技术Background technique

近二十年来出现了多种多目标进化算法,包括基于Pareto的多目标进化算法(Multi Objective Evolutionary Algorithms,MOEAs),基于分解的MOEAs和基于指标的MOEAs等。尽管现有的大多数多目标进化算法在解决具有少量决策变量的多目标问题上表现出很好的性能,但在解决具有数百甚至数千个决策变量的多目标优化问题(MOPs)时,即大规模MOPs(LSMOPs),它们的性能急剧下降。随着决策变量的数量线性增加,搜索空间的体积(以及复杂性)将呈指数级增长,从而导致算法过早收敛到局部最优或收敛到超大区域。近年来,学术及工业界先后提出了基于协同进化框架、基于决策变量分析和基于问题转换等多种多目标进化算法框架对LSMOPs进行优化研究,但仍存在着许多亟待解决的问题,主要表现在以下几个方面:A variety of multi-objective evolutionary algorithms have emerged in the past two decades, including Pareto-based multi-objective evolutionary algorithms (Multi Objective Evolutionary Algorithms, MOEAs), decomposition-based MOEAs and index-based MOEAs. Although most of the existing multi-objective evolutionary algorithms show good performance in solving multi-objective problems with a small number of decision variables, when solving multi-objective optimization problems (MOPs) with hundreds or even thousands of decision variables, Namely large-scale MOPs (LSMOPs), their performance drops dramatically. As the number of decision variables increases linearly, the volume (and thus complexity) of the search space will grow exponentially, causing the algorithm to converge prematurely to local optima or to very large regions. In recent years, academia and industry have successively proposed a variety of multi-objective evolutionary algorithm frameworks based on co-evolution framework, decision variable analysis and problem transformation to optimize LSMOPs, but there are still many problems to be solved, mainly in The following aspects:

基于协同进化框架的LSMOEAs需要花费大量的时间分析决策变量来完成决策变量的分组。此外,由于分组不当,导致子问题间存在关联关系时,需要依次反复优化,算法的性能也会严重下降。值得注意的是,决策变量之间的可分离性假设并不总是正确的。因此,该算法存在局限性,不适用于求解各决策变量相互作用的大规模MOPs。LSMOEAs based on the co-evolutionary framework need to spend a lot of time analyzing decision variables to complete the grouping of decision variables. In addition, due to improper grouping, when there is a correlation between the sub-problems, it needs to be optimized repeatedly in sequence, and the performance of the algorithm will also be severely degraded. It is worth noting that the assumption of separability between decision variables is not always true. Therefore, the algorithm has limitations and is not suitable for solving large-scale MOPs where various decision variables interact.

基于决策变量分析的LSMOEAs虽然通过决策变量分类一定程度上减小了问题的规模,但所产生的类别较少(收敛性变量,多样性变量以及混合变量),分解出的子问题仍可能是大规模问题,算法的总体搜索效率尚待提升。Although LSMOEAs based on decision variable analysis reduce the scale of the problem to a certain extent through the classification of decision variables, there are fewer categories (convergent variables, diversity variables and mixed variables), and the sub-problems decomposed may still be large. In terms of scale, the overall search efficiency of the algorithm needs to be improved.

基于问题转换的LSMOEAs需要找到一个问题转换函数,以保证原始问题转换为新问题后信息损失尽可能小。然而,要找到一个完美的问题变换函数是非常困难的,在特别复杂的问题中更是不可能。此外,由于一个权值对应一组决策变量,导致对决策空间的搜索不彻底,所获得最后解的质量有待改进。LSMOEAs based on problem transformation need to find a problem transformation function that guarantees as little information loss as possible after the original problem is transformed into a new problem. However, it is very difficult to find a perfect problem transformation function, and it is even impossible in particularly complex problems. In addition, since one weight value corresponds to a set of decision variables, the search of the decision space is incomplete, and the quality of the final solution obtained needs to be improved.

中国专利申请CN114819040A公开了一种基于对偶搜索的双种群协同进化方法,该方法无法处理决策变量数高达500甚至1000及以上的多目标优化问题。Chinese patent application CN114819040A discloses a dual-population co-evolution method based on dual search, which cannot handle multi-objective optimization problems with as many as 500 or even 1000 or more decision variables.

发明内容Contents of the invention

本发明的目的就是为了克服上述现有技术在优化过程中很难做到收敛性和多样性二者平衡的缺陷而提供一种基于问题重组的大规模多目标组合优化方法。The purpose of the present invention is to provide a large-scale multi-objective combined optimization method based on problem recombination in order to overcome the defect that it is difficult to achieve a balance between convergence and diversity in the optimization process of the prior art.

本发明的目的可以通过以下技术方案来实现:The purpose of the present invention can be achieved through the following technical solutions:

作为本发明的第一方面,提供一种基于问题重组的大规模多目标组合优化方法,所述方法包括收敛性优化阶段和多样性优化阶段,具体步骤包括:As a first aspect of the present invention, there is provided a large-scale multi-objective combined optimization method based on problem reorganization, the method includes a convergence optimization stage and a diversity optimization stage, and the specific steps include:

随机初始化种群P;Randomly initialize the population P;

基于决策变量聚类技术,将决策变量分为收敛性变量和多样性变量;Based on decision variable clustering technology, decision variables are divided into convergent variables and diversity variables;

收敛性优化阶段:Convergent optimization phase:

在进化过程中采用面向收敛性的定向交叉变异,并结合收敛性环境选择机制,选出最优的个体作为亲本种群P′;In the process of evolution, the convergence-oriented directional crossover mutation is adopted, combined with the convergence environment selection mechanism, to select the optimal individual as the parent population P';

在种群遇到选择压力时,进行问题重构,将大规模多目标优化转换为单目标优化,并重新选出最优的个体作为亲本种群P″;When the population encounters selection pressure, it reconstructs the problem, converts large-scale multi-objective optimization into single-objective optimization, and reselects the optimal individual as the parent population P″;

多样性优化阶段:Diversity optimization phase:

在进化过程中采用面向多样性的定向交叉变异,并结合多样性环境选择机制,选取种群作为新的亲本种群;In the evolution process, the diversity-oriented directional cross-mutation is adopted, combined with the diversity environment selection mechanism, and the population is selected as the new parent population;

在满足终止条件后,输出亲本种群作为优化目标的最优解集。After satisfying the termination condition, the parent population is output as the optimal solution set of the optimization target.

进一步的,所述收敛性优化阶段的具体演化步骤如下:Further, the specific evolution steps of the convergence optimization stage are as follows:

使用基于收敛度的二元竞赛选择,利用交叉和变异算子,从当前种群中选择个体生成N个子代Q;Using convergence-based binary competition selection, using crossover and mutation operators, select individuals from the current population to generate N offspring Q;

计算当前种群P和子代Q并集中的每个个体的收敛度,从并集中选出最优的N个个体作为新的亲本种群P′;Calculate the convergence degree of each individual in the union of the current population P and the offspring Q, and select the best N individuals from the union as the new parent population P′;

重复上述过程,直至满足终止条件;Repeat the above process until the termination condition is met;

进行问题重构,通过双向权重向量关联,将大规模多目标优化转换为单目标优化;Carry out problem reconstruction, and convert large-scale multi-objective optimization into single-objective optimization through two-way weight vector association;

通过差分进化生产子代种群A;Producing offspring population A through differential evolution;

基于收敛度策略的环境选择机制从子代种群A和权重向量种群Q′的并集中选出最优的N个个体作为新的亲本种群P″。The environment selection mechanism based on the convergence strategy selects the best N individuals from the union of the offspring population A and the weight vector population Q′ as the new parent population P″.

进一步的,所述收敛性的定向交叉以互不依赖的收敛性变量分组为单位进行交叉操作;Further, the convergent directional crossover operation is performed in units of mutually independent convergent variable groups;

所述收敛性的定向变异在收敛性变量中选择变量进行变异。The convergent directional mutation selects a variable among the convergent variables to mutate.

进一步的,解x的所述收敛度Cd计算公式如下:Further, the calculation formula of the degree of convergence C d of the solution x is as follows:

Figure BDA0004121105390000031
Figure BDA0004121105390000031

其中,M表示目标数量。Among them, M represents the number of targets.

进一步的,所述问题重组策略具体为:通过双向权重向量关联,将原始大规模多目标优化问题重新表述为相对较小权重变量的单目标优化,使用一组收敛性好,分布均匀的候选解来指导算法向最优集方向搜索。Further, the problem reorganization strategy is specifically: through two-way weight vector association, the original large-scale multi-objective optimization problem is re-expressed as a single-objective optimization with relatively small weight variables, and a group of candidate solutions with good convergence and uniform distribution are used To guide the algorithm to search in the direction of the optimal set.

进一步的,所述问题重组策略的具体演化步骤如下:Further, the specific evolution steps of the problem restructuring strategy are as follows:

权重向量关联,从当前种群中选择r个解作为参考解集,每个参考解与两个方向向量Vl和Vu与两个权重变量λr1和λr2相关联;Weight vector association, select r solutions from the current population as a reference solution set, each reference solution is associated with two direction vectors V l and V u and two weight variables λ r1 and λ r2 ;

根据方向向量和权重变量构造子问题:Construct subproblems from direction vectors and weight variables:

Z′(Λ)={z1111),z1212),...,zr1r1)zr2r2)}Z′(Λ)={z 1111 ), z 1212 ), . . . , z r1r1 )z r2r2 )}

其中,Λ={λ11,λ12,...,λr1,λr2}为重构的决策空间;Among them, Λ={λ 1112 ,...,λ r1r2 } is the reconstructed decision space;

目标空间重构,当子问题被重构,原始决策空间中决策向量x的优化就转化为权重向量Λ在重构的决策空间中的优化,新的优化问题表述为:The target space is reconstructed. When the sub-problem is reconstructed, the optimization of the decision vector x in the original decision space is transformed into the optimization of the weight vector Λ in the reconstructed decision space. The new optimization problem is expressed as:

maximize G(Λ)=H(Z′(Λ))maximize G(Λ)=H(Z′(Λ))

其中,H可以是任何性能指标。Among them, H can be any performance index.

进一步的,所述根据方向向量和权重变量构造子问题的具体步骤包括:Further, the specific steps of constructing sub-problems according to the direction vector and weight variables include:

计算每个参考解的两个方向向量:Compute the two direction vectors for each reference solution:

Vl=s1-oV l =s 1 -o

Vu=t-s1 V u =ts 1

其中,s1={x1,...,xd}为参考解,t、o分别为X的上下边界点;Among them, s 1 ={x 1 ,...,x d } is the reference solution, and t and o are the upper and lower boundary points of X respectively;

计算每个参考解的两个权重向量:Compute two weight vectors for each reference solution:

Figure BDA0004121105390000041
Figure BDA0004121105390000041

Figure BDA0004121105390000042
Figure BDA0004121105390000042

其中,λ11和λ12是两个权重变量,lmax=||t-o||;Among them, λ11 and λ12 are two weight variables, l max =||to||;

构造子问题的表达式为:The expression of the constructor problem is:

Figure BDA0004121105390000043
Figure BDA0004121105390000043

Figure BDA0004121105390000044
Figure BDA0004121105390000044

进一步的,所述多样性优化阶段的具体演化步骤如下:Further, the specific evolution steps of the diversity optimization stage are as follows:

采用基于拥挤距离的二元竞赛选择从当前群体P″中选择个体;Select individuals from the current population P″ using binary competition selection based on crowding distance;

利用上述选择的个体仅对多样性相关变量进行交叉和变异,生成N个子代Q″;Use the individual selected above to only cross and mutate the diversity-related variables to generate N offspring Q";

根据帕累托优势和拥挤距离,从当前群体P″和子代Q″的并集中选取一半的种群作为新的亲本种群P″′;According to the Pareto advantage and crowding distance, select half of the population from the union of the current population P" and the offspring Q" as the new parent population P"';

重复上述过程直至满足终止条件,输出亲本种群P″′作为优化目标的最优解集。Repeat the above process until the termination condition is satisfied, and output the parent population P"' as the optimal solution set of the optimization goal.

进一步的,所述多样性的定向交叉以所有多样性变量为单位进行交叉操作;Further, the directional crossover of the diversity performs the crossover operation in units of all diversity variables;

所述多样性的定向变异在多样性变量中选择变量进行变异。The directional variation of the diversity selects a variable among the diversity variables to mutate.

作为本发明的第二方面,提供一种如上任一所述的基于问题重组的大规模多目标组合优化方法的应用,所述方法的应用场景包括大规模数据中心的资源调度和整合优化;具体应用步骤包括:As a second aspect of the present invention, an application of the large-scale multi-objective combination optimization method based on problem reorganization as described above is provided, and the application scenarios of the method include resource scheduling and integration optimization of large-scale data centers; specifically Application steps include:

以包括能耗、资源损耗、数据通信流量和任务完成时延的指标作为问题优化目标,以服务器剩余可用计算容量为约束条件,建立大规模数据中心资源调度和整合问题的多目标约束优化模型;Taking the indicators including energy consumption, resource consumption, data communication flow and task completion delay as the problem optimization goal, and taking the remaining available computing capacity of the server as the constraint condition, a multi-objective constrained optimization model for large-scale data center resource scheduling and integration problems is established;

以待调度的虚拟机数量为染色体长度,虚拟机编号为基因位置,实现种群个体的编码;The number of virtual machines to be scheduled is the chromosome length, and the number of virtual machines is the gene position to realize the coding of the population individual;

基于编码方式初始化种群P,并按照如上任一所述的基于问题重组的大规模多目标组合优化方法进行种群的迭代优化,直到满足算法的终止条件,输出包括能耗、资源损耗、数据通信流量和任务完成时延的多个冲突指标为优化目标的Pareto最优解集。Initialize the population P based on the encoding method, and perform the iterative optimization of the population according to the large-scale multi-objective combination optimization method based on problem recombination as described above, until the termination condition of the algorithm is met, and the output includes energy consumption, resource consumption, and data communication flow. Multiple conflicting indicators with the task completion delay are the Pareto optimal solution set of the optimization objective.

与现有技术相比,本发明具有以下有益效果:Compared with the prior art, the present invention has the following beneficial effects:

1)本发明提供的大规模多目标优化方法,基于问题重构策略,可以将大规模多目标优化问题转换为对权重向量的优化,从而解决大规模问题。1) The large-scale multi-objective optimization method provided by the present invention, based on the problem reconstruction strategy, can convert the large-scale multi-objective optimization problem into the optimization of weight vectors, thereby solving large-scale problems.

2)不同于现有的大规模多目标进化算法在一次种群迭代优化过程中同时保持种群的收敛性和多样性,本发明提出的互补搜索策略,在不同优化阶段分别处理收敛性和多样性问题。在第一阶段,种群快速逼近帕累托前沿,忽略了种群的多样性。在种群收敛后,第二阶段采用决策变量聚类方法强调种群的多样性,从而避免陷入局部最优的情况。2) Different from the existing large-scale multi-objective evolutionary algorithm that maintains the convergence and diversity of the population during an iterative optimization process of the population, the complementary search strategy proposed by the present invention handles the convergence and diversity problems separately in different optimization stages . In the first stage, the population quickly approaches the Pareto front, ignoring the diversity of the population. After the population converges, the second stage adopts the decision variable clustering method to emphasize the diversity of the population, so as to avoid falling into the local optimal situation.

3)不同于现有的多目标进化算法在环境选择使采用拥挤度等方法,本发明提出了收敛度的概念,用来定量判断候选解的收敛性,以此来选择收敛性更佳的解。3) Different from the existing multi-objective evolutionary algorithm that uses methods such as crowding degree in environment selection, the present invention proposes the concept of convergence degree, which is used to quantitatively judge the convergence of candidate solutions, so as to select the solution with better convergence .

4)本发明的多样性进化可采用其他多目标优化算法的方法,从而针对不同类型的多目标优化问题,设计不同的实例化算法,扩展性强。4) The diversity evolution of the present invention can adopt other methods of multi-objective optimization algorithms, so that different instantiation algorithms can be designed for different types of multi-objective optimization problems, and the scalability is strong.

附图说明Description of drawings

图1为本发明的基于问题重组的大规模多目标组合进化方法流程示意图;Fig. 1 is a schematic flow chart of the large-scale multi-objective combinatorial evolution method based on problem reorganization of the present invention;

图2为本发明的实例化算法在测试函数LSMOF2上的近似Pareto前沿示意图;Fig. 2 is the approximate Pareto front schematic diagram of instantiation algorithm of the present invention on test function LSMOF2;

图3为本发明的实例化算法在测试函数ZDT1上的近似Pareto前沿示意图;Fig. 3 is the approximate Pareto front schematic diagram of instantiation algorithm of the present invention on test function ZDT1;

图4为本发明所提供大规模多目标组合优化方法的示例性应用流程图。Fig. 4 is an exemplary application flowchart of the large-scale multi-objective combination optimization method provided by the present invention.

具体实施方式Detailed ways

下面结合附图和具体实施例对本发明进行详细说明。本实施例以本发明技术方案为前提进行实施,给出了详细的实施方式和具体的操作过程,但本发明的保护范围不限于下述的实施例。The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

实施例1Example 1

本发明所提出的多目标优化方法,通过互补搜索策略,在不同优化阶段分别处理收敛性和多样性问题。在第一阶段,种群快速逼近Pareto前沿,忽略了种群的多样性。当遇到选择压力时,通过问题重构直接跟踪Pareto最优集(PS)。该算法首先在决策空间中获取一组参考方向,并将其与一组权重变量相关联,用于定位PS,然后将原大规模多目标优化问题转化为低维单目标优化问题。在第二阶段,利用多目标进化算法将最优解均匀分布在近似Pareto最优前沿上。在第一阶段,种群快速逼近帕累托前沿,忽略了种群的多样性。在种群收敛后,第二阶段采用决策变量聚类方法强调种群的多样性,从而避免陷入局部最优的情况。The multi-objective optimization method proposed by the present invention handles convergence and diversity problems in different optimization stages through complementary search strategies. In the first stage, the population quickly approaches the Pareto front, ignoring the diversity of the population. When selection pressure is encountered, the Pareto optimal set (PS) is directly tracked through problem reformulation. The algorithm first obtains a set of reference directions in the decision space and associates them with a set of weight variables for locating the PS, and then transforms the original large-scale multi-objective optimization problem into a low-dimensional single-objective optimization problem. In the second stage, the optimal solutions are evenly distributed on the approximate Pareto optimal frontier using the multi-objective evolutionary algorithm. In the first stage, the population quickly approaches the Pareto front, ignoring the diversity of the population. After the population converges, the second stage adopts the decision variable clustering method to emphasize the diversity of the population, so as to avoid falling into the local optimal situation.

如图1所示为基于问题重组的大规模多目标组合优化方法,该框架中分为了两个阶段优化种群:收敛性优化阶段(Convergence-oriented Stage,CS)和多样性优化阶段(Diversity-oriented Stage,DS)。收敛性优化阶段(CS)首先采用基于收敛度的二元竞赛选择,利用交叉和变异算子,从当前种群P中选择个体生成N个子代Q,其中N为种群规模。然后,由式(1)确定P和Q的并集的收敛度。最后,从并集中选出最优的N个个体作为新的亲本种群P,并在种群遇到选择压力时,采用问题重构的方式,维护一组权重向量,将大规模多目标优化转换为单目标优化,通过差分进化生产子代种群A,并基于收敛度策略的环境选择机制从子代种群A和权重向量种群Q′并集中选出最优的N个个体作为新的亲本种群P″,进一步提高种群的收敛性;多样性优化阶段(DS)采用基于拥挤距离的二元竞赛选择从当前群体P″中选择个体,然后利用上述选择的个体仅对多样性相关变量进行交叉和变异,生成子代Q″。最后,根据帕累托优势和拥挤距离,从父代P″和子代Q″的并集中选取一半的种群作为新的亲本种群。具体框架的演化步骤如下:As shown in Figure 1, a large-scale multi-objective combinatorial optimization method based on problem recombination is divided into two phases to optimize the population in this framework: the convergence-oriented stage (Convergence-oriented Stage, CS) and the diversity-oriented stage (Diversity-oriented stage). Stage, DS). The convergence optimization stage (CS) first adopts the binary competition selection based on the degree of convergence, and uses crossover and mutation operators to select individuals from the current population P to generate N offspring Q, where N is the population size. Then, the degree of convergence of the union of P and Q is determined by formula (1). Finally, select the best N individuals from the union as the new parental population P , and when the population encounters selection pressure, use the method of problem reconstruction to maintain a set of weight vectors, and convert large-scale multi-objective optimization into For single-objective optimization, the offspring population A is produced through differential evolution, and the optimal N individuals are collectively selected from the offspring population A and the weight vector population Q′ based on the environment selection mechanism of the convergence strategy as the new parent population P ″, to further improve the convergence of the population; the diversity optimization stage (DS) adopts the binary competition selection based on the crowding distance to select individuals from the current population P″, and then use the above-mentioned selected individuals to only crossover and mutate the diversity-related variables , to generate offspring Q″. Finally, according to Pareto advantage and crowding distance, select half of the population from the union of parent P″ and offspring Q″ as the new parent population. The evolution steps of the specific framework are as follows:

随机初始化种群P,种群规模为N;Randomly initialize the population P, the population size is N;

基于决策变量聚类技术,将决策变量分为两类(收敛性变量和多样性变量)。Based on the decision variable clustering technique, the decision variables are divided into two categories (convergence variables and diversity variables).

使用基于收敛度的二元竞赛选择,利用交叉和变异算子,从当前种群P中选择个体生成N个子代Q,其中N为种群规模;Using convergence-based binary competition selection, using crossover and mutation operators, select individuals from the current population P to generate N offspring Q, where N is the population size;

计算P和Q的每个个体的收敛度,从并集中选出最优的N个个体作为新的亲本种群P′;解x的收敛度Cd计算公式为:Calculate the degree of convergence of each individual of P and Q, and select the best N individuals from the union as the new parental population P′; the calculation formula for the degree of convergence Cd of solving x is:

Figure BDA0004121105390000061
Figure BDA0004121105390000061

其中,M表示目标数量。收敛度定义为x的目标值之和。对于最小化MOP,Cd的值越小,解x的收敛性越好。Among them, M represents the number of targets. Convergence is defined as the sum of the target values of x. For minimizing MOP, the smaller the value of Cd, the better the convergence of solution x.

在满足终止条件后,采用基于问题重构策略,从当前种群P中选择r个解作为参考解集。然后使用公式2计算每个参考解的两个方向向量。After satisfying the termination condition, the problem-based reconstruction strategy is used to select r solutions from the current population P ' as the reference solution set. Then use Equation 2 to calculate the two direction vectors for each reference solution.

Vll=s1-oVl l =s 1 -o

Vuu=t-s1 (2)V u u =ts 1 (2)

其中,s1={x1,…,xd}为参考解,o、t分别为X的上下边界点。Wherein, s 1 ={x 1 ,…,x d } is the reference solution, and o and t are the upper and lower boundary points of X respectively.

使用公式3计算每个参考解的两个权重向量。Compute the two weight vectors for each reference solution using Equation 3.

Figure BDA0004121105390000062
Figure BDA0004121105390000062

Figure BDA0004121105390000063
Figure BDA0004121105390000063

其中,λ11和λ12是两个权重变量,lmax=||t-o||。Wherein, λ 11 and λ 12 are two weight variables, l max =||to||.

选取一个大小为r的参考解集,一旦每个参考解与两个方向向量和两个权重变量相关联,就可以构造2r个子问题的总数。A set of reference solutions of size r is chosen, and once each reference solution is associated with two direction vectors and two weight variables, a total of 2r subproblems can be constructed.

Figure BDA0004121105390000071
Figure BDA0004121105390000071

Figure BDA0004121105390000072
Figure BDA0004121105390000072

子问题为Z′(∧)={z1111),z1212),…,zr1r1)zr2r2)},其中∧={λ11,λ12,…,λr1,λr2}为重构的决策空间。The subproblems are Z′(∧)={z 1111 ), z 1212 ),…, z r1r1 )z r2r2 )}, where ∧={λ 11 , λ 12 , ..., λ r1 , λ r2 } is the reconstructed decision space.

一旦子问题被重构,对原始决策空间中决策向量x的优化就转化为权重向量的优化。相应的,目标空间可以缩小,新的优化问题可以重新表述为Once the subproblems are reconstructed, the optimization of the decision vector x in the original decision space is transformed into the optimization of the weight vector. Accordingly, the target space can be reduced, and the new optimization problem can be reformulated as

maximize G(∧)=H(Z′(∧)) (5)maximize G(∧)=H(Z′(∧)) (5)

其中,H可以是任何性能指标。Among them, H can be any performance index.

通过差分进化生产子代种群A,并基于收敛度策略的环境选择机制从A和Q′的并集中选出最优的N个个体作为新的亲本种群P″。The offspring population A is produced through differential evolution, and the optimal N individuals are selected from the union of A and Q′ as the new parent population P″ based on the environment selection mechanism of the convergence strategy.

在满足终止条件后,进入DS,首先,采用基于拥挤距离的二元竞赛选择从当前群体P″中选择个体,然后利用上述选择的个体仅对多样性相关变量进行交叉和变异,生成N个子代Q″。最后,根据帕累托优势和拥挤距离,从P″和Q″的并集中选取一半的种群作为新的亲本种群P″′,在满足终止条件后,输出亲本种群P″′作为优化目标的最优解集。After satisfying the termination condition, enter DS, first, select individuals from the current population P″ by using binary competition selection based on crowding distance, and then use the above-mentioned selected individuals to crossover and mutate only the diversity-related variables to generate N offspring Q ". Finally, according to the Pareto advantage and crowding distance, select half of the population from the union of P″ and Q″ as the new parental population P″′, and output the parental population P″′ as the optimal optimization target after the termination condition is met. Excellent solution set.

1)CS在进化过程中采用面向收敛性的定向交叉变异,并结合收敛性环境选择机制来维持种群的收敛性;1) CS adopts convergence-oriented directional crossover mutation in the evolution process, and combines the convergence environment selection mechanism to maintain the convergence of the population;

2)DS在进化过程中采用面向多样性的定向交叉变异,并结合多样性环境选择机制来维持种群多样性。2) DS adopts diversity-oriented directional cross-mutation in the evolution process, and combines the diversity environment selection mechanism to maintain population diversity.

作为优选,上述的收敛性及多样性的交叉和变异算子分别通过收敛度计算和决策变量分析实现,具体步骤如下:As a preference, the aforementioned convergent and diverse crossover and mutation operators are respectively implemented through convergence calculation and decision variable analysis, and the specific steps are as follows:

1)决策变量聚类:该方法采用k-means聚类,将变量分为两类(收敛性变量和多样性变量)。1) Clustering of decision variables: This method uses k-means clustering to divide variables into two categories (convergence variables and diversity variables).

2)收敛性变量分类:解x的收敛度Cd计算公式(1)所示。2) Classification of convergent variables: the calculation formula (1) for the degree of convergence Cd of the solution x.

3)收敛性交叉以互不依赖的收敛性变量分组为单位进行交叉操作;多样性交叉以所有多样性变量为单位进行交叉操作;3) Convergent crossover is performed in units of independent convergent variable groups; diversity crossover is performed in units of all diversity variables;

4)收敛性变异在收敛性变量中选择变量进行变异;多样性变异在多样性变量中选择变量进行变异。4) Convergent mutation selects variables from convergent variables to mutate; diversity mutation selects variables from diverse variables to mutate.

CS在进化过程中使用的问题重构策略具体如下:The problem reconstruction strategy used by CS in the evolution process is as follows:

问题重构策略:该策略用于解决大规模决策变量引起的选择压力。具体地分为三个步骤:第一步,权重向量关联,从当前种群P中选择r个解作为参考解集,每个参考解与两个方向向量和两个权重变量相关联。第二步,构造子问题,根据公式4和5构造子问题Z′(∧)={z1111),z1212),…,zr1r1)zr2r2)},其中∧={λ11,λ12,…,λr1,λr2}为重构的决策空间。第三步,目标空间重构,一旦子问题被重构,原始决策空间中决策向量x的优化就转化为权重向量∧在重构的决策空间中的优化。新的优化问题可以表述为公式5。Problem Reframing Strategy: This strategy is used to address the selection pressure caused by large-scale decision variables. It is specifically divided into three steps: the first step, weight vector association, selects r solutions from the current population P as a reference solution set, and each reference solution is associated with two direction vectors and two weight variables. The second step is to construct sub-problems, according to formulas 4 and 5 to construct sub-problems Z′(∧)={z 1111 ), z 1212 ),…, z r1r1 ) z r2r2 )}, where ∧={λ 1112 ,…,λ r1r2 } is the reconstructed decision space. The third step is the reconstruction of the target space. Once the subproblems are reconstructed, the optimization of the decision vector x in the original decision space is transformed into the optimization of the weight vector ∧ in the reconstructed decision space. The new optimization problem can be formulated as Equation 5.

多样性进化阶段可采用其他多目标优化算法的方法,从而针对不同类型的多目标优化问题,设计不同的实例化算法,扩展性强。In the stage of diversity evolution, other multi-objective optimization algorithms can be used, so that different instantiation algorithms can be designed for different types of multi-objective optimization problems, and the scalability is strong.

表1为两种多目标进化算法在9个大规模测试用例上获得的IGD均值。为减少随机误差对计算结果的影响,本实施例中每种算法在每个算例中均独立运行30次,计算各算法在每个算例上获得的IGD指标的均值。IGD指标度量了真实Pareto前沿到算法获得的近似Pareto之间的距离。一般地,IGD指标值越小,则表明算法的收敛性和多样性越好。Table 1 shows the mean values of IGD obtained by the two multi-objective evolutionary algorithms on nine large-scale test cases. In order to reduce the impact of random errors on the calculation results, each algorithm in this embodiment is independently run 30 times in each calculation example, and the average value of the IGD index obtained by each algorithm on each calculation example is calculated. The IGD indicator measures the distance between the real Pareto front and the approximate Pareto obtained by the algorithm. Generally, the smaller the IGD index value, the better the convergence and diversity of the algorithm.

表1Table 1

ProblemProblem Mm DD. 本框架实例化的算法The algorithm instantiated by this framework LSMOFLSMOF LSMOP1LSMOP1 22 10001000 2.6390e-1(1.63e-2)+2.6390e-1(1.63e-2)+ 6.2856e-1(2.77e-2)6.2856e-1 (2.77e-2) LSMOP2LSMOP2 22 10001000 1.1624e-2(3.74e-4)+1.1624e-2(3.74e-4)+ 1.8858e-2(3.47e-4)1.8858e-2 (3.47e-4) LSMOP3LSMOP3 22 10001000 1.5680e+0(1.61e-3)+1.5680e+0(1.61e-3)+ 1.5729e+0(4.09e-4)1.5729e+0(4.09e-4) LSMOP4LSMOP4 22 10001000 2.5755e-2(7.90e-4)+2.5755e-2(7.90e-4)+ 3.8112e-2(1.95e-3)3.8112e-2 (1.95e-3) LSMOP5LSMOP5 22 10001000 6.8558e-1(4.40e-2)+6.8558e-1(4.40e-2)+ 7.4209e-1(3.39e-16)7.4209e-1 (3.39e-16) LSMOP6LSMOP6 22 10001000 5.6957e-1(1.62e-1)-5.6957e-1 (1.62e-1)- 3.1236e-1(4.03e-4)3.1236e-1 (4.03e-4) LSMOP7LSMOP7 22 10001000 1.5087e+0(4.30e-4)-1.5087e+0(4.30e-4)- 1.5083e+0(7.70e-4)1.5083e+0(7.70e-4) LSMOP8LSMOP8 22 10001000 5.3281e-1(2.17e-1)+5.3281e-1(2.17e-1)+ 7.4209e-1(3.39e-16)7.4209e-1 (3.39e-16) LSMOP9LSMOP9 22 10001000 5.1013e-1(4.32e-3)+5.1013e-1(4.32e-3)+ 8.0686e-1(8.94e-4)8.0686e-1 (8.94e-4)

图2是本发明的方法在2-目标,1000个决策变量的LSMOP2基准函数上获得的近似Pareto前沿,图3是本发明的方法在2-目标,1000个决策变量的ZDT1基准函数上获得的近似Pareto前沿。Fig. 2 is that the method of the present invention obtains on 2-target, the approximate Pareto front on the LSMOP2 benchmark function of 1000 decision variables, and Fig. 3 is that the method of the present invention obtains on 2-target, the ZDT1 benchmark function of 1000 decision variables Approximate Pareto front.

实施例2Example 2

作为本发明的第二方面,提供如上实施例所述方法的应用,该方法的一种典型的应用场景是大规模数据中心的资源调度和整合优化。如图4所示具体应用过程:As a second aspect of the present invention, an application of the method described in the above embodiments is provided, and a typical application scenario of the method is resource scheduling and integration optimization of a large-scale data center. The specific application process is shown in Figure 4:

步骤1:首先,以能耗、资源损耗、数据通信流量、任务完成时延等指标作为问题优化目标,以服务器剩余可用计算容量为约束条件,建立大规模数据中心资源调度和整合问题的多目标约束优化模型;Step 1: Firstly, using energy consumption, resource consumption, data communication flow, task completion delay and other indicators as the optimization objectives of the problem, and taking the remaining available computing capacity of the server as the constraint condition, establish a multi-objective problem for large-scale data center resource scheduling and integration Constrained optimization model;

步骤2:然后,以待调度的虚拟机数量为染色体长度,虚拟机编号为基因位置,实现种群个体的编码;Step 2: Then, take the number of virtual machines to be scheduled as the chromosome length, and the virtual machine number as the gene position to realize the coding of the population individual;

步骤3:最后,基于编码方式初始化种群P,并按照图1所示的基于问题重组的大规模多目标组合优化方法进行种群的迭代优化,直到满足算法的终止条件,输出以能耗、资源损耗、数据通信流量、任务完成时延等多个冲突指标为优化目标的Pareto最优解集。Step 3: Finally, initialize the population P based on the encoding method, and perform iterative optimization of the population according to the large-scale multi-objective combination optimization method based on problem recombination shown in Figure 1, until the termination condition of the algorithm is met, and the output is in terms of energy consumption and resource consumption , data communication flow, task completion delay and other conflicting indicators as the optimal Pareto solution set for the optimization goal.

以上详细描述了本发明的较佳具体实施例。应当理解,本领域的普通技术人员无需创造性劳动就可以根据本发明的构思做出诸多修改和变化。因此,凡本技术领域中技术人员依本发明的构思在现有技术的基础上通过逻辑分析、推理或者有限的实验可以得到的技术方案,皆应在由权利要求书所确定的保护范围内。The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (10)

1. The large-scale multi-objective combination optimization method based on the problem recombination is characterized by comprising a convergence optimization stage and a diversity optimization stage, and comprises the following specific steps of:
randomly initializing a population P;
based on a decision variable clustering technology, dividing decision variables into convergence variables and diversity variables;
convergence optimization stage:
in the evolution process, adopting directional cross variation facing convergence, and combining with a convergence environment selection mechanism, selecting an optimal individual as a parent population P';
when the population encounters selection pressure, problem reconstruction is carried out, large-scale multi-objective optimization is converted into single-objective optimization, and the optimal individuals are reselected as parent populations P';
diversity optimization stage:
in the evolution process, adopting diversity-oriented directional cross variation, and combining a diversity environment selection mechanism to select a population as a new parent population;
and after the termination condition is met, outputting the parent population as an optimal solution set of the optimization target.
2. The problem recombination-based large-scale multi-objective combinatorial optimization method of claim 1, wherein the specific evolution steps of the convergence optimization stage are as follows:
using binary competition selection based on convergence, and selecting individuals from the current population to generate N sub-generations Q by using crossover and mutation operators;
calculating the convergence degree of each individual in the current population P and the offspring Q, and selecting the optimal N individuals from the union as a new parent population P';
repeating the above process until the termination condition is satisfied;
performing problem reconstruction, and converting large-scale multi-objective optimization into single-objective optimization through bi-directional weight vector association;
producing a progeny population a by differential evolution;
the convergence policy based environmental selection mechanism selects the optimal N individuals from the union of the offspring population a and the weight vector population Q' as the new parent population P ".
3. The method for large-scale multi-objective combinatorial optimization based on problem recombination according to claim 2, wherein,
the directional crossing of the convergence performs crossing operation by taking independent convergence variable groups as units;
the directional variation of the convergence selects a variable from the convergence variables to vary.
4. The problem recombination-based massive multi-objective combinatorial optimization method according to claim 2, wherein the convergence degree C of solution x d The calculation formula is as follows:
Figure FDA0004121105380000021
where M represents the target number.
5. The large-scale multi-objective combination optimization method based on problem recombination according to claim 1, wherein the problem recombination strategy is specifically: through bi-directional weight vector association, the original large-scale multi-objective optimization problem is re-expressed into single-objective optimization with relatively smaller weight variables, and a group of candidate solutions with good convergence and uniform distribution are used for guiding the algorithm to search the direction of the optimal set.
6. The method for large-scale multi-objective combinatorial optimization based on problem recombination according to claim 5, wherein the specific evolution steps of the problem recombination strategy are as follows:
weight vector correlation, selecting r solutions from the current population as a reference solution set, each reference solution being associated with two direction vectors V l And V u And two weight variables lambda r1 And lambda (lambda) r2 Associating;
constructing a sub-problem according to the direction vector and the weight variable:
Z′(∧)=(z 1111 ),z 1212 ),...,z r1r1 )z r2r2 )}
wherein, lambada= { lambda 11 ,λ 12 ,...,λ r1 ,λ r2 A reconstructed decision space;
target space reconstruction, when the sub-problem is reconstructed, the optimization of the decision vector x in the original decision space is converted into the optimization of the weight vector Λ in the reconstructed decision space, and the new optimization problem is expressed as follows:
maximize G(Λ)=H(Z′(Λ))
where H may be any performance indicator.
7. The method for massive multi-objective combinatorial optimization based on problem recombination according to claim 6, wherein the specific step of constructing the sub-problem according to the direction vector and the weight variable comprises:
two direction vectors for each reference solution are calculated:
V l =s 1 -o
V u =t-s 1
wherein s is 1 ={x 1 ,...,x d The } is a reference solution, and t and o are upper and lower boundary points of X respectively;
two weight vectors for each reference solution are calculated:
Figure FDA0004121105380000031
Figure FDA0004121105380000032
where λ11 and λ12 are two weight variables, l max =||t-o||;
The expression of the constructor problem is:
Figure FDA0004121105380000033
Figure FDA0004121105380000034
8. the problem recombination-based large-scale multi-objective combinatorial optimization method of claim 1, wherein the specific evolution steps of the diversity optimization stage are as follows:
selecting individuals from the current population P' using a binary competition selection based on crowding distances;
utilizing the selected individuals to only cross and mutate the diversity related variables to generate N offspring Q';
selecting half of the current population P ' and offspring Q ' from the union set as a new parent population P ' according to the pareto dominance and crowding distance;
repeating the above process until the termination condition is satisfied, and outputting the parent population P' as the optimal solution set of the optimization target.
9. The method for large-scale multi-objective combinatorial optimization based on problem recombination according to claim 8, wherein,
the directional crossing of the diversity performs crossing operation by taking all diversity variables as units;
the directed variation of diversity selects variables among the diversity variables for variation.
10. Application of the problem recombination-based large-scale multi-objective combination optimization method according to any of claims 1-9, characterized in that the application scenario of the method comprises resource scheduling and integration optimization of a large-scale data center; the specific application steps comprise:
taking indexes including energy consumption, resource loss, data communication flow and task completion time delay as problem optimization targets, taking the residual available computing capacity of a server as constraint conditions, and establishing a multi-target constraint optimization model of a large-scale data center resource scheduling and integration problem;
taking the number of virtual machines to be scheduled as the length of a chromosome, and taking the number of the virtual machines as the gene position, so as to realize the coding of population individuals;
initializing a population P based on a coding mode, performing iterative optimization of the population according to the large-scale multi-objective combination optimization method based on the problem recombination as claimed in any one of claims 1-9 until the termination condition of an algorithm is met, and outputting a Pareto optimal solution set with a plurality of conflict indexes including energy consumption, resource loss, data communication flow and task completion time delay as optimization objectives.
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CN117910410A (en) * 2024-03-19 2024-04-19 电子科技大学 Large-scale multi-target simulation chip circuit evolution optimization design method

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* Cited by examiner, † Cited by third party
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CN117910410A (en) * 2024-03-19 2024-04-19 电子科技大学 Large-scale multi-target simulation chip circuit evolution optimization design method
CN117910410B (en) * 2024-03-19 2024-05-31 电子科技大学 Large-scale multi-target simulation chip circuit evolution optimization design method

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