An exact bit-parallel algorithm for the maximum clique problem

This paper presents a new exact maximum clique algorithm which improves the bounds obtained in state of the art approximate coloring by reordering the vertices at each step. Moreover, the algorithm can make full use of bit strings to sort vertices in constant time as well as to compute graph transitions and bounds efficiently, exploiting the ability of CPUs to process bitwise operations in blocks of size the ALU register word. As a result it significantly outperforms a current leading algorithm.     

最大团问题的改进遗传算法求解

最大团问题是组合优化中经典的NP完全问题,该问题的枚举算法只适用于求解中小规模的图。提出了基于遗传算法的最大团问题求解算法,引入概率模型指导变异产生新的个体,并结合启发式局部算法搜索最大团。经算例测试,获得了较好的效果。     

A fast algorithm for the maximum weight clique problem

We present a branch and bound method which finds a maximum weight clique in an arbitrary weighted graph. The main ingredients are a weighted coloring heuristic which simultaneously produces lower and upper bounds and a branching rule that uses the information obtained in the coloring. The algorithm performs comparable to the fastest method known so far but is much easier to implement.     

A simple simulated annealing algorithm for the maximum clique problem

Simulated annealing technique has mostly been used to solve various optimization and learning problems, and it is well known that the maximum clique problem is one of the most studied NP-hard optimization problems owing to its numerous applications. In this note, a simple simulated annealing algorithm for the maximum clique problem is proposed and tested on all 80 DIMACS maximum clique instances. Although it is simple, the proposed simulated annealing algorithm is efficient on most of the DIMACS maximum clique instances. The simulation results show that the proposed simulated annealing algorithm outperforms a recent efficient simulated annealing algorithm proposed by Xu and Ma, and the solutions obtained by the proposed simulated annealing algorithm have the equal quality with those obtained by a recent trust region heuristic algorithm of Stanislav Busygin.     

An effective local search for the maximum clique problem

We propose a variable depth search based algorithm, called k-opt local search (KLS), for the maximum clique problem. KLS efficiently explores the k-opt neighborhood defined as the set of neighbors that can be obtained by a sequence of several add and drop moves that are adaptively changed in the feasible search space. Computational results on DIMACS benchmark graphs indicate that KLS is capable of finding considerably satisfactory cliques with reasonable running times in comparison with those of state-of-the-art metaheuristics.     

一种基于匹配交叉求解最大团问题的Memetic算法

针对基于适应值的选择交叉机制在优化具有欺骗性的最大团问题中性能退化的问题,提出一种新的基于匹配交叉的Memetic算法.该算法提出交叉匹配度的概念,用来估计两个体交叉所能获得的最佳适应值.通过匹配度的计算对交叉方向的选择进行控制,保证了交叉操作以较大的概率生成新的优良模式.在40个最大团问题标准算例上的测试结果表明,新算法优于目前在最大团问题求解中性能最好的多阶段动态局部搜索算法.     

基于有导向变异算子的GM-EA算法*

为了进一步提高演化算法的效率,提出基于有导向变异算子的GM-EA算法（guided mutation evolutio-nary algorithm）。通过结合粒子群优化的方法改进郭涛算法,更好地利用当前最优解指导变异,并将算法分为探索与开采两个阶段;在开采阶段基于模拟退火方法决定是否用新个体取代旧个体,在巩固所获取的建筑块成分的同时,尽可能克服早熟收敛问题。实验结果证明了新算法的有效性。     

求解最大子团的随机抽样免疫遗传算法

针对遗传算法在最大子团求解中保持群体多样性能力不足、早熟、耗时长、成功率低等缺陷,利用随机抽样方法对交叉操作进行重新设计,结合免疫机理定义染色体浓度,设计克隆选择策略,提出了求解最大子团问题的随机抽样免疫遗传算法。用仿真算例说明了新算法在解的质量、收敛速度等各项指标上均有提高,且不比DLS-MC、QUALEX等经典搜索算法差,对某些算例还得到了更好解。     

MapReduce平台上面向大规模Web服务组合问题的并行引导变异进化算法

大规模服务组合是一种通过将不同领域的大量服务按照一定的流程组合起来以满足用户需求的策略。然而,在当今的服务数量巨大并且种类颇多,外加用户需求日益复杂的情况下,快速生成一个满足用户要求的最佳QoS的复合服务是一项值得研究的问题。对此提出了以MapReduce模型为基础的引导变异进化算法（MR-GMEA）,该算法能够更好地适用于当前大规模服务组合的主观与客观需求并且可以缩短执行时间,此外其中引入的skyline算子在开始阶段剔除了大量冗余服务从而提高了效率。最后通过仿真验证,证明了该方法的可行性与优越性。     

An evolutionary algorithm for the resource-constrained project scheduling problem with minimum and maximum time lags

In this paper, we present an evolutionary algorithm (EVA) for solving the resource-constrained project scheduling problem with minimum and maximum time lags (RCPSP/max). EVA works on a population consisting of several distance-order-preserving activity lists representing feasible or infeasible schedules. The algorithm uses the conglomerate-based crossover operator, the objective of which is to exploit the knowledge of the problem to identify and combine those good parts of the solution that have really contributed to its quality. In a recent paper, Valls et al. (European J. Oper. Res. 165, 375–386, 2005) showed that incorporating a technique called double justification (DJ) in RCPSP heuristic algorithms can produce a substantial improvement in the results obtained. EVA also applies two double justification operators DJmax and DJU adapted to the specific characteristics of problem RCPSP/max to improve all solutions generated in the evolutionary process. Computational results in benchmark sets show the merit of the proposed solution method.     

最大团问题的加权分治算法

分支降阶是目前广泛用于求解组合优化领域中难题的技术之一,该技术的核心思想是将原问题分支成若干个子问题,并递归求解这些子问题。加权分治技术是算法设计和时间复杂度分析中的一种新技术。设计一个基于分支降阶的递归算法求解最大团问题。运用常规技术对该算法进行时间复杂度分析,得出其时间复杂度为[O(1.380np(n)),]其中[p(n)]表示问题规模数[n]的多项式函数。运用加权分治技术对原算法进行时间复杂度分析,将该算法的时间复杂度由原来的[O(1.380np(n))]降为[O(1.325np(n))]。研究结果表明运用加权分治技术能够得到较为精确的时间复杂度。     

Payoff-monotonic game dynamics and the maximum clique problem

Evolutionary game-theoretic models and, in particular, the so-called replicator equations have recently proven to be remarkably effective at approximately solving the maximum clique and related problems. The approach is centered around a classic result from graph theory that formulates the maximum clique problem as a standard (continuous) quadratic program and exploits the dynamical properties of these models, which, under a certain symmetry assumption, possess a Lyapunov function. In this letter, we generalize previous work along these lines in several respects. We introduce a wide family of game-dynamic equations known as payoff-monotonic dynamics, of which replicator dynamics are a special instance, and show that they enjoy precisely the same dynamical properties as standard replicator equations. These properties make any member of this family a potential heuristic for solving standard quadratic programs and, in particular, the maximum clique problem. Extensive simulations, performed on random as well as DIMACS benchmark graphs, show that this class contains dynamics that are considerably faster than and at least as accurate as replicator equations. One problem associated with these models, however, relates to their inability to escape from poor local solutions. To overcome this drawback, we focus on a particular subclass of payoff-monotonic dynamics used to model the evolution of behavior via imitation processes and study the stability of their equilibria when a regularization parameter is allowed to take on negative values. A detailed analysis of these properties suggests a whole class of annealed imitation heuristics for the maximum clique problem, which are based on the idea of varying the parameter during the imitation optimization process in a principled way, so as to avoid unwanted inefficient solutions. Experiments show that the proposed annealing procedure does help to avoid poor local optima by initially driving the dynamics toward promising regions in state space. Furthermore, the models outperform state-of-the-art neural network algorithms for maximum clique, such as mean field annealing, and compare well with powerful continuous-based heuristics.     

A new parallel tabu search algorithm for the optimization of the maximum vertex weight clique problem

The efficiency of metaheuristic algorithms depends significantly on the number of fitness value evaluations performed on candidate solutions. In addition to various intelligent techniques used to obtain better results, parallelization of calculations can substantially improve the solutions in cases where the problem is NP-hard and requires many evaluations. This study proposes a new parallel tabu search method for solving the Maximum Vertex Weight Clique Problem (MVWCP) on the Non-Uniform Memory Access (NUMA) architectures using the OpenMP parallel programming paradigm. Achieving scalability in the NUMA architectures presents significant challenges due to the high complexity of their memory systems, which can lead to performance loss. However, our proposed Tabu-NUMA algorithm provides up to $18\times$ speed-up with 64 cores for ten basic problem instances in DIMACS-W and BHOSLIB-W benchmarks. And it improves the performance of the serial Multi Neighborhood Tabu Search (MN/TS) algorithm for 38 problem instances in DIMACS-W and BHOSLIB-W benchmarks. We further evaluate our algorithm on larger datasets with thousands of edges and vertices from Network Data Repository benchmark problem instances, and we report significant improvements in terms of speed up. Our results confirm that the Tabu-NUMA algorithm is among the best recent algorithms for solving MVWCP on the NUMA architectures.     

Performance analysis of evolutionary algorithm for the maximum internal spanning tree problem

The Journal of Supercomputing - The maximum internal spanning tree (MIST) problem is to find a spanning tree with maximum number of internal node for an undirected graph. It is a variation of the...     

An adaptive differential evolutionary algorithm incorporating multiple mutation strategies for the economic load dispatch problem

As growing the demand for electrical energy, economic load dispatch (ELD) has become one of the most important and complex issues in the operation of power systems. Owing to the confined optimum convergence and the additional constraints, it does not proficient to crack such problems by the predictable optimization algorithms. In this paper, a self-adaptable differential evolution algorithm integrating with multiple mutation strategies (ADE-MMS) is proposed for the ELD problems. In order to improve the exploration and exploitation capabilities of the original differential evolution algorithm (DE), ADE-MMS has three extensions to DE. Firstly, four types of advanced vectors generated by the different methods are employed in the mutation strategies. Secondly, a self-adaptable selection mechanism for the multiple mutation strategies is implemented in the iterations. Thirdly, the main control parameters are updated according to the fitness value under the tolerance threshold. Additionally, an effective repair method is proposed to handle the equality constraints of the ELD problems. ADE-MMS not only improve the convergence speed of the original DE but also keep equilibrium state between the exploration and the exploration. A tolerance threshold for the main control parameters makes the original DE more adaptive. Moreover, the modified equality constraints handling method is benefit to meet the equality constraints and minimize the impact on the algorithm. The performances of four DE algorithms are tested on the ten ELD problems with diverse complexities. Experimental results and comparisons with other recently reported ELD algorithms confirm that ADE-MMS is capable of obtaining excellent and feasible solutions. It reveal that ADE-MMS has good potential to solvating the ELD problems.     

基于均匀免疫优化算法的最大团问题求解

最大团问题是一种典型的组合优化问题,具有广泛的应用背景。针对最大团问题的NP特性,提出了一种基于免疫克隆优化的智能求解算法。描述了最大团问题的数学模型,设计了求解最大团问题的抗体编码、亲和度函数、变异算子及抗体修正方法。在免疫克隆参数设置时,将其描述为多因素多水平的均匀设计,减少了设置参数的实验次数。通过最大团问题的基准算例进行了实验。结果表明,本算法求解效果较好,并且求解速度较快。     

An improved algorithm for the maximum agreement subtree problem

In this paper, we solve the maximum agreement subtree problem for a set T of k rooted leaf-labeled evolutionary trees on n leaves where T contains a binary tree. We show that the O(kn³)-time dynamic-programming algorithm proposed by Bryant [Building trees, hunting for trees, and comparing trees: theory and methods in phylogenetic analysis, Ph.D. thesis, Dept. Math., University of Canterbury, 1997, pp. 174-182] can be implemented in O(kn²+n²logk−2nloglogn) and O(kn3−1/(k−1)) time by using multidimensional range search related data structures proposed by Gabow et al. [Scaling and related techniques for geometry problems, in: Proc. 16th Annual ACM Symp. on Theory of Computing, 1984, pp. 135-143] and Bentley [Multidimensional binary search trees in database applications, IEEE Trans. Softw. Eng. SE-5 (4) (1979) 333-340], respectively. When k<2+(logn−logloglogn)/(loglogn), the first implementation will be significantly faster than Bryant's algorithm. For k=3, it yields the best known algorithm which runs in O(n²lognloglogn)-time.     

An effective heuristic algorithm for the maximum satisfiability problem

Stochastic local search algorithms (SLS) have been increasingly applied to approximate solutions of the weighted maximum satisfiability problem (MAXSAT), a model for solutions of major problems in AI and combinatorial optimization. While MAXSAT instances have generally a strong intrinsic dependency between their variables, most of SLS algorithms start the search process with a random initial solution where the value of each variable is generated independently with the same uniform distribution. In this paper, we propose a new SLS algorithm for MAXSAT based on an unconventional distribution known as the Bose-Einstein distribution in quantum physics. It provides a stochastic initialization scheme to an efficient and very simple heuristic inspired by the co-evolution process of natural species and called Extremal Optimization (EO). This heuristic was introduced for finding high quality solutions to hard optimization problems such as colouring and partitioning. We examine the effectiveness of the resulting algorithm by computational experiments on a large set of test instances and compare it with some of the most powerful existing algorithms. Our results are remarkable and show that this approach is appropriate for this class of problems.