置信传播和模拟退火相结合求解约束满足问题

约束满足问题是人工智能领域的一个重要问题。针对一个具有精确相变现象和能产生大量难解实例的随机约束满足问题,提出了置信传播和模拟退火相结合的求解算法。这种算法先通过置信传播方程收敛后得到变量取值的边际概率分布,分别采用最大概率和最小分量熵的策略产生一组启发式的初始赋值,再用模拟退火对这组赋值进行修正。实验结果表明：该算法大大提高了初始赋值向最优解收敛的速度,表现出了显著优越于模拟退火算法的求解性能。     

BK-means:骨架初始解K-means

K-means是典型的启发式聚类算法,容易受到初始解的影响而无法获得高质量的聚类结果。骨架是近年来启发式算法设计的研究热点,它是指所有全局最优解中相同的部分,对于提高启发式算法性能具有重要意义。给出的骨架初始解K-means算法(BK-means)的基本思想是:首先利用K-means算法得到一组局部最优解(聚类结果),通过对局部最优解求交得到骨架簇。利用骨架簇构造骨架初始解及新的搜索空间。最后以骨架初始解引导K-means算法在新的搜索空间中搜索聚类结果。在15组仿真数据集和4组实际数据集上的实验结果表明,BK-means算法具有获得高内聚、高分离的聚类结果能力。     

混合启发式算法在排课问题上的应用

对排课问题做出了形式化描述,提出了一种用于排课的混合启发式算法,该算法合并使用了模拟退火和迭代局部搜索两种算法。先依据图着色算法产生初始可行解,然后应用模拟退火算法寻找最优解,为使算法更好地跳出局部最优,实现全局搜索,在模拟退火算法应用过程中,迭代使用两个邻域,标准邻域和双Kempe链邻域。实验结果表明,此算法能够很好地提高解的质量。     

最小赋权支配集的迭代禁忌搜索算法

最小赋权支配集是一个NP困难的组合优化问题,有着广泛的应用背景。提出了一个高效的求解最小赋权支配集的迭代禁忌搜索算法。该算法采用随机贪心构造算法构造初始解,并利用快速的局部禁忌搜索算法寻找局部最优解,通过随机扰动和修复策略来搜索新的区域,以期跳出当前的局部最优解。用顶点数为800到1 000的大规模标准测试例子测试提出的算法。数值实验结果和与现存的启发式算法比较结果表明了算法是有效的。     

基于TS的动态车辆调度问题的混合算法研究

对带时间窗的动态车辆调度问题进行分析,采用实时再优化方法进行研究,引入时间轴概念,建立动态车辆调度模型,并给出求解的混合禁忌搜索算法。该算法先用C-K节约算法求得初始解,然后用禁忌搜索进行优化,得到全局最优解。禁忌搜索算法中采用动态邻域移动方法构造候选解和动态禁忌长度选取策略设置紧急长度,提高算法的收敛速度。最后用实例证明该混合算法的可行性和有效性。     

基于捕食搜索策略的模拟退火优化算法

针对传统模拟退火算法初始温度和降温函数难以确定以及接收劣质解同时容易遗失当前最优解等缺陷,将禁忌搜索算法的禁忌表功能引入SA算法,避免遗失最优解和对某个解进行多次重复地搜索;根据函数的复杂程度确定初始温度,并定义新的降温函数,提高算法的搜索效率和精度;引入捕食搜索策略,平衡算法搜索能力和开发能力,避免陷入局部最优。通过对5个典型的基准测试函数的仿真表明,改进算法具有较强的全局搜索能力,同时寻优精度和收敛速度比原算法也有较大的提高。     

约束满足混合算法求解提前/拖期Job Shop调度问题

针对提前/拖期Job Shop调度问题,建立其约束满足优化问题模型,提出了一种约束满足与禁忌搜索结合的混合算法。该算法基于约束满足思想,通过约束传播技术和启发式修复算法,得到可行调度作为禁忌搜索算法的初始解;再进行关键路径上的邻域变换,优化当前解;并采用一种全局邻域交换策略,扩大搜索空间,改善优化结果。数据实验表明了该混合算法的可行性和有效性。     

基于全局和声搜索的模拟退火算法改进

本文针对传统的模拟退火算法存在收敛速度慢的问题,采用全局和声搜索算法对其进行了改进,即在保持模拟退火原有机制的基础上,使用一个函数随机产生模拟退火算法的初始解,采用全局和声搜索算法中产生候选解的方法产生新解。该方法的优点在于保留中间最优解并及时更新,从而既保证了优化质量又提高了算法的搜索效率。最后,采用benchmark测试函数进行仿真,仿真实验结果表明,该方法在收敛速度及优化质量上都优于传统的模拟退火及其它算法,值得进一步研究。     

有车辆数限制的开放式车辆调度问题研究

有车辆数限制的开放式车辆调度问题(m-OVRP)是车辆调度类问题(VRP)的一个新的分支.本文通过多初始解选优、平滑动态的禁忌长度等改进手段,基于遗传算法中变异的思想,设计了改进的禁忌搜索算法来解决m-OVRP问题.实验结果表明,本文提出的算法不仅能很好地解决m-OVRP问题,对OVRP问题也能得到稳定的结果.本算法核心包括:提出一种全新的构造初始解的贪心算法,在禁忌搜索初始解的选取中采用多初始解选优的策略;提出在禁忌搜索中采用平滑动态的禁忌长度.本算法可以很方便地应用到其他的一些启发式搜索问题的求解中.     

流不平衡条件下飞机恢复的优化模型与算法研究

为更有效地解决航空公司飞机恢复问题,在经典的资源指派优化模型中放宽飞机流平衡约束,加入合并航班的恢复策略;在贪婪随机自适应算法(GRASP)和模拟退火算法的基础上,提出一种新的启发式算法贪婪随机模拟退火算法,降低了陷入局部最优解的概率,同时通过限定路径对的种类和候选解的数量,提高了算法的时间效率.实例计算结果表明,本文提出的模型和算法能有效处理流不平衡条件下大规模飞机恢复问题,在有效的时间内求得最优解或近似最优解.     

Parallel machine total tardiness scheduling with a new hybrid metaheuristic approach

This work proposes a hybrid metaheuristic (HMH) approach which integrates several features from tabu search (TS), simulated annealing (SA) and variable neighbourhood search (VNS) in a new configurable scheduling algorithm. In particular, either a deterministic or a random candidate list strategy can be used to generate the neighbourhood of a solution, both a tabu list mechanism and the SA probabilistic rule can be adopted to accept solutions, and the dimension of the explored neighbourhood can be dynamically modified. The considered class of scheduling problems is characterized by a set of independent jobs to be executed on a set of parallel machines with non-zero ready times and sequence dependent setups. In particular, the NP-hard generalized parallel machine total tardiness problem (GPMTP) recently defined by Bilge et al. [A tabu search algorithm for parallel machine total tardiness problem. Computers & Operations Research 2004;31:397–414], is faced. Several alternative configurations of the HMH have been tested on the same benchmark set used by Bilge et al. The results obtained highlight the appropriateness of the proposed approach.     

针对移动云计算任务迁移的快速高效调度算法

计算量较大的应用程序由于需要大量的能耗,因此在电池容量有限的移动设备上运行时十分受限。云计算迁移技术是保证此类应用程序在资源有限的设备上运行的主流方法。针对无线网络中应用程序任务图的调度和迁移问题,提出了一种快速高效的启发式算法。该算法将能够迁移到云端的任务都安排在云端完成这种策略作为初始解,通过逐次计算可迁移任务在移动端运行的能耗节省量,依次将节省量最大的任务迁移到移动端,并依据任务间的通讯时间及时更新各个任务的能耗节省量。为了寻找全局最优解,构造了适用于此问题的禁忌搜索算法,给出了相应的编码方法、禁忌表、邻域解以及算法终止准则。构造的禁忌搜索算法以提出的启发式解为初始解进行全局搜索,并实现对启发解的进一步优化。通过 实验 将所提方法与无迁移、随机迁移、饱和迁移3类算法进行对比,结果表明提出的启发式算法能够快速有效地给出能耗更小的解。例如,在宽度为10的任务图上,当深度为8时,无迁移、随机迁移与饱和迁移的能耗分别为5461、3357和2271能量单位,而给出的启发解对应的能耗仅为2111。在此基础上禁忌搜索算法又将其能耗降低到1942, 这进一步说明了提出的启发式算法能够产生高质量的近似解。     

Capacitated Clustering Problems by Hybrid Simulated Annealing and Tabu Search

The capacitated clustering problem (CCP) is the problem in which a given set of weighted objects is to be partitioned into clusters so that the total weight of objects in each cluster is less than a given value (cluster ‘capacity’). The objective is to minimize the total scatter of objects from the ‘centre’ of the cluster to which they have been allocated. A simple constructive heuristic, a R-interchange generation mechanism, a hybrid simulated annealing (SA) and tabu search (TS) algorithm which has computationally desirable features using a new non-monotonic cooling schedule, are developed. A classification of the existing SA cooling schedules is presented. The effects on the final solution quality of the initial solutions, the cooling schedule parameters and the neighbourhood search strategies are investigated. Computational results on randomly generated problems with size ranging from 50 to 100 customers indicate that the hybrid SA/TS algorithm out-performs previous simulated annealing algorithms, a simple tabu search and local descent algorithms.     

一种用于PFSP节能优化的混合禁忌搜索算法

为了追求节能减排与净利润最大化,建立一种置换流水车间订单接受与调度模型。禁忌搜索是一类启发式全局搜索算法,传统禁忌搜索对初始解依赖较大,没有对考虑能效的置换流水车间调度问题进行更深入的优化。鉴于问题的复杂性,提出了一种节能混合禁忌搜索算法,结合了NEH构造启发式算法的优势,并在该算法中设计了订单接受与拒绝编码方式、能耗调整与交货期配置策略。最后采用大量随机实例对性能进行分析。实验结果表明,通过上述改进,改善了算法的全局搜索能力与解决复杂模型的寻优能力,节能混合禁忌搜索较单一算法而言性能更优,可以有效增加企业总净利润,降低能源消耗。     

Heuristics for composite Web service decentralization

A composite service is usually specified by means of a process model that captures control-flow and data-flow relations between activities that are bound to underlying component services. In mainstream service orchestration platforms, this process model is executed by a centralized orchestrator through which all interactions are channeled. This architecture is not optimal in terms of communication overhead and has the usual problems of a single point of failure. In previous work, we proposed a method for executing composite services in a decentralized manner. However, this and similar methods for decentralized composite service execution do not optimize the communication overhead between the services participating in the composition. This paper studies the problem of optimizing the selection of services assigned to activities in a decentralized composite service, both in terms of communication overhead and overall quality of service, and taking into account collocation and separation constraints that may exist between activities in the composite service. This optimization problem is formulated as a quadratic assignment problem. The paper puts forward a greedy algorithm to compute an initial solution as well as a tabu search heuristic to identify improved solutions. An experimental evaluation shows that the tabu search heuristic achieves significant improvements over the initial greedy solution. It is also shown that the greedy algorithm combined with the tabu search heuristic scale up to models of realistic size.     

A fault-tolerant parallel heuristic for assignment problems

This paper presents a new approach for parallel heuristic algorithms based on adaptive parallelism. Adaptive parallelism was used to dynamically adjust the parallelism degree of the application with respect to the system load. This approach demonstrates that high-performance computing using a hundred of heterogeneous workstations combined with massively parallel machines is feasible to solve large optimization problems with respect to the personal character of workstations. The fault-tolerant algorithm allows a minimal loss of computation in case of failures. The proposed algorithm exploits the properties of this class of applications in order to reduce the complexity of the algorithm in terms of the checkpoint files size and the control messages exchanged. The parallel heuristic algorithm combines different search strategies: simulated annealing and tabu search. Encouraging results have been obtained in solving the quadratic assignment problem. We have improved the best known solutions for some large real-world problems.     

并行机间歇过程生产调度的遗传局部搜索算法

研究了一类集成分批的并行机间歇过程调度问题(parallel machine batch process scheduling problem,简称PBPSP),将此问题转化为固定费用运输问题(6xed charge transportation problem,简称FCTP)后,提出了具有集中邻域搜索机制和局部最优逃逸机制的遗传局部搜索算法(genetic local search algorithm,简称GLSA).GLSA算法用先根遍历边排列模式编码生成树解,具有高效的子树补充式单点交叉操作.将基于网络单纯型方法的邻域搜索作为变异算子,并提出了连续随机节点邻域搜索的集中邻域搜索策略以及随机旋转变异与全局邻域搜索相结合的局部最优逃逸策略,极大地强化了遗传局部搜索算法的全局寻优能力.实验表明:GLSA算法获得的解质量优于基于排列编码的遗传算法和基于矩阵编码的遗传算法,得到了所有Benchmark问题的最优解,且具有高鲁棒性.针对一定规模的FCTP问题,GLSA算法比Tabu启发式搜索算法具有更高的获得最优解几率.     

基于融合算法的测试优化选择问题研究

测试优化选择是个集覆盖问题,而启发式算法是求解集覆盖问题的有效方法。文中将遗传算法、BP神经网络和模拟退火算法进行融合,提出了一种融合算法,该算法充分利用遗传算法全局搜索能力强、BP神经网络训练能力强和模拟退火算法搜索速度快的优点,既避免陷入局部最优的现象,又提高了搜索的效率和精度。该算法已应用于求解测试优化问题。实例证明,该算法能够快速有效地求得测试优化问题的最优解。