混合算法在网格任务调度中的应用研究

研究网格任务优化调度问题,针对需求的复杂和网格系统具有异构性和动态性,导致网络任务调度过程相当困难.传统调度算法调度效率低、资源负载不平衡.为了提高任务调度效率,降低资源负载不平衡性,提出一种混合的网格任务调度优化算法.首先采用遗传算法全局搜索能力快速形成初始解,然后将遗传算法的调度结果作为蚁群算法的初始信息素分布,最后利用蚁群算法所正反馈性机制迅速地形成任务调度的最优解.仿真结果表明,混合算法减少网格任务调度系统任务完成时间,提高了任务调度效率,为网格设计提供了依据.     

一种基于遗传—蚁群算法的网格任务调度策略*

针对遗传调度算法局部求解能力不足、容易早熟和退化的问题,以及蚁群调度算法初始搜索阶段效率低下的缺陷,充分应用遗传算法全局搜索能力较好和蚁群算法求解精度较高的优势,提出了一种基于遗传-蚁群算法的网格任务调度策略.该方法集成了遗传算法和蚁群算法的双重优点.仿真测试结果表明,提出的网格任务调度方法总体上优于遗传算法和蚁群算法...     

基于改进遗传算法的网格任务调度研究

网格任务调度是一个NP完全问题,它关注大规模的资源和任务调度,要求采用具有高效性的调度算法.提出了一种基于改进遗传算法的网格任务调度算法,在算法初始化种群产生时引入min-min算法和max-min算法,从而提高初始化种群的质量;算法迭代过程中采用了一种新的局部收敛判断以及改进的变异操作来防止局部收敛.仿真结果表明,该改进算法能更有效地解决网格任务调度问题.     

基于克隆算法的网格资源调度探讨

针对传统的遗传算法的网格任务调度中存在的问题,提出了一种免疫克隆算法的网格资源调度算法,仿真证明,该算法在保证调度均衡的状态下保持了较好的效率。     

云计算环境下基于遗传蚁群算法的任务调度研究

对云计算中任务调度进行了研究,针对云计算的编程模型框架,提出一种融合遗传算法与蚁群算法的混合调度算法。在该求解方法中,遗传算法采用任务-资源的间接编码方式,每条染色体代表一种具体调度方案;选取任务平均完成时间作为适应度函数,再利用遗传算法生成的优化解,初始化蚁群信息素分布。既克服了蚁群算法初期信息素缺乏,导致求解速度慢的问题,又充分利用遗传算法的快速随机全局搜索能力和蚁群算法能模拟资源负载情况的优势。通过仿真实验将该算法和遗传算法进行比较,实验结果表明,该算法是一种云计算环境下有效的任务调度算法。     

基于动态负载均衡策略的网格任务调度优化模型和算法

任务调度是一个NP-hard问题,而且是并行与分布式计算中一个必不可少的组成部分,特别是在网格计算环境中任务调度更加复杂。结合免疫克隆算法和模拟退火算法的优点,提出了一种网格任务调度优化模型和算法。仿真实验结果表明,这种调度算法有效地实现了资源的负载均衡,克服了遗传算法容易陷入局部最优的缺点,可以成功地应用于网格任务调度中。     

离散微粒群优化算法在网格任务调度中的应用

网格任务调度算法是影响网格成功与否的关键技术之一.在研究现有任务调度策略的基础上,指出Min-Min算法的负载不均衡性.借鉴遗传算法中的交叉操作过程,提出了一种新的任务调度算法.该算法对传统的连续型微粒群优化算法进行改进,使其适用于网格任务调度问题的优化处理,实现网格资源的优化分配.仿真研究表明该算法更符合网格调度的复杂环境,能得到较短的任务执行时间和较好的负载均衡性.对比分析表明,离散微粒群优化算法所得结果优于常用的Min-Min调度方案,是一种高效的调度方法.     

基于改进遗传算法的星地任务优化调度研究

星地任务优化调度是利用特定的星地资源合理地安排星地任务。由于星地任务众多而资源有限,而且星地任务受星地可见性以及多方面约束,星地任务调度问题十分复杂。针对星地任务的特点,建立了星地任务调度问题模型,提出了基于改进遗传算法的星地任务优化调度算法。算法采用按适应度排名轮盘赌选择、顺序交叉、随机对换变异的算法要素。针对遗传算法局部搜索能力弱的特点,提出了利用爬山算法优化新一代个体的方法,以增强遗传算法的局部搜索能力,给出了基于改进遗传算法的星地任务调度算法。     

基于聚类和改进共生演算法的云任务调度策略

针对云计算环境中一些基于服务质量（QoS）调度算法存在寻优速度慢、调度成本与用户满意度不均衡的问题,提出了一种基于聚类和改进共生演算法的云任务调度策略。首先将任务和资源进行模糊聚类并对资源进行重排序放置,依据属性相似度对任务进行指导分配,减小对资源的选择范围;然后依据交叉和旋转学习机制改进共生演算法,提升算法的搜索能力;最后通过加权求和方式构造驱动模型,均衡调度代价与系统性能间关系。通过不同任务量的云任务调度仿真实验,表明该算法相比改进遗传算法、混合粒子群遗传算法和离散共生演算法,有效减少了进化代数,降低了调度成本并提升了用户满意度,是一种可行有效的任务调度算法。     

遗传算法在网格任务调度的应用研究

研究了网格任务调度问题.针对传统任务调度算法在网格环境下存在不能很好地平衡节点负载和满足用户服务质量需求等缺点,导致网格系统负载极不均衡,调度效果低.为了提高网格任务调度的效果,提出一种基于遗传算法的网格任务调度方法.将网格任务编码成种群中的个体,网络任务目标作为遗传算法的适应度函数,通过遗传算法的强全局搜索及交叉、变异操作,获得最优的任务调度方案.仿真结果表明,采用遗传算法进行网格任务调度可以减少系统总执行时间和任务完成时间,提高了资源调度效率,使网格系统负载均衡度更好,在网格任务调度具有广泛的应用前景.     

Multimodal genetic algorithms-based algorithm for automatic point correspondence

In this paper, the problem of automatic determination of point correspondence between two images is formulated as a multimodal function optimization and the usefulness of genetic algorithms (GAs) as a multimodal optimizer is explored. Initially, a number of variations of GAs, capable of simultaneously discovering multiple extremes of an objective function are evaluated on a mathematical benchmark objective function with multiple unequal maxima. The variation of the GAs that performs best on the benchmark function, in terms of the number of maxima discovered, is selected for the determination of automatic point correspondence between two images. The selected variation of the GAs involves an iterative procedure for the formation of a genetic population of individuals (or chromosomes). Each individual encodes the position of a point of interest on one of the available images as well as parameters of a local transformation that generates the position of the corresponding point on the other image. The proposed algorithm aims to discover individuals that corresponds to local maxima of an objective function that measures the similarity between patches of the two images. When the GAs-based multimodal optimization algorithm terminates, pairs of corresponding points between the two images are obtained that can be used for the generation of a dense deformation field by means of the thin plate splines model.The proposed algorithm is applied to 2D medical images (dental and retinal images) under known transformations (similarity and elastic transformation) and is also assessed on medical images with unknown transformations (computer tomography transverse slices). The proposed algorithm is compared against the iterative closest point (ICP) algorithm, and a well-known non-rigid registration algorithm, based on free-form deformations (FFD) using various quantitative criteria. The obtained results indicate that in case of known similarity transformations, the proposed multimodal GAs-based algorithm and the ICP algorithm present equivalent performance, whereas the FFD algorithm is clearly outperformed. In the case of known sinousoidal deformations, the proposed multimodal GAs-based and the FFD algorithm achieve equivalent performance and clearly outperform the ICP algorithm. Finally, in the case of unknown elastic deformations, the proposed GAs-based algorithm appears to perform marginally better than the FFD algorithm, whereas it clearly outperforms the ICP algorithm.     

An Integrated Technique for Task Matching and Scheduling onto Distributed Heterogeneous Computing Systems

This paper presents a problem-space genetic algorithm (PSGA)-based technique for efficient matching and scheduling of an application program that can be represented by a directed acyclic graph, onto a mixed-machine distributed heterogeneous computing (DHC) system. PSGA is an evolutionary technique that combines the search capability of genetic algorithms with a known fast problem-specific heuristic to provide the best-possible solution to a problem in an efficient manner as compared to other probabilistic techniques. The goal of the algorithm is to reduce the overall completion time through proper task matching, task scheduling, and inter-machine data transfer scheduling in an integrated fashion. The algorithm is based on a new evolutionary technique that embeds a known problem-specific fast heuristic into genetic algorithms (GAs). The algorithm is robust in the sense that it explores a large and complex solution space in smaller CPU time and uses less memory space as compared to traditional GAs. Consequently, the proposed technique schedules an application program with a comparable schedule length in a very short CPU time, as compared to GA-based heuristics. The paper includes a performance comparison showing the viability and effectiveness of the proposed technique through comparison with existing GA-based techniques.     

基于任务复制的网格任务调度算法

网格中资源之间存在着通信延迟，通过任务复制的冗余，可以减少任务之间的通信开销，缩短整个计算程序的计算时间。目前网格中的任务调度算法基本上是没有考虑任务复制的；而基于任务复制调度算法往往会产生过多的复制任务，增大系统开销，甚至有可能延迟计算时间。由于基于任务复制的任务调度是一个NP问题，因此本文提出了一种基于任务复制的网格资源调度算法，以减少调度长度为主要目标、减少任务复制量和资源占用量为次要目标。该算法在调度长度和任务复制数量以及占用资源数量方面都等于或优于其它算法。     

A comparison of multiprocessor task scheduling algorithms with communication costs

Both parallel and distributed network environment systems play a vital role in the improvement of high performance computing. Of primary concern when analyzing these systems is multiprocessor task scheduling. Therefore, this paper addresses the challenge of multiprocessor task scheduling parallel programs, represented as directed acyclic task graph (DAG), for execution on multiprocessors with communication costs. Moreover, we investigate an alternative paradigm, where genetic algorithms (GAs) have recently received much attention, which is a class of robust stochastic search algorithms for various combinatorial optimization problems. We design the new encoding mechanism with a multi-functional chromosome that uses the priority representation—the so-called priority-based multi-chromosome (PMC). PMC can efficiently represent a task schedule and assign tasks to processors. The proposed priority-based GA has show effective performance in various parallel environments for scheduling methods.     

A Novel State Transition Method for Metaheuristic-Based Scheduling in Heterogeneous Computing Systems

Much of the recent literature shows a prevalance in the use of metaheuristics in solving a variety of problems in parallel and distributed computing. This is especially ture for problems that have a combinatorial nature, such as scheduling and load balancing. Despite numerous efforts, task scheduling remains one of the most challenging problems in heterogeneous computing environments. In this paper, we propose a new state transitionscheme , called the Duplication-based State Transition (DST) method specially designed for metaheuristics that can be used for the task scheduling problem in heterogeneous computing environments. State transition in metaheuristics is a key component that takes charge of generating variants of a given state. The DST method produces a new state by first overlapping randomly generated states with the current state and then the resultant state is refined by removing ineffectual tasks. The proposed method is incorporated into three different metaheuristics: genetic algorithms (GAs), simulated annealing (SA), and artificial immune system (AISs). They are experimentally evaluated and are also compared with existing algorithms. The experimental results confirm DST's promising impact on the performance of metaheuristics.     

A genetic algorithm-based approach to flexible flow-line schedulingwith variable lot sizes

Genetic algorithms (GAs) have been used widely for such combinatorial optimization problems as the traveling salesman problem (TSP), the quadratic assignment problem (QAP), and job shop scheduling. In all of these problems there is usually a well defined representation which GA's use to solve the problem. We present a novel approach for solving two related problems-lot sizing and sequencing-concurrently using GAs. The essence of our approach lies in the concept of using a unified representation for the information about both the lot sizes and the sequence and enabling GAs to evolve the chromosome by replacing primitive genes with good building blocks. In addition, a simulated annealing procedure is incorporated to further improve the performance. We evaluate the performance of applying the above approach to flexible flow line scheduling with variable lot sizes for an actual manufacturing facility, comparing it to such alternative approaches as pair wise exchange improvement, tabu search, and simulated annealing procedures. The results show the efficacy of this approach for flexible flow line scheduling.     

Using parallelization and hardware concurrency to improve the performance of a genetic algorithm

Genetic algorithms (GAs) are powerful tools for solving many problems requiring the search of a solution space having both local and global optima. The main drawback for GAs is the long execution time normally required for convergence to a solution. This paper discusses three different techniques that can be applied to GAs to improve overall execution time. A serial software implementation of a GA designed to solve a task scheduling problem is used as the basis for this research. The execution time of this implementation is then improved by exploiting the natural parallelism present in the algorithm using a multiprocessor. Additional performance improvements are provided by implementing the original serial software GA in dedicated reconfigurable hardware using a pipelined architecture. Finally, an advanced hardware implementation is presented in which both pipelining and duplicated hardware modules are used to provide additional concurrency leading to further performance improvements. Copyright © 2006 John Wiley & Sons, Ltd.     

Effects of different chromosome representations in developing genetic algorithms to solve DFJS scheduling problems

This paper attempts to compare the effect of using different chromosome representations while developing a genetic algorithm to solve a scheduling problem called DFJS (distributed flexible job shop scheduling) problem. The DFJS problem is strongly NP-hard; most recent prior studies develop various genetic algorithms (GAs) to solve the problems. These prior GAs are similar in the algorithmic flows, but are different in proposing different chromosome representations. Extending from this line, this research proposes a new chromosome representation (called S_OP) and develops a genetic algorithm (called GA_OP) to solve the DFJS problem. Experiment results indicate that GA_OP outperforms all prior genetic algorithms. This research advocates the importance of developing appropriate chromosome representations while applying genetic algorithms (or other meta-heuristic algorithms) to solve a space search problem, in particular when the solution space is high-dimensional.     

Time scheduling of transit systems with transfer considerations using genetic algorithms

Scheduling of a bus transit system must be formulated as an optimization problem, if the level of service to passengers is to be maximized within the available resources. In this paper, we present a formulation of a transit system scheduling problem with the objective of minimizing the overall waiting time of transferring and nontransferring passengers while satisfying a number of resource- and service-related constraints. It is observed that the number of variables and constraints for even a simple transit system (a single bus station with three routes) is too large to tackle using classical mixed-integer optimization techniques. The paper shows that genetic algorithms (GAs) are ideal for these problems, mainly because they (i) naturally handle binary variables, thereby taking care of transfer decision variables, which constitute the majority of the decision variables in the transit scheduling problem; and (ii) allow procedure-based declarations, thereby allowing complex algorithmic approaches (involving if then-else conditions) to be handled easily. The paper also shows how easily the same GA procedure with minimal modifications can handle a number of other more pragmatic extensions to the simple transit scheduling problem: buses with limited capacity, buses that do not arrive exactly as per scheduled times, and a multiple-station transit system having common routes among bus stations. Simulation results show the success of GAs in all these problems and suggest the application of GAs in more complex scheduling problems.     

基于多种群及水平集的任务调度算法

随着任务调度问题的广泛研究,包括遗传算法在内的许多新方法被引入到任务调度领域。然而,传统的遗传算法存在早熟收敛和后期进化停滞两个严重不足。为了克服这些不足,提出了算法MPLS。MPLS算法采用多种群共同进化的思想来维持种群多样性。同时,MPLS算法将水平集概念引入到任务调度研究中,以改进迭代收敛速度。基于第三方测试数据集,将MPLS的性能和GTMS、MSGS和NGS算法进行了对比。比较结果表明,MPLS算法获得的调度长度远好于GTMS、MSGS算法,略好于NGS算法。MPLS算法能将种群多样性维持在一个很高的水平。MPLS算法在调度长度和种群多样性方面要优于其它算法。