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排序方式: 共有614条查询结果,搜索用时 46 毫秒
1.
In this paper, we propose a new dispatching rule and a set of local search algorithms based on the filtered beam search, GRASP and simulated annealing methodologies to construct short-term observation schedules of space mission projects, mainly for NASA's Hubble Space Telescope (HST). The main features of generating short-term observations of HST are state dependent set up times, user specified deadlines, visibility windows of the targets and the priorities assigned to the observations. The objective of HST scheduling is to maximize the scientific return. We have tested the relative performances of the proposed algorithms including the nearest neighbor rule both in objective function value and computational time aspects by utilizing a full-factorial experimental design.  相似文献   
2.
模拟退火法用于气体红外光谱数据的识别分类   总被引:1,自引:0,他引:1  
本文介绍了一种新的分类方法,它克服了传统的线性局部搜索的缺点,引入了跳跃式搜索,使得算法能够跳出局部极优解的陷阱,从而找到全局最优解。文中详细地介绍了其原理,并利用模拟退火的跳跃式搜索方法进行算法训练。通过实例比较,说明本方法应用于大气遥感红外光谱数据的分类和识别时,是行之有效的。  相似文献   
3.
A supply chain is dynamic and involves the constant flow of information, production, services, and funds from suppliers to customers between different stages. In this paper, a memetic algorithm (MA, a hybrid genetic algorithm) is developed to find the strategy that can give the lowest cost of the physical distribution flow. The proposed MA is combined with the genetic algorithm (GA), a multi-greedy heuristic method (GH), three local search methods (LSMs): the pairwise exchange procedure (XP), the insert procedure (IP), and the remove procedure (RP), the Fibonacci number procedure, and the linear programming technique (LP) to improve the tradition genetic algorithm (GA). Preliminary computational experiments demonstrate the efficiency and performance of the proposed MA.  相似文献   
4.
一种有效的基于并行量子进化算法的图像边缘检测方法   总被引:14,自引:0,他引:14  
李映  焦李成 《信号处理》2003,19(1):69-74
本文基于费用函数最小化方法,提出一种混合并行量子进化算法用于文本图像的边缘检测。量子进化算法是一种基于量予计算的概念和理论(诸如量子比特和量子叠加态)的进化算法,它采用了量子编码来表征染色体,由于量子比特的概率表示,能够表示出解的线性叠加状态。此外,量子进化算法具有收敛快和好的全局搜索特性,因此它比传统的进化算法更适于并行结构的实现。我们将这一算法和局部搜索算法相结合,用于图像的边缘检测问题,得到了令人满意的检测效果,并对噪声有较好的抑制作用。  相似文献   
5.
Hybrid algorithms combining local and systematic search often use nondeterminism in fundamentally different ways. They may differ in the strategy to explore the search tree and/or in how computation states are represented. This paper presents nondeterministic control structures to express a variety of hybrid search algorithms concisely and elegantly. These nondeterministic abstractions describe the search tree and are compiled in terms of first-class continuations. They are also parameterized by search controllers that are under user control and specify the state representation and the exploration strategy. The resulting search language is thus high-level, flexible, and directly extensible. The abstractions are illustrated on a jobshop scheduling algorithm that combines tabu search and a limited form of backtracking. Preliminary experimental results indicate that the control structures induce small, often negligible, overheads.  相似文献   
6.
Covering arrays can be applied to the testing of software, hardware and advanced materials, and to the effects of hormone interaction on gene expression. In this paper we develop constraint programming models of the problem of finding an optimal covering array. Our models exploit global constraints, multiple viewpoints and symmetry-breaking constraints. We show that compound variables, representing tuples of variables in our original model, allow the constraints of this problem to be represented more easily and hence propagate better. With our best integrated model, we are able to either prove the optimality of existing bounds or find new optimal solutions, for arrays of moderate size. Local search on a SAT-encoding of the model is able to find improved solutions and bounds for larger problems.  相似文献   
7.
We consider the problem of finding a linear combination of at most t out of K column vectors in a matrix, such that a target vector is approximated as closely as possible. The motivation of the model is to find a lower-dimensional representation of a given signal vector (target) while minimizing loss of accuracy. We point out the computational intractability of this problem, and suggest some local search heuristics for the unit norm case. The heuristics, all of which are based on pivoting schemes in a related linear program, are compared experimentally with respect to speed and accuracy.  相似文献   
8.
This paper addresses the non-preemptive scheduling problem of scheduling jobs on identical parallel machines to minimize the maximum completion time or makespan. The problem has been proved to be NP-hard in the strong sense. The NP-hardness of the problem motivates us to develop a new methodology to obtain near-optimal solutions. We formulate the problem as an integer programming and then propose a new iterated local search (ILS) algorithm based on a variable number of cyclic exchanges to solve it. The properties of the solutions are derived and the results are used to improve the computational efficiency of our algorithm. Computational experiments show that the cyclic exchange neighborhood embedded in an iterated local search framework is effective for solving the scheduling problems with up to 1000 jobs and 40 machines within a reasonable amount of computation time. Received: April 2005 / Accepted: January 2006  相似文献   
9.
We propose a job-shop scheduling model with sequence dependent set-up times and release dates to coordinate both inbound and outbound traffic flows on all the prefixed routes of an airport terminal area and all aircraft operations at the runway complex. The proposed model is suitable for representing several operational constraints (e.g., longitudinal and diagonal separations in specific airspace regions), and different runway configurations (e.g., crossing, parallel, with or without dependent approaches) in a uniform framework. The complexity and the highly dynamic nature of the problem call for heuristic approaches. We propose a fast dynamic local search heuristic algorithm for the job-shop model suitable for considering one of the different performance criteria and embedding aircraft position shifting control technique to limit the controllers/pilots’ workload. Finally, we describe in detail the experimental analysis of the proposed model and algorithm applied to two real case studies of Milan-Malpensa and Rome-Fiumicino airport terminal areas. This work has been partially supported by grant CNR FPCCR021074 from the Italian National Research Council.  相似文献   
10.
This paper investigates the necessary features of an effective clause weighting local search algorithm for propositional satisfiability testing. Using the recent history of clause weighting as evidence, we suggest that the best current algorithms have each discovered the same basic framework, that is, to increase weights on false clauses in local minima and then to periodically normalize these weights using a decay mechanism. Within this framework, we identify two basic classes of algorithm according to whether clause weight updates are performed additively or multiplicatively. Using a state-of-the-art multiplicative algorithm (SAPS) and our own pure additive weighting scheme (PAWS), we constructed an experimental study to isolate the effects of multiplicative in comparison to additive weighting, while controlling other key features of the two approaches, namely, the use of pure versus flat random moves, deterministic versus probabilistic weight smoothing and multiple versus single inclusion of literals in the local search neighbourhood. In addition, we examined the effects of adding a threshold feature to multiplicative weighting that makes it indifferent to similar cost moves. As a result of this investigation, we show that additive weighting can outperform multiplicative weighting on a range of difficult problems, while requiring considerably less effort in terms of parameter tuning. Our examination of the differences between SAPS and PAWS suggests that additive weighting does benefit from the random flat move and deterministic smoothing heuristics, whereas multiplicative weighting would benefit from a deterministic/probabilistic smoothing switch parameter that is set according to the problem instance. We further show that adding a threshold to multiplicative weighting produces a general deterioration in performance, contradicting our earlier conjecture that additive weighting has better performance due to having a larger selection of possible moves. This leads us to explain differences in performance as being mainly caused by the greater emphasis of additive weighting on penalizing clauses with relatively less weight.  相似文献   
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