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排序方式: 共有2138条查询结果,搜索用时 171 毫秒
991.
992.
R. Baños C. Gil B. Paechter J. Ortega 《Journal of Mathematical Modelling and Algorithms》2007,6(2):213-230
Real optimization problems often involve not one, but multiple objectives, usually in conflict. In single-objective optimization
there exists a global optimum, while in the multi-objective case no optimal solution is clearly defined but rather a set of
solutions, called the Pareto-optimal front. Thus, the goal of multi-objective strategies is to generate a set of non-dominated
solutions as an approximation to this front. However, the majority of problems of this kind cannot be solved exactly because
they have very large and highly complex search spaces. In recent years, meta-heuristics have become important tools for solving
multi-objective problems encountered in industry as well as in the theoretical field. This paper presents a novel approach
based on hybridizing Simulated Annealing and Tabu Search. Experiments on the Graph Partitioning Problem show that this new
method is a better tool for approximating the efficient set than other strategies also based on these meta-heuristics. 相似文献
993.
994.
995.
Optimizing heuristic search in forest planning 总被引:3,自引:0,他引:3
Heuristic search methods are being used more and more in forest planning since the current formulations of exact methods such as linear programming are not suitable to all today's planning problems. A practical problem with most heuristics is that their performance greatly depends on the parameters that guide their search process. The effect of parameters is hard to know without extensive tests, but these tests cannot be conducted in forest planning practice, because of lacking time and experience. This study presented a method that uses Hooke and Jeeves direct search to optimize the parameters of a heuristic, taking into account the allowed computing time. The method was used to optimize three local-improvement heuristics in a non-spatial and a spatial forest planning problem, and with a short and long computing time. The heuristics were simulated annealing, threshold accepting, and tabu search, all of which are used in forestry. The results were logical and showed that while the optimal values of some parameters were rather constant the others were sensitive to problem type, allowed computing time, or problem size. The objective function value of the forest planning problem was not sensitive to small changes in the parameters of the heuristics. However, because computing time was very sensitive to many parameters, there was not much freedom to set the parameters if both the quality of the solution and speed of the algorithm had to be maintained. 相似文献
996.
基于传统的Wolfe线搜索,提出了一种新的非精确线搜索.在无需限制参数σ≤1/2的情况下(即盯的取值范围扩展至0<σ<1),证明了FR算法的全局收敛性.数值实验表明了这种线搜索下的FR算法的有效性. 相似文献
997.
Qun-yan Zhou Wen-yu Sun 《计算数学(英文版)》2006,24(6):761-770
In this paper,an algorithm for unconstrained optimization that employs both trustregion techniques and curvilinear searches is proposed.At every iteration,we solve thetrust region subproblem whose radius is generated adaptively only once.Nonmonotonicbacktracking curvilinear searches are performed when the solution of the subproblem isunacceptable.The global convergence and fast local convergence rate of the proposedalgorithms are established under some reasonable conditions.The results of numericalexperiments are reported to show the effectiveness of the proposed algorithms. 相似文献
998.
In this paper, we present a novel meta-heuristic technique for the nurse scheduling problem (NSP). This well-known scheduling
problem assigns nurses to shifts per day maximizing the overall quality of the roster while taking various constraints into
account. The problem is known to be NP-hard.
Due to its complexity and relevance, many algorithms have been developed to solve practical and often case-specific models
of the NSP. The huge variety of constraints and the several objective function possibilities have led to exact and meta-heuristic
procedures in various guises, and hence comparison and state-of-the-art reporting of standard results seem to be a utopian
idea.
We present a meta-heuristic procedure for the NSP based on the framework proposed by Birbil and Fang (J. Glob. Opt. 25, 263–282, 2003). The Electromagnetic (EM) approach is based on the theory of physics, and simulates attraction and repulsion
of sample points in order to move towards a promising solution. Moreover, we present computational experiments on a standard
benchmark dataset, and solve problem instances under different assumptions. We show that the proposed procedure performs consistently
well under many different circumstances, and hence, can be considered as robust against case-specific constraints. 相似文献
999.
GLOBAL CONVERGENCE RESULTS OF A THREE TERM MEMORY GRADIENT METHOD WITH A NON-MONOTONE LINE SEARCH TECHNIQUE 总被引:4,自引:0,他引:4
孙清滢 《数学物理学报(B辑英文版)》2005,25(1):170-178
In this paper, a new class of three term memory gradient method with nonmonotone line search technique for unconstrained optimization is presented. Global convergence properties of the new methods are discussed. Combining the quasi-Newton method with the new method, the former is modified to have global convergence property. Numerical results show that the new algorithm is efficient. 相似文献
1000.
Hideki Hashimoto Toshihide Ibaraki Mutsunori Yagiura 《Discrete Applied Mathematics》2006,154(16):2271-2290
We generalize the standard vehicle routing problem by allowing soft time window and soft traveling time constraints, where both constraints are treated as cost functions. With the proposed generalization, the problem becomes very general. In our algorithm, we use local search to determine the routes of vehicles. After fixing the route of each vehicle, we must determine the optimal start times of services at visited customers. We show that this subproblem is NP-hard when cost functions are general, but can be efficiently solved with dynamic programming when traveling time cost functions are convex even if time window cost functions are non-convex. We deal with the latter situation in the developed iterated local search algorithm. Finally we report computational results on benchmark instances, and confirm the benefits of the proposed generalization. 相似文献