平方度量的k层设施选址问题的近似算法

本文中,我们研究平方度量的k层设施选址问题,该问题中设施分为k层,每个顾客都要连接到位于不同层上的k个设施,顾客与设施以及设施与设施之间的距离是平方度量的.目标是使得开设费用与连接费用之和最小.基于线性规划舍入技巧,我们给出了9-近似算法.进一步,我们研究了平方度量的k层软容量设施选址问题,并给出了线性规划舍入12.2216-近似算法.     

设施选址问题的近似算法综述

设施选址问题是运筹学和理论计算机科学中的经典问题之一.本文介绍设施选址问题及其变形的近似算法设计与分析思想,并总结设施选址问题的研究中若干未解决的重要问题.     

离散设施选址问题研究综述

本文首先回顾了设施选址问题百年发展历史,认为其研究经历了零散研究、系统研究、不确定性研究三个阶段.离散选址问题包括中值问题、覆盖问题、中心问题、多产品问题、动态问题、多目标问题、路径选址问题、网络中心选址问题8个子问题.最后作者讨论了选址问题研究中存在的问题以及今后发展的趋势.     

一类多商品设施选址问题的基于线性松弛解的启发式方法

多商品设施选址问题是众多设施选址问题中一类重要而困难的问题.在这一问题中,顾客的需求可能包含不止一种商品.对于大规模问题,成熟的商业求解器往往不能在满意的时间内找到高质量的可行解.研究了无容量限制的单货源多商品设施选址问题的一般形式,并给出了应用于此类问题的两个启发式方法.这两个方法基于原选址问题的线性规划松弛问题的最优解,分别通过求解紧问题和邻域搜索的方式给出了原问题的一个可行上界.理论分析指出所提方法可以实施于任意可行问题的实例.数值结果表明所提方法可以显著地提高求解器求解此类设施选址问题的求解效率.     

带有异常点的平方度量设施选址问题

传统的设施选址问题一般假设所有顾客都被服务,考虑到异常点的存在不仅会增加总费用(设施的开设费用与连接费用之和),也会影响到对其他顾客的服务质量.研究异常点在最终方案中允许不被服务的情况,称之为带有异常点的平方度量设施选址问题.该问题是无容量设施选址问题的推广.问题可描述如下:给定设施集合、顾客集,以及设施开设费用和顾客...     

连续设施选址:模型、方法与应用

给定度量空间和该空间中的若干顾客,设施选址为在该度量空间中确定新设施的位置使得某种目标达到最优。连续设施选址是设施选址中的一类重要问题,其中的设施可在度量空间的某连续区域上进行选址。本文对连续设施选址的模型、算法和应用方面的工作进行了综述。文章首先讨论了连续设施选址中几个重要元素,包括新设施个数、距离度量函数、目标函数;然后介绍了连续选址中的几种经典模型和拓展模型;接着概述了求解连续选址问题的常用优化方法和技术,包括共轭对偶、全局优化、不确定优化、变分不等式方法、维诺图;最后介绍了连续设施选址的重要应用并给出了研究展望。     

带次模惩罚的优先设施选址问题的近似算法

研究带次模惩罚的优先设施选址问题, 每个顾客都有一定的服务水平要求, 开设的设施只有满足了顾客的服务水平要求, 才能为顾客提供服务, 没被服务的顾客对应一定的次模惩罚费用. 目标是使得开设费用、连接费用与次模惩罚费用之和最小. 给出该问题的整数规划、 线性规划松弛及其对偶规划. 基于原始对偶和贪婪增广技巧, 给出该问题的两个近似算法, 得到的近似比分别为3和2.375.     

基于Benders分解算法的反恐应急设施选址-定容-分配问题

反恐应急设施的合理布局和资源配置可缩短救援到达时间并提高应急效率。对已有反恐应急设施选址研究拓展，进一步考虑设施容量有限的情形，并将袭击前后关于应急设施的选址、定容和救援物资分配问题进行集成考虑。将该问题构造为三层规划模型，上中下各层规划分别对应袭击前的选址定容问题、袭击时的袭击点选择问题和袭击后的救援物资分配问题。利用下层规划的对偶变换转化为双层规划，并设计Benders分解算法求解。最后，结合南疆交通网络进行仿真分析，验证了模型和算法的有效性。     

设施选址博弈问题的无支付机制设计研究

选址博弈是目前国际相关学术领域的重要前沿课题之一. 在选址博弈问题中, 存在n个相互影响的``理性"居民, 他们的住址等信息是其私有信息;设计者需要设计选址机制, 以居民汇报的住址信息为输入, 输出设施位置. 在进行机制设计的过程中, 如何在没有金钱的刺激下, 保证所有居民``说真话", 设计出防策略性无支付机制是其中的重要研究内容. 设施选址博弈问题的无支付机制设计是组合优化和理论计算机科学的交叉学科课题, 在管理科学、信息科学以及社会经济学等领域有着重要的应用, 具有重要的理论意义和实际的应用价值. 现根据不同设施类型及个数、不同个人偏好、不同度量空间以及不同社会总体目标等条件, 介绍各种类型的设施选址博弈模型, 罗列相关的研究成果, 并总结其中尚待解决的问题.     

带补偿机制的垃圾焚烧厂选址问题研究

研究了带补偿机制的垃圾焚烧厂选址问题,在综合考虑选址成本、补偿标准等因素的前提下,建立了以垃圾焚烧厂对附近居民造成的负面影响极小化和垃圾焚烧厂的总运行费用极小化为目标的垃圾焚烧厂选址问题的双目标规划模型,通过一个具体算例验证了模型的有效性,得到了符合实际的结果.模型可推广应用于其它邻避型设施选址问题.     

Online facility location with facility movements

In the online facility location problem demand points arrive one at a time and the goal is to decide where and when to open a facility. In this paper we consider a new version of the online facility location problem, where the algorithm is allowed to move the opened facilities in the metric space. We consider the uniform case where each facility has the same constant cost. We present an algorithm which is 2-competitive for the general case and we prove that it is 3/2-competitive if the metric space is the line. We also prove that no algorithm with smaller competitive ratio than \({(\sqrt{13}+1)/4\approx 1.1514}\) exists. We also present an empirical analysis which shows that the algorithm gives very good results in the average case.     

The approximation gap for the metric facility location problem is not yet closed

We consider the 1.52-approximation algorithm of Mahdian et al. for the metric uncapacitated facility location problem. We show that their algorithm does not close the gap with the lower bound on approximability, 1.463, by providing a construction of instances for which its approximation ratio is not better than 1.494.     

软容量约束的动态设施选址问题的近似算法

考虑软容量约束的动态设施选址问题.假设设施的开放费用及连接费用都与时间有关,而且每一个设施均有容量约束.对此问题给出了第一个近似比为6的原始对偶(组合)算法.运行贪婪增加程序后,近似比进一步改进到3.7052.     

Approximating the two-level facility location problem via a quasi-greedy approach

We propose a quasi-greedy algorithm for approximating the classical uncapacitated 2-level facility location problem (2-LFLP). Our algorithm, unlike the standard greedy algorithm, selects a sub-optimal candidate at each step. It also relates the minimization 2-LFLP problem, in an interesting way, to the maximization version of the single level facility location problem. Another feature of our algorithm is that it combines the technique of randomized rounding with that of dual fitting. This new approach enables us to approximate the metric 2-LFLP in polynomial time with a ratio of 1.77, a significant improvement on the previously known approximation ratios. Moreover, our approach results in a local improvement procedure for the 2-LFLP, which is useful in improving the approximation guarantees for several other multi-level facility location problems. An additional result of our approach is an O(ln (n))-approximation algorithm for the non-metric 2-LFLP, where n is the number of clients. This is the first non-trivial approximation for a non-metric multi-level facility location problem. An extended abstract of this paper appeared in the Proceedings of the 15th ACM-SIAM Symposium on Discrete Algorithms (SODA), January 2004.     

Successive computation of some efficient locations of the Weber problem with barriers

We transform a continuous Weber problem with barriers to a discrete problem by computing some efficient locations, which are considered as promising locations for a new facility. A theorem determining conditions for a location to be efficient is introduced. A method for constructing the weighted coefficients and travel costs modeled by some distance metrics, is derived. This method provides successive computation of some efficient locations. Also, we propose an algorithm for the verification of location’s efficiency. Numerical examples are provided using squared Euclidean and Manhattan distance metrics, as well as the implementation details in programming package MATHEMATICA.     

鲁棒动态设施选址问题的近似算法

设施选址问题是组合优化中重要问题之一。动态设施选址问题是传统设施选址问题的推广,其中度量空间中设施的开设费用和顾客的需求均随着时间的变化而变化。更多地,经典设施选址问题假设所有的顾客都需要被服务。在这个模型假设下,所有的顾客都需要服务。但事实上,有时为服务距离较远的顾客,需要单独开设设施,导致了资源的浪费。因此,在模型设置中,可以允许一些固定数目的顾客不被服务 (带异常点的设施选址问题),此外也可以通过支付一些顾客的惩罚费用以达到不服务的目的 (带惩罚的设施选址问题)。本文将综合以上两种鲁棒设置考虑同时带有异常点和惩罚的动态设施选址问题,通过原始-对偶框架得到近似比为3的近似算法。     

Cooperative location games based on the minimum diameter spanning Steiner subgraph problem

In this paper we introduce and analyze new classes of cooperative games related to facility location models. The players are the customers (demand points) in the location problem and the characteristic value of a coalition is the cost of serving its members. Specifically, the cost in our games is the service diameter of the coalition.We study the existence of core allocations for these games, focusing on network spaces, i.e., finite metric spaces induced by undirected graphs and positive edge lengths.     

Placing a finite size facility with a center objective on a rectangular plane with barriers

This paper addresses the finite size 1-center placement problem on a rectangular plane in the presence of barriers. Barriers are regions in which both facility location and travel through are prohibited. The feasible region for facility placement is subdivided into cells along the lines of Larson and Sadiq [R.C. Larson, G. Sadiq, Facility locations with the Manhattan metric in the presence of barriers to travel, Operations Research 31 (4) (1983) 652–669]. To overcome complications induced by the center (minimax) objective, we analyze the resultant cells based on the cell corners. We study the problem when the facility orientation is known a priori. We obtain domination results when the facility is fully contained inside 1, 2 and 3-cornered cells. For full containment in a 4-cornered cell, we formulate the problem as a linear program. However, when the facility intersects gridlines, analytical representation of the distance functions becomes challenging. We study the difficulties of this case and formulate our problem as a linear or nonlinear program, depending on whether the feasible region is convex or nonconvex. An analysis of the solution complexity is presented along with an illustrative numerical example.