A novel feature-based approach to characterize algorithm performance for the traveling salesperson problem

Meta-heuristics are frequently used to tackle NP-hard combinatorial optimization problems. With this paper we contribute to the understanding of the success of 2-opt based local search algorithms for solving the traveling salesperson problem (TSP). Although 2-opt is widely used in practice, it is hard to understand its success from a theoretical perspective. We take a statistical approach and examine the features of TSP instances that make the problem either hard or easy to solve. As a measure of problem difficulty for 2-opt we use the approximation ratio that it achieves on a given instance. Our investigations point out important features that make TSP instances hard or easy to be approximated by 2-opt.     

Erratum to: Minimizing total tardiness on parallel machines with preemptions

In this note, we correct a mistake which was made in the paper “Minimizing Total Tardiness on Parallel Machines with Preemptions” (see J Schedul 15:193–200, 2012).     

A kinect-based vocational task prompting system for individuals with cognitive impairments

Difficulties in executing daily living tasks hamper the quality of life of many individuals with cognitive impairments who are otherwise physically mobile. With sufficient and appropriate support on the job, many people with developmental disabilities and cognitive impairments are capable of participating in the world of work to various levels. Kinect is used as assistive technology for individuals with cognitive impairments to achieve the goal of performing task steps independently. In a community-based rehabilitation program under the guidance of three job coaches, a task prompting system called Kinempt was designed to assist four participants involving pre-service food preparation training. The study assessed the effectiveness of Kinempt in terms of precision and recall. A follow-up comparative study then evaluated a baseline method and the system of least prompts against the Kinempt system. Results indicate that for participants with cognitive disabilities, acquisition of job skills may be facilitated by use of Kinempt in conjunction with operant conditioning strategies. Our findings suggest that the image recognition technology may be able to facilitate task prompts needed by people with cognitive impairments. Therefore, the system may be helpful for pre-service training while increasing independence in the process of community integration.     

服务器也可如此精致——Apple Mac mini with Snow Leopard Server

今年年初我们曾经向大家介绍过Apple推出的Mac OS X Snow Leopard Server服务器操作系统,当时的硬件平台是上一代Macmini。最近Apple推出了升级更新后的Apple Macmini with Snow Leopard Server（简称Macmini Server）。这款定位于小型企业及工作组用户的迷你服务器究竟有何特色呢？     

A simple linear time certifying LBFS-based algorithm for recognizing trivially perfect graphs and their complements

We introduce a simple, linear time algorithm for recognizing trivially perfect (TP) graphs. It improves upon the algorithm of Yan et al. [J.-H. Yan, J.-J. Chen, G.J. Chang, Quasi-threshold graphs, Discrete Appl. Math. 69 (3) (1996) 247–255] in that it is certifying, producing a P₄ or a C₄ when the graph is not TP. In addition, our algorithm can be easily modified to recognize the complement of TP graphs (co-TP) in linear time as well. It is based on lexicographic BFS, and in particular the technique of partition refinement, which has been used in the recognition of many other graph classes [D.G. Corneil, Lexicographic breadth first search—a survey, in: WG 2004, in: Lecture Notes in Comput. Sci., vol. 3353, Springer, 2004, pp. 1–19].     

Expected runtimes of evolutionary algorithms for the Eulerian cycle problem

Evolutionary algorithms are randomized search heuristics, which are applied to problems whose structure is not well understood, as well as to problems in combinatorial optimization. They have successfully been applied to different kinds of arc routing problems. To start the analysis of evolutionary algorithms with respect to the expected optimization time on these problems, we consider the Eulerian cycle problem. We show that a variant of the well-known (1+1)$(1+1)$ EA working on the important encoding of permutations is able to find an Eulerian tour of an Eulerian graph in expected polynomial time. Altering the operator used for mutation in the considered algorithm, the expected optimization time changes from polynomial to exponential.     

很小很强大 打造超迷你平台客厅电脑 系列专题之一 平台搭建篇

“好小啊！”几乎所有人第一次看到NVIDIA离子平台的时候,都会发出这样的惊呼,然后人们会有三种反应,要反围观之后走开,要么打听哪里可以买到,而我们发烧级DLYer则会想：它为什么这么小,我们能自己搭建一台出来吗？为了实现打造超迷你平台客厅电脑的愿望,     

扫描仪分辨率的花样多

看着扫描仪的规格说明书,2400dpi×4800dpi的光学分辩率、19200dpi×19200dpi的插值分辩率并列写在上面;准备扫描资料,结果发现可以选择的分辨率从75dpi到2400dpi,项目似乎更多了。这些分辨率究竟是怎么回事呢？     

整合办公，节约高效——实战SOHO办公硬件组建方案

根据本刊2007年的年度调查结果显示,有高达70％的读者是有固定收入的上班族,其中信息传播、计算机服务和软件行业的读者比例达到18．47％、教育行业的读者有14．63％、制造业的读者达10．96％,国家机构和金融业的读者也有10％左右。他们一直希望在本刊看到更多关于商务产品、技术和解决方案的内容报道。而对于大多数企业来说,如何能用经济的成本买到最适合需要的办公设备也一直是个难题。