Prefix computations on a generalized mesh-connected computer withmultiple buses

The mesh-connected computer with multiple buses (MC-CMB) is a well-known parallel organization, providing broadcast facilities in each row and each column. In this paper, we propose a 2D generalized MCCMB (2-GMCCMB) for the purpose of increasing the efficiency of executing some important applications of prefix computations such as solving Linear recurrences and tridiagonaI systems, etc. A k₁n₁ ×k₁n₂ 2-GMCCMB is constructed from a k ₁n₁×k₁n₂ mesh organization by enhancing the power of each disjoint n₁×n₂ submesh with multiple buses (sub-2-MCCMB). Given n data, a prefix computation can be performed in O(n^1/10) time on an n^3/5×n^2/5 2-GMCCMB, where each disjoint sub-2-MCCMB is of size n^1/2×n^3/10. This time bound is faster than the previous time bound of O(n^1/8) for the same computation on an n^5/8×n^3/8 2-MCCMB. Furthermore, the time bound of our parallel prefix algorithm can be further reduced to O(n^1/11) if fewer processors are used. Our result can be extended to the d-dimensional GMCCMB, giving a time bound of O(n¹ (d2(d)+d)/) for any constant d; here, we omit the constant factors. This time bound is less than the previous time bound of O(n¹(d2(d))/) on the d-dimensional MCCMB     

An efficient parallel recognition algorithm forbipartite-permutation graphs

We present a parallel recognition algorithm for bipartite-permutation graphs. The algorithm can be executed in O(log n) time on the CRCW PRAM if O(n³/log n) processors are used, or O(log² n) time on the CREW PRAM if O(n³/log² n) processors are used. Chen and Yesha (1993) have presented another CRCW PRAM algorithm that takes O(log²n) time if O(n ³) processors are used. Compared with Chen and Yesha's algorithm, our algorithm requires either less time and fewer processors on the same machine model, or fewer processors on a weaker machine model. Our algorithm can also be applied to determine if two bipartite-permutation graphs are isomorphic     

Parallel dynamic programming

Recurrence formulations for various problems, such as finding an optimal order of matrix multiplication, finding an optimal binary search tree, and optimal triangulation of polygons, assume a similar form. A. Gibbons and W. Rytter (1988) gave a CREW PRAM algorithm to solve such dynamic programming problems. The algorithm uses O(n⁶/log n) processors and runs in O(log² n) time. In this article, a modified algorithm is presented that reduces the processor requirement to O(n⁶/log ⁵n) while maintaining the same time complexity of O(log² n)     

Utilizing the multiple facets of WWW contents

Current query languages for the Web (e.g., W3QL, WebLog and WebSQL) explore the structure of the Web. However, usually, the structure of the Web has little to do with the semantics of the data. Therefore, it is practically difficult to pose database queries over the Web. We introduce a new type of tags for denoting the semantics of data stored in HTML pages. These semantic tags (implemented as HTML comments) superimpose on HTML pages semistructured objects in the style of the OEM model. The paper discusses two implemented tools for fully utilizing the semantics. The first is a visualization tool for displaying both the HTML reading of Web pages and the OEM reading of Web pages. The second tool is a query language, similar to LOREL, that can query the HTML structure and/or the OEM reading. The above formalism and tools provide data-modeling capabilities for the Web that fit its heterogeneous nature. Real database queries, taking the OEM point of view, can be formulated, including queries about the schema as well as queries about the HTML structure of Web pages. Therefore, the query language is not restricted to portions of the Web in which semantic tags are used.     

Efficient routing and sorting schemes for de Bruijn networks

We consider the problems of routing and sorting on a de Bruijn network. First, we show that any deterministic oblivious routing scheme for permutation routing on a d-ary de Bruijn network with N=dⁿ nodes, in the worst case, will take Ω(√N) steps under the single-port model. This improves the existing lower bounds provided d is not a constant. We also show that the lower bound is indeed a tight one. Second, we present a deterministic nonoblivious permutation routing algorithm which runs in O(d.n²) time on a d-ary de Bruijn network with N=dⁿ nodes. This algorithm is currently the fastest known nonoblivious deterministic routing algorithm for de Bruijn networks of arbitrary degree. Finally, we present an efficient general sorting algorithm for the de Bruijn networks of arbitrary degree. This algorithm is the best sorting algorithm known so far. It runs in O((log d).d.n²) time for directed de Bruijn network with dⁿ nodes, degree d, and diameter n. As a corollary, we show that on a binary de Bruijn network of Nnodes, our sorting scheme requires at most 2 log² Nsteps     

Square meshes are not optimal for convex hull computation

Recently it has been noticed that for semigroup computations and for selection, rectangular meshes with multiple broadcasting yield faster algorithms than their square counterparts. The contribution of the paper is to provide yet another example of a fundamental problem for which this phenomenon occurs. Specifically, we show that the problem of computing the convex hull of a set of n sorted points in the plane can be solved in O(n^1/8 log ^3/4) time on a rectangular mesh with multiple broadcasting of size n^3/8 log^1/4 n×n^5/8/log^1/4n. The fastest previously known algorithms on a square mesh of size √n×√n run in O(n^1/6) time in case the n points are pixels in a binary image, and in O(n^1/6log^3/2 n) time for sorted points in the plane     

An improved algorithm for implication testing involving arithmeticinequalities

Implication testing of arithmetic inequalities has been widely used in different areas in database systems and has received extensive research as well. Klug and Ullman (A. Klug, 1988; and J.D. Ullman, 1989) proposed an algorithm that determines whether S implies T, where T and S consist of inequalities of form (X op Y), X and Y are two variables, and opϵ {=<, ⩽, ≠, >, ⩾}. The complexity of the algorithm is O(n³), where n is the number of inequalities in S. We reduce the problem to matrix multiplication, thus improving the time bound to O(n^2.376). We also demonstrate an O(n² ) algorithm if the number of inequalities in T is bounded by O(n). Since matrix multiplication has been well studied, our reduction allows the possibility of directly adopting many practical results for managing matrices and their operations, such as parallel computation and efficient representation of sparse matrices     

基于网页上下文的Deep Web数据库分类

讨论了提高Deep Web数据库分类准确性的若干新技术,其中包括利用HTML网页的内容文本作为理解数据库内容的上下文和把数据库表的属性标记词归一的过程.其中对网页中的内容文本的发现算法是基于对网页文本块的多种统计特征.而对数据库属性标记词的归一过程是把同义标记词用代表词进行替代的过程.给出了采用分层模糊集合对给定学习实例所发现的领域和语言知识进行表示和基于这些知识对标记词归一化算法.基于上述预处理,给出了计算Deep Web数据库的K-NN(k nearest neighbors)分类算法,其中对数据库之间语义距离计算综合了数据库表之间和含有数据库表的网页的内容文本之间的语义距离.分类实验给出算法对未预处理的网页和经过预处理后的网页在数据库分类精度、查全率和综合F1等测度上的分类结果比较.     

Constructing Euclidean minimum spanning trees and all nearestneighbors on reconfigurable meshes

A reconfigurable mesh, R-mesh for short, is a two-dimensional array of processors connected by a grid-shaped reconfigurable bus system. Each processor has four I/O ports that can be locally connected during execution of algorithms. This paper considers the d-dimensional Euclidean minimum spanning tree (EMST) and the all nearest neighbors (ANN) problem. Two results are reported. First, we show that a minimum spanning tree of n points in a fixed d-dimensional space can be constructed in O(1) time on a √(n³)×√(n³) R-mesh. Second, all nearest neighbors of n points in a fixed d-dimensional space can be constructed in O(1) time on an n×n R-mesh. There is no previous O(1) time algorithm for the EMST problem; ours is the first such algorithm. A previous R-mesh algorithm exists for the two-dimensional ANN problem; we extend it to any d-dimensional space. Both of the proposed algorithms have a time complexity independent of n but growing with d. The time complexity is O(1) if d is a constant     

Optimal Initialization and Gossiping Algorithms for Random Radio Networks

The initialization problem, also known as naming, consists to give a unique identifier ranging from 1 to n to a set of n indistinguishable nodes in a given network. We consider a network where n nodes (processors) are randomly deployed in a square (respectively, cube) X. We assume that the time is slotted and the network is synchronous, two nodes are able to communicate if they are within distance at most of r of each other (r is the transmitting/receiving range). Moreover, if two or more neighbors of a processor u transmit concurrently at the same time slot, then u would not receive either messages. We suppose also that the anonymous nodes know neither the topology of the network nor the number of nodes in the network. Under this extremal scenario, we first show how the transmitting range of the deployed processors affects the typical characteristics of the network. Then, by allowing the nodes to transmit at various ranges we design sublinear randomized initialization protocols: In the two, respectively, three, dimensional case, our randomized initialization algorithms run in O(n^1/2 log n^1/2), respectively, O(n^1/3 log n^2/3), time slots. These latter protocols are based upon an optimal gossiping algorithm which is of independent interest     

基于约束树编辑距离与导航树的信息采集

介绍基于网站和网页结构的信息采集算法,提出一种基于约束树编辑距离的导航树算法。该算法通过提取网页的HTML的重要标记生成网页结构的标签树,对网页进行结构分析,通过约束树编辑距离算法判断爬行到的网页与主题的相关性,并根据网站基于URL的拓扑结构,提出基于导航树的信息采集约束信息采集器的爬行路径,提高了目标页面采集的效率和准确率。     

一种从HTML页面到RDF文档的转化方法

传统互联网页面是基于HTML语法结构的，这种结构适合于计算机上的显示．但页面所表达的含义需要用户在浏览的时候加以识别，这对于信息的检索和实现知识的共享是非常不便的。文章介绍了一种根据HMTL语法结构来实现HTML页面到RDF文档的转化方法，它可以将HTML文档从结构上转换为以XML语法为基础的RDF文档。     

Graph matching by relaxation of fuzzy assignments

Graphs are very powerful and widely used representational tools in computer applications. We present a relaxation approach to (sub)graph matching based on a fuzzy assignment matrix. The algorithm has a computational complexity of O(n²m²) where n and m are the number of nodes in the two graphs being matched, and can perform both exact and inexact matching. To illustrate the performance of the algorithm, we summarize the results obtained for more than 12 000 pairs of graphs of varying types (weighted graphs, attributed graphs, and noisy graphs). We also compare our results with those obtained using the graduated assignment algorithm     

Edge congestion and topological properties of crossed cubes

An n-dimensional crossed cube, CQ_n, is a variation of hypercubes. In this paper, we give a new shortest path routing algorithm based on a new distance measure defined herein. In comparison with Efe's algorithm, which generates one shortest path in O(n²) time, our algorithm can generate more shortest paths in O(n) time. Based on a given shortest path routing algorithm, we consider a new performance measure of interconnection networks called edge congestion. Using our shortest path routing algorithm and assuming that message exchange between all pairs of vertices is equally probable, we show that the edge congestion of crossed cubes is the same as that of hypercubes. Using the result of edge congestion, we can show that the bisection width of crossed cubes is 2^n-1. We also prove that wide diameter and fault diameter are [n/2]+2. Furthermore, we study embedding of cycles in cross cubes and construct more types than previous work of cycles of length at least four     

Parallel algorithms for relational coarsest partition problems

Relational Coarsest Partition Problems (RCPPs) play a vital role in verifying concurrent systems. It is known that RCPPs are P-complete and hence it may not be possible to design polylog time parallel algorithms for these problems. In this paper, we present two efficient parallel algorithms for RCPP in which its associated label transition system is assumed to have m transitions and n states. The first algorithm runs in O(n^1+ϵ) time using m/n^ϵ CREW PRAM processors, for any fixed ϵ<1. This algorithm is analogous to and optimal with respect to the sequential algorithm of P.C. Kanellakis and S.A. Smolka (1990). The second algorithm runs in O(n log n) time using m/n CREW PRAM processors. This algorithm is analogous to and nearly optimal with respect to the sequential algorithm of R. Paige and R.E. Tarjan (1987)     

A Web page classification system based on a genetic algorithm using tagged-terms as features

The incredible increase in the amount of information on the World Wide Web has caused the birth of topic specific crawling of the Web. During a focused crawling process, an automatic Web page classification mechanism is needed to determine whether the page being considered is on the topic or not. In this study, a genetic algorithm (GA) based automatic Web page classification system which uses both HTML tags and terms belong to each tag as classification features and learns optimal classifier from the positive and negative Web pages in the training dataset is developed. Our system classifies Web pages by simply computing similarity between the learned classifier and the new Web pages. In the existing GA-based classifiers, only HTML tags or terms are used as features, however in this study both of them are taken together and optimal weights for the features are learned by our GA. It was found that, using both HTML tags and terms in each tag as separate features improves accuracy of classification, and the number of documents in the training dataset affects the accuracy such that if the number of negative documents is larger than the number of positive documents in the training dataset, the classification accuracy of our system increases up to 95% and becomes higher than the well known Naïve Bayes and k nearest neighbor classifiers.     

Clustering Web pages based on their structure

Several techniques have been recently proposed to automatically generate Web wrappers, i.e., programs that extract data from HTML pages, and transform them into a more structured format, typically in XML. These techniques automatically induce a wrapper from a set of sample pages that share a common HTML template. An open issue, however, is how to collect suitable classes of sample pages to feed the wrapper inducer. Presently, the pages are chosen manually. In this paper, we tackle the problem of automatically discovering the main classes of pages offered by a site by exploring only a small yet representative portion of it. We propose a model to describe abstract structural features of HTML pages. Based on this model, we have developed an algorithm that accepts the URL of an entry point to a target Web site, visits a limited yet representative number of pages, and produces an accurate clustering of pages based on their structure. We have developed a prototype, which has been used to perform experiments on real-life Web sites.     

一种基于分类算法的网页信息提取方法

在目前的Web信息提取技术中,很多都是基于HTML结构的,由于HTML结构的经常变化,使提取模板需要经常更新,而提取模板的更新需要很多领域知识.本文提出一种基于分类算法的Web信息提取方法,通过将网页文本按照其显示属性的不同进行分组,以显示属性值为基础对Web页面文本进行分类,获取所关注文本,从而完成对web页面的信息提取.这种提取方法操作简单,易于实现,对网页结构的依赖性小.     

A parallel algorithm for computing Fourier transforms on the stargraph

The n-star graph, denoted by S_n, is one of the graph networks that have been recently proposed as attractive alternatives to the n-cube topology for interconnecting processors in parallel computers. We present a parallel algorithm for the computation of the Fourier transform on the star graph. The algorithm requires O(n² ) multiply-add steps for an input sequence of n! elements, and is hence cost-optimal with respect to the sequential algorithm on which it is based. This is believed to be the first algorithm, and the only one to date, for the computation of the Fourier transform on the star graph     

An optimal algorithm for the angle-restricted all nearest neighborproblem on the reconfigurable mesh, with applications

Given a set S of n points in the plane and two directions r₁ and r₂, the Angle-Restricted All Nearest Neighbor problem (ARANN, for short) asks to compute, for every point p in S, the nearest point in S lying in the planar region bounded by two rays in the directions r₁ and r₂ emanating from p. The ARANN problem generalizes the well-known ANN problem and finds applications to pattern recognition, image processing, and computational morphology. Our main contribution is to present an algorithm that solves an instance of size n of the ARANN problem in O(1) time on a reconfigurable mesh of size n×n. Our algorithm is optimal in the sense that Ω(n²) processors are necessary to solve the ARANN problem in O(1) time. By using our ARANN algorithm, we can provide O(1) time solutions to the tasks of constructing the Geographic Neighborhood Graph and the Relative Neighborhood Graph of n points in the plane on a reconfigurable mesh of size n×n. We also show that, on a somewhat stronger reconfigurable mesh of size n×n², the Euclidean Minimum Spanning Tree of n points can be computed in O(1) time