ppxscal/embedding_network huggingface dataset:
Approximating k-Spanner Problems for k < 2
Authors: M. Elkin, D. Peleg
Venue:  (2000)

Given a graph G = (V,E), a subgraph G? = (V,H), H I E is a k-spanner (respectively, k-DSS) of G if for any pair of vertices u,w I V it satisfies d>sub<H>/sub<(u,w) # k ?d>sub<G>/sub<(u,w) (resp., d>sub<H>/sub<(u,w) # k). The basic k-spanner (resp., k-DSS ) problem is to find a k-spanner (resp., k-DSS) of a given graph G with the smallest possible number of edges. This paper considers approximation algorithms for these and some related problems for k < 2. Both problems are known to be W(2log1 - e n)-inapproximable [11,13]. The basic k-spanner problem over undirected graphs with k < 2 has been given a sublinear ratio approximation algorithm (with ratio roughly O(n[2/(k+1)])), but no such algorithms were known for other variants of the problem, including the directed and the client-server variants, as well as for the k-DSS problem. We present the first approximation algorithms for these problems with sublinear approximation ratio. The second contribution of this paper is in characterizing some wide families of graphs on which the problems do admit a logarithmic and a polylogarithmic approximation ratios. These families are characterized as containing graphs that have optimal or ``near-optimal'''' spanners with certain desirable properties, such as being a tree, having low arboricity or having low girth. All our results generalize to the directed and the client-server variants of the problems. As a simple corollary, we present an algorithm that given a graph G builds a subgraph with [O\tilde](n) edges and stretch bounded by the tree-stretch of G, namely the minimum maximal stretch of a spanning tree for G. The analysis of our algorithms involves the novel notion of edge-dominating systems developed in the paper. The technique introduced in the paper enables us to reduce the studied algorithmic questions of approximability of the k-spanner and k-DSS problems to purely graph-theoretical questions concerning the existence of certain combinatorial objects in families of graphs.
Texture Classification using the Conjugate Gradient Backpropagation Neural Network Learning Algorithm
Authors: Mark Morrison, Christakis Charalambous, Yianni Attikiouzel
Venue:  (1990)

It has been shown that the conjugate Gradient backpropagation learning algorithm yields significant training speed advantages over the standard momentum backpropagation algorithm for relatively simple problems. This paper investigates the performance of the new algorithm when faced with the more difficult task of texture classification. It is shown that the new algorithm is indeed signficantly faster and ehibits vastly superior convergence properties.
Three BCPL Machines
Authors: Harvey Abramson
Venue:  (1979)

We describe three virtual BCPL machines designed in the Department of Computer Science at the University of British Columbia. The first machine is the Pica-B which is an Intcode machine with an added interrupt register, plus several execute instructions to manipulate this register, and a modification of the routine calling mechanism so that interrupts can be treated as unexptected routine calls. An inline code command, the \underline{vile} command, allows the writing of interrupt routines in BCPL, and also facilitates the portability of the BCPL library by allowing certain routines such as level, longjump, and aptovec to be written in BCPL. The second machine is the SLIM (\underline{S}tack \underline{L}anguage for \underline{I}ntermediate \underline{M}achine) machine which is a stack machine with an accumulator. This architecture permits the representation of BCPL programs with fewer instructions than the OCODE representation requires. The third machine is the ICE machine which permits highly space-efficent representations of BCPL programs by having a large instruction set which includes many variants of the BCPL operators.
Stability Restrictions on Second Order, Three Level Finite Difference Schemes for Parabolic Equations
Authors: James M. Varah
Venue:  (1978)

In this paper we are concerned with second order schemes which are easy to use, and apply readily to nonlinear equations. We examine the stability restrictions for such schemes using linear stability analysis, and illustrate their behaviour on Burgers'' equation.
PRECOMPILING C++ FOR GARBAGE COLLECTION
Authors: Daniel R. Edelson
Venue:  (1992)

Our research is concerned with compiler-independent, efficient and convenient garbage collection for C++. Most collectors proposed for C++ have either been implemented in a library or in a compiler. As an intermediate step between those two, this paper proposes using precompilation techniques to augment a C++ source program with code to allow mostly type-accurate garbage collection. There are two key precompiler transformations. The first is automatic generation of *smart pointer* classes. The precompiler defines the smart pointer classes and the user utilizes them instead of raw pointers. These smart pointers supply functionality that allows the collector to locate the root set for collection. The second transformation augments the C++ program with code that allows the garbage collector to locate internal pointers within objects. This paper describes the precompiler and the garbage collector. The paper includes a brief (1500 word) survey of related techniques.
Study of the dynamic and equivalent static analysis methods for seismic design of bridges: ranges of applicability, effect of modelling assumptions, and support conditions
Authors: M. M. Bakhoum, S. Athanasious
Venue: Proceedings of the eighth international conference on The application of artificial intelligence to civil and structural engineering computing (2001)

The paper presented several studies concerning the structural analysis in the seismic design of bridges on (1) the dynamic and equivalent static analysis methods used currently in the seismic design of bridges, and the limits of applicability of the different methods are studied. A parametric study is carried out and presented. (2) Then, the modeling assumptions used to prepare input data for the analysis are discussed. The effect of soil-structure interaction (SSI), and cracking of the reinforced concrete columns (effective cross section properties) are studied. (3) Finally, a comparison of the response of different bridge structural systems to earthquakes is presented. The effect of the boundary / support conditions on the forces and deformations developed in the bridge due to seismic actions is studied.
Segmentation of Natural Images for CBIR
Authors: Paul S Williams, Mike D. Alder
Venue:  (1998)

This paper examines the problem of segmenting colour images into homogeneous regions for use in content based image retrieval (CBIR) or object recognition in general. Low level features provide intensity, colour and texture characteristics across the entire image. From these feature vectors a measure of local homogeneity is obtained. Through iterative modelling a seed and grow style algorithm is used to locate each segment. The final segment models provide sufficient information for higher level processing or classification. Segmentation and classification results are illustrated from a database of 1000 Corel Photo CD image.
Analysis of the Java Class File Format
Authors: Denis N. Antonioli, Markus Pilz
Venue:  (1998)

The wide acceptance of Java as a network programing language has made the Java class file to one of the most popular, portable intermediate program representations. Such a representation must be as small as possible and still ideally support interpretation and code generation. This report presents the result of an analysis that examined a set of 4016 different class files for size and bytecode usage.
TRANSIENT ANALYSIS OF COUPLED TRANSMISSION LINES CHARACTERIZED WITH FREQUENCY-DEPENDENT LOSSES OR MEASURED SCATTERING-PARAMETER DATA AND OPTIMAL DESIGN OF SELF-DAMPED INTERCONNECTS (Ph.D. Thesis)
Authors: Jimmy S Wang
Venue:  (1995)

As the packaging density and the clock speed of the multichip modules (MCMs) increase, crosstalk induced noise can become one of the major sources of noise which will limit the performance of the high-speed digital systems. In addition, as the magnitudes of the harmonics of the transmitted signals above $1$ GHz become more significant, the interconnects exhibit more frequency-dependent conductor losses (skin effect) and the dielectric losses (dispersion). In order to design the interconnects more accurately and more efficiently, the S-parameters macromodels of the coupled lossless and lossy transmission lines with frequency-dependent losses are constructed in this thesis. Since the discontinuities in interconnects are hard to describe with close form equations, they are better characterized with measured S-parameter data. Thus, it is equally important to include the measured S-parameter macromodel in the transient analysis. The task of designing interconnections does not stop at viewing simulation waveforms, it requires the design optimization as well. For today''s Computer-Aided Design tools, it usually takes several iterations between the layout and the simulation tools to find the optimal design of the interconnects. A simple and robust method of designing the lossy-transmission-line interconnects in a network for multichip modules has been developed. It uses wire-sizing to solve the problems encountered in propagating high-speed signals through unterminated lossy transmission lines on the substrates of multichip modules. The optimal self-damped design concept is used to relate the layout parameter (line width) and the transfer function (damping ratio, and natural undamped frequency) to the signal propagation delay. This method can produce a fast and a more stable signal propagation for single-source multi-receiver networks on multichip modules, without using termination resistors. There are further improvements that can be gained by incorporating an incremental simulation and a sensitivity analysis into the optimal design to improve the efficiency. Building these scattering parameter macromodels greatly improves the accuracy and the efficiency of the transient analysis. Together with the optimal design, they provides a faster turn around time in producing high-performance MCM designs.
Defining Software Quality Measures: A Systematic Approach Embedded in the Objectives, Principles, Attributes Framework
Authors: Gary N. Bundy, James D. Arthur
Venue:  (1992)

Currently, software quality measures and metrics are being developed in isolation and often without the benefit of a guiding framework. In this paper we describe a systematic process for identifying measurement approaches and defining corresponding metrics that definitively support software quality assessment. That systematic process embodies five well-defined steps that reflect quality assessment within a framework which links the achievement of desirable software engineering objectives to the use of appropriate principles, and the use of principles to the manifestation of desirable product attributes. Ada is the language we have chosen to examine; the Ada package is used to illustrate the identification and definition process.
The Virtual Hand Laboratory Architecture
Authors: Valerie A. Summers
Venue:  (1999)

The Virtual Hand Lab (VHL) is an augmented reality environment for conducting experiments in human perception and motor performance that involve grasping, manipulation, and other complex 3D tasks that people perform with their hands. Our system supports a wide range of experiments and is used by (non-programmer) experimenters. Our system co-locates the hand and the manipulated objects (whether physical or virtual) in the same visual space. Spatial and temporal accuracy are maintained by using a high precision tracker and an efficient implementation of the software architecture which carefully synchronizes the timing equipment and software. There are many issues which influence architectural design; two of which are modularization and performance. We balance these concerns by creating a layered set of modules upon which the application is built and an animation control loop which cuts across module boundaries to control the timing of equipment and application. Augmented objects are composed of both physical and graphical components. The graphical object inheritance hierarchy has several unusual features. First, we provide a mechanism to decouple the movement of the graphical component of an augmented object from its physical object counterpart. This provides flexibility in the types of experiments supported by the testbed. Second, we create subclasses based on properties of the physical component of the augmented objects before creating subclasses based on the virtual components. Specifically, we categorize physical objects as either rigid or flexible based on their level of deformation. This allows us to efficiently implement many of the manipulation techniques. Third, after subclasses based on the physical objects have been created, the implementation of concrete virtual object classes is driven by the goal of creating an easy interface for the experimenters. This was based on our user centered design approach.
An Artificial Intelligence Environment for Information Retrieval Research
Authors: Robert K. France, Edward A. Fox
Venue:  (1988)

The CODER (COmposite Document Expert/Extended/Effective Retrieval) project is a multi-year effort to investigate how best to apply artificial intelligence methods to increase the effectiveness of information retrieval systems. Particular attention is being given to analysis and representation of heterogeneous documents, such as electronic mail digests or messages, which vary widely in style, length, topic,and structure. In order to ensure system adaptability and to allow reconfiguration for controlled experimentation, the project has been designed as a moderated expert system. This thesis covers the design problems involved in providing a unified architecture and knowledge representation scheme for such a system, and the solutions chosen for CODER. An overall object-oriented environment is constructed using a set of message-passing primitives based on a modified Prolog call paradigm. Within this environment is embedded the skeleton of a flexible expert system, where task decomposition is performed in a knowledge-oriented fashion and where subtask managers are implemented as members of a community of experts. A three-level knowledge representation formalism of elementary data types, frames, and relations is provided, and can be used to construct knowledge structures such as terms, meaning structures, and document interpretations. The use of individually tailored specialist experts coupled with standardized blackboard modules for communication and control and external knowledge bases for maintenance of factual world knowledge allows for quick prototyping, incremental development and flexibility under change. The system as a whole is structured as a set of communicating modules, defined functionally and implemented under UNIX^TM using sockets and the TCP/IP protocol for communication. Inferential modules are being coded in MU-Prolog; non-inferential modules are being prototyped in MU-Prolog and will be re-implemented as needed in C++.
MULTI-DIMENSIONAL TREES FOR CONTROLLED VOLUME RENDERING AND COMPRESSION
Authors: Jane Wilhelms, Allen VanGelder
Venue:  (1994)

This paper explores the use of multi-dimensional trees to provide spatial and temporal efficiencies in imaging large data sets. Each node of the tree contains a model of the data in terms of a fixed number of basis functions, a measure of the error in that model, and a measure of the importance of the data in the region covered by the node. A divide-and-conquer algorithm permits efficient computation of these quantities at all nodes of the tree. The flexible design permits various sets of basis functions, error criteria, and importance criteria to be implemented easily. Selective traversal of the tree provides images in acceptable time, by drawing nodes that cover a large volume as single objects when the approximation error and/or importance are low, and descending to finer detail otherwise. Trees over very large datasets can be pruned by the same criterion to provide data representations of acceptable size and accuracy. Compression and traversal are controlled by a user-defined combination of modeling error and data importance. For imaging decisions additional parameters are considered, including grid location, allowed time, and projected screen area. To analyse results, two evaluation metrics are used: the first compares the hierarchical model to actual data values, and the second compares the pixel values of images produced by different parameter settings.
A RESTAMPING APPROACH TO CLOCK RECOVERY IN MPEG-2 SYSTEMS LAYER
Authors: Christos Tryfonas, Anujan Varma
Venue:  (1998)

This paper addresses the clock recovery problem while transporting MPEG-2 Systems Layer streams over packet-switched networks. The packet delay variation (jitter) introduced by the network affects the stability and thus the quality of the recovered clock. A decoder design methodology is described in which a jitter estimator that performs restamping on all the incoming packets containing clock values is used in conjunction with a standard phase-locked loop (PLL). A simple implementation of this methodology is described, where a new heuristic has been added to the standard PLL to eliminate the effects of the jitter. The methodology is evaluated by both analysis and extensive simulation experiments in a multi-hop ATM network using constant bit-rate MPEG-2 Transport Streams produced by hardware encoders with varying levels of cross traffic. The results show that the restamping approach outperforms standard dejittering methods, especially under heavy load conditions.
Scalability Issues for High Performance Digital Libraries on the World Wide Web
Authors: Daniel Andresen, Tao Yang, Omer Egecioglu, Oscar H. Ibarra, Terence R. Smith
Venue:  (1996)

We investigate scalability issues involved in developing high performance digital library systems. Our observations and solutions are based on our experience with the Alexandria Digital Library (ADL) testbed under development at UCSB. The current ADL system provides on-line browsing and processing of digitized maps and other geo-spatially mapped data via the World Wide Web (WWW). A primary activity of the ADL system involves computation and disk I/O for accessing compressed multi-resolution images with hierarchical data structures, as well as other duties such as supporting database queries and on-the-fly HTML page generation. Providing multi-resolution image browsing services can reduce network traffic but impose some additional cost at the server. We discuss the necessity of having a multi-processor DL server to match potentially huge demands in simultaneous access requests from the Internet. We have developed a distributed scheduling system for processing DL requests, which actively monitors the usages of CPU, I/O channels and the interconnection network to effectively distribute work across processing units to exploit task and I/O parallelism. We present an experimental study on the performance of our scheme in addressing the scalability issues arising in ADL wavelet processing and file retrieval. Our results indicate that the system delivers good performance on these types of tasks.
The Memory Game
Authors: U. Zwick, M. S. Paterson
Venue:  (1991)

The memory game is a popular card game played by children and adults around the world. Good memory is one of the qualities required in order to succeed in it. This however is not enough.When it is assumed that the players have perfect memory, the memory game can be seen as a game of strategy. The game is analysed under this assumption and the optimal strategy is found. This is simple and perhaps unexpected. In contrast to the simplicity of the optimal strategy, the analysis leading to its optimality proof is rather involved. It supplies an interesting example of concrete mathematics of the sort used in the analysis of algorithms. It is doubtful whether this analysis could have been carried out without resort to experimentation and substantial use of automated symbolic computation.
Adaptive Load Sharing for Clustered Digital Library Servers
Authors: Huican Zhu, Tao Yang, Qi Zheng, David Watson, Oscar Ibarra, Terry Smith
Venue:  (1998)

This paper investigates load balancing strategies for clustered Alexandria digital library (ADL) servers. The ADL system, which provides on-line information searching and browsing of spatially-referenced materials through the World Wide Web, involves intensive database I/O and heterogeneous CPU activities. Clustering servers can improve the scalability of the ADL system in response to a large number of simultaneous access requests. One difficulty addressed is that clustered workstation nodes may be non-uniform in terms of CPU and I/O speeds. An optimization scheme is proposed in this paper to dynamically monitor the resource availability, use a low-cost communication strategy for updating load information among nodes, and schedule requests based on both I/O and computation load indices. Since the accurate cost estimation for processing database-searching requests is difficult, a sampling and prediction scheme is used to identify the relative efficiency of nodes for satisfying I/O and CPU demands of these requests. A set of experiments using the ADL traces have been conducted to verify the effectiveness of the proposed strategies.
Remote Interprocess Communication \& Its Performance in Team Shoshin
Authors: Acton Don
Venue:  (1985)

Team Shoshin is an extension of Shoshin, a testbed for distributed software developed at the University of Waterloo. Part of the functionality of Shoshin can be attributed to its transparent treatment of remote interprocess communication. This is accomplished by having a special system process, the communications manager, handle the exchange of messages between machines. Shoshin''s new hardware environment is significantly different from what it was originally designed on. This thesis describes the problems the new hardware presented and how those problems were overcome. Performance measurements of the time required for both local and remote message exchanges are made and compared. Using this empirical data, a simple model of the remote message exchange protocol is developed to try and determine how to improve performance. The software and hardware enhancements made to Shoshin have resulted in an improvement in system interprocess communication performance by a factor of four. Finally as a demonstration of Shoshin''s interprocess communications facilities a simple UNIX based file server is implemented. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player
A Formal Model and Specification Language for Procedure Calling Conventions
Authors: Mark W. Bailey, Jack W. Davidson
Venue:  (1994)

Procedure calling conventions are used to provide uniform procedure-call interfaces. Applications, such as compilers and debuggers, which generate, or process procedures at the machine-language abstraction level require knowledge of the calling convention. In this paper, we develop a formal model for procedure calling conventions called P-FSA''s. Using this model, we are able to ensure a number of completeness and consistency properties of calling conventions. Currently, applications that manipulate procedures implement conventions in an ad-hoc manner. The resulting code is complicated with details, difficult to maintain, and often riddled with errors. To alleviate the situation, we introduce a calling convention specification language, called CCL. The combination of CCL and P-FSA''s facilitates the accurate specification of conventions that can be shown to be both consistent and complete.