ppxscal/embedding_network huggingface dataset:
Batch Updates of Key Trees
Authors: Xiaozhou Li, Y. R Yang, Mohamed Gouda, Simon S. Lam
Venue:  (2000)

Introduced the concept of key trees for secure group communications and discussed how to update a key tree due to a single rekey request (a join or a leave). In a real application, however, rekey requests are likely to be processed in batches, instead of in real-time. In this paper we consider the case where there are equal number of joins and leaves in a batch. In this case, we can replace a leave by a join at the same location in the key tree. We call this an update. We describe a method, called the rekey ssubtree method, to efficiently process batch updates. The method identifies the keys that need to be updated and updates those keys only once. The method saves server cost substantially, compared to the naive approach, which processes updates one after another. We also describe how to modify the rekey subtree method when joins and leaves are unequal. To analyze the rekey subtree method''s performance, we derive the exact expressions for the best, worst, and average case server''s encryption costs. We also derive the exact expression for a user''s average decryption cost. If an application only wants to minimize the server''s cost, it can use server cost expressions to decide what degree the key tree should use. Our analysis and experiments show that 4 is usually the optimal degree when the number of updates is below some threshold (about 1/4 of the number of users), when the number of updates is above the threshold, key star (key tree of degree equal to the number of users) is optimal. If the application has users of limited capacity, it should choose a larger degree to reduce the user''s work, at the cost of increasing the server''s.
An Analysis of OO Software Metrics
Authors: Jer Hogan
Venue:  (1997)

This paper is a survey of software metrics with particular reference to reuse, quality, and productivity, and was prepared as part of the MOOD project. The paper has three main parts: the literature survey, the selected metrics list, and the information to be gathered for process metrics. In the literature survey, papers which relate to metrics are outlined; in the selected metrics list some selected metrics are outlined. This paper is useful for the MOOD project or any project with broadly similar aims, such as to measure and improve reuse, productivity and software quality. 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
TWO-WAY TCP TRAFFIC OVER RATE CONTROLLED CHANNELS: EFFECTS AND ANALYSIS
Authors: Lampros Kalampoukas, Anujan Varma, K. K. Ramakrishnan
Venue:  (1997)

We examine the performance of bidirectional TCP/IP connections over a network which uses rate-based flow and congestion control mechanisms. An example of such a network is an Asynchronous Transfer Mode (ATM) network using the Available Bit Rate (ABR) service. The sharing of a common buffer by TCP packets and acknowledgements has been known to result in an effect called ack compression, where acks of a connection arrive at the source bunched together, resulting in unfairness and degraded throughput. It has been the expectation that maintaining a smooth flow of data using rate-based flow control would mitigate, if not eliminate, the various forms of burstiness experienced with the TCP window flow control. However, we show that the problem of TCP ack compression re-appears even while operating over a rate-controlled channel, although the queues are primarily at the end systems now. By analyzing the periodic bursty behavior of the source IP queue, we are able to predict the peak values for the queue and arrive at a simple robust predictor for the degraded throughput, applicable for relatively general situations. The degradation in throughput due to bidirectional traffic can be significant. For example, even in the simple case of symmetrical connections with adequate window sizes, the throughput of each connection is only 66.67% of that under one-way traffic. We validate our analysis using simulation on an ATM network using the Explicit Rate option of the ABR service. We show that the analysis predicts the behavior of the queue and the throughput degradation not only in simple configurations, but also in more general situations, such as multiple synchronized connections between a pair of end-systems, multiple end-systems having different round-trip delays, and in configurations with significant amounts of cross-traffic. We observe the need to separate the flow of acknowledgements and data for the bidirectional TCP connection and for interleaving their processing at the end-systems to overcome the problem of ack compression. We show that the rate-controlled channel localizes the effect of TCP burstiness and the accompanying dynamics to the outgoing queue at the source, requiring source-based approaches to reduce ack compression.
Relational Database Structure for Storage and Manipulation of DependencyGraphs
Authors: Sivagnanam R Easwar
Venue:  (1988)

This thesis provides a first step towards resolution of the problem, of converting sequential Fortran programs to parallel, by capturing the potential parallel computation structure of a Fortran program in a Relational Database. Parallel languages are required to fully utilize the Parallel machines that have been developed. Many Man-years of Sequential Programs (in FORTRAN) have already been written. Re-writing these programs in some parallel language would be almost impossible. The Database produced by this thesis can then be used by other programs, to generate specific parallel computation structures, appropriate for given environments. 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
Guaranteeing the quality of services in networks on chip
Authors: Kees Goossens, John Dielissen, Jef van Meerbergen, Peter Poplavko, Andrei Rădulescu, Edwin Rijpkema, Erwin Waterlander, Paul Wielage
Venue: Networks on chip (2003)

Users expect a predictable quality of service (QOS) of embedded systems, even for future, more dynamic, applications. System-on-chip designers use networks on chip (NOC) to solve deep submicron problems, and to divide global problems into local, decoupled problems. NOCs provide services through protocol stacks, and introducing guaranteed services enables IP re-use and platform-based design. It also provides globally predictable behaviour, as required by the user, when combining local, decoupled solutions. There are several levels of QOS commitment (correctness, completion, completion bounds), with increasing cost. A combination of guaranteed and best-effort (no commitment) services combines their respective attractive features: predictable behaviour, and good average resource utilisation. The ÆTHEREAL NOC is an example of this approach, and forms the basis of a QOS-based design style, as advocated in this chapter.
A Standard for a Graph Representation for Functional Programs
Authors: M. S. Joy, T. H. Axford
Venue:  (1987)

The data structures used in the authors'' functional language graph reduction implementations are described, together with a standard notation for representing the graphs in a textual format. The graphs employed are compatible with FLIC and with the functional languages in use at Birmingham and Warwick. The textual format is designed to be transmittable easily across networks.
jContractor: A Reflective Java Library to Support Design by Contract
Authors: Murat Karaorman, Urs Holzle, John Bruno
Venue:  (1999)

jContractor is a purely library and design-pattern based approach to support Design By Contract specifications such as preconditions, postconditions, class invariants, and recovery and exception handling in Java. jContractor uses an intuitive naming convention, and standard Java syntax to instrument Java classes and enforce Design By Contract constructs. The designer of a class specifies a contract by defining protected methods which conform to the jContractor design patterns. jContractor uses Java Reflection to synthesize an instrumented version of a Java class containing jContractor contract specifications. The instrumented version contains code which enforces the Design By Contract specifications. Programmers enable the run-time enforcement of contracts by either incorporating the jContractor class loader or by instantiating&#x00A0; objects directly from the instrumented subclass through the jContractor&#x00A0; factory. Programmers can use exactly the same syntax for invoking methods and passing object references regardless of whether contracts are present or not. Since jContractor is purely library-based, it works with any Java implementation and requires no special tools such as modified compilers, modified JVMs, or pre-processors.
Theory of Globally Convergent Probability-One Homotopies For Nonlinear Programming
Authors: Watson Layne T.
Venue:  (1999)

For many years, globally convergent probability-one homotopy methods have been remarkably successful on difficult realistic engineering optimization problems, most of which were attacked by homotopy methods because other optimization algorithms failed or were ineffective. Convergence theory has been derived for a few particular problems, and considerable fixed point theory exists, but generally convergence theory for the homotopy maps used in practice for nonlinear constrained optimization has been lacking. This paper derives some probability-one homotopy convergence theorems for unconstrained and constrained optimization, for linear and nonlinear constraints, and with and without convexity. Some insight is provided into why the homotopies used in engineering practice are so successful, and why this success is more than dumb luck. By presenting the theory as variations on a prototype probability-one homotopy convergence theorem, the essence of such convergence theory is elucidated.
Automatically sharing web experiences through a hyperdocument recommender system
Authors: Alessandra Alaniz Macedo, Khai N. Truong, José Antonio Camacho-Guerrero, Maria da GraÇa Pimentel
Venue: Proceedings of the fourteenth ACM conference on Hypertext and hypermedia (2003)

As an approach that applies not only to support user navigation on the Web, recommender systems have been built to assist and augment the natural social process of asking for recommendations from other people. In a typical recommender system, people provide suggestions as inputs, which the system aggregates and directs to appropriate recipients. In some cases, the primary computation is in the aggregation; in others, the value of the system lies in its ability to make good matches between the recommenders and those seeking recommendations.In this paper, we discuss the architectural and design features of WebMemex, a system that (a) provides recommended information based on the captured history of navigation from a list of people well-known to the users --- including the users themselves, (b) allows users to have access from any networked machine, (c) demands user authentication to access the repository of recommendations and (d) allows users to specify when the capture of their history should be performed.
CHARACTERIZING PAC-LEARNABILITY OF SEMILINEAR SETSAND COMMUTATIVE REGULAR LANGUAGES
Authors: Naoki Abe
Venue:  (1989)

We characterize learnability of the class of letter-counts of regular languages (semilinear sets), commutative regular languages and other related classes of subsets of N^m , with respect to the distribution-free learning model of Valiant (PAC-learning model). By utilizing the notion of reducibility among learning problems due to Pitt and Warmuth called `Prediction Preserving Reducibility'', and a special case thereof, we show a number of positive as well as partially negative results. On the positive side, we show that the class of semilinear sets of dimensions 1 and 2 is learnable when the integers are encoded in unary. We also show that the entire class of commutative deterministic finite-state automata on an arbitrary alphabet size is learnable. On the neutral to negative side, we show that, when the integers are encoded in binary, the learning problem for semilinear sets as well as a class of subsets of N^m much simpler than semilinear sets is as hard as learning DNF, a central open problem in the field. We also show that all of our positive results are for concept representation classes for which the problem of finding a minimum consistent representation is NP-hard.
Regaining Control of Exception Handling
Authors: Martin P. Robillard, Gail C. Murphy
Venue:  (1999)

Just as the structure of the normal operations of a system tends to degrade as the system evolves, the structure of exception handling also degrades. In this paper, we draw on our experience building and analyzing the exception structure of Java programs to describe why and how exception structure degrades. Fortunately, we need not let our exception structure languish. We also relate our experience at regaining control of exception structure in several existing programs using a technique based on software containment.
Effiziente Parallelisierung von Algorithmen der digitalen Bildverarbeitungund Mustererkennung (eingeladener Beitrag)
Authors: Hans Burkhardt, Michael Nolle, Gerald Schreiber
Venue:  (1995)

In this paper we develop a concept for the efficient parallelization of typical algorithms in the area of digital image processing and pattern recognition. From an analysis of the algorithmic data dependencies we derive classes of algorithms that are topologically equivalent, such as algorithms with local or global data dependencies. Assuming distributed memory MIMD systems, the mapping of algorithms onto topologically similar communication networks leads to efficient implementations. For the universal applicability of our approach, efficient homogeneous and heterogeneous graph embeddings have to be supplied in order to ensure portability and scalability. We close with experimental results obtained on a massive parallel Transputer based system. Our paper is of exemplary character for some classes of algorithms whereas the focus is on the concept of our approach.
3D Distance Metric for Pose Estimation and Object Recognition for 2D Projections
Authors: Y. Hel-Or
Venue:  (1994)

Model based object recognition and model based pose estimation require some distance metric to find the optimal pose and to measure the distance between the measurements and possible models during the recognition process. When the measurements are given in 2D (such as in orthographic and perspective projections) the commonly used distance between the 3D model features and the 2D image features is the 2D Euclidean distance measured in the image plane. However, this 2D distance does not, usually, increase monotonically with the real 3D distance and thus does not really represent the distance being measured. In this paper we propose a new scheme in which both, the optimal positioning and the evaluation of similarity between the 2D image and the model is performed relative to the 3D distance. This distance is calculated between the model features and a 3D predicted object which is a permissible reconstruction of the measured object and is the ``closest'''' to the model features. 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 Simple LP-Free Approximation Algorithm for The Minimum Weight Vertex Cover Problem
Authors: Teofilo F. Gonzalez
Venue:  (1993)

We present a simple LP-free (i.e., not requiring linear programming) approximation algorithm for the minimum weight vertex cover problem. Our new approximation algorithm does not need to solve a linear programming problem, nor such a formulation is needed to establish its approximation bound. The algorithm takes linear time with respect to the number of nodes and edges in the graph, and generates solutions that are within twice the weight of a minimum weight vertex cover. Both the algorithm and its proof of correctness are elegant and simple.
Efficient Cryptographic Schemes Provably as Secure as Subset Sum
Authors: R. Impagliazzo, M. Naor
Venue:  (1993)

We show very efficient constructions for a pseudo-random generator and for a universal one-way hash function based on the intractability of the subset sum problem for certain dimensions. (Pseudo-random generators can be used for private key encryption and universal one-way hash functions for signature schemes). The increase in efficiency in our construction is due to the fact that many bits can be generated/hashed with one application of the assumed one-way function. All our construction can be implemented in NC using an optimal number of processors.
Sensitivity of inverse boundary element techniques to errors in photoelastic measurements
Authors: P. Wang, A. A. Becker, I. A. Jones, T. H. Hyde
Venue: Proceedings of the eighth international conference on The application of artificial intelligence to civil and structural engineering computing (2001)

This paper presents an inverse boundary element (BE) technique to reconstruct the boundary conditions in the unknown regions using photoelastic measurement data regarding the differences of the principal stresses and their orientations at interior points. The separate individual Cartesian stress components are then obtained using the forward BE method. The accuracy of the reconstructed tractions and displacements by using the inverse BE technique depends largely on the errors in the photoelastic measurements. This sensitivity study shows how to choose the number of interior points and their locations, and how to improve the accuracy of the numerical algorithm. Examples show good agreement with other solutions even if up to 5% random 'noise' is added to the photoelastic measurement data.
Ein neues Verfahren zur Berechnung von Translationsinvarianten
Authors: Sabine Kroner
Venue:  (1994)

Die von Wagh und Kanetkar in citeWa77 definierte Klasse CsetD T von translationsinvarianten Transformationen bietet eine schnelle Berechnungsmoglichkeit fur Invarianten von 1D-Signalen und 2D-Bildern. Sie ist jedoch weder vollstandig gegenuber der Gruppe der zyklischen Translationen noch gegenuber der Erweiterung auf die spezielle Menge Iset_Cset T von Permutationen, in der alle Permutationen eines Musters enthalten sind, die durch die Transformationen der Klasse CsetD T auf dieselbe Invariante abgebildet werden. Dies fuhrt zu Problemen bei der Klassifizierung der Invarianten verschiedener zu separierender Muster. In Anlehnung an die Berechnungsstruktur der Klasse CsetD T wurde ein neues translationsinvariantes Verfahren entwickelt, das vollstandig ist gegenuber der Permutationsmenge Iset_Cset T. Unabhangig von der Wahl der Operatoren ist dabei gewahrleistet, da? die von Burkhardt in citeBu79 angegebene theoretisch unterste Grenze der Zahl der Originalbilder zu einer Invarianten der Klasse CsetD T auch in der Anwendung erreicht wird. Gleichzeitig verbessert sich damit das Vollstandigkeitsma? fur zyklische Translationen eines Musters, so da? die Separierfahigkeit von unterschiedlichen verschobenen Mustern erhoht wird.
Inference of Structure: Hands
Authors: Robert A. McLaughlin, Mike Alder, Christopher J.S. deSilva
Venue:  (1994)

Many images can be viewed in terms of simpler components, such as a hand viewed as a collection of fingers and a palm. Recognition can then be achieved by finding these components and examining the relationships between them. If each component can be further decomposed into sub-components, then this approach may be applied recursively to the image until some low level primitives are obtained. This decomposition imposes a hierarchy upon the recognition, as the same image is described at several different levels as a collection of increasingly simple parts. This paper explores an attempt to solve a recognition problem using such an approach. Notably each level of the problem is solved using essentially identical techniques. This uniformity of approach suggests a great potential for generalisation to many different types of recognition problem.
PARALLELIZING THE FAST FOURIER TRANSFORM
Authors: Don Fong
Venue:  (1990)

The Fourier transform is an operator which maps functions from the temporal or spatial domain to the frequency domain. The *discrete* Fourier transform (DFT) is the digital analogue of the Fourier transform; it maps the discrete representation of a function to the frequency domain. The *fast* Fourier transform (FFT) is a method---in actuality, any one of a number of methods--- for rapid calculation of the DFT. This report describes an investigation into the parallelization properties of the FFT. The first phase (1) of the investigation was a brief look at the mathematical basis of the FFT. The second phase (2) consisted of coding a non-parallel test program using a particular FFT algorithm. The third phase (3) consisted of experiments with a particular parallelizing FORTRAN compiler to test its ability to parallelize, vectorize, optimize, and reorganize FFT code. 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
Buffer Sharing Schemes for Continuous-Media Systems
Authors: Dwight J. Makaroff, Raymond T. Ng
Venue:  (1995)

Buffer management in continuous-media systems is a frequently studied topic. One of the most interesting recent proposals is the idea of buffer sharing for concurrent streams. As analyzed in~\cite{ny94}, by taking advantage of the temporal behaviour of concurrent streams, buffer sharing can lead to a 50\% savings in total buffer space. In this paper, we study how to actually implement buffer sharing. To this end, we develop the CES Buffer Sharing scheme that is very efficient to implement, and that permits savings asymptotically very close to the ideal savings predicted by the analysis in~\cite{ny94}. We show that the CES scheme can operate effectively under varying degrees of disk utilizations, and during transition periods when the number of concurrent streams changes. We also demonstrate how the scheme can be further improved, particularly for situations when the number of concurrent streams is small. In ongoing work, we will integrate the proposed scheme into a distributed continuous-media file system which is under development at the University of British Columbia.
Surface and Shading Models from Real Images fro Computer Graphics
Authors: Jiping Lu, Jim Little
Venue:  (1997)

In this technical report we present an object modeling and rendering technique from real images for computer graphics. The technique builds the surface geo- metric model and extracts the surface shading model from a real image sequence of a rotating object illuminated under a collinear light source (where the illuminant direction of the light source is the same as the viewing direction of the camera). In building the surface geometric model, the object surface reflectance function is extracted from the real images and used to recover the surface depth and orientation of the object. In building the surface shading model, the different shading components, the ambient component, the diffuse component and the specular component, are calculated from the surface reflec- tance function extracted from the real images. Then the obtained shading model is used to render the recovered geometric model of the surface in arbi- trary viewing and illuminant directions. Experiments have been conducted on diffuse surface and specular surface. The synthetic images of the recovered object surface rendered with the extracted shading model are compared with the real images of the same objects. The results shows that the technique is feasible and promising.