ppxscal/embedding_network huggingface dataset:
A STUDY OF THE RELIABILITY OF INTERNET SITES
Authors: D. D. E. Long, J. L. Carroll, C. J. Park
Venue:  (1990)

It is often assumed that the failure and repair rates of components are exponentially distributed. This hypothesis is testable for failure rates, though the process of gathering the necessary data and reducing it to a usable form can be difficult. While no amount of testing can prove that a sample is drawn from an exponential distribution, the hypothesis that a population distribution is exponential can in many cases be rejected with confidence. For this study, data were collected from as many hosts as was feasible using only data that could be obtained via the Internet with no special privileges or added monitoring facilities. The Internet was used to poll over 100,000 hosts to determine the length of time that each had been up, and again polled after several months to determine average host availability. A surprisingly rich collection of information was gathered in this fashion, allowing estimates of availability, mean-time-to-failure (MTTF) and mean-time-to-repair (MTTR) to be derived. The measurements reported here correspond with common experience and certainly fall in the range of reasonable values. By applying an appropriate test statistic, some of the samples were found to have a realistic chance of being drawn from an exponential distribution, while others can be confidently classed as non-exponential. With very large sample sizes, sufficient evidence could be accumulated to reject the exponential hypothesis. However, for moderately-sized samples, it was often not possible to exhibit the deviation from exponentiality, lending credence to the common practice of assuming the MTTF is exponentially distributed.
Magnetohydrodynamic Flow and Heat Transfer About a Rotating Disk with Suction and Injection at the Disk Surface
Authors: Kishore S. Kumar, William I. Thacker, Layne T. Watson
Venue:  (1986)

This paper studies the effects of a partial magnetic field on the flow and heat transfer about a porous rotating disk. Using modem quasi-Newton and globally convergent homotopy methods, numerical solutions are obtained for a wide range of magnetic field strengths and injection and suction velocities. Results are presented graphically in terms of three nondimensional parameters. There is excellent agreement with previous work and asymptotic formulas.
Verifying a Self-Timed Divider
Authors: Tarik Ono-Tesfaye, Christoph Kern, Mark Greenstreet
Venue:  (1998)

This paper presents an approach to verifying timed designs based on refinement: first, correctness is established for a speed-independent model; then, the timed design is shown to be a refinement of this model. Although this approach is less automatic than methods based on timed state space enumeration, it is tractable for larger designs. Our method is implemented using a proof checker with a built-in model checker for verifying properties of high-level models, a tautology checker for establishing refinement, and a graph-based timing verification procedure for showing timing properties of transistor level models. We demonstrate the method by proving the timing correctness of Williams'' self-timed divider.
WAVELETS: AN ELEMENTARY INTRODUCTION AND EXAMPLES
Authors: Ueda Masami, Suresh Lodha
Venue:  (1995)

Wavelets have been found to be very useful in many scientific and engineering applications including computer graphics, scientific visualization, data compression and signal processing. Unfortunately, the two most well known monographs on wavelets by Chui and Daubechies are still unaccessible to a beginner due to the level of mathematical sophistication needed to go through these monographs. Moreover both these monographs introduce wavelets from a signal processing perspective. The objective here is to introduce wavelets via scaling functions using the theory of multiresolution analysis. The primary focus is to describe many examples of scaling functions and their corresponding wavelets without proofs. The two-scale reconstruction and decomposition relations are described in order to provide the reader with a quick working knowledge of wavelets. Examples of wavelets included in this monograph are Haar wavelets, B-spline wavelets and Daubechies wavelets on real line, and Legendre wavelets and flatlet wavelets on bounded intervals.
The World of the Stop Consonant
Authors: Katrina Hicks
Venue:  (1990)

This report is a preliminary investigation into the problems of recognising plosives. It surveys the leterature and comments on results using the IRIS workstation DSP system. 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
THE CASE FOR GARBAGE COLLECTION IN C++
Authors: Daniel Edelson, Ira Pohl
Venue:  (1990)

C++ is an object-oriented imperative programming language that provides low-level access to the machine and efficient run-time code. C++ provides access to dynamically allocated storage in a way that allows class designers to create customized memory allocators and deallocators. Unlike Eiffel and Modula-3, C++ does not provide garbage collection. The benefits of garbage collection are substantial: rapid-prototyping and runtime efficiency. However, it has not been clear that garbage collection could be provided for C++ in a way that is consistent with the language''s design goals. We argue that garbage collection should be an option for C++ programmers. We cite an implementation that demonstrates that it can be provided in a way that is consistent with the C++ design goals and philosophy.
MASSIVELY PARALLEL BIOSEQUENCE ANALYSIS
Authors: Richard Hughey
Venue:  (1993)

Massive parallelism is required for the analysis of the rapidly growing biosequence databases. First, this paper compares and benchmarks methods for dynamic programming sequence analysis on several parallel platforms. Next, a new hidden Markov model method and its implementation on several parallel machines is discussed. Finally, the results of a series of experiments using this massively parallel implementation are described. 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
MULTI-LEVEL HIERARCHICAL RETRIEVAL
Authors: Robert Levinson, Gerard Ellis
Venue:  (1992)

As large databases of conceptual graphs are developed for complex domains, efficient retrieval techniques must be developed to manage the complexity of graph-matching while maintaining reasonable space requirements. This paper describes a novel method ``the multi-level hierarchical retrieval method" that exploits redundancy to improve both space and execution time efficiency. The method involves search in multiple partially ordered (by ``more-general-than") hierarchies such that search in a simpler hierarchy reduces the search time in the hierarchy of next complexity. The specific hierarchies used are: the traditional partial order over conceptual graphs; a partial order over node descriptors; a partial order over ``descriptor units"; and finally, the simplest partial order is the traditional type hierarchy.
A Formal Framework for ASTRAL Inter-Level Proof Obligations
Authors: Alberto Coen-Porisini, Richard A. Kemmerer, Dino Mandrioli
Venue:  (1993)

ASTRAL is a formal specification language for realtime systems. It is intended to support formal software development, and therefore has been formally defined. This paper focuses on how to formally prove the mathematical correctness of ASTRAL specifications. ASTRAL is provided with structuring mechanisms that allow one to build modularized specifications of complex systems with layering. A realtime system is modeled by a collection of process specifications and a single global specification. Each process specification consists of a sequence of levels; each level is an abstract data type view of the process being specified. In this paper further details of the ASTRAL refinement process, which were not fully developed in previous papers, are presented. Formal proofs in ASTRAL can be divided into two categories: inter-level proofs and intra-level proofs. The former deal with proving that the specification of level i+1 is consistent with the specification of level i, while the latter deal with proving that the specification of level i is consistent and satisfies the stated critical requirements. This paper concentrates on inter-level proofs. The necessary proof obligations to assure that a refinement is a correct implementation are presented. The approach is motivated with a communication example.
Unification Based Conditional Binding Constructs
Authors: Harvey Abramson
Venue:  (1982)

The unification algorithm, heretofore used primarily in the mechanization of logic, can be used in applicative programming languages as a pattern matching tool. Using SASL (St. Andrews Static Language) as a typical applicative programming language, we introduce several unification based conditional binding (ie, pattern matching) constructs and show how these can promote clarity and conciseness of expression in applicative languages, and we also indicate some applications of these constructs. In particular, we present an interpreter for SASL functions defined by recursion equations.
"Common" web paths in a group adaptive system
Authors: Maria Barra, Delfina Malandrino, Vittorio Scarano
Venue: Proceedings of the fourteenth ACM conference on Hypertext and hypermedia (2003)

In this paper we describe how we use a group of users' accesses and interactions with web pages to discover and recommend relevant common navigation paths to other users. We collect data using a social navigation environment called GAS (Group Adaptive System) that we developed and are currently integrating the common path navigation tool into the system. The goal is to use the common path of a subset of users in the system as a recommendation for other users.
Ontologies supporting business process re-engineering
Authors: Alexandra Galatescu, Taisia Greceanu
Venue: Enterprise information systems IV (2003)

The paper motivates the ontologies for the automation of a Business Process Re-engineering (BPR) methodology (in particular, for the continuous and incremental improvement of the business processes using TQM - Total Quality Management). It describes and exemplifies an upper-level ontology with linguistic features and its application to three particular ontologies: BPR, domain and communication ontology. The main benefits from ontologies for BPR are: (1) they facilitate the (virtual) team work by providing a common vocabulary and understanding, (2) the ontological axioms support the organization and formalization of the BPR specific knowledge, as well as the inferences upon it, (3) an upper-level ontology helps for the integration of BPR and domain specific information and knowledge.
Tertiary Storage: Current Status and Future Trends
Authors: Sunil Prabhakar, Divyakant Agrawal, Amr El Abbadi, Ambuj Singh
Venue:  (1996)

This report summarizes current state of the art in tertiary storage systems. We begin with a comprehensive discussion of magnetic tape and optical storage technologies. This is followed by a classification of commercial products based on their performance characteristics. Our analysis of product data indicates that in contrast to disk technology, tertiary storage products have significant variablility in terms of data transfer rates as well as other performance figures. We then summarize efforts in the areas of operating systems, databases and advanced applications to integrate tertiary storage. We point out that different assumptions about the underlying technology result in entirely different algorithms and system design. We conclude the report with a speculation of future trends.
An Architecture-Independent Unified Approach to FPGA Routing
Authors: Michael J. Alexander, Gabriel Robins
Venue:  (1993)

Field-programmable gate arrays (FPGAs) are an inexpensive and flexible low risk design alternative to custom integrated circuits. While FPGA partitioning and technology mapping have been well-studied, FPGA routing has received much less attention. In this paper we propose a unified general framework for FPGA routing, which allows simultaneous optimization of multiple competing objectives under a smooth designer-controlled tradeoff. Our approach is based on a new and general multi-weighted graph formulation, enabling a good theoretical performance characterization, as well as an effective, practical implementation. Our router is architecture-independent, computationally efficient, and performs very well on industrial benchmarks. Finally, our multi-weighted graph formulation is quite general and is directly applicable to many other areas of combinatorial optimization.
Schwarz Splitting Using ELLPACK
Authors: Bennett W. Cleveland, Calvin J. Ribbens
Venue:  (1988)

This report describes a high level implementation of Schwarz splitting, an approach to solving partial differential equations which seems particularly attractive from the point of view of parallelism. We discuss the basic scheme of Schwarz splitting and an implementation using ELLPACK. We consider two numerical examples in detail. The appendices contain a listing of an ELLPACK program which implements Schwarz splitting, and a complete set of data from the two examples. The examples were done on a sequential machine, but they provide clues as to the potential for parallelism exhibited by the Schwarz technique.
Lexic Scanners
Authors: R. A. Fraley
Venue:  (1977)

A fast algorithm for a general purpose scanner is presented. It includes a mechanism for permitting user-defined special character tokens. The scanner is able to separate strings of special characters without imposing arbitrary spacing rules on the programmer. An analysis shows that most special character tokens from selected languages could be handled properly by the scanner, even if they were in the same language. Many of the omitted tokens could be confused for combinations of operators, demonstrating the utility of the scanner for preventing lexical ambiguity. The special character analysis is extended to other classes of tokens.
STAT -- A State Transition Analysis Tool For Intrusion Detection
Authors: Phil Porras
Venue:  (1993)

This thesis proposes a new approach to representing computer penetrations and applies the approach to the development of a real-time intrusion detection tool. The approach, referred to as penetration state transition analysis, views a penetration as a sequence of state changes that lead a computer system from an initial prerequisite state to a target compromised state. State transitions are defined in terms of critical actions and assertions that describe the pre- and post-action states of the system. A state transition diagram, which is the graphical representation of state transition analysis, identifies precisely the requirements and compromise of a penetration and lists only those critical events that must occur for the successful completion of the penetration. The State Transition Analysis Tool (STAT) is an advanced rule-based expert system that analyzes the audit trails of multi-user computer systems in search of impending security violations. STAT represents state transition diagrams within its rule-base and uses them to seek out those state transitions within the target system that correspond to known penetration scenarios. Unlike comparable analysis tools that pattern match sequences of audit records to the expected audit trails of known penetrations, STAT rules focus on the effects that the individual steps of a penetration have on the state of the computer system. The resulting rule-base is not only more intuitive to read and update than current penetration rule-bases, but also provides greater functionality to detect impending compromises.
Preconditioned Conjugate Gradient Algorithms for Homotopy CurveTracking
Authors: Kashmira M. Irani, Calvin J. Ribbens, Homer F. Walker, Layne T. Watson, Manohar P. Kamat
Venue:  (1989)

These are alogorithms for finding zeros or fixed points of nonlinear systems of equations that are globally convergent for almost all starting points, i.e., with probability one. The essence of all such algorithms is the construction of an appropriate homotopy map and then tracking some smooth curve in the zero set of this homotopy map. HOMPACK is a mathematical software package implementing globally convergent homotopy algorithms with three different techniques for tracking a homotopy zero curve, and has separate routines for dense and sparse Jacobian Matrices. The HOMPACK alogorithms for sparse Jacobian matrices use a preconditioned conjugate gradient algorithm for the computation of the kernel of the homotopy Jacobian matrix, a required linear algebra step for homotopy curve tracking. Here variants of the conjugate gradient algorithms are implemented in the context of homotopy curve tracking and compared with Craig''s preconditioned conjugate gradient method used in HOMPACK. The test problems used include actual large scale, sparse structural mechanics problems.
Static Global Scheduling for Optimal Computer Vision and Image Processing Operations on Distributed-Memory Multiprocessor
Authors: Cheolwhan Lee, Yuan Wang, Tao Yang
Venue:  (1994)

In this paper, we develop a static global scheduling scheme for mapping computer vision and image processing (CVIP) operations on distributed-memory multiprocessors. Unlike most current parallel image processing research which focuses on parallelizing individual processing algorithms on a particular parallel architecture, our scheduler is for optimizing processor assignment and data partition for an entire image processing pipeline. The scheduler operates on task graphs specified by conventional visual languages such as Khoros and Explorer. A task graph is assumed to be a linear chain of operations with any number of nested loops. The task chain is first decomposed into simpler subchains; each a linear sequence of tasks without loops. The communication and computation costs of the component tasks in the subchains are determined by a taxonomy of CVIP operations. Data redistribution overheads in between tasks can also be tabulated in advance for many popular data partitioning schemes. The scheduler then employs a shortest path algorithm to optimize the parallel time, taking into consideration possible variation in the task and resource parameters (such as the image size and number of processors used), and both the intra-operation and the inter-operation computation and communication times. In this paper, we present the scheduling scheme, and provide analyses and experimental results to verify our approach.
A Tight Upper Bound on the Cover Time for Random Walks on Graphs
Authors: U. Feige
Venue:  (1993)

We prove that the expected time for a random walk to cover all n vertices of a connected graph is at most [4/ 27]n3+o(n3). 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
On Detecting Regularity of Functions: A Probabilistic Analysis
Authors: Samuel T. Chanson, Alan Wagner, Gao F., Wasilkowski G.W.
Venue:  (1991)

In order to effectively program Multicomputers users must be able to evaluate how well the system performs for a given application. In this paper we present an efficient execution model that can be used for tree structured computations. We provide a general framework for analyzing the performance of this type of computation for any given topology. This framework is used to derive models for two widely used parallel programming strategies: Processor Farms and Divide and Conquer. These models were validated on a large multicomputer and the accuracy of the model is such that they can be used to predict the performance of applications that use these strategies. We discuss how these models can be used to evaluate performance and how they could be used to restructure the application to improve performance. \n%E TR-91-27
Collocation for Singular Perturbation Problems III: Nonlinear Problems without Turning Points
Authors: Uri Ascher, R. Weiss
Venue:  (1982)

A class of nonlinear singularly perturbed boundary value problems is considered, with restrictions which allow only well-posed problems with possible boundary layers, but no turning points. For the numerical solution of these problems, a close look is taken at a class of general purpose, symmetric finite difference schemes arising from collocation. .br It is shown that if locally refined meshes, whose practical construction is discussed, are employed, then high order uniform convergence of the numerical solution is obtained. Nontrivial examples are used to demonstrate that highly accurate solutions to problems with extremely thin boundary layers can be obtained in this way at a very reasonable cost.
Bounds on Memory Bandwidth in Streamed Computations
Authors: Sally A. McKee, Wm Wulf, Trevor C. Landon
Venue:  (1995)

The growing disparity between processor and memory speeds has caused memory bandwidth to become the performance bottleneck for many applications. In particular, this performance gap severely impacts stream-orientated computations such as (de)compression, encryption, text searching, and scientific (vector) processing. This paper looks at streaming computations and derives analytic upper bounds on the bandwidth attainable from a class of access reordering schemes. We compare these bounds to the simulated performance of a particular dynamic access ordering scheme, the Stream Memory Controller (SMC). We are building the SMC, and where possible we relate our analytic bounds and simulation data to the simulation performance of the hardware. The results suggest that the SMC can deliver nearly the full attainable bandwidth with relatively modest hardware costs.
Performance Evaluation of the ARPANET Transmission Control Protocol in a Local Area Network Environment
Authors: Samuel T. Chanson, K. Ravindran, Stella Atkins
Venue:  (1985)

The Transmission Control Protocol (TCP) of ARPANET is one of the most popular transport level communication protocols in use today. Originally designed to handle unreliable and hostile subnets in a long-haul network TCP has been adopted by many local area networks (LAN) as well. It is, for example, available in 4.2 BSD UNIX for interface to Ethernet and several other LAN technologies. This is convenient but not desirable from a performance standpoint since the control structure is far more complex than is necessary for LANs. This paper describes what we learned in measuring and tuning the performance of TCP in transferring large files between two hosts of different speeds over the Ethernet. Models are presented which allow the optimal buffer size and the flow control parameter to be determined. Based on observed traffic patterns and those reported elsewhere, we formulated guidelines for the design of transport protocols for a single LAN environment. We then present a new, much simpler LAN transport level protocol which replaces TCP with significant improvement in network throughput. Internet packets will use the full TCP. This is done at the gateway. Since the majority of the packets in a LAN are for local usage, this scheme improves the overall network throughput rate as well as the mean packet delay time.