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Numerical solution of saddle point problems

Acta Numerica 2005年 14卷 1-137页

作者： Benzi, Michele Golubt, Gene H. Liesen, Jörg Department of Mathematics and Computer Science Emory University Atlanta GA 30322 United States Scientific Computing and Computational Mathematics Program Stanford University Stanford CA 94305-9025 United States Institut für Mathematik Technische Universität Berlin D-10623 Berlin Germany

Large linear systems of saddle point type arise in a wide variety of applications throughout computational science and engineering. Due to their indefiniteness and often poor spectral properties, such linear systems represent a significant challenge for solver developers. In recent years there has been a surge of interest in saddle point problems, and numerous solution techniques have been proposed for this type of system. The aim of this paper is to present and discuss a large selection of solution methods for linear systems in saddle point form, with an emphasis on iterative methods for large and sparse problems. © Cambridge University Press, 2005.

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Online particle size estimation on one-pass edge detection and particle shape

Online particle size estimation on one-pass edge detection a...

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International Conference on Machine Learning and Cybernetics (ICMLC)

作者： Wei-Xing Wang Bergholm Department of Computer Science & Technology Chongqing University of Posts and Telecommunications China Department of Scientific Computing University of Uppsala Sweden

In order to quickly and accurately estimate average size of densely packed aggregate particles on a moving conveyor belt, a new image processing method is studied, the method consists of the two major algorithms, the one is one-pass edge detection algorithm, and the other is the average size estimation based on image edge density. The method calculates average particle size without explicit delineating complicated aggregates. To prove the new method, two different aggregate samples were taken for testing, the testing result is satisfactory. The new method is much fast than ordinary particle segmentation algorithm, and is applicable for the image sequence of the densely packed complicated particles.

关键词： Image edge detection Shape Aggregates Image segmentation Belts Image processing Machine learning algorithms Testing Inspection computer science

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Performance Prophet: a performance modeling and prediction tool for parallel and distributed programs

Performance Prophet: a performance modeling and prediction t...

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International Conference on Parallel Processing Workshops (ICPPW)

作者： S. Pllana T. Fahringer Institute of Scientific Computing University of Technology Vienna Vienna Austria Institute of Computer Science University of Innsbruck Innsbruck Austria

High-performance computing is essential for solving large problems and for reducing the time to solution for a single problem. Current top high-performance computing systems contain 1000's of processors. Therefore, new tools are needed to support the program development that will exploit high degrees of parallelism. The issue of model-based performance evaluation of real world programs on large scale systems is addressed in this paper. We present the Performance Prophet, which is a performance modeling and prediction tool for parallel and distributed programs. One of the main contributions of this paper is our methodology for reducing the time needed to evaluate the model. In addition, we describe our method for automatic performance model generation. We have implemented Performance Prophet in Java and C++. We illustrate our approach by modeling and simulating a real-world material science parallel program.

关键词： Predictive models Concurrent computing Unified modeling language Distributed computing Parallel processing Large-scale systems Computational modeling Power engineering computing Performance evaluation Mathematical model

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Towards an efficient and scalable discontinuous galerkin atmospheric model

Towards an efficient and scalable discontinuous galerkin atm...

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19th IEEE International Parallel and Distributed Processing Symposium, IPDPS 2005

作者： Dennis, J.M. Levy, M. Nair, R.D. Tufo, H.M. Voran, T. Scientific Computing Division National Center for Atmospheric Research 1850 Table Mesa Dr. Boulder CO 80305 United States Department of Computer Science University of Colorado Engineering Center - 430UCB Boulder CO 80309 United States

ISBN: (纸本)0769523129

An efficient and scalable Discontinuous Galerkin shallow water model on the cubed sphere is developed by extending the transport scheme of Nair et al. [16], The continuous flux form nonlinear shallow water equations in curvilinear coordinates are developed. Spatial discretization is a nodal basis set of Legendre polynomials. Fluxes along internal element interfaces are approximated by a Lax-Friedrichs scheme. A third-order total variation diminishing Runge-Kutta scheme is applied for time integration, without any filter or limiter. The standard shallow-water test suite of Williamson et al. [23] is used to validate the model. It is observed that the numerical solutions are accurate, the model conserves mass to machine precision, and there are no spurious oscillations in a test case where zonal flow impinges a mountain,. Development time was substantially reduced by building the model in the High Order Method Modeling Environment (HOMME) developed at the National Center for Atmospheric Research (NCAR). Performance and scaling data for the steady state geostrophic flow problem [23] is presented. Sustained performance in excess of 10% of peak is observed out to 64 processors on a Linux cluster.

关键词： Parallel processing systems

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A robust content-based image retrieval system using multiple features representations

A robust content-based image retrieval system using multiple...

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IEEE International Conference on Networking, Sensing and Control

作者： M.A. Tahoun K.A. Nagaty T.I. El-Arief M. A-Megeed Computer Science Department Faculty of Computers and Informatics Suez-Canal University Egypt Computer Science Department Faculty of Computer and Information Science Ain Shams University Egypt Scientific Computing Department Faculty of Computer and Information Science Ain Shams University Egypt

The similarity measurements and the representation of the visual features are two important issues in content-based image retrieval (CBIR). In this paper, we compared between the combination of wavelet-based representations of the texture feature and the color feature with and without using the color layout feature. To represent the color information, we used global color histogram (GCH) beside the color layout feature and with respect to the texture information; we used Haar and Daubechies wavelets. Based on some commonly used Euclidean and Non-Euclidean similarity measures, we tested different categories of images and measured the retrieval accuracy when combining such techniques. The experiments showed that the combination of GCH and 2-D Haar wavelet transform using the cosine distance gives good results while the best results obtained when adding the color layout feature to this combination by using the Euclidean distance. The results reflected the importance of using the spatial information beside the color feature itself and the importance of choosing good similarity distance measurements.

关键词： Image retrieval Content based retrieval Histograms Image databases Spatial databases Feature extraction computer science Testing Wavelet transforms Distance measurement

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A framework for network media optimization in multihomed QoS networks

A framework for network media optimization in multihomed QoS...

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DIN 2005 - First International ACM Workshop on Dynamic Internnection of Networks

作者： Koga, Hiroyuki Haraguchi, Hiroaki Iida, Katsuyoshi Oie, Yuji Kitakyushu JGN2 Research Center National Institute of Information and Communications Technology Japan Yaskawa Information Systems Corporation Japan Global Scientific Information and Computing Center Tokyo Institute of Technology Japan Department of Computer Science and Electronics Kyushu Institute of Technology Japan

ISBN: (纸本)1595931449

Future pervasive networks will be constructed by various access networks, which are managed by different operators. Wireless LAN hotspot services will be available in numerous locations, and cellular services, which provide a wide cover-age area, will also be available. In order to realize efficient mobile computing in such an environment, mobile hosts must have multiple network media as well as functions to select the optimum network among them based upon the current situation without the disconnecting communications. In order to provide mobile hosts with such a function, we propose an association layer, which is inserted between the transport and network layers. The association layer selects the appropriate network medium for each flow according to the network conditions and flow characteristics, providing end-to-end QoS in multihomed networks. Furthermore, we show the effectiveness of the proposed scheme through simulation results and demonstrate proof of concept based on empirical evaluations of a prototype implementation. Copyright 2005 ACM.

关键词： Telecommunication networks

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A failure-aware model for estimating and analyzing the efficiency of Web services compositions

A failure-aware model for estimating and analyzing the effic...

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11th Pacific Rim International Symposium on Dependable computing, PRDC 2005

作者： Lakhal, Neila Ben Kobayashi, Takashi Yokota, Haruo Tokyo Institute of Technology Department of Computer Science 2-12-1 Oh-Okayama Meguro-ku Tokyo 152-8552 Japan Tokyo Institute of Technology Global Scientific Information and Computing Center 2-12-1 Oh-Okayama Meguro-ku Tokyo 152-8552 Japan

ISBN: (纸本)0769524923

More and more within the last couple of years, there is a recognition that the Web services composition concept will constitute a major breakthrough and will revolutionize the way we deal with integrating disparate and distributed computing environments. Yet, to rise to such a position, a chief concern is to guarantee a high-dependability level of the Web services compositions, which is significantly critical, specially in view of the particularities of the Web services environment(unpredictability, heterogeneity, autonomy), if confronted with other computing environments. Our present work falls within this context since we tackle the problem of QoS (Quality of Service) in the Web services context by verifying to what extent fault-tolerant and dynamically-executed Web services compositions are efficiently serving their purposes. And in pursuing this goal, we introduce a novel model that characterizes, estimates and analyzes several QoS properties of dynamically-executed fault-tolerant Web services compositions-namely the reliability and the execution time. Our model allows acquiring more accurate estimations since it confers a paramount importance to the repercussions of failures. In addition, contrary to other QoS estimations models in the Web services context, which use QoS estimations published in UDDIs by the Web Services owners/providers, our model computes QoS estimations on the base of the compositions execution observations, where the observation results are collected in a history. Finally, since Web services are stateless, tracking the failures and determining their locations is almost impossible. To overcome this limitation, we propose to attach to each of the composition's component a state. In doing so, obtained estimations can contribute in acquiring more accurate information about the failures locations and can be used later to improve the composition QoS in the future.

关键词： Telecommunication services

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Adaptation point analysis for computation migration/checkpointing 05

Adaptation point analysis for computation migration/checkpoi...

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20th Annual ACM Symposium on Applied computing

作者： Ji, Yanqing Jiang, Mai Chaudhary, Vipin Elec. and Comp. Eng. Dept. Wayne State University MI 48201 United States Dept. of Computer Science Arkansas State University AR 72467 United States Institute for Scientific Computing Wayne State University MI 48201 United States

ISBN: (纸本)9781581139648

Finding the appropriate location of adaptation points for computation migration/checkpointing is critical since the distance between two consecutive adaptation points determines the migration/checkpointing scheme's sensitivity and overheads. This paper proposes a heuristic adaptation point placement algorithm to improve the computation migration/checkpointing schemes' performance in terms of sensitivity and flexibility. This heuristic algorithm enables automatic and transparent insertion of checkpoints in user's source code. Copyright 2005 ACM.

关键词： Computational methods

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Using automatic differentiation to compute derivatives for a quantum-chemical computer program

Using automatic differentiation to compute derivatives for a...

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作者： Steiger, Rainer Bischof, Christian H. Lang, Bruno Thiel, Walter Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 D-45470 Mülheim an der Ruhr Germany Institute for Scientific Computing Aachen University D-52056 Aachen Germany Applied Computer Science Group University of Wuppertal D-42097 Wuppertal Germany

The ADIFOR 2.0 tool for Automatic Differentiation of Fortran programs has been used to generate analytic gradient code for all semiempirical SCF methods available in the MNDO97 program. The correctness and accuracy of the new code have been verified. Its performance has been compared with that of hand-coded analytic derivative routines and with numerical differentiation. From a quantum-chemical point of view, the major advance of this work is the development of previously unavailable analytic gradient code for the recently proposed OM1 and OM2 methods. © 2004 Elsevier B.V. All rights reserved.

关键词： Automation

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A failure-aware model for estimating and analyzing the efficiency of Web services compositions

A failure-aware model for estimating and analyzing the effic...

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Pacific Rim International Symposium on Dependable computing

作者： N.B. Lakhal T. Kobayashi H. Yokota Department of Computer Science Tokyo Institute of Technology Tokyo Institute of Technology Global Scientific Information and Computing Center Meguro-ku Tokyo Japan

More and more within the last couple of years, there is a recognition that the Web services composition concept constitute a major breakthrough and revolutionize the way we deal with integrating disparate and distributed computing environments. Yet, to rise to such a position, a chief concern is to guarantee a high-dependability level of the Web services compositions, which is significantly critical, specially in view of the particularities of the Web services environment unpredictability, heterogeneity, autonomy), if confronted with other computing environments. Our present work falls within this context since we tackle the problem of QoS (quality of service) in the Web services context by verifying to what extent fault-tolerant and dynamically-executed Web services compositions are efficiently serving their purposes. And in pursuing this goal, we introduce a novel model that characterizes, estimates and analyzes several QoS properties of dynamically-executed fault-tolerant Web services compositions - namely the reliability and the execution time. Our model allows acquiring more accurate estimations since it confers a paramount importance to the repercussions of failures. In addition, contrary to other QoS estimations models in the Web services context, which use QoS estimations published in UDDIs by the Web services owners/providers, our model computes QoS estimations on the base of the compositions execution observations, where the observation results are collected in a history. Finally, since Web services are stateless, tracking the failures and determining their locations is almost impossible. To overcome this limitation, we propose to attach to each of the composition's component a state. In doing so, obtained estimations can contribute in acquiring more accurate information about the failures locations and can be used later to improve the composition QoS in the future.

关键词： Failure analysis Web services Quality of service Fault tolerance Distributed computing Context-aware services Context modeling computer architecture computer science History

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