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Fast Methods (fast + methods)

Distribution by Scientific Domains
Engineering50%

Selected Abstracts

Speed-up and performance evaluation of piecewise-linear DC analysis

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2007
Janne RoosArticle first published online: 29 NOV 200
Abstract The good convergence properties of piecewise-linear (PWL) DC analysis have been thoroughly discussed in many papers. This paper, in turn, concentrates on the speed of PWL DC analysis, where the boundary crossing of linear regions plays a crucial role. Fast methods are presented for performing the following boundary-crossing computations: LU-decomposition update, matrix-equation solution, boundary-crossing direction, and damping-factor determination. Special attention is given to those PWL DC analysis methods that perform PWL modelling of the non-linear components on the fly; an adaptive method is proposed for controlling the accuracy of PWL modelling and speeding up simulation. The computational efficiency of the accelerated PWL DC analysis is discussed and compared with that of conventional, Newton,Raphson iteration-based, DC analysis. Finally, the performance evaluation is completed with realistic simulation examples: it is demonstrated that the speed of the accelerated PWL DC analysis is comparable with that of the conventional DC analysis. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Performance of a parallel implementation of the FMM for electromagnetics applications

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2003
G. Sylvand
Abstract This paper describes the parallel fast multipole method implemented in EADS integral equations code. We will focus on the electromagnetics applications such as CEM and RCS computation. We solve Maxwell equations in the frequency domain by a finite boundary-element method. The complex dense system of equations obtained cannot be solved using classical methods when the number of unknowns exceeds approximately 105. The use of iterative solvers (such as GMRES) and fast methods (such as the fast multipole method (FMM)) to speed up the matrix,vector product allows us to break this limit. We present the parallel out-of-core implementation of this method developed at CERMICS/INRIA and integrated in EADS industrial software. We were able to solve unprecedented industrial applications containing up to 25 million unknowns. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Design and implementation of real-time software-based H.261 video codec

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 2 2002
Wen-Shiung Chen
Abstract ITU-T H.261 is a video coding standard for videophone and video-conferencing applications on LAN and ISDN, which requires a great amount of computing power for DCT and motion estimation, traditionally provided by hardware. Since motion estimation is a major problem in developing real-time video codec, in this paper we propose a simple and fast motion estimation algorithm to reduce searching time. Mainly, a real-time software-based H.261 video codec is investigated and implemented, in which several fast methods such as programming technique and Intel MMXÔ instruction are used to improve computing speed. The experimental results have demonstrated that our H.261 codec can compress video in CIF format over 30 fps and in QCIF at 105 fps, and can achieve a very high decoding rate. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 73,83, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10013 [source]

A new fast stratospheric ozone chemistry scheme in an intermediate general-circulation model.

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 610 2005
I: Description, evaluation
Abstract Simulation of future climate-composition changes requires simulations of coupled dynamical-radiative-chemical models of many decades in length. Yet, to assure the generality of the simulation's results against uncertainties in emissions, unforced year-to-year variability and dependence on initial conditions, it is necessary to repeat them a significant number of times. The computational cost of such an exercise is still too large when using complex three-dimensional coupled models. We introduce in this paper a computationally efficient chemical scheme, the FAst STratospheric Ozone Chemistry (FASTOC) scheme, which has advantages over many existing fast methods, as it does not rely on relaxation to assumed conditions, does not rely on tuning parameters, and does not rely on linearization approximations. The scheme is nevertheless three orders of magnitude faster than a stiff kinetic equations solver. Part I of the paper gives a detailed description of the FASTOC model and some performance evaluations when incorporated in a general-circulation model (GCM). In Part II, the FASTOC model, coupled to a GCM, is specifically applied to study the impact of climate,chemistry interactions on stratospheric ozone in the middle of the twenty-first century. Copyright © 2005 Royal Meteorological Society [source]