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CONCURRENT NULLSPACE methods FOR MULTIBODY SYSTEMS.

CONCURRENT NULLSPACE METHODS FOR MULTIBODY SYSTEMS.

parallel and distributed processing in Structural Engineering, Proceedings. Presented in Conjunction with the ASCE National Convention.

作者： Kurdila, Andrew Kamat, Manohar Georgia Inst of Technology Atlanta GA USA Georgia Inst of Technology Atlanta GA USA

ISBN: (纸本)0872626407

This paper presents a new concurrent multiprocessing algorithm for simulating the dynamics of constrained multibody systems. The systems considered are quite general in nature;they may be comprised of any number of rigid and linearly elastic bodies subject to linear, nonholonomic constraints. The method is based upon the recently introduced class of algorithms that generate the nullspace of the constraints. These algorithms are comprised essentially of four computational steps: (i) the calculation of an orthonormal basis for the nullspace of the constraints and its orthogonal complement, (ii) the assembly and factorization of a system coefficient matrix, (iii) the calculation of the product of a right-inverse and a vector, and (iv) the formation and assembly of system vectors. Concurrent multiprocessing implementations of the QR decomposition, singular value decomposition and modified Gram-Schmidt technique are discussed to enable a parallel calculation of the orthonormal bases in step (i) above.

关键词： STRUCTURAL ANALYSIS

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A global object name space for the intel hypercube 3

A global object name space for the intel hypercube

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3rd Conference on Hypercube Concurrent Computers and Applications, C3P 1988

作者： Bain, William L. Block Island Technologies United States

ISBN: (纸本)0897912780

The Intel iPSC® and iPSC®/2 concurrent computer systems provide the processing power and memory to solve very large parallel programming problems. However, their distributed memory and large grain process model complicate the implementation of object oriented programs. As part of the Interwork ii™ Concurrent Programming Toolkit, software facilities have been constructed for the management of a large number of objects (up to 2∗∗32) in a global object name space. This simplifies the iPSC's programming model by allowing uniform access to objects from any node within the hypercube. Objects are dynamically created and destroyed, and two methods of object access are provided. First, a process can gain exclusive access to an object using the Openjobj procedure;the object migrates to the process's local node as a side effect. A second and more efficient access method is to execute one of an object's associated procedures using the Apply procedure. The current implementation transports the procedure name and arguments to the node on which the object resides for execution;a copy of the code exists on every node. Interwork ii uses the global object name space to support a distributed, lightweight process model. This allows processes to be uniformly accessed throughout the cube. Additional objects for inter-process communication are also provided. The global object name space is implemented in a fully distributed manner in order to eliminate performance bottlenecks. Techniques for caching object references to further speed up object access are described.

关键词： parallel programming

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Improved optimistic concurrency control and its use in distributed database systems

Improved optimistic concurrency control and its use in distr...

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Annual Hawaii International Conference on System Sciences (HICSS)

作者： R. Unland G. Schlageter Department of Computer Science University of Hagen Hagen Germany

The original optimistic concurrency control scheme (H.T. Kung, and J.T. Robinson, 1979) has weaknesses with respect to the validation technique, the treatment of long transactions, and the problem of starvation. Some alternatives for the validation-phase are considered that not only avoid these disadvantages but also improve the performance of the original approach. Most promising is a technique which supports read-transactions, thereby decreasing the number of backups substantially. An adaptation of a centralized optimistic concurrency control scheme to a distributed environment is presented. The proposed algorithm is deadlock-free and offers high parallelism.< >

关键词： Concurrency control Database systems Transaction databases System recovery Optimization methods Proposals Computer science Electronic mail Concurrent computing parallel processing

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image ALGEBRA TECHNIQUES FOR parallel image-processing

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JOURNAL OF parallel AND distributed COMPUTING 1987年第1期4卷 7-44页

作者： RITTER, GX GADER, PD UNIV FLORIDA DEPT MATHGAINESVILLEFL 32611

An image algebra has been defined which is capable of expressing a wide variety of gray-level image-to-image transformations. The purpose of this paper is fourfold: (1) to introduce the reader to the basic concepts of the image algebra; (2) to show how it suggests a general-purpose cellular pyramid array processor for real time image processing tasks; (3) to demonstrate how the image algebra can be used to formulate the problem of mapping algorithms to specific hardware; and (4) to show how algebraic techniques can be used to develop systematic methods for deriving parallel algorithms.

关键词： image processing

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parallel fitting of quadric patches for structural analysis of range imagery

Parallel fitting of quadric patches for structural analysis ...

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Visual Communications and image processing ii 1987

作者： Perez, A. Abidi, M.A. Gonzalez, R.C. Department of Electrical and Computer Engineering University of Tennessee KnoxvilleTN37996-2100 United States Perceptics Corporation Pellissippi Center KnoxvilleTN37932 United States

Surface fitting allows for pose estimation and recognition of objects in range scenes. Unfortunately, surface fitting is computation-intensive. One way to speed-up this task is to use parallel processing, since its availability is on the increase. Mathematically, surface fitting can be formulated as an overdetermined linear system which can be solved in the least-square sense. Because of numerical stability and ease of implementation, the QR-factorization using the Givens transformation is best suited for the parallel solution of overdetermined systems. In this paper we present two algorithms to carry out a QR- factorization on both distributed-memory and shared-memory parallel computers. These algorithms have been implemented and evaluated in terms of speed-up time. © 1987 SPIE. All rights reserved.

关键词： Linear systems

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distributed scene analysis for autonomous road vehicle guidance

Distributed scene analysis for autonomous road vehicle guida...

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Mobile Robots ii 1987

作者： Mysliwetz, Birger D. Dickmanns, E.D. Aerospace Engineering Department Universität der Bundeswehr München Neubiberg8014 Germany

An efficient distributed processing scheme has been developed for visual road boundary tracking by 'VaMoRs', a testbed vehicle for autonomous mobility and computer vision. Ongoing work described here is directed to improving the robustness of the road boundary detection process in the presence of shadows, ill-defined edges and other disturbing real world effects. The system structure and the techniques applied for real-time scene analysis are presented along with experimental results. All subfunctions of road boundary detection for vehicle guidance, such as edge extraction, feature aggregation and camera pointing control, are executed in parallel by an onboard multiprocessor system. On the image processing level local oriented edge extraction is performed in multiple 'windows', tighly controlled from a hierarchically higher, modelbased level. The interpretation process involving a geometric road model and the observer's relative position to the road boundaries is capable of coping with ambiguity in measurement data. By using only selected measurements to update the model parameters even high noise levels can be dealt with and misleading edges be rejected. © 1987 SPIE. All rights reserved.

关键词： image processing

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DIRECT RECOVERY OF DEPTH - MAP - I: DIFFERENTIAL methods.

DIRECT RECOVERY OF DEPTH - MAP - I: DIFFERENTIAL METHODS.

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Proceedings of the IEEE Computer Society Workshop on Computer Vision.

作者： Subbarao, Muralidhara State Univ of New York Stony Brook NY USA State Univ of New York Stony Brook NY USA

ISBN: (纸本)0818607793

Three methods are described for recovering the depth-map (i. e. distance of visible surfaces from a camera) of a scene from images formed by a convex lens. The recovery is based on observing the change in the scene's image due to a small known change in one of the three intrinsic camera parameters: (i) distance between the lens and the image detector plane, (ii) focal length of the lens, and (iii) diameter of the lens aperture. No assumptions are made about the scene being analyzed. The recovery process is parallel, involving simple local computations. In comparison with some shape-recovery processes such as stereo vision and motion analysis, the methods are direct in the sense that three-dimensional scene geometry is recovered directly from intensity images of the scene;spatial properties of the intensity distribution are not computed as an intermediate step, and further the correspondence problem does not arise. These methods are relevant to both machine vision and human vision.

关键词： image processing

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MAPPING image-processing OPERATIONS ONTO A LINEAR SYSTOLIC MACHINE

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distributed COMPUTING 1986年第4期1卷 246-257页

作者： KUNG, HT WEBB, JA 1. Department of Computer Science Carnegie Mellon University 15213 Pittsburgh PA USA

A high-performance systolic machine, called Warp, is operational at Carnegie Mellon. The machine has a programmable systolic array of linearly connected cells, each capable of performing 10 million floating-point operations per second. Many image processing operations have been programmed on the machine. This programming experience has yielded new insights in the mapping of image processing operations onto a parallel computer. This paper identifies three major mapping methods that are particularly suited to a Warp-like parallel machine using a linear array of processing elements. These mapping methods correspond to partitioning of input dataset, partitioning of output dataset, and partitioning of computation along the time domain (pipelining). parallel implementations of several important image processing operations are presented to illustrate the mapping methods. These operations include the Fast Fourier transform (FFT), connected component labelling, Hough transform image warping and relaxation.

关键词： image processing Systolic arrays parallel processing Connected component labelling Hough transform image warping Relaxation

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image-ANALYSIS USING MULTIGRID RELAXATION methods

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1986年第2期8卷 129-139页

作者： TERZOPOULOS, D M.I.T Artificial Intelligence Laboratory 54 Technology Square Cambridge MA 02139

image analysis problems, posed mathematically as variational principles or as partial differential equations, are amenable to numerical solution by relaxation algorithms that are local, iterative, and often parallel. Although they are well suited structurally for implementation on massively parallel, locally interconnected computational architectures, such distributed algorithms are seriously handi capped by an inherent inefficiency at propagating constraints between widely separated processing elements. Hence, they converge extremely slowly when confronted by the large representations of early vision. Application of multigrid methods can overcome this drawback, as we showed in previous work on 3-D surface reconstruction. In this paper, we develop multiresolution iterative algorithms for computing lightness, shape-from-shading, and optical flow, and we examine the efficiency of these algorithms using synthetic image inputs. The multigrid methodology that we describe is broadly applicable in early vision. Notably, it is an appealing strategy to use in conjunction with regularization analysis for the efficient solution of a wide range of ill-posed image analysis problems.

关键词： image analysis Relaxation methods Iterative algorithms Partial differential equations Concurrent computing distributed computing Computer architecture distributed algorithms Optical propagation Ultraviolet sources Author Keywords variational principles image analysis inverse problems lightness multigrid relaxation multiresolution algorithms optical flow parallel algorithms partial differential equations shape from shading

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TREE-STRUCTURED parallel processing SYSTEM FOR image GENERATION BY RAY TRACING.

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Systems and Computers in Japan 1986年第12期17卷 51-62页

作者： Deguchi, Hiroshi Shirakawa, Isao Omura, Koichi Nishida, Masato Nishimura, Hitoshi Kawata, Toru Osaka Univ Suita Jpn Osaka Univ Suita Jpn

An image generation system by ray tracing was implemented on a distributed parallel processing system composed of loosely coupled multimicrocomputers. An improvement was made by extending the architecture from the star structure to the hierarchical tree structure. This improvement makes it possible for an animated image to be generated at high speed with shading which can represent the shape and texture of three-dimensional objects with high quality. This paper outlines the hierarchical tree-structured image generation system, discussing the parallel processing mechanisms of the system, such as data transfer and hierarchical load distribution schemes. Experiments were made to evaluate the performance. Problems in the tree-structured system are pointed out, and remedies are proposed (area redistribution, and area subdivision). Experiments are made to evaluate the effectiveness of these methods. Thus, it is demonstrated that the tree-structured system is useful in the image generation using ray tracing.

关键词： image processing

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