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CompEuro

作者： D.J. Soudris M.K. Birbas C.E. Goutis Department of Electrical Engineering VLSI Design Laboratory University of Patras Patras Greece

A systematic framework for mapping a class of iterative algorithms onto processor array architectures is presented. The iterative algorithm is directly mapped on the array without the requirement of transforming it into any intermediate form, such a uniform recurrent equation (URE). The principles of Lamport's coordinate method are used. The important subclass of algorithms known as weak single assignment codes (WSACs) is treated in an optimal way. Due to the structure of the algorithm and/or the multidimensional mapping, the resulting architectures can be either regular arrays (RAs) or piecewise regular arrays (PRAs).< >

关键词： Design methodology iterative algorithms Very large scale integration Integrated circuit technology Systolic arrays Computer architecture Laboratories Equations Multidimensional systems Concurrent computing

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Two iterative algorithms for blind symbol timing estimation of M-PSK signals

Two iterative algorithms for blind symbol timing estimation ...

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International Workshop on Satellite and Space Communications (IWSSC)

作者： Markus Flohberger Wilfried Gappmair Stefano Cioni Institute of Communication Networks and Satellite Communications Graz University of Technology Austria Department of Electronics Computer Science and Systems University of Bologna Italy

Carrier-blind and non-data-aided (NDA) feedforward solutions for symbol timing recovery are particularly important for initial acquisition in burst modems; the Oerder and Meyr (O&M) algorithm is perhaps the most prominent example in this respect. Since usually operated with an oversampling rate of four, alternatives using only two samples per symbol have been suggested in the open literature. On the other hand, Moeneclaey and Batsele introduced an error detector for blind NDA recovery in feedback loops, based on only one sample per symbol. In the current paper, it is shown that this approach can be successfully applied to a feedforward solution. In this context, two estimator variants are developed exhibiting no self-noise effect for M-ary PSK schemes, whereas it turns out that this does not hold true for nonconstant modulus constellations.

关键词： iterative algorithms Timing Detectors Feedback Signal to noise ratio Communication networks Satellite communication Appropriate technology Paper technology Computer science

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VLSI circuit design concept for parallel iterative algorithms in nanoscale

VLSI circuit design concept for parallel iterative algorithm...

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International Symposium on Communications and Information Technologies (ISCIT)

作者： Chi-Chia Sun Jurgen Gotze Information Processing Laboratory Dortmund University Dortmund Germany

ISBN: (纸本)9781424445219

Modern VLSI manufacturing technology has kept shrinking down to the nanoscale level with a very fast trend. Integration with the advanced nano-technology now makes it possible to realize advanced parallel iterative algorithms directly which was almost impossible 10 years ago. In this paper, we want to discuss the influences of evolving VLSI technologies for iterative algorithms and present design strategies from an algorithmic and architectural point of view. We can simplify the parallel implementation of the iterative algorithm (i.e., processor elements of the multiprocessor array) in any way as long as the convergence is guaranteed. However, the modification of the algorithm (processors) usually increases the number of required iterations which also means that the switch activity of interconnects is increasing. We implemented a 3times3 Jacobi EVD array with the mu-CORDIC PE in both 0.18 mum and 45 nm technologies in order to further study the trade-off between the performance/complexity of processors and the load/throughput of interconnects. Our experimental results show that using the mu-CORDIC PE is beneficial concerning the design criteria since it yields smaller chip area, faster overall computation timing and less energy consumption per operation than the full CORDIC PE.

关键词： Very large scale integration Circuit synthesis iterative algorithms Switches Integrated circuit interconnections Manufacturing Algorithm design and analysis Jacobian matrices Throughput Timing

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A finite parameterization and iterative algorithms for constrained minimum norm signal reconstruction

A finite parameterization and iterative algorithms for const...

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Multidimensional Signal Processing Workshop

作者： K.S. Arun L.C. Potter Coordinated Science Laboratory Department of Electrical and Computer Engineering University of Illinois Urbana IL USA

Summary form only given. Signal reconstruction from a limited set of linear measurements of a signal and prior knowledge of signal characteristics expressed as convex constraint sets were treated. The problem was posed in Hilbert space as the determination of the minimum norm element in the intersection of convex constraint sets and a linear variety with finite codimension. A finite parameterization for the optimal solution was derived, and the optimal parameter vector was shown to satisfy a system of nonlinear equations in a finite-dimensional Euclidean space. iterative algorithms for determining the parameters were obtained, and convergence was shown to be quadratic for many applications. The results were applied to example multidimensional reconstruction problems.< >

关键词： iterative algorithms Signal reconstruction Hilbert space Coordinate measuring machines Electric variables measurement Vectors Nonlinear equations Multidimensional systems Cost function Constraint theory

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Load balancing and parallel implementation of iterative algorithms for row-continuous Markov chains

Load balancing and parallel implementation of iterative algo...

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Scalable High Performance Computing Conference

作者： M. Colajanni M. Angelaccio Università Roma Tor Vergata Rome Italy

Presents the first parallel algorithms for solving row-continuous or generalized birth-death (GBD) Markov chains on distributed memory MIMD multiprocessors. These systems are characterized by very large transition probability matrices, decomposable in heterogeneous tridiagonal blocks. The parallelization of three aggregation/disaggregation iterative methods is carried out by a unique framework that keeps into account the special matrix structure. Great effort has been also devoted to define a general algorithm for approximating the optimum workload. Various computational experiments show that Vantilborgh's (1985) method is the fastest of the three algorithms on any data set dimension.< >

关键词： Load management iterative algorithms Matrix decomposition iterative methods Vectors Biological system modeling Power system modeling Stochastic processes Steady-state Gaussian processes

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Performance of iterative tomographic algorithms applied to non-destructive evaluation with limited data

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NDT & E INTERNATIONAL 1997年第6期30卷 359-370页

作者： Subbarao, PMV Munshi, P Muralidhar, K INDIAN INST TECHNOL DEPT MECH ENGNKANPUR 208016UTTAR PRADESHINDIA

iterative tomographic algorithms have been applied to the reconstruction of a two-dimensional object with internal defects from its projections. Nine distinct algorithms with varying numbers of projections and projection angles have been considered. Each projection of the solid object is interpreted as a path integral of the light-sensitive property of the object in the appropriate direction. The integrals are evaluated numerically and are assumed to represent exact data. Errors in reconstruction are defined as the statistics of difference between original and reconstructed objects and are used to compare one algorithm with respect to another. The algorithms used in this work can be classified broadly into three groups, namely the additive algebraic reconstruction technique (ART), the multiplicative algebraic reconstruction technique (MART) and the maximization reconstruction technique (MRT). Additive ART shows a systematic convergence with respect to the number of projections and the value of the relaxation parameter. MART algorithms produce less error at convergence compared to additive ART but converge only at small values of the relaxation parameter. The MRT algorithm shows an intermediate performance when compared to ART and MART. An increasing noise level in the projection data increases the error in the reconstructed field. The maximum and RMS errors are highest in ART and lowest in MART for given projection data. Increasing noise levels in the projection data decrease the convergence rates. For all algorithms, a 20% noise level is seen as an upper limit, beyond which the reconstructed field is barely recognizable. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.

关键词： absorption tomography iterative algorithms convergence rates sensitivity to noise errors

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Dynamic precision iterative algorithms

Dynamic precision iterative algorithms

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Frontiers of Massively Parallel Computation

作者： D.A. Kramer I.D. Scherson Department of Electrical Engineering Princeton University Princeton NJ USA Department of I.C.S University of California Irvine Irvine CA USA

The authors address the use of DP (dynamic precision) in fixed point iterative numerical algorithms. These algorithms are used in a wide range of numerically intensive scientific applications. One such algorithm, Muller's method, detects complex roots of an arbitrary function. This algorithm was implemented in DP on various architectures, including a MasPar MP-1 massively parallel processor and a Cray Y-MP vector processor. The results show that the use of DP can lead to a significant speedup of iterative algorithms on multiple-range architectures.< >

关键词： iterative algorithms Computer architecture Heuristic algorithms Concurrent computing Vector processors Hardware Supercomputers Floating-point arithmetic Parallel machines Displays

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Radar imaging based on iterative algorithms

Radar imaging based on iterative algorithms

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IEEE International Conference on Radar

作者： Qiangfu Zhao Zhong Wang Youan Ke Depertment of Electronic Engineering Beijing Institute of Technology Beijing China

A discrete model for radar imaging is developed, and, based on this model, the maximum entropy algorithm is adapted to radar imaging. Although such iterative algorithms are usually time-consuming, it is shown that, if the algorithms are appropriately simplified, it is possible to realize them even in real time. The efficiency of iterative algorithms is shown through computer simulations.< >

关键词： Radar imaging iterative algorithms iterative methods Image reconstruction Computed tomography Reconstruction algorithms Image quality Computer simulation Least squares approximation Data engineering

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A STUDY OF RECONSTRUCTION ARTIFACTS IN CONE BEAM TOMOGRAPHY USING FILTERED BACKPROJECTION AND iterative EM algorithms

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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 1990年第2期37卷 759-767页

作者： ZENG, GL GULLBERG, GT Department of Radiology University of Utah Medical Center Salt Lake UT USA

Reconstruction artifacts in cone beam tomography are studied for filtered backprojection (Feldkamp) and iterative EM algorithms. The filtered backprojection algorithm uses a voxel-driven, interpolated backprojection to reconstruct the cone beam data, whereas the iterative EM algorithm performs ray-driven projection and backprojection operations for each iteration. Two weighting schemes for the projection and backprojection operations in the EM algorithm are studied. One weights each voxel by the length of the ray through the voxel and the other equates the value of a voxel to the functional value of the midpoint of the line intersecting the voxel, which is obtained by interpolating between eight neighboring voxels. Cone beam reconstruction artifacts such as rings, bright vertical extremities, and slice-to-slice cross-talk are not found with parallel beam and fan beam geometries. When using filtered backprojection and iterative EM algorithms, the line-length weighting is susceptible to ring artifacts which are improved by using interpolated projector-backprojectors.< >

关键词： Tomography iterative algorithms Image reconstruction Extremities Geometry Biomedical imaging Algorithm design and analysis Radiology Cities and towns X-ray imaging

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Enhanced iterative processing algorithms for restoration and superresolution of tactical sensor imagery

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OPTICAL ENGINEERING 2004年第1期43卷 199-208页

作者： Sundareshan, MK Bhattacharjee, S Univ Arizona Dept Elect & Comp Engn Tucson AZ 85721 USA

Imagery data acquired in practice to support tactical surveillance and tracking missions in hostile environments typically suffer from a variety of degradations making it essential to subject the data to digital postprocessing aimed at restoration and superresolution before they can be used for any image exploitation tasks (visualization, target detection and characterization, etc.). A number of novel iterative techniques for resolution enhancement are presently being developed, with statistical optimization and set-theoretic estimation offering two popular approaches for algorithm design. The challenges posed by the processing needs of tactical imagery data often require greater capabilities than what the existing algorithms can offer, however, and typically require more enhanced procedures to achieve satisfactory restoration and superresolution. We outline three such enhancements: parallel projection implementation with adaptive relaxation, use of scene-derived information for constraint set design, and a hybrid statistical and set-theoretic estimation procedure. The restoration and superresolution performance of an iterative algorithm that incorporates these enhancements is illustrated by application to tactical imagery data [images acquired from state-of-the-art synthetic aperture radar (SAR) and passive millimeter-wave (PMMW) sensors]. (C) 2004 Society of Photo-optical Instrumentation Engineers.

关键词： resolution enhancement image restoration superresolution iterative algorithms image processing tactical sensors

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