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12th International Conference on Parallel Processing and Applied Mathematics (PPAM)

作者： Mikkelsen, Carl Christian Kjelgaard Karlsson, Lars Umea Univ Dept Comp Sci S-90187 Umea Sweden

ISBN: (纸本)9783319780245;9783319780238

We consider the problem of computing a scaling a such that the solution x of the scaled linear system Tx = ab can be computed without exceeding an overflow threshold Omega. Here T is a non-singular upper triangular matrix and b is a single vector, and Omega is less than the largest representable number. This problem is central to the computation of eigenvectors from Schur forms. We show how to protect individual arithmetic operations against overflow and we present a robust scalar algorithm for the complete problem. Our algorithm is very similar to xLATRS in LAPACK. We explain why it is impractical to parallelize these algorithms. We then derive a robust blocked algorithm which can be executed in parallel using a task- based run- time system such as StarPU. The parallel overhead is increased marginally compared with regular blocked backward substitution.

关键词： Triangular linear systems Overflow Blocked algorithms robust algorithms

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Achieving robust wireless localization resilient to signal strength attacks

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WIRELESS NETWORKS 2012年第1期18卷 45-58页

作者： Li, Xiaoyan Chen, Yingying Yang, Jie Zheng, Xiuyuan Lafayette Coll Dept Comp Sci Easton PA 18042 USA Stevens Inst Technol Dept Elect & Comp Engn Hoboken NJ 07030 USA

Received signal strength (RSS) based algorithms have been very attractive for localization since they allow the reuse of existing communication infrastructure and are applicable to many commodity radio technologies. Such algorithms, however, are sensitive to a set of non-cryptographic attacks, where the physical measurement process itself can be corrupted by adversaries. For example, the attacker can perform signal strength attacks by placing an absorbing or reflecting material around a wireless device to modify its RSS readings. In this work, we first formulate the all-around signal strength attacks, where similar attacks are launched towards all landmarks, and experimentally show the feasibility of launching such attacks. We then propose a general principle for designing RSS-based algorithms so that they are robust to all-around signal strength attacks. To evaluate our approach, we adapt a set of representative RSS-based localization algorithms according to our principle. We experiment with both simulated attacks and two sets of real attack scenarios. All the experiments show that our design principle can be applied to a wide spectrum of algorithms to achieve comparable performance with much better robustness.

关键词： Wireless localization Signal strength attacks robust algorithms Design principle

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robust ML wideband beamforming in reverberant fields

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2003年第2期51卷 338-349页

作者： Di Claudio, ED Parisi, R Univ Roma La Sapienza INFOCOM Dept Rome Italy

Adaptive beamforming of sensor arrays immersed into reverberant fields can easily result in the cancellation of the useful signal because of the temporal correlation existing among the direct and the reflected path signals. Wideband beamforming can somewhat mitigate this phenomenon, but adaptive solutions based on the minimum variance (MV) criterion remain nonrobust in many practical applications, such as multimedia systems, underwater acoustics, and seismic prospecting. In this paper, a steered wideband adaptive beamformer, optimized by a novel concentrated maximum likelihood (NIL) criterion in the frequency domain, is presented and discussed in the light of a very general reverberation model. It is shown that NIL beamforming can alleviate the typical cancellation problems encountered by adaptive MV beamforming and preserve the intelligibility of a wideband and colored source signal under interference, reverberation, and propagation mismatches.\ The difficult optimization of the NIL cost function, which incorporates a robustness constraint to prevent signal cancellation, is recast as an iterative least squares problem through the concept of descent in the neuron space, which was originally developed for the training of multilayer neural networks. Finally, experiments with computer-generated and real-world data demonstrate the superior performance of the proposed beamformer with respect to its MV counterpart.

关键词： acoustics adaptive beamforming cepstrum maximum likelihood minimum variance multipath neural network learning reverberation ridge regression robust algorithms sensor arrays wideband coherent focusing

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robust phase retrieval via median-truncated smoothed amplitude flow

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INVERSE PROBLEMS IN SCIENCE AND ENGINEERING 2021年第13期29卷 3024-3040页

作者： Luo, Qi Lin, Shijian Wang, Hongxia Natl Univ Def Technol Dept Math Changsha 410073 Hunan Peoples R China Natl Univ Def Technol Dept Comp Sci Changsha Peoples R China

Phase retrieval (PR) is an inverse problem about recovering a signal from phaseless linear measurements, which arises in various fields. In practical scenarios, partial measurements can be inevitably corrupted by outliers that can take arbitrary values. To handle this, we propose the median-SAF method which is the smoothed amplitude flow (SAF) method equipped with the median truncation strategy. We find that median-SAF has some inherent advantages in suppressing outliers. Theoretical analysis ensures that median-SAF converges linearly to the original signal via the gradient algorithm from an delicate initial estimate with high probability. Substantial numerical tests empirically illustrate that the proposed method is superior to other state-of-the-art methods in terms of the recovery rate and the performance on suppressing outliers.

关键词： Statistical signal processing nonconvex optimization phase retrieval gradient descent robust algorithms

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robust Methods of Ellipsoidal Estimation of Dynamical Systems State under Restrictions on Noise of Output Measurements and Rate of their Variation

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JOURNAL OF AUTOMATION AND INFORMATION SCIENCES 2008年第10期40卷 38-46页

作者： Volosov, V. V. Shevchenko, V. N. Natl Acad Sci Ukraine Inst Space Res Kiev Ukraine Natl Space Agcy Ukraine Kiev Ukraine

We obtained new robust algorithms of ellipsoidal estimate of the vector of state of dynamical systems by the results of measurement of their outputs, which are distorted by additive noise. In contrast to known algorithms, which account only boundedness of noises, we additionally take into account boundedness of rate of their variation. Efficiency of the obtained algorithms is shown by results of computer modeling of their use in the problem of control of orbital spacecraft orientation.

关键词： robust algorithms ellipsoidal estimate vector of state of dynamical systems results of measurement of outputs additive noise bounded noises bounded rate of noises variation efficiency results of computer modeling problem of control of orbital spacecraft orientation

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A robust Parallel Algorithm for Combinatorial Compressed Sensing

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2018年第8期66卷 2167-2177页

作者： Mendoza-Smith, Rodrigo Tanner, Jared W. Wechsung, Florian Univ Oxford Math Inst Oxford OX2 6GG England Alan Turing Inst London NW1 2DB England

It was shown in previous work that a vector x is an element of R-n with at most k < n nonzeros can be recovered from an expander sketch Ax in O(nnz(A) log k) operations via the parallel-l(0) decoding algorithm, where nnz(A) denotes the number of nonzero entries in A is an element of R-mxn. In this paper, we present the robust-l(0) decoding algorithm, which robustifies parallel-l(0) when the sketch Ax is corrupted by additive noise. This robustness is achieved by approximating the asymptotic posterior distribution of values in the sketch given its corrupted measurements. We provide analytic expressions that approximate these posteriors under the assumptions that the nonzero entries in the signal and the noise are drawn from continuous distributions. Numerical experiments presented show that robust-l(0) is superior to existing greedy and combinatorial compressed sensing algorithms in the presence of small to moderate signal-to-noise ratios in the setting of Gaussian signals and Gaussian additive noise.

关键词： Compressed sensing expander graphs dissociated signals robust algorithms

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robust plane sweep for intersecting segments

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SIAM JOURNAL ON COMPUTING 2000年第5期29卷 1401-1421页

作者： Boissonnat, JD Preparata, FP INRIA F-06902 Sophia Antipolis France Brown Univ Dept Comp Sci Ctr Geometr Comp Providence RI 02912 USA

In this paper, we reexamine in the framework of robust computation the Bentley-Ottmann algorithm for reporting intersecting pairs of segments in the plane. This algorithm has been reported as being very sensitive to numerical errors. Indeed, a simple analysis reveals that it involves predicates of degree 5, presumably never evaluated exactly in most implementations. Within the exact-computation paradigm we introduce two models of computation aimed at replacing the conventional model of real-number arithmetic. The first model (predicate arithmetic) assumes the exact evaluation of the signs of algebraic expressions of some degree, and the second model (exact arithmetic) assumes the exact computation of the value of such (bounded-degree) expressions. We identify the characteristic geometric property enabling the correct report of all intersections by plane sweeps. Verification of this property involves only predicates of (optimal) degree 2, but its straightforward implementation appears highly inefficient. We then present algorithmic variants that have low degree under these models and achieve the same performance as the original Bentley Ottmann algorithm. The technique is applicable to a more general case of curved segments.

关键词： computational geometry segment intersection plane sweep robust algorithms

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robust clustering by deterministic agglomeration EM of mixtures of multivariate t-distributions

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PATTERN RECOGNITION 2002年第5期35卷 1127-1142页

作者： Shoham, S Univ Utah Dept Bioengn Salt Lake City UT 84112 USA

This paper presents new robust clustering algorithms, which significantly improve upon the noise and initialization sensitivity of traditional mixture decomposition algorithms, and simplify the determination of the optimal number of clusters in the data set. The algorithms implement maximum likelihood mixture decomposition of multivariate t-distributions, a robust parametric extension of gaussian mixture decomposition. We achieve improved convergence capability relative to the expectation-maximization (EM) approach by deriving deterministic annealing EM (DAEM) algorithms for this mixture model and turning them into agglomerative algorithms (going through a monotonically decreasing number of components), an approach we term deterministic agglomeration EM (DAGEM). Two versions are derived, based on two variants of DAEM for mixture models. Simulation studies demonstrate the algorithms' performance for mixtures with isotropic and non-isotropic covariances in two and 10 dimensions with known or unknown levels of outlier contamination. (C) 2002 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.

关键词： clustering finite mixture models EM algorithm robust algorithms t-distribution deterministic annealing agglomerative algorithms

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robust EXTRACTION OF STATISTICS FROM IMAGES OF MATERIAL FRAGMENTATION

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INTERNATIONAL JOURNAL OF IMAGE AND GRAPHICS 2011年第3期11卷 377-401页

作者： Kamath, Chandrika Hurricane, Omar A. Lawrence Livermore Natl Lab Livermore CA 94551 USA Univ Calif Los Angeles Inst Plasma & Fus Res Los Angeles CA 90024 USA

The extraction of statistics of interest in experimental or observational images is often challenging due to the noise in the data and the variation across images in a dataset. For an objective analysis, any algorithms used must be relatively insensitive to the choice of parameters. In addition, to avoid manual analysis, which is tedious and error-prone, these algorithms must also lend themselves to full or partial automation, especially when the number of images is large. In this paper, we describe the use of image analysis techniques to extract various statistics from experimental images resulting from the fragmentation of materials. We show how we can use a sequence of relatively simple algorithms to provide a robust solution for the extraction of statistics on the fragments and the gaps between them.

关键词： Fragmentation of materials image enhancement segmentation feature extraction robust algorithms

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Fault Injection in GPGPU Cores to Validate and Debug robust Parallel Applications

Fault Injection in GPGPU Cores to Validate and Debug Robust ...

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IEEE 20th International On-Line Testing Symposium (IOLTS)

作者： De Carvalho, M. Sabena, D. Reorda, M. Sonza Sterpone, L. Rech, P. Carro, L. Politecn Torino Turin TO Italy Univ Fed Rio Grande do Sul Porto Alegre Brazil

ISBN: (纸本)9781479953240

General Purpose Graphic Processing Units (GPGPUs) are more efficient than CPUs for processing parallel data. Unfortunately, GPGPUs are sensible to radiation. Hence, several software mitigation techniques, as well as robust algorithms, are being developed to overcome reliability problems. In this paper we propose a software debugger-based fault injection mechanism to evaluate the resiliency of applications running on a GPGPU and to validate the software hardening techniques it possibly embeds. We report some experimental results gathered on selected case studies to show the proposed approach advantages and limitations.

关键词： fault injection reliable GPGPU applications robust algorithms transient faults

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