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On the maximum edge-pair embedding bipartite matching

THEORETICAL COMPUTER SCIENCE 2021年 882卷 109-124页

作者： Nguyen, Cam Ly Suppakitpaisarn, Vorapong Surarerks, Athasit Vajanopath, Phanu Toshiba Co Ltd Tokyo Japan Univ Tokyo Tokyo Japan Chulalongkorn Univ Bangkok Thailand Kasetsart Univ Bangkok Thailand

Given a set of edge pairs in a complete bipartite graph, we want to find a bipartite matching that includes the maximum number of those edge pairs. While the problem has many applications to wireless localization and computer vision, to the best of our knowledge, there is no theoretical work for the problem. In this work, unless P = N P, we show that there is no constant approximation for the problem. Then, we consider two special cases of the problem. Suppose that k denotes the maximum number of input edge pairs such that a particular node can be in. Inspired by experimental results, the first case is for when k is not large. While there is a simple polynomial-time algorithm for the problem when k is one, we show that the problem is NP-hard when k is greater than one. We also devise an efficient O(k)-approximation algorithm for the problem. For the second case, every pair of nodes in the same partition of the input bipartite graph are labeled with one of chi colors. We want to match, between the two partitions, a pair of nodes to a pair of nodes with the same color. Denote n as the number of nodes, we give an O (root chi(n))-approximation algorithm for this case. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Graph matching problem Wireless localization computational complexity Approximation algorithm Network optimization Quadratic assignment problem

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Frequency-Domain Diversity Combining Receiver for ACO-OFDM System

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2015年第6期7卷 1-10页

作者： Dang, J. Zhang, Z. Wu, L. Southeast Univ Natl Mobile Commun Res Lab Nanjing 210096 Jiangsu Peoples R China

This paper proposes a new receiver based on frequency-domain diversity combining (FDDC) for an asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM) system. Compared with its time-domain diversity combining (TDDC) counterpart, the FDDC receiver is capable of more effectively exploiting the frequency selectivity of the channel to further improve the detection performance, which is proved by postcombining signal-to-noise-ratio (SNR) analysis. An enhanced version of the FDDC receiver, which is called eFDDC, is also proposed subsequently. It allows for optimal selection among multiple sets of candidate symbol vectors based on signum matrix estimation. Simulation results show that the proposed FDDC and eFDDC receivers outperform the TDDC receiver. With a sufficient number of candidate symbol vector sets, the eFDDC receiver even outperforms a kind of iterative receiver, which is known to have superior performance in current literature, yet the complexity of eFDDC is lower due to the avoidance of matrix inversion. Those facts suggest that the FDDC and eFDDC receivers are strong receiver candidates for the ACO-OFDM system.

关键词： Asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM) diversity combining symbol detection candidate selection computational complexity

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Robust maximum weighted independent-set problems on interval graphs

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OPTIMIZATION LETTERS 2014年第1期8卷 227-235页

作者： Nobibon, Fabrice Talla Leus, Roel Res Fdn Flanders FWO Brussels Belgium Univ Liege HEC Management Sch QuantOM Liege Belgium Katholieke Univ Leuven ORSTAT Fac Business & Econ Louvain Belgium

We study the maximum weighted independent-set problem on interval graphs with uncertainty on the vertex weights. We use the absolute robustness criterion and the min-max regret criterion to evaluate solutions. For a discrete scenario set, we find that the problem is NP-hard for each of the robustness criteria;we also provide pseudo-polynomial time algorithms when there is a constant number of scenarios and show that the problem is strongly NP-hard when the set of scenarios is unbounded. When the scenario set is a Cartesian product, we prove that the problem is equivalent to a maximum weighted independent-set problem on the same interval graph but without uncertainty for the first objective function and that the scenario set can be reduced for the second objective function.

关键词： Combinatorial problems computational complexity Interval graphs Independent set Dynamic programming

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Multi-Feature Fusion and Enhancement Single Shot Detector for Traffic Sign Recognition

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IEEE ACCESS 2020年 8卷 38931-38940页

作者： Jin, Yanmei Fu, Yusheng Wang, Wenqin Guo, Jinhong Ren, Chunhui Xiang, Xin Univ Elect Sci & Technol China Sch Informat & Commun Engn Chengdu 611731 Peoples R China Air Force Engn Univ Xian 710051 Peoples R China

Road traffic sign detection and recognition play an important role in advanced driver assistance systems (ADAS) by providing real-time road sign perception information. In this paper, we propose an improved (Single Shot Detector) SSD algorithm via multi-feature fusion and enhancement, named MF-SSD, for traffic sign recognition. First, low-level features are fused into high-level features to improve the detection performance of small targets in the SSD. We then enhance the features in different channels to detect the target by enhancing effective channel features and suppressing invalid channel features. Our algorithm gets good results in domestic real-time traffic signs. The proposed MF-SSD algorithm is evaluated with the German Traffic Sign Recognition Benchmark (GTSRB) dataset. The experimental results show that the MF-SSD algorithm has advantages in detecting small traffic signs. Compared with existing methods, it achieves higher detection accuracy, better efficiency, and better robustness in complex traffic environment.

关键词： Feature extraction Object detection Detectors Classification algorithms computational complexity Roads Advanced driver assistance systems Traffic sign detection small target detection single shot detector feature fusion feature enhancement

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THE USE OF HUYGENS EQUIVALENCE PRINCIPLE FOR SOLVING THE VOLUME INTEGRAL-EQUATION OF SCATTERING

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 1993年第7期41卷 897-904页

作者： CHEW, WC LU, CC UNIV ILLINOIS RES PROGRAMURBANAIL 61801

A new algorithm is introduced to solve the volume integral equation of scattering. A volume scatterer is first divided into N subscatterers. Then the subscatterers are divided into four groups, and the groups are in turn divided into four subgroups and so on. By using the idea found in many fast algorithms, a smaller problem can hence be nested within a larger problem. Moreover, by way of Huygens' equivalence principle, the scattering properties of a group of subscatterers in a volume can be replaced by a group of subscatterers distributed on a surface enclosing the volume. Based on this idea, we present an algorithm which solves the scattering problem by several stages, where at each stage the interaction matrix algorithm is first used to find the scattering solution of each subgroup of subscatterers. Subscatterers are then replaced by equivalent surface subscatterers which are used in the next stage. Consequently, this results in a reduction in the number of subscatterers at every stage. This algorithm can be shown to have a CPU time asymptotically proportional to N1.5 for N subscatterers.

关键词： Integral equations Scattering computational complexity Sparse matrices Aggregates Military computing Differential equations Transforms Moment methods Strips

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Improved clipped affine projection adaptive algorithm

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IET SIGNAL PROCESSING 2019年第1期13卷 103-111页

作者： Bekrani, Mehdi Bibak, Ruhollah Lotfizad, Mojtaba Qom Univ Technol Fac Elect & Comp Engn Qom Iran Tarbiat Modares Univ Fac Elect & Comp Engn Tehran Iran

In this study, a modification to the affine projection adaptive filtering algorithm is proposed which is based on a three-level clipping of the input signal as applied to the weight update process. This clipping operation causes the input signal to be quantised into three levels, namely, 0, 1, and -1. By doing so, the proposed scheme, in addition to reducing the computational complexity, achieves an error convergence performance that is comparable to, or even at times better than that of the conventional affine projection algorithm (APA) for a certain range of the clipping threshold. The proposed adaptive algorithm is compared with some low complexity variants of APA with respect to the convergence rate and computational complexity, and its superiority to its counterparts of the same order of complexity in terms of the convergence rate is demonstrated. The mean square error analysis based on the energy conservation relation and the stability analysis is also presented for the proposed clipped APA.

关键词： filtering theory adaptive filters computational complexity error analysis mean square error methods computational complexity error convergence performance conventional affine projection algorithm clipping threshold low complexity variants convergence rate mean square error analysis clipped APA affine projection adaptive algorithm affine projection adaptive filtering algorithm three-level clipping input signal weight update process clipping operation

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complexity OF PARALLEL MATRIX COMPUTATIONS

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THEORETICAL COMPUTER SCIENCE 1987年第1期54卷 65-85页

作者： PAN, V Computer Science Department State University of New York at Albany Albany NY12222 U.S.A.

We estimate parallel complexity of several matrix computations under both Boolean and arithmetic machine models using deterministic and probabilistic approaches. Those computations include the evaluation of the inverse, the determinant, and the characteristic polynomial of a matrix. Recently, processor efficiency of the previous parallel algorithms for numerical matrix inversion has been substantially improved in (Pan and Reif, 1987), reaching optimum estimates up to within a logarithmic factor; that work, however, applies neither to the evaluation of the determinant and the characteristic polynomial nor to exact matrix inversion nor to the numerical inversion of ill-conditioned matrices. We present four new approaches to the solution of those latter problems (having several applications to combinatorial computations) in order to extend the suboptimum time and processor bounds of (Pan and Reif, 1987) to the case of computing the inverse, determinant, and characteristic polynomial of an arbitrary integer input matrix. In addition, processor efficient algorithms using polylogarithmic parallel time are devised for some other matrix computations, such as triangular and QR -factorizations of a matrix and its reduction to Hessenberg form.

关键词： Parallel algorithms computational complexity matrix computations

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A fast hierarchical motion-compensation scheme for video coding using block feature matching

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1996年第6期6卷 627-635页

作者： Lee, X Zhang, YQ GTE LABS INC WALTHAMMA 02254

This paper presents a fast hierarchical feature matching-motion estimation scheme (HEM-ME) that can be used in H.263, H.261, MPEG 1, MPEG 2, and HDTV applications, In the HFM-ME scheme, the sign truncated feature (STP) is defined and used for block template matching, as opposed to the pixel intensity values used in conventional block matching methods, The STF extraction process Can be considered as a zero-crossing phase detection with the mean as the bias and binary sign pattern as the phase deviation, Using the STF definition, a data block can be represented by a mean and a set of binary features with a much reduced data set, The block matching motion estimation is then divided to mean matching and binary phase matching, The proposed technique enables a significant reduction in computational complexity compared with the conventional full-search block matching ME because binary phase matching only involves Boolean logic operations, This feature also significantly reduces the data transfer time between the frame buffer and motion estimator, The proposed HFM-ME algorithm is implemented and compared with the conventional full-search block matching schemes, Our test results using three full-motion MPEG sequences indicate that the performance of the HFM-ME is comparable with the full-search block matching under the same search ranges, however, HFM-ME can be implemented about 64 times faster than the conventional full-search schemes, The proposed scheme can be combined with other fast algorithms to further reduce the computational complexity, at the expense of picture quality.

关键词： computational complexity feature extraction image matching image representation image sequences motion estimation search problems video codecs video coding Boolean logic operations H.261 H.263 HDTV MPEG 1 MPEG 2 MPEG sequences bias binary phase matching Video coding tabu search frame buffer block matching complexity classes logical operation Moving Pictures Experts Group Feature extraction motion estimation image representation phase deviation video codecs image matching image sequences STF

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Reasoning under minimal upper bounds in propositional logic

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THEORETICAL COMPUTER SCIENCE 2006年第1-3期369卷 82-115页

作者： Eiter, Thomas Gottlob, Georg Vienna Univ Technol Inst Informat Syst A-1040 Vienna Austria Univ Oxford Comp Lab Oxford OX1 3QD England

Reasoning from the minimal models of a theory, as fostered by circumscription, is in the area of Artificial Intelligence an important method to formalize common sense reasoning. However, as it appears, minimal models may not always be suitable to capture the intuitive semantics of a knowledge base, aiming intuitively at an exclusive interpretation of disjunctions of atoms, i.e., if possible then assign at most one of the disjuncts the value true in a model. In this paper, we consider an approach which is more lenient and also admits non-minimal models, such that inclusive interpretation of disjunction also may be possible in cases where minimal model reasoning adopts an exclusive interpretation. Nonetheless, in the spirit of minimization, the approach aims at including only positive information that is necessary. This is achieved by closing the set of admissible models of a theory under minimal upper bounds in the set of models of the theory, which we refer to as curbing. We demonstrate this method on some examples, and investigate its semantical and computational properties. We establish that curbing is an expressive reasoning method, since the main reasoning tasks are shown to be PSPACE-complete. On the other hand, we also present cases of lower complexity, and in particular cases in which the complexity is located, just as for ordinary minimal model reasoning, at the second level of the Polynomial Hierarchy, or even below. (c) 2006 Elsevier B.V. All rights reserved.

关键词： artificial intelligence circumscription computational complexity curbing knowledge representation minimal models non-monotonic reasoning propositional logic

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Large-Scale Parallelization of Human Migration Simulation

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IEEE TRANSACTIONS ON computational SOCIAL SYSTEMS 2024年第2期11卷 2135-2146页

作者： Groen, Derek Papadopoulou, Nikela Anastasiadis, Petros Lawenda, Marcin Szustak, Lukasz Gogolenko, Sergiy Arabnejad, Hamid Jahani, Alireza Brunel Univ London Dept Comp Sci Uxbridge UB8 3PH England Chalmers Univ Technol Dept Comp Sci & Engn S-41296 Gothenburg Sweden Natl Tech Univ Athens Comp Syst Lab Athens 15780 Greece Poznan Supercomp & Networking Ctr PL-61139 Poznan Poland Czestochowa Tech Univ Fac Mech Engn & Comp Sci PL-42201 Czestochowa Poland High Performance Comp Ctr Stuttgart D-70569 Stuttgart Germany

Forced displacement of people worldwide, for example, due to violent conflicts, is common in the modern world, and today more than 82 million people are forcibly displaced. This puts the problem of migration at the forefront of the most important problems of humanity. The Flee simulation code is an agent-based modeling tool that can forecast population displacements in civil war settings, but performing accurate simulations requires nonnegligible computational capacity. In this article, we present our approach to Flee parallelization for fast execution on multicore platforms, as well as discuss the computational complexity of the algorithm and its implementation. We benchmark parallelized code using supercomputers equipped with AMD EPYC Rome 7742 and Intel Xeon Platinum 8268 processors and investigate its performance across a range of alternative rule sets, different refinements in the spatial representation, and various numbers of agents representing displaced persons. We find that Flee scales excellently to up to 8192 cores for large cases, although very detailed location graphs can impose a large initialization time overhead.

关键词： AMD Rome benchmarks computational complexity global challenges global systems science (GSS) high performance computing (HPC) Intel Xeon migration modeling parallelization refugees

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