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PASM: parallel aligned surface meshing

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2021年第15期122卷 3705-3732页

作者： Yu, Fei Cao, Jie Shan, Julin Lo, S. H. Guan, Zhenqun Dalian Univ Technol Dept Engn Mech State Key Lab Struct Anal Ind Equipment Dalian Peoples R China Shanghai Geyu Software Co Ltd Shanghai Peoples R China Univ Hong Kong Dept Civil Engn Hong Kong Peoples R China

Computer-aided design (CAD) models of industrial design are often plagued with a series of defects, including minute features, gaps, self-intersections, and misalignments. The development of schemes in automatic defeaturing, gaps repairing, and intersection removal usually requires a discrete representation of the geometry. However, existing surface meshing methods could not effectively handle sliver surfaces and assemblies with complex contact conditions, including multiple misaligned curves/surfaces and degenerated or free-form-shaped interface of contact. A surface meshing method based on a meshing-and-synchronizing strategy is proposed, which tackles the mesh generation of sliver surfaces and the cleanup of misaligned assemblies by means of mesh alignment. The mesh generation is performed in a hierarchical manner with curves and surfaces being meshed in sequence. By incorporating the synchronization strategy into the curve/surface meshing process, curve/surface mesh alignment is achieved automatically without compromising the mesh quality. Thanks to the alignment, the curve mesh generated by aligned curve meshing (ACM) is free of intersections, which enhances the meshing of sliver surfaces. By enforcing mesh alignment, aligned surface meshing (ASM) can handle misaligned assemblies with complex contact conditions. ASM is parallelized by using OpenMP. Various assemblies characterized with difficult misaligned features and touches are well processed by parallel ASM.

关键词： assembly cleanup finite element mesh generation mesh alignment parallel algorithms surface patch meshing

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Two parallel versions of VF3: Performance analysis on a wide database of graphs

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PATTERN RECOGNITION LETTERS 2021年 146卷 150-157页

作者： Carletti, Vincenzo Foggia, Pasquale Percannella, Gennaro Ritrovato, Pierluigi Vento, Mario Univ Salerno Dept Informat Engn Elect Engn & Appl Math Salerno Italy

An important combinatorial problem is subgraph isomorphism, which formalizes the task of searching for occurrences of a known substructure within a larger structure represented by a graph: applications are in the fields of chemistry, biology, medicine, databases, social network analysis. Subgraph isomorphism has been proven to be NP-complete in the general case, but several algorithms exist that use heuristics to achieve an affordable run time for common classes of graphs. The need of working with larger and larger graphs makes attractive the idea of parallelizing this task;however, a consensus has not yet been reached on what is the best strategy for doing so. In this paper, we present two versions of a new, parallel algorithm that is based on a re-design of the well known VF3 algorithm. We discuss the changes that were made to efficiently distribute the work among multiple processors. The algorithms have been evaluated with a comprehensive experimentation, using several publicly available graph datasets, to demonstrate their effectiveness in exploiting the parallelism. (c) 2021 Elsevier B.V. All rights reserved.

关键词： Exact graph matching Subgraph isomorphism parallel algorithms VF3

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parallel Computation of Discrete Orthogonal Moment on Block Represented Images Using OpenMP

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INTERNATIONAL JOURNAL OF parallel PROGRAMMING 2021年第3期49卷 440-462页

作者： Spiliotis, Iraklis M. Sitaridis, Charalampos Bekakos, Michael P. Democritus Univ Thrace Rept Elect & Comp Engn Xanthi 67100 Greece

Herein, a parallel implementation of Discrete Orthogonal moments on block represented images is investigated. Moments and moment functions have been used widely as features for image analysis and pattern recognition tasks. The main disadvantage of all moment sets, is the high computational cost which is increased as higher-order moments are involved in the computations. In image block representation (IBR) the image is represented by homogeneous areas which are called blocks. The IBR allows moment computation with zero computational error for binary images, low computational error for gray images, low computational complexity, while can achieve high processing rates. The results from parallel implementation on a multicore computer using OpenMP, exhibit significant performance.

关键词： Discrete orthogonal moments Image block representation Fast image analysis parallel algorithms OpenMP

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A PGAS-Based Implementation for the parallel Minimum Spanning Tree Algorithm 13th

A PGAS-Based Implementation for the Parallel Minimum Spannin...

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13th International Conference on Large-Scale ScientificComputations (LSSC)

作者： Bejanyan, Vahag Astsatryan, Hrachya Natl Acad Sci Republ Armenia Inst Informat & Automat Problems 1 Paruyr Sevak St Yerevan 0014 Armenia

ISBN: (纸本)9783030975494;9783030975487

The minimum spanning tree is a critical problem for many applications in network analysis, communication network design, and computer science. The parallel implementation of minimum spanning tree algorithms increases the simulation performance of large graph problems using high-performance computational resources. The minimum spanning tree algorithms generally use traditional parallel programming models for distributed and shared memory systems, like Massage Passing Interface or OpenMP. Furthermore, the partitioned global address space model offers new capabilities in the form of asynchronous computations on distributed shared memory, positively affecting the performance and scalability of the algorithms. The paper aims to present a new minimum spanning tree algorithm implemented in a partitioned global address space model. The experiments with diverse parameters have been conducted to study the efficiency of the asynchronous implementation of the algorithm.

关键词： Minimum spanning tree PGAS model parallel algorithms Large-scale graphs HPC

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Highly parallel boundary element method for solving extremely large, wide-area power-line models

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INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS 2021年第2期35卷 136-153页

作者： Adelman, Ross DEVCOM Army Res Lab 2800 Powder Mill Rd Adelphi MD 20783 USA

The electric and magnetic fields around power lines carry an immense amount of information about the power grid and can be used to improve stability, balance loads, conserve power, and reduce outages. To study this, an extremely large model of transmission lines over a 70-km(2) tract of land near Washington, DC, has been built. The terrain was modeled accurately using 1-m-resolution LIDAR data. The 140-million-element power-line model was solved using the boundary element method, and the solvers were parallelized across DEVCOM Army Research Laboratory's Centennial supercomputer using a modified version of the domain decomposition method. The code on each node was accelerated using the fast multipole method and, when available, GPUs. Additionally, larger test models were used to characterize the scalability of the code. The largest test model had 10,010,944,000 elements, and was solved on 1,024 nodes in 4.3 hours.

关键词： Power lines electric field boundary element method fast multipole method domain decomposition method parallel algorithms supercomputers

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parallel kd-tree with Batch Updates

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Proceedings of the ACM on Management of Data 2025年第1期3卷 1-26页

作者： Ziyang Men Zheqi Shen Yan Gu Yihan Sun University of California Riverside Riverside USA

The kd-tree is one of the most widely used data structures to manage multi-dimensional data. Due to the ever-growing data volume, it is imperative to consider parallelism in kd-trees. However, we observed challenges in existing parallel kd-tree implementations, for both constructions and *** goal of this paper is to develop efficient in-memory kd-trees by supporting high parallelism and cache-efficiency. We propose the Pkd-tree (parallel kd-tree), a parallel kd-tree that is efficient both in theory and in practice. The Pkd-tree supports parallel tree construction, batch update (insertion and deletion), and various queries including k-nearest neighbor search, range query, and range count. We proved that our algorithms have strong theoretical bounds in work (sequential time complexity), span (parallelism), and cache complexity. Our key techniques include 1) an efficient construction algorithm that optimizes work, span, and cache complexity simultaneously, and 2) reconstruction-based update algorithms that guarantee the tree to be weight-balanced. With the new algorithmic insights and careful engineering effort, we achieved a highly optimized implementation of the *** tested Pkd-tree with various synthetic and real-world datasets, including both uniform and highly skewed data. We compare the Pkd-tree with state-of-the-art parallel kd-tree implementations. In all tests, with better or competitive query performance, Pkd-tree is much faster in construction and updates consistently than all baselines. We released our code.

关键词： kd-tree parallel algorithms parallel trees spatial partition trees

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A Simpler and parallelizable O(√log n)-approximation Algorithm for SPARSEST CUT 24

A Simpler and Parallelizable O(√log n)-approximation Algori...

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36th ACM Symposium on parallelism in algorithms and Architectures (SPAA)

作者： Kolmogorov, Vladimir Inst Sci & Technol Austria ISTA Klosterneuburg Austria

ISBN: (纸本)9798400704161

Currently, the best known tradeoff between approximation ratio and complexity for the Sparsest Cut problem is achieved by the algorithm in [Sherman, FOCS 2009]: it computes O(root(log n)/epsilon)-approximation using O(n(epsilon) log(O(1))n) maxflows for any epsilon is an element of[Theta(1/log n), Theta(1)]. It works by solving the SDP relaxation of [Arora-Rao-Vazirani, STOC 2004] using the Multiplicative Weights Update algorithm (MW) of [Arora-Kale, JACM 2016]. To implement one MW step, Sherman approximately solves a multicommodity flow problem using another application of MW. Nested MW steps are solved via a certain "chaining" algorithm that combines results of multiple calls to the maxflow algorithm. We present an alternative approach that avoids solving the multicommodity flow problem and instead computes "violating paths". This simplifies Sherman's algorithm by removing a need for a nested application of MW, and also allows parallelization: we show how to compute O(root(log n)/epsilon)-approximation via O(log(O(1)) n) maxflows using O(n(epsilon)) processors. We also revisit Sherman's chaining algorithm, and present a simpler version together with a new analysis.

关键词： SPARSEST CUT approximation algorithms parallel algorithms

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Analysis of a parallel MCMC algorithm for graph coloring with nearly uniform balancing

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PATTERN RECOGNITION LETTERS 2021年 149卷 30-36页

作者： Conte, Donatello Grossi, Giuliano Lanzarotti, Raffaella Lin, Jianyi Petrini, Alessandro Univ Tours Lab Informat Fondamentale & Appl Tours LIFAT EA 6 64 Ave Jean Portalis F-37000 Tours France Univ Milan Dipartimento Informat Via Celoria 18 I-20133 Milan Italy Univ Cattolica Sacro Cuore Dipartimento Sci Stat Largo A Gemelli 1 I-20123 Milan Italy

We propose the analysis of a scalable parallel MCMC algorithm for graph coloring aimed at balancing the color class sizes, provided that a suitable number of colors is made available. Firstly, it is shown that the Markov chain converges to the target distribution by repeatedly sampling from suitable proposed distributions over the neighboring colors of each node, independently and hence in parallel manner. We prove that the number of conflicts in the improper colorings genereted thoughout the iterations of the algorithm rapidly converges in probability to 0. As for the balancing, given to the complexity of the distributions involved, we propose a qualitative analysis about the balancing level achieved. Based on a collection of multinoulli distributions arising from the color occurrences within every node neighborhood, we provide some evidence about the character of the final color balancing, which results to be nearly uniform over the color classes. Some numerical simulations on big social graphs confirm the fast convergence and the balancing trend, which is validated through a statistical hypothesis test eventually. (c) 2021 Elsevier B.V. All rights reserved.

关键词： Graph coloring Markov chain Monte Carlo method Color balancing parallel algorithms

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HI-FFT: Heterogeneous parallel In-Place Algorithm for Large-Scale 2D-FFT

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IEEE ACCESS 2021年 9卷 120261-120273页

作者： Kang, Homin Lee, Jaehong Kim, Duksu Korea Univ Technol & Educ KOREATECH Sch Comp Engn Cheonan 31253 South Korea

Fast Fourier Transform (FFT) is a fundamental operation for 2D data in various applications. To accelerate large-scale 2D-FFT computation, we propose a Heterogeneous parallel In-place 2D-FFT algorithm, HI-FFT. Our novel work decomposition method makes it possible to run our parallel algorithm on the original data (i.e., in-place), unlike prior parallel algorithms that require additional memory space (i.e., out-of-place) to guarantee independence among sub-tasks. Our work decomposition method also removes the duplicated operations on the out-of-place approaches. Using our decomposition method, we introduced an in-place heterogeneous parallel algorithm that utilizes both multi-core CPU and GPU simultaneously. To maximize the utilization efficiency of the computing resources, we also propose a priority-based dynamic scheduling method. We compared the performance of seven different 2D-FFT algorithms, including ours, for large-scale 2D-FFT problems whose sizes varied from 20K(2) to 120K(2). As a result, we found that our method achieved up to 2.92 and 4.42 times higher performance than the conventional homogeneous parallel algorithms based on the state-of-the-art CPU and GPU libraries, respectively. Also, our method showed up to 2.27 times higher performance than the prior heterogeneous algorithms while requiring two times less memory space. To check the benefit of our HI-FFT on an actual application, we applied it to a CGH (Computer Generated Holography) process. We found that it successfully reduces the hologram generation time. These results demonstrate the advantage of our approach for large-scale 2D-FFT computation.

关键词： Graphics processing units parallel algorithms Libraries Discrete Fourier transforms Memory management Matrix decomposition Heterogeneous networks 2D-FFT heterogeneous parallel CPU GPU in-place

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parallel algorithms for Edge Detection in an Image

Parallel Algorithms for Edge Detection in an Image

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International Conference on Network-Based Information Systems (NBIS)

作者： C. Mala M. Sridevi Department of Computer Science and Engineering National Institute of Technology Tiruchirappalli India

Edge detection is an important process in image segmentation, object recognition, template matching, etc. It computes gradients in both horizontal and vertical directions of the image at each pixel position to find the image boundaries. The conventional edge detectors take significant time to detect the edges in the image. To reduce the computational time, this paper proposes parallel algorithms for edge detection with Sobel, Prewitt and Robert first order derivatives using a Shared Memory - Single Instruction Multiple Data (SM - SIMD) parallel architecture. From the experimental results, it is inferred that the proposed parallel algorithms for edge detection are faster than the conventional methods.

关键词： Image edge detection Image segmentation Convolution Detectors Program processors parallel algorithms

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