基于有向弧的多边形拓扑关系生成算法

本文提出了一种基于结点弧段邻接关系自动生成多边形拓扑关系的算法,对每个结点的关联弧段按方位角排序并对这种排序进行了补充定义,对弧段的方向也作了相关规定。以此为基础,本算法避免了多边形内角的重复计算和反复搜索,提高了建立多边形拓扑关系的效率。最后,对该算法进行了分析和实例计算。     

矢量多边形栅格化算法快速并行化方法研究

本文在分析典型多边形栅格化算法的基础上,研究了串行算法并行化思路,提出一种多边形栅格化算法并行框架。该并行框架包括MPI与OpenMP的双层并行模式、顾及负载均衡的矢量多边形数据划分方法、多边形栅格化基本算子调用接口。利用本文形成的并行框架对扫描线算法、边界代数法进行了并行化,并利用大规模土地现状数据验证本文所提出的并行化方法的有效性。试验结果表明,该方法能够解决矢量多边形栅格化串行算法快速并行化的问题,并行化后的算法大大减少了矢量多边形转换时间,具有良好的并行效率。     

一种GIS拓扑多边形链搜索的改进算法

针对GIS拓扑多边形链搜索中悬挂弧段的处理问题,提出了一种改进算法。该算法利用在一趟搜索中,非悬挂弧段仅经过一次,而悬挂弧段会经过两次这一规律来识别并标记悬挂弧段;在进行多边形链搜索时,通过避让悬挂弧段以避免将其对应的关联弧段加入多边形链,从而保证搜索结果的正确性。测试结果表明,该算法能明显提高多边形链搜索的效率。     

面向SoC的系统级并行划分方法

为缩短复杂SoC系统的设计周期,降低系统设计的复杂性,提出了一种SoC系统级的并行划分方法.引入带有信号激活率和输入输出延时的过程模型图,为SoC系统构建模型.设计一启发式算法对该过程模型图进行并行划分,同时,该算法能解决有环图的划分问题.通过大量的实验证明,划分结果同要求吻合,说明该划分方法是可行、有效的.     

基于夹角变化趋势的多边形自动搜索和生成算法

利用左转算法生成多边形是GIS中面域组织和拓扑关系建立的常用算法。根据算法规则,对于由顺时针方向和逆时针方向建立的多边形都可以生成多边形文件,这就会产生一些重复多边形和无效的多边形。为此,提出了基于夹角变化趋势判断多边形搜索方向的算法,根据左转或右转算法得到的点组顺序,分别计算由起始点出发的弧段的方位角,根据相邻弧段夹角的和来判断多边形的搜索方向,实现了每一多边形都是由左转算法生成,完成了多边形的自动建立。该算法有效地判断了多边形的搜索方向,避免了无效多边形的生成。     

一个基于图的多边形拓扑关系生成算法

本文提出了一种基于图的多边形拓扑关系自动生成算法和实例。该算法只需利用图中弧与多边的拓扑信息,避免了多边形内角的计算与比较,算法中根据图的拓扑特征采有效的策略,加快了多边形自动生成的速度。     

基于OpenCL的并行kNN算法设计与实现

kNN算法是机器学习和数据挖掘程序中经常使用的经典算法。随着数据量的增大,kNN算法的执行时间急剧上升。为了有效利用现代计算机的GPU等计算单元减少kNN算法的计算时间,提出了一种基于OpenCL的并行kNN算法,该算法对距离计算和排序两个瓶颈点进行并行化,在距离计算阶段使用细粒度并行化策略和优化的线程模型,排序阶段使用优化内存模型的双调排序。以UCI数据集letter为测试集,分别使用E8400和GTS450运行kNN算法进行测试,采用GPU加速的并行kNN算法的计算速度比CPU版提高了40.79倍。     

钣金冲孔中直角多边形快速干涉检验算法

针对钣金冲孔中的直角多边形孔的刀具匹配中涉检验提出了一种高效的算法.该算法先对直角多边形的顶点按逆时针方向排序,然后建立起基于空间分区思想的四向辅助图,利用四向辅助图中的规律判断待加工边的可能干涉情况,从而确定刀具的允许最大宽度.算法分析表明:该算法对直角多边形刀具涉检验具有线性的时间复杂度,有效地提高了板材加工中直角多边形孔自动刀具匹配的效率.     

基于有向弧的改进多边形拓扑关系生成算法

文章提出了一种基于有向弧段的多边形拓扑关系生成算法,改进了传统算法.算法对每个结点的关联孤段按方位角排序并对这种有序性进行了补充定义,同时为弧段增加两个方向相关的字段,分别表示弧段的方向和是否被遍历过,搜索多边形的同时对遍历过的有向孤段加以标记.本算法避免了多边形的反复搜索和内角的计算,提高了建立多边形拓扑关系的效率.最后,时该算法进行了分析和实例计算.     

一种精确的调用图生成技术

调用图是过程间分析和程度自动并行化的基础。生成精确调用图可以进一步开发程序的并行性。此文针对Ｆｏｒｔｒａｎ程序，提出了一项完全消除哑过程，产生精确调用图的技术与相应的算法。该算法已在面向ＭＰＰ Ｆｏｒｔｒａｎ的程序自动并行化工具中实现。     

Systolic Architecture for Boolean Operations on Polygons and Polyhedra

In Computer-Aided Design applications there is often a need to compute the union, intersection and Merence of two polygons or polyhedra. The sequential algorithms for this problem are characterized by poor speed of response and large computational complexity. In order to remove these defects, an algorithm amenable to implementation on a parallel architecture is proposed. The parallel architecture designed is a systolic one which forms a dedicated subsystem to perform set-theoretic operations on polygons. The improvement in speed gained by using the systolic array as compared to a uniprocessor has been evaluated using simulation techniques. Extensions of this architecture to perform the same operations on polyhedra are also discussed.     

隐式曲面的快速适应性多边形化算法

通过将隐式曲面多边形化过程分为“构造”和“适应性采样”两个阶段，实现了隐式曲面多边形逼近网格的适应性构造．通过基于空间延展的Marching Cubes方法得到隐式曲面较为粗糙的均匀多边形化逼近，根据曲面上的局部曲率分布，运用适应性细分规则对粗糙网格进行细分迭代，并利用梯度下降法将细分出的新顶点定位到隐式曲面上；最终得到的多边形网格是适应性的单纯复形网格，其在保持规定逼近精度的前提下，减少了冗余三角形的产生，网格质量有明显改善．该算法可用于隐式曲面的交互式可视化过程．     

平面扩展多边形分层表示的构造方法及简单应用

平面多边形的分层表示(L-REP)是一种基于三角形片的多边形表示模型，具有构造简单、鲁棒性强等优点，并且在许多问题上都有着很好的应用．文中在这一工作的基础上进行扩展，使其可以应用到带圆锥曲线边的平面扩展多边形上，提出平面扩展多边形的分层表示方法(CL-REP)，并给出了完整的数学模型和两种典型的构造算法．最后给出了使用该方法的几个简单应用，主要是布尔运算和包容测试等，可见使用CL-REP能够简单、有效地解决这些问题。     

Data Parallel Implementation of Belief Propagation in Factor Graphs on Multi-core Platforms

We investigate data parallel techniques for belief propagation in acyclic factor graphs on multi-core systems. Belief propagation is a key inference algorithm in factor graph, a probabilistic graphical model that has found applications in many domains. In this paper, we explore data parallelism for basic operations over the potential tables in belief propagation. Data parallel techniques for these table operations are developed for shared memory platforms. We then propose a complete belief propagation algorithm using these table operations to perform exact inference in factor graphs. The proposed algorithms are implemented on state-of-the-art multi-socket multi-core systems with additional NUMA-aware optimizations. Our proposed algorithms exhibit good scalability using a representative set of factor graphs. On a four-socket Intel Westmere-EX system with 40 cores, we achieve 39.5 $\times $ speedup for the table operations and 39 $\times $ speedup for the complete algorithm using factor graphs with large potential tables.     

Drawing complete binary trees inside rectilinear polygons

Most of graph drawing algorithms draw graphs on unbounded planes. However, there are applications that require graphs to be drawn on the plane inside a given polygon. In this paper, a new algorithm for planar orthogonal drawing of complete binary trees inside rectilinear polygons is presented. Uniform distribution of nodes of graphs on drawing regions is one of the aesthetics criteria in graph drawing. The goal of this paper is to produce planar orthogonal drawings with a relatively uniform node distribution and few edge bends. The proposed algorithm can be considered as a generalization of the H-tree layout method for rectilinear polygons. A new linear time algorithm is also given for bisecting rectilinear polygons into two equi-area rectilinear sub-polygons.     

Decomposition of convex polygonal morphological structuringelements into neighborhood subsets

A discussion is presented of the decomposition of convex polygon-shaped structuring elements into neighborhood subsets. Such decompositions will lead to efficient implementation of corresponding morphological operations on neighborhood-processing-based parallel image computers. It is proved that all convex polygons are decomposable. Efficient decomposition algorithms are developed for different machine structures. An O(1) time algorithm, with respect to the image size, is developed for the four-neighbor-connected mesh machines; a linear time algorithm for determining the optimal decomposition is provided for the machines that can quickly perform 3×3 morphological operations     

知识图谱划分算法研究综述

知识图谱是人工智能的重要基石,因其包含丰富的图结构和属性信息而受到广泛关注.知识图谱可以精确语义描述现实世界中的各种实体及其联系,其中顶点表示实体,边表示实体间的联系.知识图谱划分是大规模知识图谱分布式处理的首要工作,对知识图谱分布式存储、查询、推理和挖掘起基础支撑作用.随着知识图谱数据规模及分布式处理需求的不断增长,...     

Straight-Line Drawing Algorithms for Hierarchical Graphs and Clustered Graphs

Hierarchical graphs and clustered graphs are useful non-classical graph models for structured relational information. Hierarchical graphs are graphs with layering structures; clustered graphs are graphs with recursive clustering structures. Both have applications in CASE tools, software visualization and VLSI design. Drawing algorithms for hierarchical graphs have been well investigated. However, the problem of planar straight-line representation has not been solved completely. In this paper we answer the question: does every planar hierarchical graph admit a planar straight-line hierarchical drawing? We present an algorithm that constructs such drawings in linear time. Also, we answer a basic question for clustered graphs, that is, does every planar clustered graph admit a planar straight-line drawing with clusters drawn as convex polygons? We provide a method for such drawings based on our algorithm for hierarchical graphs.     

Graph grammar‐driven parallel partial differential equation solver

The paper presents an extension of the composite programmable graph grammar (CP‐graph grammar) suitable for modeling the parallel direct solver algorithm utilized by the hp finite element method (hp‐FEM). In the proposed graph grammar model, the computational mesh is represented by a CP‐graph. The presented graph grammar models the solver algorithm by a set of graph grammar productions. The graph grammar model makes it possible to examine the concurrency of the algorithm by analyzing the interdependence between the atomic tasks, tasks and super‐tasks. The atomic tasks correspond to the graph grammar productions, representing basic undividable parts of the algorithms. The level of atomic tasks models the concurrency for the shared memory architectures. On the other hand, the tasks correspond to the groups of atomic tasks with predefined inter‐task communication channels. They constitute the grain for the decomposition of the parallel algorithm for the distributed memory architecture. Finally, the super‐tasks correspond to a group of tasks resulting from the execution of load balancing algorithm. The solver algorithm is tested on distributed memory linux cluster for up to 192 processors. Copyright © 2009 John Wiley & Sons, Ltd.     

Efficient algorithms for shortest distance queries on special classes of polygons

The problem of finding a rectilinear minimum bend path (RMBP) between two designated points inside a rectilinear polygon has applications in robotics and motion planning. In this paper, we present efficient algorithms to solve the query version of the RMBP problem for special classes of rectilinear polygons given their visibility graphs. Specifically, we show that given an unweighted graph G = (V, E), with ¦V¦ = N and ¦E¦ = M, algorithms to preprocess G in linear space and time such that the shortest distance queries — queries asking for the distance between any pair of nodes in the graph — can be answered in constant time and space are presented in this paper. For the case of a chordal graph G, our algorithms give a distance which is at most one away from the actual shortest distance. When G is a K-chordal graph, our algorithm produces an exact shortest distance in O(K) time. We also present a non-trivial parallel implementation of the sequential preprocessing algorithm for the CREW-PRAM model which runs in O(log² N) time using O(N + M) processors. After the preprocessing, we can answer the queries in constant time using a single processor.