A memory organization for parallel computers

In this paper a computer memory system intended for storing an arbitrary sequence of multidimensional arrays is described. This memory system permits a parallel access to the cuts distinguished in the given array by fixing one of the coordinates and to the large set of parallelepipeds which are the same dimension subarrays of the given arrays.     

A system organization for parallel image processing

One of the problems in the development of multiprocessor systems for image analysis is the selection and efficient utilization of an interconnection network between the multiple processing units. This paper proposes a system organization centered around a class of interconnection networks and a global bus. Control schemes are developed for realizing the intertask communication requirements typically encountered in the parallel formulation of problems for image analysis. These schemes are simple, distributed and efficient. The utility of this organization is demonstrated by evaluating the performance of two applications.     

A parallel shooting technique for solving dissipative ODE's

In this paper, we study different modifications of a class of parallel algorithms, initially designed by A. Bellen and M. Zennaro for difference equations and called “across the steps” methods by their authors, for the purpose of solving initial value problems in ordinary differential equations (ODE's) on a massively parallel computer. Restriction to dissipative problems is discussed which allow these problems to be solved efficiently, as shown by the simulations.     

A parallel pruning technique for highly asymmetric assignmentproblems

We introduce a new two-phase technique to solve highly asymmetric assignment problems. In the first phase, the assignment problem is decomposed into subproblems which are solved in parallel. The first phase is used to exclude certain suboptimal assignments from consideration in the second phase. In the second phase, the optimal assignment is finalized. We show that the two-phase algorithm can reduce the theoretical time bound for solving an n×k assignment problem (nk/_n     

A query-oriented file organization technique

A new technique for organizing and accessing a table of queries satisfied by at least one record of a file is proposed.

The time required to search for an entry in such a table depends only on the number of the keywords of the query and not on the number of entries of the table.     

An in-depth study of graph partitioning measures for perceptual organization

In recent years, one of the effective engines for perceptual organization of low-level image features is based on the partitioning of a graph representation that captures Gestalt inspired local structures, such as similarity, proximity, continuity, parallelism, and perpendicularity, over the low-level image features. Mainly motivated by computational efficiency considerations, this graph partitioning process is usually implemented as a recursive bipartitioning process, where, at each step, the graph is broken into two parts based on a partitioning measure. We focus on three such measures, namely, the minimum, average, and normalized cuts. The minimum cut partition seeks to minimize the total link weights cut. The average cut measure is proportional to the total link weight cut, normalized by the sizes of the partitions. The normalized cut measure is normalized by the product of the total connectivity (valencies) of the nodes in each partition. We provide theoretical and empirical insight into the nature of the three partitioning measures in terms of the underlying image statistics. In particular, we consider for what kinds of image statistics would optimizing a measure, irrespective of the particular algorithm used, result in correct partitioning. Are the quality of the groups significantly different for each cut measure? Are there classes of images for which grouping by partitioning does not work well? Also, can the recursive bipartitioning strategy separate out groups corresponding to K objects from each other? In the analysis, we draw from probability theory and the rich body of work on stochastic ordering of random variables. Our major conclusion is that optimization of none of the three measures is guaranteed to result in the correct partitioning of K objects, in the strict stochastic order sense, for all image statistics.     

面向大规模并行数值模拟的一种高效数据组织方式

针对现代大规模并行数值模拟数据的存储与I/O问题,提出一种高效的数据组织方式。该方式基于XML VTK格式数据I/O通用模块,输出支持随机访问、数据压缩及可移植二进制编码的并行数据文件。与传统方式相比,按照这种方式组织数据,可以降低数据的存储规模,提高可视化处理的速度。经测试,数据存储开销可降低到原存储开销的30%,数据载入到可视化软件的速度提高90%以上。且这种组织方式适于引入out-of-core技术进一步提高可视化处理效率。     

A parallel algorithm for exact solution of linear equations via congruence technique

We present a parallel algorithm for computing the exact solution of a system of linear equations via the congruence technique. The basic idea of the technique is to convert the original system of equations into a system of congruences modulo various primes, and combine the solutions by the application of the Chinese remainder theorem. The parallel congruence algorithm proposed in this paper requires only local communication among the processors and is particularly suitable for implementation on distributed-memory multiprocessors and systolic computing systems. We have implemented the parallel congruence algorithm on an Intel cube and obtained an efficiency of greater than 90%.     

Multiskewing-a novel technique for optimal parallel memory access

The disparity between the processing speed and the data access rates presents a serious bottleneck in pipelined/vector processors. The memory bank conflict in interleaved system can be alleviated by skewing, for scientific computations performing functions on varieties of submatrices. So far uniskewing involving periodic and linear functions have been studied. Several difficulties encountered in such schemes are that they require a prime number of memory modules, may create wasted memory space, or addressing functions and the alignment network become complex. We present a new technique, termed multiskewing, which applies multiple functions on different sections of the array. Each of these functions may be as simple as a linear shift. We show that some of the advantages are that it does not require a prime number of memory, memory utilization factor is 100%, maintains the logical structure of the array, and allows optimal memory access of a large class of submatrices     

An axiomatic proof technique for parallel programs I

Summary A language for parallel programming, with a primitive construct for synchronization and mutual exclusion, is presented. Hoare's deductive system for proving partial correctness of sequential programs is extended to include the parallelism described by the language. The proof method lends insight into how one should understand and present parallel programs. Examples are given using several of the standard problems in the literature. Methods for proving termination and the absence of deadlock are also given.This research was partially supported by National Science Foundation grant GJ-42512.     

Deterministic organization of index-based numerical parallel processing

A technique is proposed for deterministic organization or index-based parallel computing. The technique is designed for numerical methods of algebra and calculus and utilizes a special multiprocessor architecture.Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 133–152, July–August, 1992.     

Classified road detection from satellite images based on perceptual organization

Extracting roads from satellite images is an important task in both research and practice. This work presents an improved model for road detection based on the principles of perceptual organization and classification fusion in human vision system (HVS). The model consists of four levels: pixels, primitives, structures and objects, and two additional sub‐processes: automatic classification of road scenes and global integration of multiform roads. Based on the model, a novel algorithm for detecting roads from satellite images is also proposed, in which two types of road primitives, namely blob‐like primitive and line‐like primitive are defined, measured, extracted and linked using different methods for dissimilar road scenes. A hierarchical search strategy driven by saliency measurement is adopted in both linking processes. The blob primitives are linked using heuristic grouping and the line primitives are connected through genetic algorithm (GA) evolution. Finally, all of the linked road segments are normalized with centre‐main lines and integrated into global smooth road curves through tensor voting. Experimental results show that the algorithm is capable of detecting multiform roads from real satellite images with high adaptability and reliability.     

A new parallel breadth first tabu search technique for solving production planning problems

This paper presents a new parallel breadth first oriented tabu search extension, which can be used to improve existing tabu search procedures for production planning problems. Especially it is shown that this distributed technique considerably improves existing efficient sequential procedures for a well-known assembly line balancing problem. Since this technique does not require any communication besides exchanging the solutions reached at the end of the computation, it can be installed on nearly every distributed system.     

基于五层十五级遥感数据结构的并行算法研究

针对当前环境与监测预报小卫星宽覆盖和海量数据显示与处理不足的现状,设计五层十五级遥感数据组织结构,并依据此结构设计一种新的并行计算算法,得到并行计算的最大近优估算值,优化环境与监测预报小卫星海量数据的遥感产品生产能力,提高环境监测预报效率。     

A camera calibration technique using three sets of parallel lines

This paper presents a new method for three-dimensional camera calibration in which the rotation parameters are decoupled from the translation parameters. First, the rotation parameters are obtained by projecting three sets of parallel lines independently of the translation parameters and the imaging distance from the lens to the image plane. The virtual line passing through the image center, which is calculated by perspective projection of a set of parallel lines, depends only on the rotation parameters. Next, the translation parameters and the imaging distance are analytically obtained. Experimental results are used to show how the camera model can be accurately reconstructed in an easily prepared environment.     

面向并行负载平衡的数据剖分技术*

对传统的数据剖分技术和负载平衡对大规模并行计算性能的影响进行了综述,介绍了目前典型的几何剖分方法和图剖分方法的特点,并分析比较各种剖分算法及常用剖分软件包(ParMETIS、Zoltan、JOSTLE等)在实际应用中的优缺点,深入探讨了数据剖分技术是如何对超大规模数值模拟计算任务进行高效划分以解决负载平衡问题的,以期为开展并行计算研究和并行性能优化的研究人员提供参考。     

On an automatically parallel generation technique for tetrahedral meshes

A program for the efficient parallel generation of tetrahedral meshes in a wide class of three-dimensional domains having a generalized cylindrical shape is presented. The applied mesh generation strategy is based on the decomposition of some 2D-reference domain into simply connected subdomains. By means of the reference triangulations of these subdomains the tetrahedral layers are built up in parallel. Adaptive grid controlling as well as nodal renumbering algorithms are involved. In the paper several examples are included to demonstrate both the capabilities of the program and the adequate handling with the implemented method of parallelization.     

The perceptual organization of texture flow: a contextual inference approach

Locally parallel dense patterns-sometimes called texture flows-define a perceptually coherent structure of particular significance to perceptual organization. We argue that with applications ranging from image segmentation and edge classification to shading analysis and shape interpretation, texture flows deserve attention equal to edge segment grouping and curve completion. This paper develops the notion of texture flow from a geometrical point of view to argue that local measurements of such structures must incorporate two curvatures. We show how basic theoretical considerations lead to a unique model for the local behavior of the flow and to a notion of texture flow "good continuation." This, in turn, translates to a specification of consistency constraints between nearby flow measurements which we use for the computation of globally (piecewise) coherent structure through the contextual framework of relaxation labeling. We demonstrate the results on synthetic and natural images.     

The complex role of perceptual organization in visual display design theory

Two experiments were performed to test and extend the current ‘emergent features’ approach to display design for dynamic failure detection tasks. It was predicted that a display whose emergent features were well-mapped to goal-relevant task invariants would lead to better failure detection performance than either of two alternative displays. Contrary to prediction, Experiment 1 showed no differences in failure detection speed or accuracy across displays. The reason for this may have been that subjects did not discover the mapping between the mathematical properties of the task and the emergent feature, so in Experiment 2 subjects were explicitly instructed about the mapping and were advised on how to use the display geometry to help their performance. A significant difference in failure detection speed emerged, but the display supporting fastest performance was not the one with the well-mapped emergent feature. These results suggest that alternative perceptual organizational factors were at work which overpowered the intended effect. The results also underscore the difficulty of developing a theory of display design, and their impact on current theories is outlined.