三维合成炮叠前深度偏移

对国际上标准的SEG/EAEG模型进行了三维合成炮叠前偏移研究。与三维单炮叠前深度偏移不同 ,三维合成炮叠前偏移有一个叠前数据的合成过程 ,由于合成后数据量大大减少 ,所以合成炮偏移的计算量要比单炮偏移小得多。阐述了三维合成炮叠前偏移的实现过程 ,给出了相应公式。对SEG/EAEG盐丘模型的一个数据集进行了MPI并行计算 ,取得了良好的成像效果。所作的较多计算表明了三维合成炮叠前偏移的正确性和有效性 ,这为野外实际数据的三维叠前深度偏移提供了另一条有效途径。     

Map Reduce inspired loop mapping for coarse-grained reconfigurable architecture

Our work investigates how to map loops efficiently onto Coarse-Grained Reconfigurable Architecture （CGRA）. This paper examines the properties of CGRA and builds MapReduce inspired models for the loop parallelization problem. The proposed model has a more detailed performance metric and a more flexible unrolling scheme that can unroll different loop levels with different factors. A Geometric Programming based approach is proposed to resolve the optimization problem of loop parallelization problem. The proposed approach can find the optimal unrolling factor for each level loop, resulting in better parallelization of loops. Experimental results show that the proposed approach achieved up to 44% performance gain compared to the state-of-the-art loop mapping scheme.     

改进变异算子的差分进化算法并行性分析

针对并行差分进化算法的全局搜索能力和寻优的稳定性弱的现状,基于DE/best/1变异算子提出了一种改进的差分进化算法变异算子.该算子前期采用DE/best/1变异方法,当进化代数超过设定的进化代数值时,采用改进的变异算子.通过拓宽变异算子的搜索域来提高种群的多样性,提高了差分进化算法的寻优能力.对改进变异算子的并行差分进化算法进行了函数测试,实验结果表明:相比普通的变异算子,在相同种群规模的前提下,改进的差分变异算子拓宽了遗传算法的搜索域,提高了算法的全局搜索能力;在不同的种群规模下,改进的变异算子增强了算法的寻优稳定性.     

A two‐scale generalized finite element approach for modeling localized thermoplasticity

Predicting localized, nonlinear, thermoplastic behavior and residual stresses and deformations in structures subjected to intense heating is a prevalent challenge in a range of modern engineering applications. The authors present a generalized finite element method targeted at this class of problems, involving the solution of intrinsically parallelizable local boundary value problems to capture localized, time‐dependent thermo‐elasto‐plastic behavior, which is embedded in the coarse, structural‐scale approximation via enrichment functions. The method accommodates approximation spaces that evolve in between time or load steps while maintaining a fixed global mesh, which avoids the need to map solutions and state variables on changing meshes typical of traditional adaptive approaches. Representative three‐dimensional examples exhibiting localized, transient, nonlinear thermal and thermomechanical effects are presented to demonstrate the advantages of the method with respect to available approaches, especially in terms of its flexibility and potential for realistic future applications in this area. Parallelism of the approach is also discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

面向多核的基于RSTM系统的冲突管理策略

程序并行化是充分发挥多核处理器性能的有效手段。现有编程模型受锁、管道等同步方式的约束,并行度很难提高。针对上述问题,提出一种面向多核的基于Rochester软件事务存储(RSTM)系统的冲突管理策略,在现有编程语言中提供接口,通过事务方式提高程序并行度,以优先级方式解决2个事务发生冲突时的裁决问题,减少不必要的一致性验证,减小系统开销。     

基于Isolation Forest的并行化异常探测设计

异常探测具有广泛的应用,受到了工业界和学术界的共同关注。在众多异常探测方法中,Isolation Forest算法具有执行效率高、探测准确度好的特点,获得了众多应用。但是,传统Isolation Forest算法难以处理大规模数据。为解决此问题,设计了一种基于云计算平台的算法。具体地,使用Hadoop分布式存储系统和MapReduce分布式计算框架设计并实现了基于Isolation Forest的并行化异常探测算法PIFH。通过将探测模型构建和数据异常评价的过程并行化,提升了PIFH算法探测异常的执行效率,扩展了其应用范围。利用真实世界数据集验证了所提算法的执行效率和可扩展性。     

TMS320TCI6618中FFTC协处理器在LTE中的应用

采用DSP进行数字基带处理的基站以及软件无线电面临着严峻的考验,鉴于此,德州仪器公司(TI)推出了TMS320TCI6618 DSP,其中快速傅里叶变换协处理器(FFTC)将大幅度提升基带处理的性能.FFTC是一个可编程的加速器,专门针对LTE系统中的FFT与IFFT变换,本文详细介绍了其在LTE系统中的应用和DSP多核并行化处理,最后根据实测数据对FFTC协处理器的性能进行了评估.     

Generation of Efficient Nested Loops from Polyhedra

Automatic parallelization in the polyhedral model is based on affine transformations from an original computation domain (iteration space) to a target space-time domain, often with a different transformation for each variable. Code generation is an often ignored step in this process that has a significant impact on the quality of the final code. It involves making a trade-off between code size and control code simplification/optimization. Previous methods of doing code generation are based on loop splitting, however they have nonoptimal behavior when working on parameterized programs. We present a general parameterized method for code generation based on dual representation of polyhedra. Our algorithm uses a simple recursion on the dimensions of the domains, and enables fine control over the tradeoff between code size and control overhead.     

一种基于蚁群算法的TSP问题分段求解算法

群居性昆虫行为的研究为计算机科学家提供了设计分布式控制和优伦算法的有力方法。对以蚁群算法为代表的群集群能的研究已经逐渐成为一个研究热点。该文首先在蚁群算法的基础上提出了相遇算法,提高了蚁群算法蚂蚁一次周游的质量,然后将相遇算法与采用并行策略的分段算法相结合,提出一种基于蚁群算法的TSP问题分段求解算法。实验结果表明该算法有较好的有效性。     

Distributed Symbolic Bounded Property Checking

In this paper we describe an algorithm for distributed, BDD-based bounded property checking and its implementation in the verification tool SymC. The distributed algorithm verifies larger models and returns results faster than the sequential version.The core algorithm distributes partitions of the state set to computation nodes after reaching a threshold size. The nodes proceed with image computation on the nodes asynchronously. The main scalability problem of this scheme is the overlap of state set partitions. We present static and dynamic overlap reduction techniques.