A Class of Real-Time Parallel Combined Methods ofDigital Simulation for Large Systems

In this paper, a class of real-time parallel combined methods (RTPCM) of the digital simulation for a partitioned large system is presented. By means of combination of the parallelism across the system with the parallelism across the method, stiff and non-stiff subsystems are solved in parallel on parallel computer by a parallel Rosenbrock method and a parallel RK method, respectively. Their construction, convergence and numerical stability are discussed, and the digitalsimulation experiments are conducted.

Class of modified parallel combined methods of real-time numerical simulation for a stiff system

A class of modified parallel combined methods of real-time numerical simulation are presented for a stiff dynamic system. By combining the parallelism across the system with the parallelism across the method, and relaxing the dependence of stage value computation on sampling time of input function, a class of modified real-time parallel combined methods are constructed. Stiff and nonstiff subsystems are solved in parallel on a parallel computer by a parallel Rosen-brock method and a parallel RK method, respectively. Their order conditions and convergences are discussed. The numerical simulation experiments show that this class of modified algorithms can get high speed and efficiency.

Space decomposition based parallelization solutions for the combined finiteediscrete element method in 2D

The combined finiteediscrete element method （FDEM） belongs to a family of methods of computationalmechanics of discontinua. The method is suitable for problems of discontinua, where particles aredeformable and can fracture or fragment. The applications of FDEM have spread over a number of disciplinesincluding rock mechanics, where problems like mining, mineral processing or rock blasting canbe solved by employing FDEM. In this work, a novel approach for the parallelization of two-dimensional（2D） FDEM aiming at clusters and desktop computers is developed. Dynamic domain decompositionbased parallelization solvers covering all aspects of FDEM have been developed. These have beenimplemented into the open source Y2D software package and have been tested on a PC cluster. Theoverall performance and scalability of the parallel code have been studied using numerical examples. Theresults obtained confirm the suitability of the parallel implementation for solving large scale problems. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

A GPU-Based Parallel Algorithm for 2D Large Deformation Contact Problems Using the Finite Particle Method

Large deformation contact problems generally involve highly nonlinear behaviors,which are very time-consuming and may lead to convergence issues.The finite particle method(FPM)effectively separates pure deformation from total motion in large deformation problems.In addition,the decoupled procedures of the FPM make it suitable for parallel computing,which may provide an approach to solve time-consuming issues.In this study,a graphics processing unit(GPU)-based parallel algorithm is proposed for two-dimensional large deformation contact problems.The fundamentals of the FPM for planar solids are first briefly introduced,including the equations of motion of particles and the internal forces of quadrilateral elements.Subsequently,a linked-list data structure suitable for parallel processing is built,and parallel global and local search algorithms are presented for contact detection.The contact forces are then derived and directly exerted on particles.The proposed method is implemented with main solution procedures executed in parallel on a GPU.Two verification problems comprising large deformation frictional contacts are presented,and the accuracy of the proposed algorithm is validated.Furthermore,the algorithm’s performance is investigated via a large-scale contact problem,and the maximum speedups of total computational time and contact calculation reach 28.5 and 77.4,respectively,relative to commercial finite element software Abaqus/Explicit running on a single-core central processing unit(CPU).The contact calculation time percentage of the total calculation time is only 18%with the FPM,much smaller than that(50%)with Abaqus/Explicit,demonstrating the efficiency of the proposed method.

Combination Method for Parallel Computation in ODEs

In this paper, a 3rd order combination method with three processes and a 4th order combination method with five processes for solving ODEs are discussed. These methods are the Runge-Kutta method combined with a linear multistep method, which overcomes the defect of the 3rd order parallel Runge-Kutta method discussed in [1].

High performance parallel computing of large eddy simulation of the flow in a curved duct with square cross section

Large eddy simulation(LES) cooperated with a high performance parallel computing method is applied to simulate the flow in a curved duct with square cross section in the paper. The method consists of parallel domain decomposition of grids, creation of virtual diagonal bordered matrix, assembling of boundary matrix, parallel LDL^T decomposition, parallel solving of Poisson Equation, parallel estimation of convergence and so on. The parallel computing method can solve the problems that are difficult to solve using traditional serial computing. Furthermore, existing microcomputers can be fully used to resolve some large-scale problems of complex turbulent flow.

基于VIKOR的多网并行传输选网算法

海上异构无线网络通信场景下,针对单一无线网络难以承载大带宽业务的现实问题,提出了一种基于VIKOR的多网并行传输网络选择算法。该算法首先将多个网络的参数聚合,筛选可用网络组合;然后,结合网络属性的主客观权重和用户偏好权重得到网络属性的综合权重;最后,根据VIKOR方法对网络组合进行排序,选出最佳网络组合方案。仿真结果表明:该算法具有可行性,相较于传统算法,在舰船通信业务繁忙情况下选网综合性能更优。

PARALLEL ROSENBROCK METHODS FOR SOLVING STIFF SYSTEMS IN REAL-TIME SIMULATION

In this paper parallel Rosenbrock methods in real-time simulation are presented on parallel computers. Their construction, their convergence and their numerical stability are studied, and the numerical simulation experiments are conducted on a personal computer and a parallel computer respectively. [ABSTRACT FROM AUTHOR]

一种面向舰船结构毁伤的大变形流固耦合数值计算方法

水下爆炸导致舰船结构毁伤是一个复杂的非线性大变形流固耦合过程,高精度的流固耦合计算是获得高置信模拟结果的关键。基于浸没边界思想,本文提出一种面向大变形壳理论的流固耦合数值方法,可精确刻画流固耦合界面并高效求解流固界面约束方程。基于该方法,本文提出了完整的适用于水下爆炸舰船结构毁伤的大变形流固耦合数值计算方案,并基于大规模并行编程框架,研发形成适用于舰船结构毁伤的流固耦合大规模并行计算软件。与泰勒平板理论解和水下爆炸结构冲击响应实验数据等进行对比表明,本文方法可有效模拟大变形流固耦合工程问题,具备较高数值求解精度。在此基础上,完成了水下爆炸整船结构毁伤过程大规模数值模拟。该方法可有效应用于舰船毁伤等级评估,应用前景广阔。

盖挖与明挖组合建造地下交通枢纽方案研究

为满足北京城市副中心地下交通枢纽区域内的城市道路先行投入运营的需求,提出采用盖挖法与明挖法组合方法进行地下枢纽基坑开挖与支护的方案,主要特点如下:(1)将地下交通枢纽基坑分割为“盖挖基坑、明挖基坑和多级放坡基坑”等3个并列布置基坑;(2)盖挖区基坑与明挖基坑共用围护结构;(3)先完成盖挖区顶板结构施工,恢复城市道路运营,然后采用逆作法完成盖挖区负一层施工,随后同步开挖支护盖挖区两侧的明挖基坑和放坡区基坑;(4)盖挖区负二层和负三层采用顺作法施工。论文详细阐述了盖挖与明挖组合工法的施工工序,分析了组合工法的优势。鉴于盖挖区钢管柱始终处于基坑开挖扰动中,为此采用数值模拟方法并结合现场监测结果,分析了基坑开挖期间的钢管柱变形规律。结果表明,钢管柱水平变形和隆起变形指标均满足控制要求。本文提出的盖挖与明挖组合建造方案不但能确保地下交通枢纽区域内的城市道路尽快投入运营,而且并列基坑群中的3个基坑开挖支护及结构浇筑基本上相互独立,有效降低了盖挖区和明挖区基坑施工的相互影响,提高了施工效率。

一种基于敏捷集群计算系统的并行GMRES方法

随着通信系统和人工智能的飞速发展,以智慧城市、智慧工厂和智能制造等为代表的多种新型应用场景不断涌现,使得通信、感知和计算等系统的一体化成为技术发展的新趋势。人工智能新型应用场景对大规模高效敏捷计算提出了新的要求,基于敏捷集群计算系统,提出了一种并行广义最小残差(Generalized Minimal Residual, GMRES)方法,主要通过并行矩阵向量乘法和并行高瘦矩阵QR(Tall and Skinny QR,TSQR)分解实现Krylov子空间的高效并行构造,充分利用集群计算系统的计算和通信性能,实现大规模线性方程组Ax=b的快速求解,其中A为一个n×n的矩阵,在工程实践中,n可达数十万甚至百万规模。通过求解二维泊松方程的有限元离散得到的刚度方程,验证了算法的有效性。

COMBINATION METHOD FOR PARALLEL COMPUTATION IN ODE

In this paper,a 4th order parallel computation method with four processes for solving ODEs is discussed.This method is the Runge-Kutta method combined with a linear multistep method,which overcomes the difficulties of the 4th order parallel Runge-Kutta method discussed in [1].The concept of critical speedup for parallel methods is also defined,and speedups of some methods are analyzed by using this concept.

并行加速的局部变分迭代法及其轨道计算应用

为满足航天工程对轨道计算精度和实时性的高要求,近年来发展出了可以通过大步长积分修正实现快速精确求解的积分修正类方法.积分修正类方法有可并行计算的特点,然而在串行计算环境下会受到计算资源的限制,无法充分发挥其可并行加速的优势.此外,合理的计算参数通常难以预先确定,也使积分修正类方法大步长快速计算的优势难以充分体现.针对以上问题,利用积分修正类方法可并行计算的特点,提出了并行加速的局部变分迭代法PA-LVIM,通过将传统局部变分迭代法LVIM的并行计算量均摊到多个计算节点上,显著提高了计算速度.此外,还使用根据系统状态二阶导数分布确定计算参数的打磨法优化了PA-LVIM的计算参数,进一步发挥了其大步长快速计算的优势.求解了三个经典的轨道递推问题,仿真结果表明,PA-LVIM的加速效果明显,且经打磨法优化计算参数后,其计算效率又进一步得到提高,将当前主流方法的计算效率提高了5倍以上.

面向电大多尺度模型的大规模并行对称半正定亚网格FDTD算法

针对计算电磁学算法应用于实际工程问题时面临的计算模型电大尺寸多尺度瓶颈,基于自研的高性能并行计算框架JASMIN,通过提出融合h-自适应时间积分算法流程的对称半正定亚网格FDTD算法流程,实现了具备大规模并行能力的亚网格时域有限差分(FDTD)算法.该算法保留了FDTD算法高并行可扩展性优势,同时可局部使用细化网格剖分电大尺寸模型精细结构部位,支持粗网格区域和细网格区域分别采用大时间步长和小时间步长进行迭代计算.算例表明,该方法在解决电大多尺度电磁模拟问题时,具有较强的并行可扩展性,同时能够保证数值计算结果的精度和稳定性,与传统的FDTD算法相比,可显著降低内存需求,提高计算效率.

基于并行深度卷积神经网络的舰船通信异常数据检测研究

为了提高通信异常数据检测效果,设计基于并行深度卷积神经网络算法的大规模舰船通信异常数据检测方法。采集大规模舰船通信数据,采用小波变换对数据实施降噪处理,将降噪后数据输入并行深度卷积神经网络中,经过模型训练提取特征,利用Softmax分类函数得出舰船通信异常数据特征,输出舰船通信异常数据检测结果。实验结果表明:该方法可有效实现大规模舰船通信异常数据检测,其加速比最高,并行效果最优;具有较强的大规模舰船通信数据集检测能力,提高大规模舰船通信异常数据检测效果。

国产化大功率船舶DC/DC变换器研制

设计了一台用于船舶综合电力系统直流区域配电系统的全国产化25kWDC/DC变换器。首先,介绍了电路工作原理,给出了参数设计方法和关键器件的国产化选型,提出了多模块串并联组合均压均流控制策略。其次,基于状态空间平均法建立了系统小信号模型,设计了闭环控制器。最后,搭建了实验样机,验证了其可行性。

大模型分布式训练方法研究综述

随着ChatGPT的问世,各种大模型(Large Language Model,LLM)产品不断涌现,一个属于大模型的时代正在来临。然而,由于大模型面临着参数规模大、训练时间长的难点,现有传统机器学习模型训练方法并不适用于大模型的训练,亟需探索新的分布式训练方法与策略。针对这些问题,从三个方面综述大模型分布式训练方法在过去十几年里的进展,包含分布式训练的架构并行加速策略以及内存和计算优化方面的内容,最后提出了未来可以探索的研究方向。

不同加热条件下脱水设备与工艺的试验研究

针对传统的蔬菜热风加热干燥和远红外辐射加热干燥方式所存在的问题,采用组合加热和并流引风技术方案,将远红外辐射与热风两种加热方式优化组合,充分发挥各自优点,整合成为一种新的组合加热式干燥技术。不同加热条件下的对比试验结果表明,组合加热的干燥速度最快,平均单位能耗较低。综合分析认为,蔬菜干燥中应采用"先热风、后远红外"的组合加热形式。设备引风管和供风管的连接管直径自上而下依次减小,即供给各层干燥箱的热风量和从各层干燥箱的引风量自上而下也相应地减小,满足了各层干燥箱对风量的需求。

大规模GNSS基准站网快速同步处理方法研究

目前我国GNSS连续运行基准站网已基本建设完毕,全国范围内建设完成约2000个GNSS连续运行基准站。随着站点规模的加大,数据计算的效率也迫切需要提高,采用传统的高精度数据处理软件已适应不了大规模GNSS网的数据解算要求。本文基于BERNESE5.2软件研究了我国"陆态网络工程"260个基准站的大规模GNSS网同步数据处理方法,通过修改源程序及利用并行计算技术,成功实现了陆态网络基准站快速、高效、高精度的数据计算能力。实例验证表明,陆态网络单天260个站的数据在无需分区的情况下,可在1 h内获得全球框架下的约束解,解算的框架点坐标精度在毫米量级,大大提高了国家数据中心的大规模GNSS网数据处理能力。

大跨屋盖结构风致抖振响应研究

建立基于非定常风荷载的大跨屋盖结构风致动力响应的试验和分析方法。该方法采用多通道测压系统扩大同步测压点的数目,更全面地获得屋盖表面风压的时空特性,为准确计算结构风致响应奠定了基础。在动力分析方法上应用CQC法计算屋盖结构的风振响应,考虑多模态及模态间的耦合影响,编制了结构风致动力效应计算程序SWDP。最后对上海铁路南站工程屋盖结构的抖振响应结果进行了计算和分析。结果表明,采用多通道测压系统可以有效地扩大同步测压点的数目;基于非定常风荷载的CQC方法是计算复杂大跨屋盖结构风振响应的有效方法;背景响应对于总响应的贡献通常是不可忽略的。