高可扩展可容错的无网格/粒子程序petaPar及其测试

petaPar 粒子模拟程序面向千万亿次级计算,在统一框架下实现两种广受关注的粒子模拟算法：光滑粒子流体动力学（Smoothed Particle Hydrodynamics,SPH）和物质点法（Material Point Method,MPM)。代码支持多种材料模型、强度模型和失效模型,适合模拟大变形、高应变率和流固耦合问题。支持纯 MPI 和 MPI+X 混合两种并行模型。系统具有可容错性,支持无人值守变进程重启。在Titan 上测试表明,petaPar 可线性扩展到 26 万 CPU 核,SPH 和 MPM 算法并行效率相对 8 192 核分别为 87% 和 90%。     

三维有限差分计算中大规模网格生成及显示技术

针对爆炸与冲击问题并行仿真计算软件PMMIC-3D（Parallel Multi-Material in Cell 3D）的计算网格为正交六面体网格的特点,开发与PMMIC-3D接口统一的可对任意复杂三维实体模型进行大规模有限差分网格生成的三维前处理软件MESH-3D.MESH-3D采用CSG和STL模型两种建模方式进行复杂实体建模,并采用基于边的整体切片算法,借鉴计算机图形学中的扫描线填充算法完成三维有限差分网格划分.在绘制网格时,删除网格单元的公共面,大大缩短计算时间和减少存储空间,实现对网格的快速消隐显示.MESH-3D可实现百亿量级网格单元的生成和显示.三维前处理软件MESH-3D的开发有力地支持爆炸与冲击问题的仿真计算.     

确定简单多边形旋转时碰撞部位的扫描算法

给定平面内任意两个互不相交的简单多边形Ｐ是Ｑ。若Ｐ在平面内绕０点旋转时与ＡＱ碰撞,讨论其碰撞部位的判定问题,通过分析多边形关于０点的单调边,在平面扫描算法的榧耻提出了曲线扫描法,给这一总理２的Ｏ（（ｍ＋ｎ）ｌｏｇ（ｍ＋ｎ））算法,与现有的算法相比,降低了时间复杂性,这一方法在计算几何和计算机图形学等领域具有一定的理论和实吓价值。     

基于GPU粒子系统的烟花模拟

针对复杂3D烟花模拟方法存在计算量大,效率不高和逼真性不够等问题,提出了一种基于GPU粒子系统的烟花模拟方法.采用三维网格模拟烟花形状,通过扩展双面深度剥离算法在网格上快速均匀采样,提高顶点信息收集效率;提出并行迭代聚类算法,实现多层次的烟花爆炸,达到烟花的多重性效果;应用逆动力学原理控制烟花中粒子的运动,给出形状约束粒子的速度公式.实验结果表明,该算法对烟花模拟效果在真实性和速度上都有所提高.     

基于二次插值重构有限元法的动态裂纹扩展模拟

基于二次插值重构有限元法（Twice interpolation Finite Element Method, TFEM）分析动态断裂力学问题并进行数值实验,考察TFEM在裂纹动态扩展模拟中的准确性和可靠性.由于TFEM保证节点处梯度场的连续性,因此裂尖附近的应力场可以得到较好的逼近.把该算法成功移植到自主开发的三维裂纹扩展仿真软件（ZonCrack）中.利用ZonCrack进行的裂纹扩展,分析结果表明：TFEM得到裂尖应力强度因子（Stress Intensity Factor, SIF)与解析解基本一致;裂纹扩展的模拟结果与实验值吻合良好.     

网络通信协议的属性文法规格说明

本文给出一个基于属性文法的网络通信协议的形式说明与自动生成的模型.首先引入了一个扩展的属性文法描述工具,讨论了用其描述协议的并行、同步、延时（时序）等特性的有关问题；然后研究了基于属性文法的网络通信协议自动生成环境及其核心算法——属性计算（即语义分析）算法.     

考虑冲击温度影响的物质点法算法

针对超高速冲击使结构瞬间产生极高的温度并造成结构软化现象的问题,提出考虑冲击温度影响的改进物质点法算法,采用Taylor杆的撞击过程模拟分析这一现象。将模拟结果与经典物质点法算法对同一算例的计算结果进行对比,结果显示改进物质点法算法计算结果精度可提高0.77%。     

EPCCL理论的求交知识编译算法

超扩展规则是对扩展规则的扩充,基于超扩展规则能够求得任意两个非互补且不相互蕴含的子句所能扩展出极大项集的交集、差集和并集,并将所得结果以EPCCL（each pair of clauses contains complementary literals）理论的形式保存.基于超扩展规则的性质,本文提出了一种新的EPCCL理论编译算法：求交知识编译算法IKCHER（intersection approach to knowledge compilation based on hyper extension rule）,该算法适合难解类SAT问题的知识编译,同时是一种可并行的知识编译算法.本文还研究了如何实现多个EPCCL理论的求交操作,证明了EPCCL理论的求交过程是可并行执行的,并设计了相应并行求交算法PIAE（parellel intersection of any number of EPCCL）.通过对输入EPCCL理论对应普通子句集的利用,设计了一种高效的并行求交算法imp-PIAE（improvement of PIAE）.基于上述算法本文还设计了两个并行知识编译算法P-IKCHER（IKCHER with PIAE）和impP-IKCHER（IKCHER withimp-PIAE）,分别采用PIAE并行合并算法和imp-PUAE并行合并算法.最后,通过实验验证了大部分情况下IKCHER算法的编译质量是目前为止所有EPCCL理论编译器中最优的,P-IKCHER算法所使用的合并策略并没有起到加速的效果,反而使得编译效率和编译质量有所下降,而impP-IKCHER算法提高了IKCHER算法的编译效率,四核并行下最高可提高两倍.     

一种基于内点保留和边缘点删除的二值图象细化算法

提出了一种同时基于边级点删除和内点保留了实现并行细化算法的新方法,与目前已有的算法比较,它能够完整地保持原图象的连通性,所获得的骨架对称性好且能够保证骨架宽度为１个象素点等,用Ｃ／Ｃ＋＋编程实现后,在ＩＢＭ４８６微机上进行实验,结果表明,提出的细化算法为解决二值图象（特别是复杂二值图象）的细化问题提供了一种新方法。     

基于Spring的轻量级数据访问框架扩展点研究

针对传统方法对扩展点协同运算考虑不足，导致扩展点运算速度较慢和精度较低等问题，提出基于Spring的轻量级数据访问框架扩展点研究。使用Spring开源框架进行框架开发，在框架中建立扩展点等参单元，确定框架扩展点的积分点个数、坐标等基本参数。确定后在框架扩展点中添加适应度函数进行并行辨识，运用MPSCO算法对框架扩展点的协同运算进行优化。模拟多种访问数据对所设计框架的应用效果进行验证，实验结果表明，搭载设计框架扩展点的框架在运算时精度更高，时延更低，证明该框架可以满足设计要求。     

Development of parallel 3D RKPM meshless bulk forming simulation system

A parallel computational implementation of modern meshless system is presented for explicit for 3D bulk forming simulation problems. The system is implemented by reproducing kernel particle method. Aspects of a coarse grain parallel paradigm—domain decompose method—are detailed for a Lagrangian formulation using model partitioning. Integration cells are uniquely assigned on each process element and particles are overlap in boundary zones. Partitioning scheme multilevel recursive spectrum bisection approach is applied. The parallel contact search algorithm is also presented. Explicit message passing interface statements are used for all communication among partitions on different processors. The parallel 3D system is developed and implemented into 3D bulk metal forming problems, and the simulation results demonstrated the efficiency of the developed parallel reproducing kernel particle method system.     

非均匀区域油藏模拟负载平衡的分区并行算法*

基于分布式并行计算机系统,对一类非均匀区域的油藏数值模拟问题,采用了区域分解方法并行求解,给出了并行求解的负载平衡模型及区域负载平衡的一种有效分区算法,从而将这类油藏数值模拟问题均衡映射到并行环境中,高效地并行求解.在黑油油藏数值模拟并行软件的研究中,实验结果表明,该算法有利于提高加速比.     

A high performance framework for modeling and simulation of large-scale complex systems

Due to the quick advances in the scale of problem domain of complex systems under investigation, the complexity of multi-input component models used to construct logical processes (LP) has significantly increased. High-performance computing technologies have therefore been extensively used to enable parallel simulation execution. However, the traditional multi-process parallel method (MPM) executes LPs in parallel on multi-core platforms, which ignores the intrinsic parallel capabilities of multi-input component models. In this study, a vectorized component model (VCM) framework has been proposed. The design aims to better utilize the parallelism of multi-input component models. A two-level composite parallel method (CPM) has then been constructed within the framework, which can sustain complex system simulation applications consisting of multi-input component models. CPM first employs MPM to dispatch LPs onto a multi-core computing platform. It then maps VCMs to the multiple-core platform for parallel execution. Experimental results indicate that (1) the proposed VCM framework can better utilize the parallelism of multi-input component models, and (2) CPM can significantly improve the performance comparing to the traditional MPM. The results also show that CPM can effectively cope with the size and complexity of complex simulation applications with multi-input component models.     

A multi-mesh MPM for simulating the meshing process of spur gears

A numerical scheme is presented to simulate the meshing process of spur gears, based on the material point method (MPM). To allow engagements at successive contact points and subsequent separation between neighboring gear teeth, a contact/sliding/separation procedure in a multi-mesh environment without using master/slave nodes is proposed so that the no-slip contact constraint inherent in the existing MPM can be released. Individual drive members rotate around corresponding axes, through which simulated angular velocity transmission is in good agreement with the analytical solution. It appears from the simulation results presented here that the multi-mesh MPM could become a robust spatial discretization tool for gear design problems that involve large rotation, contact/sliding and separation.     

A Novel Plastic Phase-Field Method for Ductile Fracture with GPU Optimization

In this paper, we articulate a novel plastic phase-field (PPF) method that can tightly couple the phase-field with plastic treatment to efficiently simulate ductile fracture with GPU optimization. At the theoretical level of physically-based modeling and simulation, our PPF approach assumes the fracture sensitivity of the material increases with the plastic strain accumulation. As a result, we first develop a hardening-related fracture toughness function towards phase-field evolution. Second, we follow the associative flow rule and adopt a novel degraded von Mises yield criterion. In this way, we establish the tight coupling of the phase-field and plastic treatment, with which our PPF method can present distinct elastoplasticity, necking, and fracture characteristics during ductile fracture simulation. At the numerical level towards GPU optimization, we further devise an advanced parallel framework, which takes the full advantages of hierarchical architecture. Our strategy dramatically enhances the computational efficiency of preprocessing and phase-field evolution for our PPF with the material point method (MPM). Based on our extensive experiments on a variety of benchmarks, our novel method's performance gain can reach 1.56× speedup of the primary GPU MPM. Finally, our comprehensive simulation results have confirmed that this new PPF method can efficiently and realistically simulate complex ductile fracture phenomena in 3D interactive graphics and animation.     

基于粒子分解的SPH并行算法研究与应用

作为一种典型的拉格朗日型无网格数值方法,光滑粒子流体动力学（SPH）方法在模拟自由表面流问题时具有天然优势。但是,该方法计算量大、耗时长,为此提出了一种基于粒子分解的SPH并行算法。该算法将所有粒子平均分配到各个进程进行计算,每个时间步通信仅调用一次发送、接收和广播函数,因此易于实现且可扩展性较好。应用该并行算法对二维溃坝流和三维液滴冲击液膜问题进行数值模拟,结果表明：该并行算法能显著减少模拟所消耗的计算时间,有利于进行三维大规模计算问题的数值模拟;当粒子数大于百万时,最大加速比可达30以上。     

舰载机飞行仿真可视化研究

航空母舰的研究主要分布在舰载机的起降方式及飞行甲板的布置上,仅仅通过理论分析这些过程是很难发现问题的,提出了飞行可视化研究;基于高层体系结构(HLA)仿真平台搭建整个舰载机的飞行仿真系统,并利用MultiGen Creator/ Vega和VC 的虚拟现实仿真平台实现了舰载机飞行仿真全过程的可视化,论述了多自由度(DOF)三维模型的建立、视景仿真系统的软件设计、坐标转换、数据平滑等关键技术,给出了三维仿真结果.应用结果表明,该仿真系统结构合理可靠,可逼真地演示舰载机的整个飞行过程,成为验证舰载机的调度、导引、控制等算法的正确性和有效性的有效手段.     

三维几何约束求解的自由度归约算法

三维几何约束求解在装配设计、几何造型和动力学分析等领域有着广泛的应用．在分析基本几何元素间的约束关系对刚体自由度状态影响的基础上,提出刚体自由度的归约算法,以求得满足约束后刚体的自由度状态空间;以刚体自由度状态空间分析为基础,实现对合理约束的推理求解和约束一致性维护,该算法解决了三维几何约束求解中自由度计算问题,同时避免了一些推理求解算法中出现的“组合爆炸”问题．