Application of Bernstein Expansion to the Solution of Control Problems

We survey some recent applications of Bernstein expansion to robust stability, viz. checking robust Hurwitz and Schur stability of polynomials with polynomial parameter dependency by testing determinantal criteria and by inspection of the value set. Then we show how Bernstein expansion can be used to solve systems of strict polynomial inequalities.     

一种求解符号回归问题的粒子群优化算法

符号回归以构建一个能拟合给定数据集的函数模型为目的, 是对基本函数、运算符、变量等进行组合优化的过程.本文提出了一种求解符号回归问题的粒子群优化算法.算法以语法树对函数模型进行表达, 采用基因表达式将语法树编码为一个粒子, 设计了粒子的飞行方法及$r$-邻域环状拓扑的粒子学习关系.为使粒子具有跳出局部极值的能力和减轻粒子快速趋同对全局寻优造成的不利影响, 分别设计了突变算子和散开算子.此外, 为了得到比较简洁的函数模型, 在粒子的评价函数中以罚函数的方式对编码的有效长度进行控制.仿真实验表明, 提出的算法可以获得拟合精度更高、简洁性更好的函数模型.     

嵌入式系统程序优化方法的研究

嵌入式系统往往对实时性、系统功耗和程序代码长度有特殊的要求，本文从程序设计的角度讨论满足这些要求的程序代码优化方法。文中首先讨论了程序执行时间的优化方法，随后讨论了程序代码长度的优化方法，最后讨论了程序功耗的优化方法。     

Applications of Symbolic Execution to Program Testing

The advanced method of symbolic evaluation can be applied to program testing situations with results close to those of formal correctness proofs–but without the high cost.     

Formalization of Bernstein Polynomials and Applications to Global Optimization

This paper presents a formalization in higher-order logic of a practical representation of multivariate Bernstein polynomials. Using this representation, an algorithm for finding lower and upper bounds of the minimum and maximum values of a polynomial has been formalized and verified correct in the Prototype Verification System (PVS). The algorithm is used in the definition of proof strategies for formally and automatically solving polynomial global optimization problems.     

Symbolic Semantics and Program Reduction

A class of transformations of functional programs based on symbolic execution and simplification of conditionals is presented. The operational symbolic semantics of a family of functional languages is defined exploiting a set-theoretic notion of symbolic constants. An effective transformation able to simplify a functional program via removal of conditionals is discussed. Finally, it is shown that a structural approach, based on abstract data type specifications, provides a suitable representation for symbolic constants.     

An Approach to Reachability Determination for Static Analysis Defects with the Help of Dynamic Symbolic Execution

Programming and Computer Software - Program analysis methods for error detection are conventionally divided into two groups: static analysis methods and dynamic analysis methods. In this paper, we...     

Program Behavior at the Symbolic Level

No application programmer writes machine-language programs–i.e., strings of ones and zeroes. That primitive pursuit has long been reserved for those few who create the very first modules of a software system for new hardware. Instead, programmers make use of a wide spectrum of symbolic programming languages, ranging from assembly code to high-level languages such as Fortran, Cobol, and the Algol family. Every programming language has semantics which define some abstract machine. For the assembly-language programmer this machine bears a great resemblance to the actual hardware on which the program will be interpreted, but even here the programmer will frequently use system-defined subroutines or macros which represent extensions of the base hardware facilities. The high-level language programmer's abstract machine reflects the control mechanisms and data structures characteristic of the language. The Fortran programmer, for example, can think in terms of multidimensional array structures, DO loops, subprogram facilities, and so on. In principle he need never be concerned with the manner in which his abstract Fortran machine is to be realized by a particular hardware and software system. The user of a modern electronic hand calculator needs no knowledge of the works inside the box, and a modern high-level language system should present to its users an equally consistent environment, completely defined in terms of the syntax and semantics of the source language.     

An Approximate Simulation Approach to Symbolic Control

This paper introduces a methodology for the symbolic control of nonlinear systems based on an approximate notion of simulation relation. This notion generalizes existing exact notions of simulation and is completely characterized in terms of known stabilizability concepts. Equipped with this notion we show how, under certain stabilizability assumptions, we can construct finite or symbolic models for nonlinear control systems. Synthesizing controllers for the original control system can then be done by using supervisory control techniques on the finite models and by refining the resulting finite controllers to hybrid controllers enforcing the specification on the original continuous control system. The proposed design methodology can be seen as a correct-by-design way of obtaining both the feedback control laws as well as the control software responsible for deciding which law is executed and when.      

PVM并行程序向GAMMA迁移的方法

首先分析了PVM消息传递的通信机制以及影响其通信效率的原因，然后介绍了一种基于主动消息技术的通信系统GAMMA。在此基础上提出了将PVM程序迁移到GAMMA的方法。     

Space-Time Domain Expansion Approach to VLSI and Its Application to Hierarchical Scene Matching

VLSI technology has recently received increasing attention due to its high performance and high reliability. Designing a VLSI structure systematically for a given task becomes a very important problem to many computer engineers. In this paper, we present a method to transform a recursive computation task into a VLSI structure systematically. The main advantages of this approach are its simplicity and completeness. Several examples, such as vector inner product, matrix multiplication, convolution, comparison operations in relational database and fast Fourier transformation (FFT), are given to demonstrate the transformation procedure. Finally, we apply the proposed method to hierarchical scene matching. Scene matching refers to the process of locating or matching a region of an image with a corresponding region of another view of the same image taken from a different viewing angle or at a different time. We first present a constant threshold estimation for hierarchical scene matching. The VLSI implementation of the hierarchical scene matching is then described in detail.     

一种Java程序Chopping方法

程序Chopping对于程序理解、分析、调试、测试等具有重要的意义。已有的Chopping方法主要基于相互连接的系统依赖图(SDG),对于大程序这种SDG描述通常非常复杂,易导致程序Chopping结果不准确。针对这一问题,基于带标签的Java程序描述方法,提出一种Java程序Chopping方法。该方法利用这种描述附带的程序依赖信息,分析参数依赖关系,并在此基础上给出Chopping算法。此程序Chopping方法能把Java程序方法间的程序Chopping问题转换到Java程序方法内进行分析,程序依赖图具有结点少、可重用、可并发构造等优点。最后通过实例和实验给出程序Chopping方法的实施过程及有效性。     

A Symbolic Approach to Freeform Parametric Surface Blends

This paper presents a symbolic approach to the computation of blend surfaces across piecewise polynomial and rational surfaces. Curves in the parameter space of the primary surfaces can be specified as the rail curves, also known as trimlines, of the blend. Several techniques which require various levels of user interaction are presented for defining the cross-boundary tangent curves along the rail curves. The resulting blend is represented as a polynomial surface having tangent plane continuity with the primary surfaces to an accuracy bounded only by the machine precision. Also presented is a normalization method that approximates unit vector fields, an approach that might benefit other applications such as offset approximation and animation curve construction. © 1997 by John Wiley & Sons, Ltd.     

The Qualified Function Approach to Analysis of Program Behavior and Performance

The notion of a qualified function is introduced as a general means of representing the parameters of dynamic systems. Two specific types of qualified functions are defined for the analysis of the behavior and performance of structured programs. Transformation functions represent the values of variables during execution and timing algorithms express the execution times of programs symbolically. Complete rules of derivation for transformation functions and timing algorithms are given for the control mechanisms of sequence, selection, fixed loop, and while statement. Deterministic and stochastic simplification of transformation functions and timing algorithms are investigated and methods of eliminating recursion for expressions corresponding to while statements are studied.     

进化算法与符号执行结合的程序复杂度分析方法

程序的最坏执行路径是计算程序复杂度的一项重要指标,有助于发现系统可能存在的复杂性漏洞.近年来将符号执行应用于程序复杂度分析的研究取得了不小的进展,但现有方法存在通用性较差、分析时间较长的问题.文中提出一种面向最坏路径探测的进化算法——EvoWca,其核心思想是利用程序在较小输入规模下的已知最坏路径特征指导较大输入规模下初始路径集合的构建,然后模拟进化算法,对路径进行组合、突变和选择迭代,使得在搜索范围内探测到的最坏路径逼近于最坏时间复杂度对应的路径.基于该算法实现了一个用于程序复杂度分析的原型工具EvoWca2j,使用该工具和已有技术对一组Java程序进行最坏路径探索和执行效率评估,实验结果表明,相比现有方法,EvoWca2j的通用性和探索效率都有明显提高.     

一种基于程序功能标签切片的制导符号执行分析方法

提出了一种基于程序功能标签切片的制导符号执行分析方法OPT-SSE.该方法从程序功能文档提取功能标签,利用程序控制流分析,建立各功能标签和程序基本块的映射关系,并根据功能标签在程序执行中的顺序关系生成功能标签执行流.针对给定的代码目标点,提取与之相关的功能执行流切片,根据预定义好的功能标签流制导规则进行符号执行分析,在路径分析过程中,及时裁剪无关的功能分支路径以提升制导效率.通过对不同的功能标签流进行分离制导符号执行分析,可避免一直执行某复杂循环体的情形,从而提高对目标程序的整体分支覆盖率和指令覆盖率.实验结果表明,通过对binutils、gzip、coreutils等10个不同软件中的20个应用工具上的分析,OPT-SSE与KLEE提供的主流搜索策略相比,代码目标制导速度平均提升到4.238倍,代码目标制导成功率平均提升了31%,程序指令覆盖率平均提升了8.95%,程序分支覆盖率平均提升了8.28%.     

一种面向CPS的控制应用程序协同验证方法

信息-物理融合系统是一种新型嵌入式系统计算模式,它集成了控制计算过程和受控对象,二者相互影响并有机结合.随着信息技术在现实世界中更加广泛、深入的应用,智能化程度不断提升,在具有信息物理紧密耦合特点的嵌入式系统中,嵌入式控制软件的功能比重急剧上升,作用更加突出.作为安全攸关的系统,需要引入形式化验证方法来保证嵌入式控制应用软件的安全性.本文基于自动机理论建立统一的系统验证模型,并针对系统的可达性、安全性（safety）和活性（liveness）等属性要求,提出了对该模型进行形式化验证的算法：基于有界模型检验方法,基于可达性将对系统模型的相关属性验证问题转换为可满足性判定问题.将活性转换为Büchi自动机,并基于四值语义进行判断.在求解过程中,通过偏序规约等手段化简了问题求解的规模,提高可验证系统的规模.另外结合协同仿真技术,灵活配置验证的场景,提高验证的可用性.实验结果表明,结合仿真,形式化协同验证方法可以有效地对系统进行验证.     

程序执行时间的静态预估与可视化分析方法

软件时间性能分析与评估技术是实时软件开发中的一个重要课题.提出了一种基于控制流程图的程序执行时间的可视化分析框架,研究了中间代码段与源程序中语句的对应关系的自动分析、源程序语句行的CPU周期数的提取和计算方法、基于控制流程图的点到点最大时间分析算法和CPU周期的绝对时间估计方法.设计并实现了一个实用的基于控制流程图的程序执行时间静态分析与评估工具.最后,对研究工作进行了相关比较和总结.     

高校计算机实验室网络防护初探

计算机和网络两者在当今飞速发展,高校计算中心的发展却总是比较滞后.而企业的网络安全问题由来已久.所以对于企业级别的网络管理模式结合计算中心的实际情况进行了研究,从软、硬、管三方面入手,找到了一条科学配置中心人力资源、硬件资源和管理资源,从而更好的让网络资源给教学和科研服务之路.