在静态编译器中实现Java异常机制的算法

将Java程序静态编译成可执行程序是使用Java虚拟机动态编译／解释执行Java程序的另一种运行Java程序的方式。针对Java异常机制的特点和静态编译的需求,在介绍Java异常处理逻辑的基础上,提出一种在静态编译器中实现Java异常机制的算法,结合Open64开源编译器,给出该算法的具体步骤以及实现方式,以SPECjvm98为测试集,验证该算法的有效性。     

一致性测试的静态需求测试研究

针对一致性测试中的静态需求测试通常采用手工方法而产生的效率低问题,提出一种基于统计学习的方法,包括静态需求的关联规则表示,并对采样的协议数据进行关联规则挖掘,如果得到的规则与需求规则一致,静态需求就可以得到统计上的测试检验。该方法在OSPFv3协议测试中取得了较好的效果。     

Applying Dynamic Training‐Subset Selection Methods Using Genetic Programming for Forecasting Implied Volatility

Volatility is a key variable in option pricing, trading, and hedging strategies. The purpose of this article is to improve the accuracy of forecasting implied volatility using an extension of genetic programming (GP) by means of dynamic training‐subset selection methods. These methods manipulate the training data in order to improve the out‐of‐sample patterns fitting. When applied with the static subset selection method using a single training data sample, GP could generate forecasting models, which are not adapted to some out‐of‐sample fitness cases. In order to improve the predictive accuracy of generated GP patterns, dynamic subset selection methods are introduced to the GP algorithm allowing a regular change of the training sample during evolution. Four dynamic training‐subset selection methods are proposed based on random, sequential, or adaptive subset selection. The latest approach uses an adaptive subset weight measuring the sample difficulty according to the fitness cases' errors. Using real data from S&P500 index options, these techniques are compared with the static subset selection method. Based on mean squared error total and percentage of non‐fitted observations, results show that the dynamic approach improves the forecasting performance of the generated GP models, especially those obtained from the adaptive‐random training‐subset selection method applied to the whole set of training samples.     

机翼气动结构耦合数值分析方法

针对机翼的静气动弹性问题,为准确预测其气动特性,研究一种实用有效的气动结构耦合仿真方法.以客机机翼设计为例,通过机翼的静气动弹性问题分析和机翼的气动结构耦合分析流程的分解,建立参数化、自动化、模块化的气动结构耦合仿真分析平台.该平台的流程包括基于全速势方程的气动分析、基于MSC Nastran的结构仿真、应用MATLAB的载荷到结构模型的传递、结构变形向气动外形的映射等环节.算例表明该方法能较好地解决机翼的静气动弹性分析问题.     

HEDP及其取代物对碳酸钙阻垢机理的研究

采用分子动力学方法,模拟计算了阻垢剂HEDP及其取代物与方解石(104,(102),(202),(113)面的相互作用,计算并分析了阻垢剂与方解石(104),(102),(202),(113)面作用的相互作用能,包括结合能,库仑能和范德华作用能.并且分析了方解石(104)晶面上的钙离子与阻垢剂中双键氧原子、整个(104)晶面与阻垢剂中所有氧原子之间和整个(104)晶面与整个阻垢剂分子之间的对关联函数,结果表明:阻垢剂分子中的氧原子与碳酸钙的Ca2+形成的离子键对吸附起到了主要作用,同时阻垢剂与晶面间存在较弱的范德华力相互作用,阻垢剂与各晶面的的结合能强弱顺序为(102)＞(202)≥(113)≈(104).苯环的大π键有利于阻垢效果的提高.     

PowerBuilder中利用DropDownListBox控件显示数据库字段值的实现

针对在PowerBuilder中利用DropDownLintBox控件显示数据库字段值存在一定难度的问题,提出了三种不同的实现方法。     

Timing Analysis for Instruction Caches

This paper contributes a comprehensive study of a framework to bound worst-case instruction cache performance for caches with arbitrary levels of associativity. The framework is formally introduced, operationally described and its correctness is shown. Results of incorporating instruction cache predictions within pipeline simulation show that timing predictions for set-associative caches remain just as tight as predictions for direct-mapped caches. The low cache simulation overhead allows interactive use of the analysis tool and scales well with increasing associativity.The approach taken is based on a data-flow specification of the problem and provides another step toward worst-case execution time prediction of contemporary architectures and its use in schedulability analysis for hard real-time systems.     

Symbolic Cache Analysis for Real-Time Systems

Caches impose a major problem for predicting execution times of real-time systems since the cache behavior depends on the history of previous memory references. Too pessimistic assumptions on cache hits can obtain worst-case execution time estimates that are prohibitive for real-time systems. This paper presents a novel approach for deriving a highly accurate analytical cache hit function for C-programs at compile-time based on the assumption that no external cache interference (e.g. process dispatching or DMA activity) occurs. First, a symbolic tracefile of an instrumented C-program is generated based on symbolic evaluation, which is a static technique to determine the dynamic behavior of programs. All memory references of a program are described by symbolic expressions and recurrences and stored in chronological order in the symbolic tracefile. Second, a cache hit function for several cache architectures is computed based on a cache evaluation technique. Our approach goes beyond previous work by precisely modelling program control flow and program unknowns, modelling large classes of cache architectures, and providing very accurate cache hit predictions. Examples for the SPARC architecture are used to illustrate the accuracy and effectiveness of our symbolic cache prediction.     

An Approach for Recovering Distributed System Architectures

Reasoning about software systems at the architectural level is key to effective software development, management, evolution and reuse. All too often, though, the lack of appropriate documentation leads to a situation where architectural design information has to be recovered directly from implemented software artifacts. This is a very demanding process, particularly when involving recovery of runtime abstractions (clients, servers, interaction protocols, etc.) that are typical to the design of distributed software systems. This paper presents an exploratory reverse engineering approach, called X-ray, to aid programmers in recovering architectural runtime information from a distributed system's existing software artifacts. X-ray comprises three domain-based static analysis techniques, namely component module classification, syntactic pattern matching, and structural reachability analysis. These complementary techniques can facilitate the task of identifying a distributed system's implemented executable components and their potential runtime interconnections. The component module classification technique automatically distinguishes source code modules according to the executables components they implement. The syntactic pattern matching technique in turn helps to recognise specific code fragments that may implement typical component interaction features. Finally, the structural reachability analysis technique aids in the association of those features to the code specific for each executable component. The paper describes and illustrates the main concepts underlying each technique, reports on their implementation as a suit of new and off-the-shelf tools, and, to give evidence of the utility of the approach, provides a detailed account of a successful application of the three techniques to help recover a static approximation of the runtime architecture for Field, a publicly-available distributed programming environment.     

WWW业务访问特性分布研究

WWW业务表现为一系列的访问序列。而Web Server和Proxy Server的日志很好地记录了这种访问序列的过程及特性。WWW业务的特性研究是Web Server、Web中间件研究和人工合成Web负载的基础。分析了一个Web Server和两个Proxy Server的日志,重点研究了Web页面请求的概率分布、Web静态文档大小的概率分布（含传输文档）、Web静态文档的访问距离的概率分布,并将分析结果同相关文献的结果进行了对比,同时通过试验证实了在使用Size作为Web缓存替换依据时,还应该考虑Web文档的访问频率。