编译器中激进蝴蝶优化方法的研究与实现

编译优化技术的目的是挖掘程序中的优化空间,提高程序编译或运行效率,无效代码删除优化是被广泛使用的编译优化技术之一,它旨在删除程序中不可达的代码,以提升程序的执行效率。许多应用程序的执行路径往往与运行时的输入参数值相关,并且在一些分支路径上与运行时参数值相结合,可能存在无效代码,通过现有的无效代码删除优化,很难做出优化处理。为此,提出一种依赖数据流分析的激进蝴蝶优化方法,利用SSA中间表示,根据动态运行时的参数可能值,自动为程序生成代码形状类似蝴蝶（butterfly）的分支代码,使编译器在程序编译阶段为相关优化提供可行的优化依据。最后通过实验验证了该方法的有效性和可行性。     

动态二进制翻译与优化技术研究

动态二进制翻译技术是一种即时编译技术,它将针对源体系结构编译生成的二进制代码(源机器码)动态翻译为可以在目的体系结构上运行的代码(翻译码).动态优化技术是指在运行时获取动态信息并进行代码优化的技术.动态二进制翻译及优化系统使得源软件无需重编译就可以直接在目标体系结构上高效地运行.目前几种比较有影响的动态二进制翻译及优化系统有Intel公司的IA-32 Execution Layer,IBM公司的DAISY,Transmeta的CMS及HP的Dynamo等.这些系统对动态二进制翻译系统关键技术有不同的实现.对动态二进制翻译和优化技术的研究是计算机领域的研究热点,具有深远的现实意义和应用前景.     

动态二进制翻译中的指令调度技术研究与实现

动态二进制翻译提供了无需重新编译源代码就能将源机器生成的可执行代码自动转换到目标机器的方法,很好地解决了代码兼容性问题.其核心思想是根据程序的动态运行信息找到反复执行的代码序列,对代码序列进行翻译和优化,并将结果多次重用.指令调度作为一种有效的编译优化手段,也适用于动态二进制翻译.在对gcc的指令调度器分析研究的基础上,结合动态二进制翻译的实时性特点,提出了适合动态二进制翻译的效率高、开销小的指令调度算法.     

基于值-剖面的OpenMP运行时优化系统

本文设计并实现了一个基于值一剖面的OpenMP运行时优化系统CCRG OpenMP。它能够根据常见的值的组合优化并行区域，并且在运行时只有并行区代码需要重编译和管理。CCRG OpenMP基于动态重编译技术，避免了目前静态多版本技术的不足。同时，值-剖面的收集和分析由独立的动态优化器线程完成，降低了动态重编译引入的开销。SPEC OMP2001基准测试表明，我们基于值一剖面的Open MP优化系统能够较大地提高程序性能。     

基于GCC的VLIW编译系统研究

VLIW机器在单个机器周期中同时发射并执行多个的并行操作,从而获得较高的指令级并行度,这些操作之间的依赖分析和调度工作则被完全交给相应的编译器执行,因此VLIW的并行性能能否充分发挥取决于VLIW体系结构相关编译器的质量。GNU开发的GCC是被最广泛使用的编译系统之一,它具有多语言、多平台支持的能力和开放的结构,能够运用各种成熟的常规编译优化技术生成高效的代码。文章分析了VLIW及GCC的结构特点,提出了一种基于GCC的VLIW编译系统设计方案,利用GCC进行RTL中间代码一级的体系结构无关优化和少量体系结构相关优化,在汇编代码一级针对VLIW结构进行体系结构相关的优化,从而充分利用GCC的成熟编译技术快速开发高效的VLIW多语言编译系统。     

数据流程序动态调度与优化

为了解决数据流编程模型的可用性问题,使其能在兼顾程序并行性的前提下适用于动态数据交互速率的流应用,设计了一种动态调度与静态优化相结合的数据流编译系统。编译器以COStream语言编写的源程序为输入,通过对源程序进行分析,以动态速率的数据通信边作为边界划分程序到粗粒度的子图,在子图内部应用静态优化。根据子图的每个计算单元的工作量估计计算资源的使用状况,实现子图内计算单元到处理器核的映射,经过阶段划分分配子图内计算单元到相应流水阶段。在运行时,每个子图在各个处理器核上均启动一个线程,通过对线程间通信的优化,避免了运行时多个线程对同一段内存同时读写产生的同步开销,减少了线程的上下文切换次数。使用信号量控制子图内线程间的同步,基于各子图计算单元运行时数据交互速率并结合当前线程的状态,动态调度各个子图的执行,构建动态的软件流水线,生成相应多线程目标代码。实验以通用X86-64多核处理器作为实验平台,测试和分析数据流编译的性能。实验结果表明,编译系统可以实现动态数据交互速率的数据流应用,扩大了编译系统可用性并且具有一定加速效果。     

注解信息制导的动态二进制翻译及优化

动态二进制翻译器在运行时将源体系结构机器码翻译为目标体系结构机器码.这种即时编译技术使得源机器上的软件无需重编译就可以直接在目标机上较高效地运行.然而,利用动态二进制翻译器运行源软件的效率大大低于针对目标机器重新编译运行源软件的效率.本文在比较分析动态翻译生成的目的机器码的性能偏低的原因的基础上,提出了注解信息制导的动态二进制翻译及优化的方法.本文选取了三种注解信息,在英特尔的商用动态二进制翻译器"IA-32Execution Layer"和静态编译器"Intel(r)Compiler"上实现了注解信息制导的动态二进制编译及优化技术.实验结果表明该三种注解信息较大程度地提高了动态翻译码的执行效率.     

动态二进制翻译中动态优化的成本与收益分析

传统的静态编译器优化存在着各种限制,为此,提出了一种运行期动态优化的对策。在程序的执行过程中,持续检测程序运行的profile信息,并根据这些信息对程序代码进行优化变换,创建并运行程序代码的优化版本。这种运行期动态优化操作是直接针对程序的二进制代码的,不针对程序语言或编译器。这不仅带来优化的透明性,还使得老版本的源代码即遗留代码也可以从优化技术中获得性能提升。     

C编译系统中断处理机制测试方法

处理器在实际工作中会面对大量异步中断,而编译系统生成的代码可能由于多种原因导致处理器在中断干扰下不能正确运行。本文根据中断嵌套的递归特性提出一种基于寄存器采样与比较的编译系统测试方法,着重考察代码在异步中断干扰下运行的正确性。该方法同时可用于错误诊断,能够高效实现错误定位。实际应用证明该方法能够有效揭示并定位编译系统存在的错误,是对已有编译系统测试方法的一个补充。     

GCC中基于值剖视的代码特例化

基于剖视的优化技术根据程序先前运行时收集的剖视信息来指导编译优化。文章给出了一种在GCC中基于值剖视的代码特例化实现方法。NPB和SPEC CPU2000基准程序测试结果表明,该代码特例化方法能够有效提高程序性能,同时引入的开销较小。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

正~~     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate