automated test program generation for an industrial optimizing compiler

Association for Computing Machinery, ACM; IEEE; IEEE Computer Society; SIGSOFT

基于形式描述的编译优化自动测试方法与技术研究

编译优化是现代编译器不可缺少的重要功能。编译优化技术在过去几十年里取得了显著进展，对提升程序运行速度、节省存储空间、节省能耗等起到了不可替代的作用。然而，编译优化的可靠性却不尽人意。编译优化技术种类多、处理复杂而且可复用性弱，容易出错，即便是成熟的编译器，也不断有与编译优化相关的bug被发现出来。编译器的可靠性对软件产品的可靠性和安全性有直接影响，随着编译优化在现代编译器中的比重不断增加，编译优化的可靠性也日益受到人们的关注。 软件测试是保障编译优化可靠性的基本技术手段之一，然而，编译优化测试涉及测试程序编写、测试执行等过程，人工完成相当费时费力，因此有必要研究编译优化自动测试方法，以提高编译优化测试的效率。基于这一实际需求，Intel、MEI (Matsushita Electric Industrial)、DaimlerChrysler AG等业界产商近年来也相继与有关研究机构开展合作，研究编译优化自动测试方法。 目前已有的编译器自动测试方法中大多数都是以程序设计语言的语法和语义为主要依据，适用于测试语法检查、语义检查、代码生成等基本编译功能，对于编译优化的测试则缺乏针对性，测试效率较低，而已有的若干种面向编译优化的自动测试方法也存在着对编译优化刻画不够准确、自动化程度不高等缺陷。 本文提出一种基于形式描述的编译优化自动测试方法(TEMCOFS)，其实现过程分为四个阶段，即：(1) 建立编译优化形式描述；(2) 分析编译优化描述的正确性；(3) 基于编译优化形式描述自动生成测试程序；(4) 自动执行测试。在TEMCOFS方法框架下，本文分别研究了编译优化形式化描述方法、编译优化描述正确性分析方法和基于形式描述的两种自动测试方法，实现了三类典型优化—表达式优化、数据流优化、循环优化的自动测试，主要工作包括： (1) 在编译优化形式描述方面，除了应用前人研究成果—TRANS语言描述了表达式优化和数据流优化之外，还对TRANS语言进行了扩展，建立了循环优化的形式描述机制； (2) 在编译优化正确性分析方面，首先证明了揭示程序数据依赖关系对程序变换正确性影响的依赖基础定理，为循环优化正确性分析提供了基础，然后探讨了编译优化正确性分析的一般方法； (3) 在测试自动执行方面，提出了编译优化自动变形测试执行方法，该方法将变形测试思想引入编译优化测试中，利用测试程序等价性质实现测试结果的自动判定，能够避免传统方法中测试结果判定所存在的问题； (4) 在测试程序自动生成方面，分别对应两种测试自动执行方法—比照法和变形法提出了基于编译优化形式描述的测试程序自动生成方法，能够根据表达式优化、数据流优化、循环优化的形式描述自动生成测试程序集。 在GCC编译器上的实验表明，基于本文方法自动生成的测试程序集可使GCC的编译优化模块较快达到较高的测试覆盖率。与其他编译器自动测试方法相比，本文方法对编译优化测试的针对性较好，自动化程度也较高。总而言之，本文方法对于提高编译优化测试效率、保障优化编译器的质量具有较好的实用和参考价值。

In situ doping of 3C-SiC grown on (0001) sapphire substrates by LPCVD

The heteroepitaxial growth of n-type and p-type 3C-SiC on (0001) sapphire substrates has been performed with a supply of SiH4+C2H4+H-2 system by introducing ammonia (NH3) and diborane (B2H6) precursors, respectively, into gas mixtures. Intentionally incorporated nitrogen impurity levels were affected by changing the Si/C ratio within the growth reactor. As an acceptor, boron can be added uniformly into the growing 3C-SiC epilayers. Nitrogen-doped 3C-SiC epilayers were n-type conduction, and boron-doped epilayers were p-type and probably heavily compensated.

In situ annealing treatment and In-doping of GaN epilayers grown by MOVPE

The effects of in situ annealing treatment in the initial growth stage and In-doping during growth of the GaN on the material properties were investigated. GaN was grown by LP-MOVPE. In situ annealing reduced the full-width at half-maximum (FWHM) of X-ray rocking curves and reduced etch pit density of GaN films. It improved the optical properties of the epilayer. Undoped and In-doped GaN films of initial growth stage were investigated. It was found that morphology and optical properties were improved in In-doped samples. (C) 2000 Elsevier Science B.V. All rights reserved.

Numerical and Experimental Investigation On The Prevention of Co Deflagration

The exhaust gases from industrial furnaces contain a huge amount of heat and chemical enthalpy. However, it is hard to recover this energy since exhaust gases invariably contain combustible components such as carbon monoxide (CC). If the CO is unexpectedly ignited during the heat recovery process, deflagration or even detonation could occur, with serious consequences such as complete destruction of the equipment. In order to safely utilize the heat energy contained in exhaust gas, danger of its explosion must be fully avoided. The mechanism of gas deflagration and its prevention must therefore be studied. In this paper, we describe a numerical and experimental investigation of the deflagration process in a semi-opened tube. The results show that, upon ignition, a low-pressure wave initially spreads within the tube and then deflagration begins. For the purpose of preventing deflagration, an appropriate amount of nitrogen was injected into the tube at a fixed position. Both simulation and experimental results have shown that the injection of inert gas can successfully interrupt the deflagration process. The peak value of the deflagration pressure can thereby be reduced by around 50%. (C) 2008 Elsevier Ltd. All rights reserved.

Polarization switching current of vertical cavity surface-emitting Lasers in an applied electric field

The polarization of vertical-cavity surface-emitting laser (VCSEL) can be controlled by electro-optic birefringence. We calculated the birefringence resulted from external electric field which was imposed on the top DBR of VCSEL by assuming that the two polarization modes were in the same place of the gain spectra in the absence of electric field beginning. By modifying SFM, the affection of the electric field strength on the polarization switching currents between the two polarization modes had been shown.

Study on sensing properties of tin oxide CO gas sensor with low power consumption

In this paper, the fabrication method of a new type of carbon monoxide gas sensor based on SnOx with low power consumption and its sensing characteristics have been reported. The electric conductance of this type of sensor evolves oscillation form regularly when the sensor is exposed to low level of CO gas. The oscillation amplitude is directly proportional to the concentration of CO gas over a wide range. The effects of relevant factors. such as. humidity, temperature and interference gases on the sensor properties were examined. The sensing oscillation response mechanism was also discussed.

电厂燃煤中主要有害元素的种类、迁移及潜在环境影响

Distributions of elements especially hazard trace elements in coals and their wastes from a coal fired power plant have been studied in detail using knowledge of Geology, Mineralogy, Geochemistry and Environmental chemistry. The key work is on the small particle sizes of fly ashes which escaped from electric precipitator and discharged into atmosphere. By means of X-ray powder diffraction (XRD) and scanning electron microscopy with energy-dispersive spectrometer (SEM-EDS), the characteristics of minerals and morphologies were studied. Different types of fly ash were formed in different stages and processes. More than 50% of small fly ashes belonged to inhalable particles (PM10). The very fine fly ashes preferred to attach on surface of bigger fly ash or conglutinate with each other and this decreased the environmental impact of tiny fly ashes. The trace elements in coal, fly ashes, slags and small particle sizes of fly ashes had been analysed by means of Neutron Activation Analysis (INAA), inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES). As particle sizes decreasing, distributions of most elements increased, but in contrary to most studies, this increasing trend was not very obviously because of the tendency of attachment of tiny fly ashes. The occurrence of 30 elements including hazard trace elements of Cd, Cr, Ni, Co, Pb, Zn, As, Se, Cu, V was studied by means of sequential chemical extract. The annual discharge of hazard trace elements of slag, fly ash, small fly ash (PM10), tiny fly ash (PM2.5) and air was calculated by mass balance. S, V, Cu, Pb, Se, Mo, Cd from power plant had potential impacts on environment. Hazard trace elements from the power plant had little effect on soil and aerosol comparing to those from other industrial sources and the effects were mostly on downwind direction. Both the high performance electric precipitator and high chimney made the hazard trace elements from power plant being transported far away but little environmental impacts.