The use of dynamic analysis for generation of input data that demonstrates critical bugs and vulnerabilities in programs

The article presents Avalanche—a dynamic analysis defect detection tool. Avalanche uses dynamic instrumentation provided by Valgrind [1] to collect and analyze the trace of program execution. The result of such an analysis is a set of input data which either shows an error in the program or allows next iteration to cover fragments of the program that were not yet executed and, therefore, checked. Thus, starting from a single test case, Avalanche implements iterative dynamic analysis, repeatedly executing the program with various automatically generated test data, while each execution increases the coverage of code. The article describes Avalanche internals, and discusses the results of analysis of several open source projects with Avalanche, which resulted in detection of over 15 bugs. Many of the detected bugs are confirmed and fixed by developers.     

Finding a minimal set of base paths of a program

An approach to finding a minimal set of base paths of a program is described. The program digraph is reduced to a weighted loopfree graph (WLFG) in which a node represents a subgraph of the program digraph that contains at most one outermost loop of the program. An algorithm for finding a maximal cutset of the WLFG is given such that (1) a maximal cutset does not contain two arcs that lie on a single path of the WLFG, and (2) its capacity is equal to the cardinality of a minimal set of base paths of the program. The algorithm repeatedly finds an eliminable arc and removes it from the WLFG until either the WLFG contains three nodes or no more eliminable arc can be found. An illustration is given for finding a maximal cutset and subsequently a minimal set of base paths.     

VLIW处理器循环指令缓冲器设计与实现

数字信号处理软件中循环程序在执行时间上占有很大比例,用指令缓冲器暂存循环代码可以减少程序存储器的访问次数,提高处理器性能。在VLIW处理器指令流水线中增加一个支持循环指令的缓冲器,该缓冲器能够缓存循环程序指令,并以软件流水的形式向功能部件派发循环程序指令。这样循环程序代码只需访存一次而执行多次,大大减少了访存次数。在循环指令运行期间,缓冲器发出信号使程序存储器进入睡眠状态可以降低处理器功耗。典型的应用程序测试表明,使用了循环缓冲后,取指流水线空闲率可达90%以上,处理器整体性能提高10%左右,而循环缓冲的硬件面积开销大约占取指流水线的9%。     

基于全局数据重组的循环倾斜优化

循环倾斜是程序优化中一种循环变换的手段,它改变空间迭代形式,将循环存在的跨迭代的并行用传统的并行标识出来,使得循环可以并行执行。但是循环倾斜后,并行执行的数据在内存中是离散的,而且每次迭代执行的次数是不一致的。为了更有效地利用SIMD,本文提出一种基于全局数据重组的循环倾斜优化方法。首先分析循环倾斜优化,针对数据离散的问题实现全局数据重组,改善数据局部性,循环易于向量化操作;针对迭代执行次数不一致问题,实现非满载向量操作,使尾循环得以向量执行。最后选择wavefront程序进行测试,优化后,程序计算可以获得平均10.73倍的加速效果。     

Inner loops in flowgraphs and code optimization

Summary A criterion is developed to define a hierarchy of inner loops in a program which constitute sections of the program which take up large proportions of the execution time; this hierarchy lends a dynamic loop structure to the program. It is assumed that the program has been given a flowgraph representation in which each vertex corresponds to a statement or a set of statements and the flow in each edge corresponds to the frequency of passage of control from one statement or set of statements to another. While developing this criterion an attempt is made to guarantee that moving a loop invariant statement from an inner loop to a point outside of the loop would always yield a more optimal code.     

基于智能机器人视觉清理系统研究

针对铸造类零件人工清理效率低、劳动强度大、成本高等问题,论文提出一种基于机器视觉的智能机器人清理系统。设计了由CCD摄像机、图像采集卡、输入输出单元、控制装置构成的机器人硬件系统,搭建了图像采集、处理分析、学习识别软件系统。通过对金属型铸造的盖板、导体类零件浇口、冒口等清理部位机械化自动化清理工作的多次实验验证,零件残留小于1mm,清理准确率达到97.6%,该系统所有指标达到设计要求,满足了工厂对于零部件毛刺智能化清理的要求。     

基于粗糙集理论的数据清洗模型

论文在基于粗糙集理论的基础上提出一个大数据系统的数据清洗模型,以利于信息不完备决策问题的实施。模型从给定的初始数据出发,在假定属性的重要性量度σ0的前提下,经过一系列的计算,比较属性实际重要性量度σCD(x)与σ0的大小,由此确定属性x的清洗,然后根据清洗后的数据得出相应的决策规则。并给出一个简单的例子来验证数据清洗模型。     

Basic Results in Automatic Transformations of Shared Memory Parallel Programs into Sequential Programs

We study the problem of developing a set of syntax-driven transformations for automatic translation of shared memory parallel programs into sequential programs. The result is a sequential program that is semantically equivalent to the original program. Consequently, the problem of debugging parallel programs is reduced to the problem of debugging sequential programs. Moreover, the efficiency of parallel programs can be increased by sequentializing code segments that include extra parallelism.The main difficulty in developing such a system is to preserve the fairness property of any actual parallel execution, which states that no process can wait forever unserved. Thus, non termination of the sequential version (namely an infinite loop) is allowed only if there is at least one fair parallel execution that does not halt as well (i.e., a process that executes an infinite loop whose termination is not dependent on any other process).We show that it is sufficient to consider the case of two sequential programs executed in parallel in order to solve the general case. We then describe several types of transformations and check their ability to preserve fairness. The results, with regards to the existence of such a transformation for general parallel programs are not conclusive; however, we do show that restricted cases (which are likely to appear in the reality) can be sequentialized using this set of transformations.     

SMOTL—A System to Construct Samples for Data Processing Program Debugging

The possibility of automatic construction of a complete set of program tests is considered. A test set system is said to be complete if every feasible program branch (segment) is executed by it. The complete test set construction algorithm for commercially oriented data processing programs is outlined, and the results of its functioning on real programs are analyzed.     

On estimating the useful work distribution of parallel programs under P3T: a static performance estimator

In order to improve a parallel program's performance it is critical to evaluate how even the work contained in a program is distributed over all processors dedicated to the computation. Traditional work distribution analysis is commonly performed at the machine level. The disadvantage of this method is that it cannot identify whether the processors are performing useful or redundant (replicated) work. The paper describes a novel method of statically estimating the useful work distribution of distributed-memory parallel programs at the program level, which carefully distinguishes between useful and redundant work. The amount of work contained in a parallel program, which correlates with the number of loop iterations to be executed by each processor, is estimated by accurately modeling loop iteration spaces, array access patterns and data distributions. A cost function defines the useful work distribution of loops, procedures and the entire program. Lower and upper bounds of the described parameter are presented. The computational complexity of the cost function is independent of the program's problem size, statement execution and loop iteration counts. As a consequence, estimating the work distribution based on the described method is considerably faster than simulating or actually compiling and executing the program. Automatically estimating the useful work distribution is fully implemented as part of P³T, which is a static parameter based performance prediction tool under the Vienna Fortran Compilation System (VFCS). The Lawrence Livermore Loops are used as a test case to verify the approach.     

选择性循环的并行方法

针对含有大量循环的串行程序存在的问题,提出一种基于线程级前瞻技术的循环选择方案。该方案对循环进行最优选择后建立一个可并行运行的循环集。对于该集合中的循环,选择并行效率高的代码段作并行处理,以加快串行程序运行速度。实验表明,相对于一般的简单内部循环或外部循环并行方法,该方案使9种基准代码的加速比平均上升23.8%,从而提高串行程序并行运行的效率。     

选择性循环的并行方法

针对含有大量循环的串行程序存在的问题,提出一种基于线程级前瞻技术的循环选择方案。该方案对循环进行最优选择后建立一个可并行运行的循环集。对于该集合中的循环,选择并行效率高的代码段作并行处理,以加快串行程序运行速度。实验表明,相对于一般的简单内部循环或外部循环并行方法,该方案使9种基准代码的加速比平均上升23.8%,从而提高串行程序并行运行的效率。     

循环程序的界函数合成

作为循环程序终止性分析的主流方法,当前的秩函数方法大多局限于线性或多项式秩函数的求解.针对循环程序若不存在对应的线性或多项式秩函数,现有秩函数方法就无法证明其终止性的问题,提出一个新的方法来合成给定循环程序对应的界函数.对于给定的循环程序,倘若能找到其界函数,则表明该循环程序是可终止的.首先将界函数的求解问题转化为一个...     

基于region的动态重用技术

1.引言指令之间的依赖使超标量计算机的处理器每个时钟周期只能执行平均1.7到2.1条指令。同时指令的运行带有很大的重复性。指令重复是指一条静态指令多次动态执行得到的结果是一样的。通常的情况下,对一条计算指令,如果它的输入是相同的,那么其结果也是相同的。但是,也存在输入不同、但结果相同的情况;例如两个数做布尔运算,在很多种情况下,结果都是一样的。在本文中我们说一条指令被重复当且仅     

EMLCLLER—a program for computing the EM response of a large loop source over a layered earth model

A simple program EMLCLLER coded in FORTRAN 77 is presented in this paper for modeling the electromagnetic (EM) response of a large circular loop source over a layered earth model in quasi-static as well as non-quasi-static (general frequency) regions. The program is based on a semi-analytical numerical approach for evaluating the improper integrals occurring in the expressions of EM field components. It takes into account both conduction as well as displacement current factors. The program is formulated in such a way that it is well suited for computing the EM response for any arbitrary position of the source loop in air or on the surface of the model, in contrast to the earlier methods which face convergence problem for source position on the surface of the model. The program has wide application and is capable of computing the EM response at any arbitrary point either inside or outside the source loop. The validity and accuracy of the program is demonstrated by computing the EM response of a large loop source over the homogeneous and multi-layer earth models. Response curves depict their characteristic variations. The computed results are in coincidence with the published results for the quasi-static region (f50 kHz) and are extension of their characteristic variation in the non-quasi-static (50 kHzf1000 kHz) region. Matching of computed results with the published results demonstrate the validity of the program.     

基于组件的计算机辅助工艺规划与管理系统

本文介绍了一个基于组件的计算机辅助工艺规划与管理系统（CAPPM），包括：工艺规划、技术文档、产品结构和数控程序管理子系统．系统采用基于Web的Windows DNA结构，建立了一组包括外观类、业务逻辑类和数据库访问类的业务逻辑组件．当外部环境变化时，用户可根据实际需求，定制满足生产要求的CAPPM系统，提高了系统的重用和重构能力．系统采用可扩展标记语言XML通讯，增强了Web环境下系统信息交互的性能．目前，CAPPM系统正在沈阳第一机床厂应用．