Parsers for indexed grammars

Three classes of parsable indexed grammars are defined. The new parsing mechanisms are derived by extending those that have been most successful for contextfree grammars, the LR and LL algorithms. Design criteria for the new grammar classes include membership decidability and unambiguity. We show that all three parsers operate in linear time for at least some grammars in our new classes. One of our new classes generates all the deterministic contextfree languages, along with some noncontextfree languages. We also show that the flag strings generated by indexed grammars are regular sets. This is done by showing that they can be generated by regular canonical systems.     

Positive and Negative Results for Higher-Order Disunification

This paper is devoted to higher-order disunification which is the process of solving quantified formulae built on simply-typed lambda-terms, the equality induced by the η and the β reductions, boolean connectives and the negation. This problem is motivated by tests of completeness of definitions in algebraic higher-order specification languages which combine the advantages of algebraic specification languages and higher-order programming languages. We show that higher-order disunification is not semi-decidable and we prove the undecidability of second-order complement problems which are the formulae expressing the completeness of some scheme, by encoding Minsky machines. On the other hand, we propose a set of transformation rules for simplifying such formulae, and we show how to extend this set of rules into a quantifier elimination procedure when we assume some restrictions on the formulae that we consider. We prove that second-order complement problems are decidable when some conditions are imposed on second-order variables and bound variables, and we are able to prove the decidability of any formula when all the terms occurring in the formula are patterns, i.e. terms s.t. the arguments of free variables are distinct bound variables. The quantifier elimination process involves classical rules for unification and their dual through negation, elimination rules for universal variables which are more complex than their first-order counterparts since variables may have arguments, and rules for solving dependence constraints which state that a function depends only on some of its arguments.     

Recursion Engineering for Reduction Incorporated Parsers

Reduction Incorporated (RI) recognisers and parsers deliver high performance by suppressing the stack activity except for those rules that generate fully embedded recursion. Automaton constructions for RI parsing have been presented by Aycock and Horspool [John Aycock and Nigel Horspool. Faster generalised LR parsing. In Compiler Construction, 8th Intnl. Conf, CC'99, volume 1575 of Lecture Notes in Computer Science, pages 32 – 46. Springer-Verlag, 1999] and by Scott and Johnstone [Adrian Johnstone and Elizabeth Scott. Generalised regular parsers. In Gorel Hedin, editor, Compiler Construction, 12th Intnl. Conf, CC'03, volume 2622 of Lecture Notes in Computer Science, pages 232–246. Springer-Verlag, Berlin, 2003] but both can yield very large tables. An unusual aspect of the RI automaton is that the degree of stack activity suppression can be varied in a fine-grained way, and this provides a large family of potential RI automata for real programming languages, some of which have manageable table size but still show high performance. We give examples drawn from ANSI-C, Cobol and Pascal; discuss some heuristics for guiding manual specification of stack activity suppression; and describe work in progress on the automatic construction of RI automata using profiling information gathered from running parsers: in this way we propose to optimise our parsers' table size against performance on actual parsing tasks.     

生物文本语义解析器的研究

自然语言解析器是一个制定语法结构句子的程序。概率解析器使用语言知识获得hand-parsed句子来产生最可能的分析新句子。斯坦福大学的自然语言解析器是一个实现英语、德语、汉语、阿拉伯语概率PCFG和依存解析器。链接语法解析器是根据链接文法和英语语法理论的一个英语语法解析器(包括其他语言)。PC-PATR是一个语法解析器,使用PARTII作为一项规则描述语言。这是一个实现了PARTII形式主义计算语言。     

Evaluating and Improving Recursive Descent Parsers

Time formulas are symbolic formulas which express the execution time of a program as a function of its input data and of variables representing the time to execute individual operations (e.g., push, pop, transfer, etc.). It is shown that in many cases the time formulas for recursive descent parsers may be generated automatically by a simple inspection of the parser code. These time formulas are instrumental in estimating the gains attained by various types of optimizations. Several of these optimizations are presented and their efficiency gains are estimated. A parser for a simple programming language is generated, optimized, and evaluated using the proposed techniques.     

一种有效的GLR分析器错误恢复方法

传统的分析器生成器多采用LALR(1)、LL(1)等确定性分析方法.近年来,随着软件再(逆向)工程的发展,GLR等非确定性的分析方法逐渐应用到分析器生成器中,但目前尚未有公开发表的文献提出并解决了自动生成的GLR分析器的错误处理和恢复问题.文中提出了一种基于子串分析的错误恢复方法,实验结果表明,该方法可以有效侦测和恢复输入串中的语法错误,具有较高的错误处理效率,有望应用到以GLR为核心算法的分析器生成器中.     

基于最小兴趣度的正、负关联规则挖掘

根据Piatetsky-Shapiro的主张,只有满足最小兴趣度条件约束的规则才是有兴趣的,论文将这一条件推广到了负关联规则,并将该条件进行了改进,使其能够对关联规则的相关性进行判断,然后在此基础上提出一个能同时挖掘正负关联规则的算法,实验表明该算法是非常有效的。     

Model-driven Transformation-based Generation of Java Stress Tests

This paper describes a practical application of transformation-based analysis and code generation. An overview is given of an approach for automatically constructing Java stress tests whose execution exercises all “interesting” class initialization sequence possibilities for a given class hierarchy.     

A Practical Method for Reducing Weak Precedence Parsers

This paper presents a practical method for constructing a more compact matrix structure of the precedence information used in a new weak precedence parsing. The parsing algorithm differs from the conventional weak precedence algorithm in that the precedence relation .> signals a sequence of reduce actions, not just one. The method can be used for any weak precedence grammars without degrading the good error detection capability of the traditional weak precedence parsers. It is shown by the empirical results that the obtained matrices are the very reasonable size and that the presented parsing algorithm is very efficient.     

基于定制时间约束的正负时态关联规则挖掘

传统关联规则挖掘是在整个事务数据库的时间范围内进行的,但有时用户想得到某一特定时间范围(如商品的促销阶段)内的关联规则,该文对这一问题进行了详细讨论,提出了基于定制时间的时态支持度、时态频繁项集、时态置信度、时态关联规则等概念,在传统Apriori算法的基础上提出了挖掘时态频繁项集的算法。另一方面,讨论了当同时考虑正、负关联规则出现的矛盾规则问题以及用相关性解决这一问题的方法,提出了挖掘正负时态关联规则的算法,实例说明了算法的执行过程及有效性。     

Automatic Generation of Unit Tests for Correlated Variables in Parallel Programs

A notorious class of concurrency bugs are race condition related to correlated variables, which make up about 30 % of all non-deadlock concurrency bugs. A solution to prevent this problem is the automatic generation of parallel unit tests. This paper presents an approach to generate parallel unit tests for variable correlations in multithreaded code. We introduce a hybrid approach for identifying correlated variables. Furthermore, we estimate the number of potentially violated correlations for methods executed in parallel. In this way, we are capable of creating unit tests that are suited for race detectors considering correlated variables. We were able to identify more than 85 % of all race conditions on correlated variables in eight applications after applying our parallel unit tests. At the same time, we reduced the number of unnecessary generated unit tests. In comparison to a test generator unaware of variable correlations, redundant unit tests are reduced by up to 50 %, while maintaining the same precision and accuracy in terms of the number of detected races.     

Hyperlink Recommendation Based on Positive and Negative Association Rules

The new HRS method for hyperlink recommendation based on positive and confined negative association rules is presented in the paper. Discovered with the new PANAMA algorithm rules are merged and used in the form of recommendation functions, both to assess the existing hyperlinks and to suggest new ones. Positively and negatively verified and new hyperlinks are presented to the content manager and can considerably facilitate the maintenance of the web site structure and its adjustment to user behaviour. The experiments confirmed the usefulness of the Hyperlink Recommender System (HRS) and in particular, of negative recommendations based on confined negative association rules.

基于正负理想点的仿真结果评估方法研究

在分布式交互仿真中,根据领导 具结果对作战方案进行综合评估是一个非常重要的问题,提出了正负理想点的方法,定量进行计算分析,并结合实例进行分析。     

一种新的正负空间同位规则挖掘算法

空间同位规则是一种新的空间数据挖掘方法.尽管人们对挖掘空间同位规则做了一些研究,但大多数研究者仅仅对正空间同位规则进行研究,没有考虑负空间同位规则.本文提出了一种新的正负空间同位规则挖掘算法(Positive and Negative Spatial Co-Location Rules Mining Algorithm,PNSCLRMA).为了减少计算量,算法利用了星形邻域去减少连接运算和定义兴趣度去删除不感兴趣的空间同位模式两项优化技术.实验表明,该算法有效可行.     

水平分布数据库的正负关联规则挖掘

目前,正负关联规则的挖掘受到越来越多的关注,在现实运用中也越来越广泛.随着信息技术和经济全球化的发展,许多企业都在全国甚至全世界范围内拥有自己的数据中心.企业通过分析这些数据的关联来为他们的战略抉择和政策制定服务.而直接在这些庞大的数据中寻找数据之间的关联不是一件容易的事.而且,在这些大量的数据中,不是所有的数据都是分析中所需要的.文中通过在文献[4]中所提的方法中引入对不同数据库赋予不同权重值的方式,使得在分布式数据库中挖掘正负关联规则更加高效.经过测试.这一改进是有效的.     

智能型正负脉冲式矿灯修复仪的研究

针对煤矿矿灯因电池极板硫化而大量报废的现象,提出了一种智能型正负脉冲式矿灯修复仪的设计方案,介绍了修复仪的组成及工作原理,给出了修复仪主电路和控制电路的实现方法。该正负脉冲式矿灯修复仪对电池因长时间充电及电池内部产生的析气不能排除而引起的硫化具有很好的修复效果,其电路具有结构简单、成本低、工作可靠等特点。     

基于正反控制模型的可逆逻辑综合

对一般Toffoli门进行了衍变和推广,给出了一个正反控制可逆级联模型(PNCRC),该模型拥有五种基本线型,并能正反控制目标位的输出.基于该模型给出了相应的可逆综合算法.对输入数不大于16的NCMCBench-mark函数进行测试并与已有的可逆综合方法比较,结果表明,利用该模型进行的可逆综合,垃圾信息数和可逆门数的优化效果都具有一定程度的改善.     

基于FP-Tree含正负项目的频繁项集挖掘算法

借鉴FP_growth算法中频繁模式树的思想,提出包含正负项目的频繁模式树的构造方法.通过对该频繁模式树进行模式扩展,可以挖掘出包含正负项目的频繁项集.该算法与直接使用FP_growth算法挖掘含负项目的频繁项集相比,无需对原始数据库进行负项目的扩展,也不用再构造并销毁额外的数据结构,只需在原始的频繁模式树上修改,在时间和空间的开销上都具有一定优势.实验表明,本文算法比现有的同类挖掘算法和直接FP_growth算法具有更好的效率.     

基于两级支持度的正、负关联规则挖掘

当同时研究正、负关联规则时会遇到一些新问题,如非频繁项集的挖掘及如何避免产生自矛盾的规则等．该文对这些问题进行了深入的研究,设计了能够同时挖掘频繁项集与非频繁项集以及能够同时挖掘这些项集中的正、负关联规则算法,实验表明该算法是非常有效的。     

基于脑电信号的正负情绪分类方法研究

驾驶员情绪状态的实时识别与预警,对保证道路交通安全系统的正常运行有着重要的作用与意义.本研究基于便携式脑电设备采集了 16位被试前额双通道脑电数据,分别从时域和频域上进行特征提取,使用集成学习分类的方法对正负情绪进行分类.结果显示频域特征以及特征的不对称指数在正负性情绪的分类起到了关键的作用,得到基于梯度提升决策树(G...