大变量逻辑函数求补的递归实现

逻辑函数求补是大变量逻辑优化的算法基础.采用二叉树结构,用C语言实现了大变量逻辑函数求补递归算法.详述了求补二叉树的结构和形成过程,以及在求补二叉树上补集的收集方法.     

逻辑函数求补算法及其改进

逻辑函数求补算法存在的主要问题是时间开销大及需要的存储空间过大。该文在对递归裂变求补算法和基于最小项求补算法进行分析研究的基础上,提出了积项输入、邻项合并、积项输出的无冗余覆盖的逻辑函数求补算法。该求补算法的时间、空间的需求将大大缩小。     

对逻辑函数3种求补算法的分析

对逻辑函数求补中几种不同的求补算法进行了系统的描述和分析研究,使其在逻辑综合领域能发挥更好的作用,这些算法均在项目课题中完成了实现。求补算法的优劣将直接影响逻辑综合优化的效率和时空复杂度,对逻辑函数求补算法进行深入的研究将具有重要的现实意义。     

积项集合的补集算法

在逻辑综合的领域内,经常使用求给定积项集合补集的过程。本文提出一个单边逻辑函数积项集合的求补算法,求补操作是通过选取函数矩阵的列覆盖进行的。与传统求补算法相比,该算法大大节省了计算机时间和内存空间。     

积项集合的补集算法

在逻辑综合的领域内,经常使用求给定积项集合补集的过程。本文提出一个单边逻辑函数积项集合的求补算法,求补操作是通过选取函数矩阵的列覆盖进行的。与传统求补算法相比,该算法大大节省了计算机时间和内存空间。     

大变量逻辑函数最佳覆盖问题研究

逻辑函数的最佳覆盖，一直是逻辑综合领域的关键环节。尤其是大变量逻辑函数最佳覆盖，对复杂的逻辑综合更为重要，但也更加困难。本文在对逻辑覆盖算法研究的基础上，提出了适合大变量逻辑函数最佳覆盖的Beister改进算法。经过大量算题的测试表明，改进的列覆盖算法在时间复杂度和选择效果方面均优于Beister算法。     

基于SBDD图的布尔匹配

在逻辑验证和综合中,布尔匹配利用有序二叉判定图OBDD来检验两个给定的逻辑函数是否相等。为了提高匹配算法的效率,文中用最小项数作为标签标定变量（变量组）。对比两函数中变量（变量组）的“标签”,可以删除不可能的排序,从而加快匹配过程。在提取变量标签时,提出简约二分决策图－SBDD,并利用其节点少的特性进一步提高“标签”提取算法的效率。实验结果表明本算法执行速度快,变量区分能力强。     

一种基于熵的OBDD变量排序算法

有序二叉决策图（OBDD）是一种有效表示布尔函数的数据结构,其大小依赖于所采用的变量序。熵是定量描述布尔函数中变量重要性的一种方法。基于变量的熵值分析了高质量变量序的特征,给出了一种基于熵的OBDD变量排序算法。实验结果表明：该算法与模拟退火算法和遗传算法结果相当。时间仅为相应算法的80．84％和29．79％。     

单边多输出逻辑函数补集软件的设计与实现

根据单边逻辑函数的特性,介绍了一种多输入多输出单边逻辑函数补集方法,该方法采用二进制特征矩阵B(F)和状态矢量R(F)来描述原函数,进行最小列覆盖的选择形成多输出补集函数的控制矩阵,由控制矩阵与补集函数的状态矢量形成单边单输出补集合逻辑函数,通过多输出逻辑函数分解与合并最终产生多输出单边逻辑函数的补集。我们设计的多输入多输出单边逻辑函数补集算法软件,在P-1．8GHz、512MBRAM的计算机上完成测试和运行,并通过测试检验程序,保证输出结果在逻辑上与输入条件求补等价。     

基于重量分析的OBDD变量排序算法

有序的二叉判决图（ＯＢＤＤ）是布尔表达式的一种有效表示方法，但它的体积对变量排序具有较强的依赖性。本文提出一种电路结构图，并在此基础上定义了原始输入重量和节点重量等参数，并建立了用重量分析来指导的ＯＢＤＤ变量排序算法。由于从考虑变量对输出函数的影响出发与从考虑ＯＢＤＤ节点共享性出发对变量排序的要求不同，本文分别设计了两类算法。实验结果表明，本文对大多数标准电路变量排序的效果都优于国际上的同类算法，     

格值交替树自动机

交替（树）自动机因其本身关于取补运算的简洁性及其与非确定型（树）自动机的等价性,成为自动机与模型检测领域研究的一个新方向.在格值交替自动机与经典交替树自动机概念的基础上,引入格值交替树自动机的概念,并研究了格值交替树自动机的代数封闭性和表达能力.首先,证明了对格值交替树自动机的转移函数取对偶运算,终止权重取补之后所得自动机与原自动机接受语言互补这一结论.其次,证明了格值交替树自动机关于交、并运算的封闭性.最后,讨论了格值交替树自动机和格值树自动机、格值非确定型自动机的表达能力;证明了格值交替树自动机与格值树自动机的等价性,并给出了二者相互转化的算法及其复杂度分析;同时,提供了用格值非确定型自动机来模拟格值交替树自动机的方法.     

On the parity complexity measures of Boolean functions

The parity decision tree model extends the decision tree model by allowing the computation of a parity function in one step. We prove that the deterministic parity decision tree complexity of any Boolean function is polynomially related to the non-deterministic complexity of the function or its complement. We also show that they are polynomially related to an analogue of the block sensitivity. We further study parity decision trees in their relations with an intermediate variant of the decision trees, as well as with communication complexity.     

一种并行乘法器的设计与实现*

根据补码的特点对Booth2算法进行了改进,在得到部分积的基础上,采用平衡的42压缩器构成的Wallace树对部分积求和,再用专门的加法器对Wallace产生的结果进行求和得到最终结果。用Verilog硬件语言进行功能描述,并用Design_analyzer对其进行综合,得出用这种改进Booth2算法实现的乘法器比传统的CSA阵列乘法器速度快、规模较大的结论。     

二层组播QoS最优生成树

具有一对多特性的组播数据大量涌入以太网,对网络服务质量提出了更高的要求.二层域中生成树协议在选择根桥时没有考虑其对组播服务质量的影响.从二层组播接收者的角度出发,提出了二层组播QoS最优生成树的概念,从理论上证明了组播源位于最优生成树的根桥上时,组播能达到最优的服务质量.而且,最优生成树对于经过根桥的单播也能达到最优的服务质量.最后,给出的最优根桥逼近查找算法可以作为生成树算法的补充.通过对比实验,验证了该算法的有效性、可靠性和可扩展性.     

Automata-based verification of programs with tree updates

This paper describes a verification framework for Hoare-style pre- and post-conditions of programs manipulating balanced tree-like data structures. Since the considered verification problem is undecidable, we appeal to the standard semi-algorithmic approach in which the user has to provide loop invariants, which are then automatically checked, together with the program pre- and post-conditions. We specify sets of program states, representing tree-like memory configurations, using Tree Automata with Size Constraints (TASC). The main advantage of this new class of tree automata is that they recognise tree languages based on arithmetic reasoning about the lengths of various (possibly all) paths in trees, like, e.g., in AVL trees or red–black trees. TASCs are closed under union, intersection, and complement, and their emptiness problem is decidable. Thus we obtain a class of automata which are an interesting theoretical contribution by itself. Further, we show that, under few restrictions, one can automatically compute the effect of tree-updating program statements on the set of configurations represented by a TASC, which makes TASC a practical verification tool. We tried out our approach on the insertion procedure for red–black trees, for which we verified that the output on an arbitrary balanced red–black tree is also a balanced red–black tree.     

机器数补码全字长数位说

大量现行教材与专著中所表述的“机器数补码首位是符号位”之说,其补码加法法则不能被解释,令人困惑。对机器数补码全字长各位定义了位权,提出了“首位负权记数制”及新的机器数补码数据模型。在这个新的模型下,建立了补码与其真值的等量映射,论证了机器数补码的表值域,论证了补码真值负与非负的判定法则及机器数补码[x]与其真值[y]二者之间相互转换的求解法则;给出了机器数补码的加法法则,论证了在封闭运算条件下机器数补码加法的等效加法运算法则。揭示了机器系统内部补码信息表示的内涵与补码加法法则的真相,建立了“机器数补码全字长数位说”。“机器数补码首位符号说”中种种无可释然的困惑,在“机器数补码全字长数位说”里不复存在。     

基于 GBDT 的铁路事故类型预测及成因分析

运用数据挖掘技术进行铁路事故类型预测及成因分析, 对于建立铁路事故预警机制具有重要意义. 为此, 本文提出一种基于梯度提升决策树(Grandient boosting decision tree, GBDT)的铁路事故类型预测及成因分析算法. 针对铁路事故记录数据缺失的问题, 提出一种基于属性分布概率的补全算法, 最大程度保持原有数据分布, 从而降低数据缺失对事故类型预测造成的影响. 针对铁路事故记录数据类别失衡的问题, 提出一种集成的GBDT模型, 完成对事故类型的鲁棒性预测. 在此基础上, 根据GBDT预测模型中特征重要度排序, 实现事故成因分析. 通过在开放数据库上进行实验, 验证了本文模型的有效性.     

Id+: Enhancing medical knowledge acquisition with machine learning

Learning from patient records may aid medical knowledge acquisition and decision making. Decision tree induction, based on ID3, is a well-known approach of learning from examples. In this article we introduce a new data representation formalism that extends the original ID3 algorithm. We propose a new algorithm, ID+, which adopts this representation scheme. ID+ provides the capability of modeling dependencies between attributes or attribute values and of handling multiple values per attribute. We demonstrate our work via a series of medical knowledge acquisition experiments that are based on a ''real-world'' application of acute abdominal pain in children. In the context of these experiments, we compare ID+ with C4.5, NewId, and a Naive Bayesian classifier. Results demonstrate that the rules acquired via ID+ improve decision tree clinical comprehensibility and complement explanations supported by the Naive Bayesian classifier, while in terms of classification, accuracy decrease is marginal.     

Tree pattern query minimization

Tree patterns form a natural basis to query tree-structured data such as XML and LDAP. To improve the efficiency of tree pattern matching, it is essential to quickly identify and eliminate redundant nodes in the pattern. In this paper, we study tree pattern minimization both in the absence and in the presence of integrity constraints (ICs) on the underlying tree-structured database. In the absence of ICs, we develop a polynomial-time query minimization algorithm called CIM, whose efficiency stems from two key properties: (i) a node cannot be redundant unless its children are; and (ii) the order of elimination of redundant nodes is immaterial. When ICs are considered for minimization, we develop a technique for query minimization based on three fundamental operations: augmentation (an adaptation of the well-known chase procedure), minimization (based on homomorphism techniques), and reduction. We show the surprising result that the algorithm, referred to as ACIM, obtained by first augmenting the tree pattern using ICs, and then applying CIM, always finds the unique minimal equivalent query. While ACIM is polynomial time, it can be expensive in practice because of its inherent non-locality. We then present a fast algorithm, CDM, that identifies and eliminates local redundancies due to ICs, based on propagating "information labels" up the tree pattern. CDM can be applied prior to ACIM for improving the minimization efficiency. We complement our analytical results with an experimental study that shows the effectiveness of our tree pattern minimization techniques.     

Determinization and Memoryless Winning Strategies

We show that Safra's determinization ofω-automata with Streett (strong fairness) acceptance condition also gives memoryless winning strategies in infinite games, for the player whose acceptance condition is the complement of the Streett condition. Both determinization and memorylessness are essential parts of known proofs of Rabin's tree automata complementation lemma. Also, from Safra's determinization construction, along with its memoryless winning strategy extension, a single exponential complementation of Streett tree automata follows. A different single exponential construction and proof first appeared in [N. Klarlund (1992), Progress measures, immediate determinacy, and a subset construction for tree automata,in“Proceedings, 7th IEEE Symposium on Logics in Computer Science”].