Undecidability of accordance for open systems with unbounded message queues

We study asynchronously communicating open systems modeled as Petri nets with an interface. An accordance preorder describes when one open system can be safely replaced by another open system without affecting some behavioral property of the overall system. Although accordance is decidable for several behavioral properties if we assume a previously known bound on the maximal number of pending messages, we show that it is not decidable without this assumption.     

二叉树的先序遍历和中序遍历的非递归算法

从二叉树先序遍历递归算法的执行过程的分析入手,总结出二叉树先序遍历的实质,从而得出利用栈的二叉树的非递归算法。最后,再从分析二叉树中序遍历与先序遍历过程实质的不同之处,得出了二叉树中序遍历的非递归算法。重点在于对二叉树先序和中序遍历过程实质的分析。     

A static view of localities

This paper proposes alternative, effective characterizations for nets of automata of the location equivalence and preorder presented by Boudol et al. in the companion paper [BCHK]. Contrary to the technical development in the above given reference, where locations are dynamically associated to the subparts of a process in the operational semantics, the equivalence and preorder we propose are based on a static association of locations to the parallel components of a net. Following this static approach, it is possible to give these distributed nets a standard operational semantics which associates with each net a finite labelled transition system. Using this operational semantics for distributed nets, we introduce effective notions of equivalence and preorder which are shown to coincide with those proposed in [BCHK].     

一种基于前缀编码的树生成算法

为了使树生成算法更为通用且效率更高,提出一种基于前缀编码的树生成算法.算法中的节点采用前缀编码的数据结构,便于用户对树中节点及其下层子节点上的关联数据进行快速查询和统计.由于在构造树之前已采用先根遍历的方式对节点进行了排序,同时建树过程中记录了最近各层节点的信息,因此无需搜索节点的上下层信息就可直接建立起树,大幅提高了建树效率,算法时间复杂度为O(n).该算法无需额外的数据预处理即可构造任意子树,且不会增加算法复杂度.     

Parallel breadth-first search algorithms for trees and graphs

Parallel Breadth-First Search (BFS) algorithms for ordered trees and graphs on a shared memory model of a Single Instruction-stream Multiple Data-stream computer are proposed. The parallel BFS algorithm for trees computes the BFS rank of eachnode of an ordered tree consisting of n nodes in time of 0(β log n) when 0(n ^1+1/β) processors are used, β being an integer greater than or equal to 2. The parallel BFS algorithm for graphs produces Breadth-First Spanning Trees (BFSTs) of a directedgraph G having n nodes in time 0(log d.log n) using 0(n ³) processors, where d is the diameter of G If G is a strongly connected graph or a connected undirected graph the BFS algorithm produces n BFSTs, each BFST having a different start node.     

POTwigStack:一种改进的XML小枝模式匹配算法

目前,基于小枝模式的XML查询算法是研究的热点。它们多数在寻找匹配节点的函数中采用了前序递归的算法,产生了大量不必要的"调用/返回"操作。因此,提出了POTwigStack算法,调用POgetNext函数来寻找匹配的节点,该函数采用后序递归的算法,可以有效地避免无用的"调用/返回"操作,从而使算法的效率进一步提高。     

EXPSPACE lower bounds for the simulation preorder between a communication-free Petri net and a finite-state system

We investigate the simulation preorder between finite-state systems and a simple subclass of BPP-nets (communication-free nets). We show EXPSPACE lower bounds for the simulation problems, in both directions, as well as for the simulation equivalence. Our results improve PSPACE and co-NP lower bounds for the simulation between finite-state systems and BPP-nets, given by Ku?era and Mayr in [A. Ku?era, R. Mayr, Simulation preorder over simple process algebras, Information and Computation 173 (2) (2002) 184-198].     

二叉树后序遍历非递归算法的改进研究

通过分析二叉树后序遍历过程的特点，结合二叉树先序遍历非递归算法的思想，对传统的二叉树后序遍历非递归算法进行了改进，提出了基于“先序遍历”思想的二叉树后序遍历非递归算法，并在课堂教学中进行了应用，取得了良好的教学效果．     

PowerBuilder编程寻找复杂支导线的计算路径

复杂支导线在矿山测量工作中比较常见,但其程序算法比较复杂.详细阐述了寻找复杂支导线的计算路径的算法,并采用PowerBuilder作为开发工具实现编程.