斐波那契树优化算法求解多峰函数全局最优解的可达性分析

为分析和验证斐波那契树优化算法（Fibonacci tree optimization algorithm,FTO）求解多峰函数全局最优解的算法性能,对算法的可达性问题进行研究.本文基于斐波那契法构造一个斐波那契树结构,在搜索空间中进行全局、局部交替搜索,不易陷入局部最优解.对斐波那契树优化算法基于该结构的可达性进行分析和证明.通过跟踪算法求解过程中坐标点的累积分布仿真实验和到达率的对比实验,分析和验证了算法求解多峰函数全局最优解的可达性.     

基于属性的用户-角色委派模型可达性分析

针对传统基于角色的访问控制(RBAC)管理模型难以表达多样化策略的问题,提出了基于属性的用户-角色委派（ABURA）模型,采用属性作为用户-角色委派的先决条件,丰富了RBAC管理策略的语义。用户-角色可达性分析是验证分布式系统中授权管理策略正确性的重要机制,定义了ABURA模型的用户-角色可达性分析问题,通过分析ABURA模型状态转换特点给出策略约减定理,设计了可达性分析算法,并通过实例对算法进行了验证。     

基于属性的用户-角色委派模型可达性分析

针对传统基于角色的访问控制(RBAC)管理模型难以表达多样化策略的问题,提出了基于属性的用户-角色委派(ABURA)模型,采用属性作为用户-角色委派的先决条件,丰富了RBAC管理策略的语义。用户-角色可达性分析是验证分布式系统中授权管理策略正确性的重要机制,定义了ABURA模型的用户-角色可达性分析问题,通过分析ABURA模型状态转换特点给出策略约减定理,设计了可达性分析算法,并通过实例对算法进行了验证。     

一种新的混杂Petri网可达性分析方法

讨论混杂Petri网的标识可达性问题.以混杂Petri网模型行为演变为基础提出了一种新的可达性分析方法.根据混杂Petri网模型行为演变划分了混杂Petri网的四种演变类型,给出并证明了每一种演变类型的可达性判定定理,基于这些定理给出了相应的可达性分析算法.另外,与已有的方法进行比较分析,分析结果表明所提出方法的有效性.     

基于双向双区间标签实现k步可达性查询

近年来,图的可达性查询已经成为一个研究热点。传统的可达性查询算法——GRAIL在处理k步可达性查询时具有较高的查询效率,但不适合处理不同分支顶点之间的k步可达性查询。为了解决上述问题,提出了一种新的双向双区间标签索引,进而实现了RE-GRAIL算法,从而有效解决了k步可达性查询问题。最后,在5个不同特征的数据集上进行实验,并从索引构建时间、索引大小、查询时间、扩展性4个方面进行验证。 实验结果表明,与众多同类算法相比,RE-GRAIL算法具有更好的性能。     

时间符号迁移图上的可达性分析

提出了以时间符号迁科为建模语言、基于可达性分析的模型检测算法，并给出了算法的正确性证明。该算法可被用于硬件设计和通信协议验证等领域。     

时间Petri网分析工具的实现

时间Petri网是非常适合描述实时系统的模型工具,由于时间的复杂性因素使得它的可达性分析变得非常困难。该文在分析了基于全局时间变量的时间Petri网的可达性算法的基础上,采用OOP技术,实现了一个时间petri网的分析工具。     

考虑出行方向的广州出租车时空可达性研究

出行方向是可达性研究中的一个关键要素, 因此, 提出一种考虑出行方向的出租车时空可达性分析方法。根据出租车经验路径分方向构建经验等级路网, 采用基于分层路网的Dijkstra算法计算得到各OD对之间的行程时间, 作为可达性评价指标, 并采用网格法和反距离加权插值法绘制得到广州市中心商业区等时线及其渲染图, 分方向、分时段对其时空可达性进行分析。结果证明了不同出行方向下, 特别是处于高峰时段, 可达性有较大的不同。     

自适应EFSM可执行测试序列生成

基于扩展有限状态机(EFSM)模型自动生成测试序列可以提高测试效率.由于EFSM模型包含丰富的变量和谓词条件,它们之间的冲突可能导致自动生成的测试序列不可执行.对EFSM变迁及变迁之间的关联关系进行了详细的讨论和分析,定义了一个邻接变迁关联图,提出了一种自适应EFSM可执行测试序列生成算法.新算法首先根据变量和谓词包含情况对变迁进行分类,然后深入挖掘了邻接变迁之间的关联关系,最后,基于自适应预测搜索函数启发式引导可达性分析树扩展生成可执行的测试序列.实验数据表明,与宽度优先可达性分析方法相比,新算法可以有效降低可达性分析过程中产生状态空间爆炸问题的概率,从而提高测试序列自动生成的效率.在最坏的情况下,新算法的计算时空复杂度也等同于宽度优先算法.     

一种保持结点可达性的高效社会网络图匿名算法

为了保护社会网络隐私信息,提出了多种社会网络图匿名化技术.图匿名化目的在于通过图修改操作来防止隐私泄露,同时保证匿名图在社会网络分析和图查询方面的数据可用性.可达性查询是一种基本图查询操作,可达性查询精度是衡量图数据可用性的一项重要指标.然而,当前研究忽略了图匿名对结点可达性的影响,导致较大的可达性信息损失.为了保持匿名图中结点的可达性,提出了可达性保持图匿名化（reachability preserving anonymization,简称RPA）算法,其基本思想是将结点进行分组并采取贪心策略进行匿名,从而减少匿名过程中的可达性信息损失.为了保证RPA算法的实用性,针对其执行效率进行优化,首先提出采用可达区间来高效地评估边添加操作所导致的匿名损失;其次,通过采用候选邻居索引,进一步加速RPA算法对每个结点的匿名过程.基于真实社会网络数据的实验结果表明了RPA算法的高执行效率,同时验证了生成匿名图在可达性查询方面的高精度.     

Relay Reachability Algorithm for Exploring Huge State Space

Since many desirable properties about finite-state model are expressed as a reachability problem, reachability algorithms have been extensively studied in model checking. On the other hand, reachability algorithms play an important role in game solving since reachability games are often described as a finite state model. In this sense, reachability algorithms are located in the intersection of the research areas of Model Checking and Artificial Intelligence.This paper interests in solving the reachability games called Push-Push. However, both exact and approximate reachability algorithms are not sufficient to the games since its state space is huge and requires lots of iterations such as 338 steps in the reachability computation. Thus we devise the new algorithm called relay reachability algorithm. It divides the global state space into several local ones. And exact reachability algorithm is applied on each local state space one by one. With these reachability algorithms, we solve all of the games.     

A compact Petri net representation and its implications foranalysis

We explore a property-independent, coarsened, multilevel representation for supporting state reachability analysis for a number of different properties. This multilevel representation comprises a reachability graph derived from a highly optimized Petri net representation that is based on task interaction graphs and associated property-specific summary information. This highly optimized representation reduces the size of the reachability graph but may increase the cost of the analysis algorithm for some types of analyses. We explore this tradeoff. To this end, we have developed a framework for checking a variety of properties of concurrent programs using this optimized representation and present empirical results that compare the cost to an alternative Petri net representation. In addition, we present reduction techniques that can further improve the performance and yet still preserve analysis information. Although worst-case bounds for most concurrency analysis techniques are daunting, we demonstrate that the techniques that we propose significantly broaden the applicability of reachability analyses     

一种基于MapReduce的OpenFlow网络属性并行验证算法

针对OpenFlow网络中流表配置错误引起转发回路、路由黑洞和访问控制规则失效等问题,提出一种并行的基于MapReduce的OpenFlow网络属性验证算法。通过在Map阶段划分规则等价类,在Reduce阶段为规则等价类构建基于交换机端口谓词的网络转发图并分析可达性,实现对网络属性的并行验证。同时,通过采用原子谓词将传统可达性分析中的规则匹配域多维集合运算转换为整数集合运算,以进一步提高可达性分析效率。此外,基于原子谓词的谓词表达方式可消除交换机端口谓词集合中的冗余项,降低存储开销。最后,通过理论分析和仿真实验验证了算法的正确性及在时间和存储开销方面的优越性。     

大图上跳数受限的可达查询算法研究与优化

判断有向图上两个顶点之间是否存在一条路径是一个经典问题,而对于一些路由规划和图分析等实际应用,要求查找是否存在跳数受限的可达路径,这是一个变种的图可达查询问题.对于大图上跳数受限的查询算法,不仅仅要对大图查询的时间效率和空间效率进行权衡,而且还要利用跳数受限的特性进行优化.普通的可达查询算法存在小度数顶点索引项占用空间过多的问题,造成空间浪费严重.为此我们提出了一种面向跳数受限的2-hop部分索引方法,采用改进的索引方法并结合局部搜索,实现跳数受限的有效可达性查询.实验结果表明,在Orkut社交网络数据集上与已有算法相比,该算法索引空间节省了32％,同时查询时间略微增加,使得我们算法可以计算更大规模图的跳数受限可达问题.     

Reachability analysis in T-invariant-less Petri nets

An algorithm for reachability analysis in place/transition Petri nets having no transition invariants (T-invariants) is proposed. Given a Petri net with initial and target markings, a so-called complemented Petri net is created first that consists of the given Petri net and an additional complementary transition. Thereby, the reachability task is reduced to computation and investigation of those minimal-support and linearly combined T-invariants of the complemented Petri net, in which the complementary transition fires only once. Then, for each T-invariant with a single firing of the complementary transition, the algorithm will try to create a reachability path from the given initial marking to the target marking.     

工作流合并规则中的冲突检测方法

在关系型规则和活动型规则形式描述工作流合并需求的基础上,提出一种基于可达关系的合并规则冲突检测算法。通过记录每条规则应用后的可达关系矩阵,以及新增可达关系对应的规则集方式,为合并规则集中存在冲突的若干规则组合进行较为准确的定位。实例分析表明,该算法为规则集的合理调整提供直接依据,可有效实施工作流的合并。     

On communication models for algorithm design in networked sensor systems: A case study

Towards building a systematic methodology of algorithm design for applications of networked sensor systems, we formally define two link-wise communication models, the Collision Free Model (CFM) and the Collision Aware Model (CAM). While CFM provides ease of programming and analysis for high level application functionality, CAM enables more accurate performance analysis and hence more efficient algorithms through cross-layer optimization, at the expense of increased programming and analysis complexity. These communication models are part of an abstract network model, above which algorithm design and performance optimization is performed. We use the example of optimizing a probability based broadcasting scheme under CAM to illustrate algorithm optimization based on the defined models. Specifically, we present an analytical framework that facilitates an accurate modeling and analysis for the probability based broadcasting in CAM (PB_CAM). Our analytical results indicate that (1) the optimal broadcast probability for either maximizing the reachability within a given latency constraint or minimizing the latency for a given reachability constraint decreases rapidly with node density, and (2) the optimal probability for either maximizing the reachability with a given energy constraint or minimizing the energy cost for a given reachability constraint varies slowly between 0 and 0.1 over the entire range of the variations in node density. Our analysis is also confirmed by extensive simulation results.