结合断言与覆盖率为导向的验证方法

伴随着半导体工艺的不断发展,可以将更多的功能集成到单系统芯片上.这对传统的验证方法和验证途径提出了种种挑战.以覆盖率为导向的验证方法中,覆盖率模型是在外部通过DUT执行的功能来统计覆盖率,很难侦测到DUT内部的工作状态,存在对功能"遗漏点"的侦测.基于断言的验证方法可以将断言加入到DUT内部,通过断言覆盖加强覆盖率检测.阐述了将断言和覆盖率为导向相结合的验证方法,并用此种方法对USB2.0系统进行了验证.讨论了如何将两种验证方法有效地结合,并且通过比较覆盖率为导向的验证方法与结合断言与覆盖率为导向的验证方法的结果,说明结合断言与覆盖率为导向的验证方法提高了验证过程中的观测性,减少了验证周期.     

基于遗传算法的随机测试生成技术探究

随着集成电路设计复杂度不断提高,功能验证的挑战也不断增大。为了加快验证进程提高覆盖率,提出了一种新的基于遗传算法（Genetic Algorithm, GA）的随机测试生成方法。该方法基于一种二进制和十进制数混合编码的双层编码模式,并使用了权值可自动调控的功能覆盖点来计算个体适应度值,并将模拟过程中的覆盖率报告自动反馈回给随机测试生成的约束产生。该方法已应用于中国科学院微电子研究所自主研发的IME-Diamond数字信号处理器RTL模型的模块功能验证。实验结果表明,该方法有效提高了验证效率。     

柔性坐标测量机结构参数标定的采样覆盖率研究

采用非线性最小二乘法作为柔性坐标测量机标定的优良算法,提出采样覆盖率来评定采样是否充分。转角范围和采样角度是各个关节采样覆盖率的必要求解因子,首先通过模拟实验计算各个关节转角变量对测量精度权的大小,并找出权重最大的关节1和关节2,然后对其进行实验对比,结果证明,良好的采样覆盖率会使采样更充分,测量结果更精确。     

基于覆盖率驱动的SoC验证技术研究

覆盖率数据是验证工程师判定SoC验证完备程度的定性度量,为SoC验证完全性提供了保障,指明了方向．文中以SoC总线仲裁器验证为例,对其结构覆盖率、功能覆盖率、断言覆盖率等多种覆盖率进行了全面的分析,然后根据覆盖率分析结果反馈到RTL设计代码和测试激励进行修正,直到验证的完整性满足设计的要求．     

覆盖率技术的提高在RVM层次化验证方法中的应用

本文首先介绍了传统验证方法的弊端,描述了RVM验证平台的层次化结构及它的可重用性原理,主要目的是强调在现有的验证平台上为了模块得到完备性验证必须提高它的覆盖率.本文使用的方法是在基于RVM的验证平台上通过验证工程师充分理解协议之后增加测试例的构造来实现覆盖率技术的提高.然后以UART(通用异步收发信机)为实例具体说明如何提高覆盖率,最后得出结论通过这种方法可以使功能覆盖率和代码覆盖率都达到100%,提高了验证的完备性.     

提高模块级的验证质量的方法学研究

验证工作中验证计划对于整个ASIC设计工作起到十分重要的作用,模块级验证质量是通过覆盖率分析进行验证质量评估.本文对TD-SCDMA终端芯片的ARM_UART模块的多种覆盖率进行了详细的分析,通过分析覆盖率得出的数据再次进行验证,直到验证的完整性满足设计者的要求.模块覆盖率是否达到验证计划的要求,可以作为判断验证工作质量的依据,所以针对模块级的芯片验证工作是以多种覆盖率为驱动的验证分析对象的,提高模块级验证质量方法是以覆盖率驱动技术为验证技术支持的.     

频谱监测设备协同部署优化方法

针对在多类型频谱监测设备协同感知情况下,如何选定设备类型、数量及其部署位置的问题,提出了一种基于自适应遗传算法的频谱监测设备协同部署优化方法。首先,分别建立覆盖率模型、监测效能模型和资源调配开销模型;其次,综合三个子模型,以满足一定覆盖率要求条件下,获得更大覆盖率、更大监测效能和更小资源调配开销为目标函数建立协同优化部署优化模型;最后,引入自适应遗传算法求解得到最优部署方案。仿真实验验证了该方法的可行性。     

基于RVM SD/MMC卡控制器验证平台的搭建

本文介绍了RVM验证方法学和覆盖率驱动技术,验证方法学的关键就是搭建验证平台.覆盖率驱动技术是让我们搭建的验证平台达到覆盖率期望的要求,从而确保DUT的功能得到充分的验证.本文是根据覆盖率驱动技术搭建了基于RVM的SD/MMC卡控制器的验证平台,该验证平台从上到下分为测试层,产生器层,功能层,命令层和信号层,最后在此基础上给出了SD/MMC卡控制器的仿真波形,并根据波形分析不断修改SD控制器的源代码完善其功能,从而达到验证目的.     

VMM中功能覆盖率收敛技术

介绍SystemVerilogVMM验证方法学在LCDController验证中的应用,指出它相对于传统Verilog验证方法的1优点,重点研究功能覆盖率的收敛技术,实验比较了多种具体的实现方法。实验结果表明,由于CCT能够收集覆盖信息,形’成闭环负反馈,以控制随机变量的生成,从而在实现快速收敛的目标方面取得了显著的效果。     

基于覆盖率的集成电路验证

随着集成电路规模和复杂度的逐渐提高,百万千万门级以上的集成电路验证消耗了整个芯片开发过程大约70%的时间,不仅需要专职的团队,而且人数通常是设计团队的1.5～2倍.针对当前超大规模集成电路验证的这个瓶颈,在传统验证平台的基础上提出了代码覆盖率和功能覆盖率、随机激励与定向激励结合的验证方法.代码覆盖率确保代码的执行,功能覆盖率确保功能点的覆盖,随机与定向激励结合在验证的各个阶段有针对性地编写测试用例,三者相互结合实现高效率验证.此方法在多协议标签交换转发芯片项目中将验证时间缩短了三个月,而且问题的收敛速度加快,验证的规格更可靠.与传统的验证方法相比,此方法提高了验证效率,缩短了验证周期,增强了可靠性,对今后的项目开发有重要借鉴意义和指导意义.     

近似镜像网页检测算法的研究与评价

当前在WWW上有众多的近似镜像web页面,如何快速准确地发现这些内容上相似的网页已经成为提高搜索引擎服务质量的关键技术之一.为基于关键词匹配的搜索引擎系统提出了5种近似镜像网页检测算法,并利用“天网”系统对这5种算法进行了实际评测.另外还将它们与现有的方法进行了对比分析.本文所论述的近似镜像检测算法已成功地被用于消除“天网”系统的重复网页,同时也可广泛应用于数字化图书馆的搭建.     

基于网络蜘蛛的搜索引擎自动发现

自动发现Web上大量的搜索引擎对于构造大规模元搜索引擎是有益的,提出一种用优化爬行规则的网络蜘蛛自动发现搜索引擎并提取其元信息的方法:通过优化爬行规则的网络蜘蛛爬取页面;利用专门的识别规则从爬取到的页面中识别搜索界面,并提取其相关的元信息。试验结果表明该方法简单有效,自动发现的查准率和查全率分别达到97%和91%。     

Feature Selection Based Correlation Attack on HTTPS Secure Searching

Search engine plays an irreplaceable role in web information organizing and accessing. It is very common for Internet users to query a search engine when retrieving web information. Sensitive data about search engine user’s intentions or behavior can be inferred from his query phrases, the returned results pages, and the webpages he visits subsequently. In order to protect contents of communications from being eavesdropped, some search engines adopt HTTPS by default to provide bidirectional encryption. This only provides an encrypted channel between user and search engine, the majority of webpages indexed in search engines’ results pages are still on HTTP enabled websites and the contents of these webpages can be observed by attackers once the user click on these links. Imitating attackers, we propose a novel approach for attacking secure search through correlating analysis of encrypted search with unencrypted webpages. We show that a simple weighted TF–DF mechanism is sufficient for selecting guessing phrase candidates. Imitating search engine users, by querying these candidates and enumerating webpages indexed in results pages, we can hit the definite query phrases and meanwhile reconstruct user’s web-surfing trails through DNS-based URLs comparison and flow feature statistics-based network traffic analysis. In the experiment including 28 search phrases, we achieved 67.86% hit rate at first guess and 96.43% hit rate within three guesses. Our empirical research shows that HTTPS traffic can be correlated and de-anonymized through HTTP traffic and secured search of search engines are not always secure unless HTTPS by default enabled everywhere.     

DESENT: decentralized and distributed semantic overlay generation in P2P networks

The current approach in web searching, i.e., using centralized search engines, rises issues that question their future applicability: 1) coverage and scalability, 2) freshness, and 3) information monopoly. Performing web search using a P2P architecture that consists of the actual web servers has the potential to tackle those issues. In order to achieve the desired performance and scalability, as well as enhancing search quality relative to centralized search engines, semantic overlay networks (SONS) connecting peers storing semantically related information can be employed. The lack of global content/topology knowledge in a P2P system is the key challenge in forming SONS, and this paper describes an unsupervised approach for decentralized and distributed generation of SONS (DESENT). Through simulations and analytical cost models we verify our claims regarding performance, scalability, and quality     

对搜索引擎中评分方法的研究

针对搜索引擎评分较为困难的问题,文中提出了一种评分方法.该方法使用协同过滤技术,在同一兴趣组中各用户所提供的搜索结果集的基础上,采用文中提出的并行关联规则算法对各用户的局部有向图进行预处理,找出兴趣组中各成员都感兴趣的页面.然后对这些页面的内容和超链接附近出现的文本以及链接结构进行分析.计算权威页面和引导页面,以找到虽不包括在检索结果中,但相关的页面.此外,在对所获得的页面进行评价时,除考虑Web页自身的链接结构和兴趣组中查询用户对页面的评价,还考虑兴趣组中其它成员对页面的评价和所有成员对页面的使用情况等因素,从而使推荐给用户的页面排序更加合理.     

Scheduling sensor activity for information coverage of discrete targets in sensor networks

In this paper, we study the problem of scheduling sensor activity to cover a set of targets with known locations such that all targets can be monitored all the time and the network can operate as long as possible. A solution to this scheduling problem is to partition all sensors into some sensor covers such that each cover can monitor all targets and the covers are activated sequentially. In this paper, we propose to provide information coverage instead of the conventional sensing disk coverage for target. The notion of information coverage is based on estimation theory to exploit the collaborative nature of geographically distributed sensors. Due to the use of information coverage, a target that is not within the sensing disk of any single sensor can still be considered to be monitored (information covered) by the cooperation of more than one sensor. This change of the problem settings complicates the solutions compared to that by using a disk coverage model. We first define the target information coverage (TIC) problem and prove its NP‐completeness. We then propose a heuristic to approximately solve our problem. Simulation results show that our heuristic is better than an existing algorithm and is close to the upper bound when only the sensing disk coverage model is used. Furthermore, simulation results also show that the network lifetime can be significantly improved by using the notion of information coverage compared with that by using the conventional definition of sensing disk coverage. Copyright © 2008 John Wiley & Sons, Ltd.     

Search strategy switching: A cost model and an analysis of backtracking

Test generation algorithms contain search strategies which are used to control decision making when the algorithm encounters a choice of signal value, or what action to perform next. Our study of traditional search strategies used in automatic test pattern generation has led us to the observation that no single strategy is superior for all faults in a circuit and all circuits. Further experimentation led to the conclusion that a combination of search strategies provides better fault coverage and/or faster ATPG for a given backtrack limit. Instead of using just one strategy up to the backtrack limit, a primary strategy is used for the first half of the backtrack limit, then a secondary strategy is used for the second half of the backtrack limit. This article presents a qualitative ATPG cost model based on the number of test generation events, uses this model to explain why search strategy switching is faster, and shows experimental evidence to verify both the cost model and search strategy switching theory. The experiments were performed with the ISCAS circuits and our implementation of the FAN algorithm.     

面向网页分类的网页摘要方法

网页分类是网络挖掘的重要研究内容之一.与文本分类相比,网页分类面临的困难更多.去除网页中的噪声信息可以提高网页分类的精度,基于摘要的网页分类方法利用了这一思想.本文对三种传统的网页摘要方法进行了分析和改进,提出了Content Body摘要方法以及基于四种摘要方法的混合摘要方法;在此基础上,进行了大量基于摘要的网页分类实验.实验结果表明,所有的摘要方法都可以提高分类效果,其中混和摘要方法效果最好,可以使分类的F1值得到12.9%的改进.     

Effective sensor deployment based on field information coverage in precision agriculture

Coverage is an importance issue in wireless sensor networks. In this work, we first propose a novel notion of information coverage, which refers to the coverage efficiency of field information covered by deployed sensor nodes. On the basis of information coverage, we consider an optimization problem of how to partition the given field into multiple parcels and to deploy sensor nodes in some selected parcels such that the field information covered by the deployed sensor nodes meets the requirement. First, we develop two effective polynomial‐time algorithms to determine the deployed locations of source nodes for information 1‐coverage and q‐coverage of the field, respectively, without consideration of communication, where information q‐coverage implies that the field information in terms of information point is covered by at least q source nodes. Also, we prove the upper bound in the theoretical for the approximate solution derived by our proposed method. Second, another polynomial‐time algorithm is presented for deriving the deployed locations of relay nodes. In the theoretical, this proposed algorithm can achieve the minimized number of relay nodes. Further, the related information 1‐coverage algorithms are applied in our wireless sensor network‐based automatic irrigation project in precision agriculture. Experimental results show the major trade‐offs of impact factors in sensor deployment and significant performance improvements achieved by our proposed method. Copyright © 2013 John Wiley & Sons, Ltd.     

基于BP网络的农业主题元搜索引擎研究

为提高传统搜索引擎对农业主题信息的搜索效果,构建了基于BP网络的农业主题搜索引擎,该搜索引擎通过利用多个搜索引擎的搜索结果来提高搜索引擎的查全率,再通过使用BP网络对搜索结果进行二次判断来提高搜索引擎的查准率.