一种应用分治策略的中文分词方法

自动分词是中文信息处理的关键步骤。由于具有结构简单、易于实现和开发周期短等优点,基于词典的分词方法被广泛应用。结合中文多字词数量少,使用频度低的特点,设计实现了一种新的词典机制,在此基础上,把分治策略引入到分词中,提出了一种新的分词算法,幷对该算法进行了理论分析和实验验证。     

利用分治策略实现DDoS攻击路径标识题

针对分布式拒绝服务(DDo S)攻击防御中的数据包标记溯源技术,基于分治策略提出用简单的递归关系分别表示攻击树构、攻击路径频率检测、数据包和路径关联这3个基本防御实现,使用单数据包带内路径标识符用于唯一的数据包和路径关联,而把攻击树构建及攻击路径频率作为独立的带外操作来处理.通过在真实网络拓扑环境下对网络流量和存储开销的测试,证明本方法可以高流量负荷下以很小的开销同时对大量受害主机的提供单一数据包回溯保证.     

基于分治策略的无线传感器网络屏障覆盖算法

利用无线传感器网络构建防护屏障以监测重要重要场所的未经授权闯入者是目前物联网的一个重要应用领域.大多数研究集中于如何在一个矩形区域内构建传感器屏障以探测只能沿受限路线移动的闯入者.提出了一个针对传感器基于泊松分布的此问题完整解决方案,可以满足在任意的形状区域内构建带状传感器屏障以探测闯入者.实验证明,该算法能有效减少延迟、验证开销以及拓扑初始化时的计算开销.     

子网级大容量异构网络管理研究

通过对构建大容量异构网络管理系统面临的主要问题进行研究,文章提出了在分治服务架构方式下,基于进程的动态可伸缩软件架构。采用嵌套分层的业务管理模型和对象动态内存管理技术,解决了子网级大容量异构网络管理的主要问题。     

基于动态描述逻辑的服务组合及质量模型

 本文提出一个基于动态描述逻辑的Web服务自动组合框架.在该框架中,Web服务自动组合被划分为逻辑层和实现层两部分,于是服务的自动组合问题在逻辑上归结为一个动作规划问题,在实现上归结为一个根据动作选择具体服务的服务选择问题.基于该框架,本文给出了一个支持非线性QoS聚合和显式数据流声明的QoS模型.得益于合理的服务组合框架和QoS模型,本文提出的服务选择方法可以将复杂服务分解为较小的服务,然后分别用递归的剪枝算法求解.实验显示该方法是有效的,不但可适应候选Web服务数量较大的情况,且相对于现有方法能更好地处理服务组合中的复杂结构.     

Security analysis of a new stream cipher

From 1st February of 2004, Europe launches the ECRYPT project, which collects lots of stream ciphers from all over the world. These new stream ciphers are unlike the tradi- tional stream ciphers that use LFSRs as basic building blocks; instead they use mo…     

A parallel scheduling algorithm for reinforcement learning in large state space

The main challenge in the area of reinforcement learning is scaling up to larger and more complex problems. Aiming at the scaling problem of reinforcement learning, a scalable reinforcement learning method, DCS-SRL, is proposed on the basis of divide-and-conquer strategy, and its convergence is proved. In this method, the learning problem in large state space or continuous state space is decomposed into multiple smaller subproblems. Given a specific learning algorithm, each subproblem can be solved independently with limited available resources. In the end, component solutions can be recombined to obtain the desired result. To address the question of prioritizing subproblems in the scheduler, a weighted priority scheduling algorithm is proposed. This scheduling algorithm ensures that computation is focused on regions of the problem space which are expected to be maximally productive. To expedite the learning process, a new parallel method, called DCS-SPRL, is derived from combining DCS-SRL with a parallel scheduling architecture. In the DCS-SPRL method, the subproblems will be distributed among processors that have the capacity to work in parallel. The experimental results show that learning based on DCS-SPRL has fast convergence speed and good scalability.     

The Static Parallelization of Loops and Recursions

We demonstrate approaches to the static parallelization of loops and recursions on the example of the polynomial product. Phrased as a loop nest, the polynomial product can be parallelized automatically by applying a space-time mapping technique based on linear algebra and linear programming. One can choose a parallel program that is optimal with respect to some objective function like the number of execution steps, processors, channels, etc. However,at best,linear execution time complexity can be atained. Through phrasing the polynomial product as a divide-and-conquer recursion, one can obtain a parallel program with sublinear execution time. In this case, the target program is not derived by an automatic search but given as a program skeleton, which can be deduced by a sequence of equational program transformations. We discuss the use of such skeletons, compare and assess the models in which loops and divide-and-conquer resursions are parallelized and comment on the performance properties of the resulting parallel implementations.     

平面最接近点对算法

描述了平面最接近点对问题,针对这一问题给出了3种算法,循环遍历算法、分治算法和平面扫描算法,并详细分析了3种算法的时间复杂度。     

Programming with Divide-and-Conquer Skeletons: A Case Study of FFT

We demonstrate an approach to parallel programming, based on skeletons – parameterized program schemas with efficient implementations over diverse architectures. The contribution of the paper is two-fold: (1) we classify divide-and-conquer (DC) algorithms and provide a family of provably correct parallel implementations for a particular DC skeleton, called DH (distributable homomorphism); (2) we adjust the mathematical specification of the Fast Fourier Transform (FFT) to the DH skeleton and, thereby, obtain a generic SPMD program, well suited for implementation under MPI. The generic program includes the efficient FFT solutions used in practice – the binary-exchange and the 2D- and 3D-transpose implementations – as special cases.