预先指定单元位置的时延驱动布局优化方法

为了在时延驱动的布局算法中减少关键路径的数量,提出一种预先指定单元位置的基于线性规划优化时延驱动的布局方法.在全局布局每次迭代优化后提取关键子电路,建立子电路的时延模型;应用线性规划优化并移动子电路上各单元位置形成新的初始布局,进行下一次布局迭代.将该方法嵌入到力指向的布局器Kraftwerk中的实验结果表明,最小负时延裕量提高了21 ps,负时延裕量总和平均提高了483 ps,同时线长仅增加了0.83%.     

力驱动三维FPGA布局算法

三维FPGA布局问题的复杂度与二维情况相比成指数倍增长,布局算法需要花费大量时间,影响了FPGA物理设计效率.为了在保证布局质量的前提下缩短布局时间,提出以线长为优化目标基于力驱动的三维FPGA布局算法——3D-WFP.该算法由整体布局、坐标合法化和层划分、布局优化3个阶段组成,通过力驱动算法快速形成整体布局,为后续2个子过程提供更精确的逻辑单元位置和时延信息.提出三维空间填充曲线,根据位置和时延信息依次对逻辑单元按照三维空间填充曲线进行坐标合法化和层划分;修正了低温模拟退火进行布局优化的解空间,大大加快了低温模拟退火的收敛速度.与已有的三维FPGA布局算法比较,3D-WFP在保证运行时间和时延性能的前提下,有效地缩短了最终布局结果,缩短的总线长达7.38%.     

LowTARP:低温交替改善的模拟退火布局算法

在模拟退火算法的基础上,提出一种"低温交替改善"的FPGA布局算法.在模拟退火的低温阶段,该算法不仅交换可配置逻辑单元(CLB)的位置,也改变逻辑单元(LE)所属的CLB,即同时对布局和装箱进行优化,并采用布局的目标函数来衡量装箱的优劣.实验数据表明,采用3种不同的装箱算法的结果作为布局的输入,布线通道宽度与最具代表性的VPR布局算法相比,分别提高21.3%,15.5%和10.7%,而引入的额外计算量不到20%.     

基于SRAM结构的FPGA抗辐射布局算法

分析由辐射造成的单粒子翻转(SEU)软错误,在通用布局布线工具的基础上,提出一种基于SRAM结构的现场可编程门阵列 (FPGA)抗辐射布局算法。该算法通过优化电路单元在FPGA中的布局位置,减少布线资源开路敏感错误、短路敏感错误以及SEU敏感点的数目。测试结果表明,该算法能减少SEU软错误,提高FPGA的抗辐射性能,并且无需增加额外的设计成本和硬件开销。     

层次式FPGA快速布局算法

随着现代FPGA规模与结构迅速发展,对FPGA物理设计的要求越来越高,为此,对商业化层次式FPGA提出一种快速布局算法.以基于划分的布局方法作为基本算法框架,针对层次式FPGA的结构制定计划分粒度控制、空间分配和线网权重分配等优化策略,对电路划分过程(整体布局过程)和详细布局过程进行优化.实验结果表明,该算法在实现快速布局的同时,嵌入的优化策略平均将总线长缩短29%;与基于结群的层次式FPGA布局算法相比,平均线长仅为基于结群算法的60%,同时平均运行速度快4倍多.     

应用于大规模集成电路非线性布局的二元结群算法

针对平面模式下非线性布局算法的设计能力远远跟不上集成电路发展速度的现状,将连接紧密的单元结合作为整体参与布局,提出一种应用于大规模非线性布局的二元结群算法,以减小电路规模和复杂度,进而提高布局算法速度、优化布局算法结果质量.该算法按2个单元之间对内连接度与对外连接度的比值排序,并按比值从大到小对单元进行结群,然后更新网表;如果其中一个单元已经被结群或是它们合并后总面积会大于目标结群面积,则放弃这2个单元的组合.将文中算法嵌入之前实现的平面非线性布局器中,可使运行时间相对于平面模式减少40％,布局结果的质量提高了12％.该布局器详细布局后的结果比当前流行的同样采用结群算法的布局器Capo,FastPlace,Fengshui和mPL5-fast算法分别优化了7％,9％,7％和5％,显示了其有效性和高效性.     

针对宏模块的合法化技术

在传统的总体布局完成之后,一个很重要的步骤是消除单元之间的重叠,即合法化过程。混合模式下的宏模块会对合法化过程带来很大困难。针对宏模块的结构特点,考虑宏模块布局合理位置(site)的约束,设计实现了特别应用于宏模块的合法化算法,并在mPL6全局布局结果上进行测试,结果表明,与FastPlace相比该方法更具合理性和有效性。     

应用于大规模FPGA的解析式布局算法

针对FPGA的结构特点,借鉴ASIC布局算法中非线性建模思想,提出一种应用于大规模FPGA的解析式布局算法.该算法以非线性线长为目标,采用较少迭代次数的共轭梯度方法作为求解器,解决组合优化方法时间大量消耗问题.实验结果表明,该方法能够在较短的时间得到较好的布局质量,与FastPlace的结果对比证明了其有效性.     

分级的混合模式布局算法

针对混合模式的布局问题提出一种分级的自动布局算法.所谓混合模式就是标准单元和宏模块相结合的布局模式.该算法在模块级和单元级两个层次上完成布局.在模块级上,首先将所有随机单元划分成若干软模块,然后采用基于序列对(sequence pair,简称SP)的方法完成模块布局;在单元级上,首先对每个软模块内部采用二次规划的布局算法进行布局,然后在全芯片范围内对布局进行改善,最后采用一种基于最小割(min-cut)和枚举相结合的快速详细布局算法完成最终布局.在一组标准单元数和宏模块数不同的电路上对该算法进行了验证,效果是令人满意的.     

CMS环境下基于智能优化算法的单元间布局问题研究*

研究了单元制造系统(CMS)设计中单元间布局设计问题,从单元制造系统的实际出发,提出了一种基于割树(Slicing-tree)的单元间布局设计模型.该模型考虑了单元形状约束、单元I/O点位置优化等诸因素对布局结果的影响.针对基于割树的描述形式,采用遗传算法求解,提出了一种新的割树编码方案,克服了以往编码方案易产生非法子串、不能覆盖整个解空间以及实现困难等缺点.计算结果表明,该算法是有效的、可行的.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.