基于重用信息的非易失性缓存动态旁路策略

非易失性存储器具有能耗低、可扩展性强和存储密度大等优势,可替代传统静态随机存取存储器作为片上缓存,但其写操作的能耗及延迟较高,在大规模应用前需优化写性能.提出一种基于缓存块重用信息的动态旁路策略,用于优化非易失性存储器的缓存性能.分析测试程序访问最后一级缓存(LLC)时的重用特征,根据缓存块的重用信息动态预测相应的写操...     

基于相变存储器的存储系统与技术综述

随着处理器和存储器之间性能差距的不断增大,“存储墙”问题日益突出,但传统DRAM器件的集成度已接近极限,能耗问题也已成为瓶颈,如何设计扎实有效的存储架构解决存储墙问题已成为必须面对的挑战.近年来,以相变存储器(phase change memory, PCM)为代表的新型存储器件因其高集成度、低功耗的特点而受到了国内外研究者的广泛关注.特别地,相变存储器因其非易失性及字节寻址的特性而同时具备主存和外存的特点,在其影响下,主存和外存之间的界限正在变得模糊,将对未来的存储体系结构带来重大变化.重点讨论了基于PCM构建主存的结构,分析了其构建主存中的写优化技术、磨损均衡技术、硬件纠错技术、坏块重用技术、软件优化等关键问题,然后讨论了PCM在外存储系统的应用研究以及其对外存储体系结构和系统设计带来的影响.最后给出了PCM在存储系统中的应用研究展望.     

基于高性能SOC FPGA阵列的NVM验证架构设计与验证

新型非易失性存储器(non-volatile memory, NVM)技术日渐成熟,延迟越来越低,带宽越来越高,未来将不仅有可能取代以动态随机存储器(dynamic random access memory, DRAM)为代表的易失型存储设备在主存中的垄断地位,还有可能取代传统Flash和机械硬盘作为外存服务未来的计算机系统.如何综合各类新型存储的特性,设计高能效的存储架构,实现可应对大数据、云计算所需求的新型主存系统已经成为工业界和学术界的研究热点.提出基于高性能SOC FPGA阵列的NVM验证架构,互联多级FPGA,利用多层次FPGA结构扩展链接多片NVM.依据所提出的验证架构,设计了基于多层次FPGA的主从式NVM控制器,并完成适用于该架构的硬件原型设计.该架构不仅可以实现测试同类型多片NVM协同工作,也可以进行混合NVM存储管理方案验证.     

新型非易失存储研究

近年来,由于处理器性能和存储性能之间的差距不断扩大,存储系统成为计算机整体系统性能提升的瓶颈.随着微电子技术的迅速发展,新型非易失存储器件由于具有非易失、低能耗、良好的可扩展性和抗震等优良特性,得到了学术界和工业界的广泛关注.介绍了4种新型非易失存储器件,分别是STT-RAM,RRAM,PCRAM和FeRAM,对比了其与传统存储器件的性能参数.讨论了目前在存储架构中的不同层面(即缓存层、主存层和外存层)针对这些非易失存储器件的利用所开展的一些探索性工作,并分析了其中针对非易失存储器件的写次数有限、读写性能不均衡等不足所作出的一些策略设计.最后,对新型非易失存储器件的研究现状进行了总结,并提出了未来可能的发展方向.     

基于持久化内存的索引设计重新思考与优化

非易失性内存(non-volatile memory, NVM)是近几年来出现的一种新型存储介质.一方面,同传统的易失性内存一样,它有着低访问延迟、可字节寻址的特性;另一方面,与易失性内存不同的是,掉电后它存储的数据不会丢失,此外它还有着更高的密度以及更低的能耗开销.这些特性使得非易失性内存有望被大规模应用在未来的计算机系统中.非易失性内存的出现为构建高效的持久化索引提供了新的思路.由于非易失性硬件还处于研究阶段,因此大多数面向非易失性内存的索引研究工作基于模拟环境开展.在2019年4月英特尔发布了基于3D-XPoint技术的非易失性内存硬件apache pass (AEP),这使得研究人员可以基于真实的硬件环境去进行相关研究工作.首先评测了真实的非易失性内存器件,结果显示AEP的写延迟接近DRAM,而读延迟是DRAM的3~4倍.基于对硬件的实际评测结果,研究发现过去很多工作对非易失性内存的性能假设存在偏差,这使得过去的一些工作大多只针对写性能进行优化,并没有针对读性能进行优化.因此,重新审视了之前研究工作,针对过去的混合索引工作进行了读优化.此外,还提出了一种基于混合内存的异步缓存方法.实验结果表明,经过异步缓存方法优化后的混合索引读性能是优化前的1.8倍,此外,经过异步缓存优化后的持久化索引最多可以降低50%的读延迟.     

基于闪存的可编程线性忆阻器及其存算一体化电路与系统

基于新型非易失性存储器和存内计算架构的神经网络推理芯片在功耗、速度和存储密度等方面展现出突出的优势,使其在物联网和边缘计算等应用领域受到广泛关注.在本文中,我们详细介绍了一款基于可编程线性忆阻器(programmable linear random-access memory,PLRAM)的存算一体化片上系统芯片的设计...     

基于非易失性存储器的存储引擎性能优化

非易失性存储器具有接近内存的读写速度,可利用其替换传统的存储设备,从而提升存储引擎的性能。但是,传统的存储引擎通常使用通用块接口读写数据,导致了较长的 I/O 软件栈,增加了软件层的读写延迟,进而限制了非易失性存储器的性能优势。针对这一问题,该文以 Ceph 大数据存储系统为基础,研究设计了基于非易失性存储器的新型存储引擎 NVMStore,通过内存映射的方式访问存储设备,根据非易失性存储器的字节可寻址和数据持久化特性,优化数据读写流程,从而减小数据写放大以及软件栈的开销。实验结果表明,与使用非易失性存储器的传统存储引擎相比,NVMStore能够显著提升 Ceph 的小块数据读写性能。     

飞思卡尔扩展MRAM产品系列引领非易失性存储器的未来

经常有人将磁阻RAM(MRAM,Magnetoresistive Random Access Memory)称作是非易失性存储器(NVRAM, Non-Volatile RAM)未来的关键性技术.作为一项非易失性存储器技术,MRAM是可以在掉电时保留数据,并且不需要定期刷新.MRAM利用磁性材料和传统的硅电路在单个器件中提供了SRAM的高速度和闪存的非易失性,它的寿命几乎是没有限制的.MRAM器件可以用于高速缓冲器、配置内存,以及其他要求高速、耐用和非易失性的商业应用.     

新型非易失存储的安全与隐私问题研究综述

近年来,以相变存储器(phase change memory, PCM)为代表的各种新型非易失存储(non-volatile memory, NVM)技术得到广泛关注.NVM同时具有传统内存的字节寻址特性和外存的非易失特性,因而可以同时替代内存和外存,也可以用于混合存储体系结构.NVM具有低延时、高密度、低功耗的优势,有效缓解了存储墙问题.然而,由于应用程序可以直接通过存取指令(load/store)接口访问NVM,并且掉电后存储在NVM上的信息不会丢失,这给NVM的应用带来了一些新的安全和隐私挑战.首先讨论了持久化内存泄漏、不经意写操作、元数据安全、恶意磨损攻击、非易失指针等NVM应用中可能存在的安全问题以及最新的解决方案;然后讨论了数据保护、信息泄露等NVM应用中可能存在的隐私问题及现有的解决方案;最后探讨了NVM还需解决的安全和隐私问题,包括非易失缓存、程序安全等,并提出了一些解决方案,包括权限和保护机制的融合、使用易失性的NVM等.     

基于动态权衡的新型非易失存储器件体系结构研究综述

作为现有存储器的潜在替代技术,新型非易失存储器受到了来自学术界和工业界越来越多的关注.目前,制约新型非易失存储器广泛应用的主要问题包括写延迟长、写操作动态功耗高、写寿命有限等.针对这些问题,传统的解决方法是利用计算机体系结构的方法,通过增加层或者调度的方式加以避免或隐藏.但是,这类解决方案往往存在软硬件开销大、无法同时针对不同问题进行优化等问题.近年来,随着对新型非易失存储材料研究的深入,一系列器件自身所包含的动态权衡特性被陆续发现,这也为体系结构研究提供了新的机遇.基于这些器件自身的动态权衡特性,研究人员提出了一系列新的动态非易失存储器优化方案.与传统的优化方案相比,这类新型方案具有额外硬件开销小、可同时针对多个目标进行优化等优点.首先对非易失存储器存在的问题及传统的优化方案进行了概括;然后对非易失存储器件中3个重要的动态权衡关系进行了介绍;在此基础上,对近年来出现的一系列基于非易失存储器动态权衡特性的体系结构优化方案进行梳理;最后,对此类研究的特点进行了总结,并对未来的发展方向进行了展望.     

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.