为了克服现有Internet架构存在的众所周知的缺点,未来网络的研究成为热点.ICN(information-centricnetworking)在众多新架构中正逐渐被公认为最有前途的方案.它把传输的内容缓存到沿途的节点.高效的缓存机制是它的一个重要研究方面.为此...为了克服现有Internet架构存在的众所周知的缺点,未来网络的研究成为热点.ICN(information-centricnetworking)在众多新架构中正逐渐被公认为最有前途的方案.它把传输的内容缓存到沿途的节点.高效的缓存机制是它的一个重要研究方面.为此,提出了一种在分布式缓存机制中嵌入中心式缓存决策的机制(content-awareplacement,discovery and replacement,简称APDR),它把内容的放置、发现、替换统一起来考虑,实现内容的有序缓存,提高网络的性能.APDR的主要思想是:Interest报文除了携带对内容的请求以外,还收集沿途各节点对该内容的潜在需求、空闲缓存等信息,使得Interest的汇聚点和目的地节点可以据此计算出一个缓存方案,并把该方案附加在Data报文上,通知返程途中的某些节点缓存该内容并设置指定的缓存时间.在多种实验条件下对APDR进行了仿真验证,结果表明,APDR可以改善网络性能,包括缓存命中率、接入代价、替换数量、转发效率以及缓存鲁棒性等;而且APDR的额外开销也不大.展开更多
煤层顶板砂岩富水性预测是有待解决的重要问题。以实际测井曲线数据为输入,利用Gassmann方程和AVO(Amplitude Variation with Offset)技术探讨煤层顶板砂岩富水性的预测方法。首先,利用实际测井曲线计算顶板砂岩的纵波速度、孔隙度和泥...煤层顶板砂岩富水性预测是有待解决的重要问题。以实际测井曲线数据为输入,利用Gassmann方程和AVO(Amplitude Variation with Offset)技术探讨煤层顶板砂岩富水性的预测方法。首先,利用实际测井曲线计算顶板砂岩的纵波速度、孔隙度和泥质含量;其次,以Han经验公式为基础,曲面拟合纵波速度、孔隙度和泥质含量间的关系式,并导出砂岩骨架纵波速度;再次,利用Castagna经验公式计算砂岩骨架的横波速度,并建立14种顶板砂岩模型;最后,利用Gassmann方程进行流体替换,计算各模型的纵横波速度和密度,从而正演模拟顶板砂岩的AVO响应。结合理论分析和实例预测,发现截距–梯度交会图可以区分砂岩孔隙度和干湿性,是顶板砂岩富水性预测的一种有效手段。展开更多
This paper describes the theory, implementation, and experimental evaluation of an Aggregation Cache Replacement （ ACR ） algorithm. By considering application background, carefully choosing weight values, using a sp...This paper describes the theory, implementation, and experimental evaluation of an Aggregation Cache Replacement （ ACR ） algorithm. By considering application background, carefully choosing weight values, using a special formula to calculate the similarity, and clustering ontologies by similarity for getting more embedded deep relations, ACR combines the ontology similarity with the value of object and decides which object is to be replaced. We demonstrate the usefulness of ACR through experiments. （a） It is found that the aggregation tree is created wholly differently according to the application cases. Therefore, clustering can direct the content adaptation more accurately according to the user perception and can satisfy the user with different preferences. （b） After comparing this new method with widely-used algorithm Last-Recently-Used （LRU） and First-in-First-out （FIFO） method, it is found that ACR outperforms the later two in accuracy and usability. （c） It has a better semantic explanation and makes adaptation more personalized and more precise.展开更多
Modern shared-memory multi-core processors typically have shared Level 2(L2)or Level 3(L3)caches.Cache bottlenecks and replacement strategies are the main problems of such architectures,where multiple cores try to acc...Modern shared-memory multi-core processors typically have shared Level 2(L2)or Level 3(L3)caches.Cache bottlenecks and replacement strategies are the main problems of such architectures,where multiple cores try to access the shared cache simultaneously.The main problem in improving memory performance is the shared cache architecture and cache replacement.This paper documents the implementation of a Dual-Port Content Addressable Memory(DPCAM)and a modified Near-Far Access Replacement Algorithm(NFRA),which was previously proposed as a shared L2 cache layer in a multi-core processor.Standard Performance Evaluation Corporation(SPEC)Central Processing Unit(CPU)2006 benchmark workloads are used to evaluate the benefit of the shared L2 cache layer.Results show improved performance of the multicore processor’s DPCAM and NFRA algorithms,corresponding to a higher number of concurrent accesses to shared memory.The new architecture significantly increases system throughput and records performance improvements of up to 8.7%on various types of SPEC 2006 benchmarks.The miss rate is also improved by about 13%,with some exceptions in the sphinx3 and bzip2 benchmarks.These results could open a new window for solving the long-standing problems with shared cache in multi-core processors.展开更多
【目的】针对目前车载社交网络(Vehicular Social Network,VSN)中存在的缓存冗余大、效率低等问题,提出适用于动态VSN的缓存决策策略和缓存替换策略。【文献范围】文章重点调研国内外对于信息中心网络(Information-Centric Networking,I...【目的】针对目前车载社交网络(Vehicular Social Network,VSN)中存在的缓存冗余大、效率低等问题,提出适用于动态VSN的缓存决策策略和缓存替换策略。【文献范围】文章重点调研国内外对于信息中心网络(Information-Centric Networking,ICN)的架构、ICN缓存、VSN的缓存机制,以及对于两者相结合的研究。【方法】本文首先以缓存内容流行度和节点间朋友关系度为指标判断是否缓存内容。然后将内容存储库进行划分,以增加缓存的多样性。最后基于节点的重要程度制定缓存替换策略。【结果】本文设计的缓存策略明显提高了兴趣包的响应效率,避免了由于频繁切换带来的损失,同时在保证包投递率的前提下,大大减少了网络开销。【局限】由于现实的局限性,使得无法在真实环境下进行实验,导致实验结果过于理想化。【结论】将ICN技术应用于VSN中,利用其内容和位置分离能更好支持终端移动性的特点,以及网内缓存机制的优势,可以降低网络延迟,实现快速的内容交付。展开更多
文摘为了克服现有Internet架构存在的众所周知的缺点,未来网络的研究成为热点.ICN(information-centricnetworking)在众多新架构中正逐渐被公认为最有前途的方案.它把传输的内容缓存到沿途的节点.高效的缓存机制是它的一个重要研究方面.为此,提出了一种在分布式缓存机制中嵌入中心式缓存决策的机制(content-awareplacement,discovery and replacement,简称APDR),它把内容的放置、发现、替换统一起来考虑,实现内容的有序缓存,提高网络的性能.APDR的主要思想是:Interest报文除了携带对内容的请求以外,还收集沿途各节点对该内容的潜在需求、空闲缓存等信息,使得Interest的汇聚点和目的地节点可以据此计算出一个缓存方案,并把该方案附加在Data报文上,通知返程途中的某些节点缓存该内容并设置指定的缓存时间.在多种实验条件下对APDR进行了仿真验证,结果表明,APDR可以改善网络性能,包括缓存命中率、接入代价、替换数量、转发效率以及缓存鲁棒性等;而且APDR的额外开销也不大.
文摘煤层顶板砂岩富水性预测是有待解决的重要问题。以实际测井曲线数据为输入,利用Gassmann方程和AVO(Amplitude Variation with Offset)技术探讨煤层顶板砂岩富水性的预测方法。首先,利用实际测井曲线计算顶板砂岩的纵波速度、孔隙度和泥质含量;其次,以Han经验公式为基础,曲面拟合纵波速度、孔隙度和泥质含量间的关系式,并导出砂岩骨架纵波速度;再次,利用Castagna经验公式计算砂岩骨架的横波速度,并建立14种顶板砂岩模型;最后,利用Gassmann方程进行流体替换,计算各模型的纵横波速度和密度,从而正演模拟顶板砂岩的AVO响应。结合理论分析和实例预测,发现截距–梯度交会图可以区分砂岩孔隙度和干湿性,是顶板砂岩富水性预测的一种有效手段。
基金Supported by the National Natural Science Foun-dation of China (60472050)
文摘This paper describes the theory, implementation, and experimental evaluation of an Aggregation Cache Replacement （ ACR ） algorithm. By considering application background, carefully choosing weight values, using a special formula to calculate the similarity, and clustering ontologies by similarity for getting more embedded deep relations, ACR combines the ontology similarity with the value of object and decides which object is to be replaced. We demonstrate the usefulness of ACR through experiments. （a） It is found that the aggregation tree is created wholly differently according to the application cases. Therefore, clustering can direct the content adaptation more accurately according to the user perception and can satisfy the user with different preferences. （b） After comparing this new method with widely-used algorithm Last-Recently-Used （LRU） and First-in-First-out （FIFO） method, it is found that ACR outperforms the later two in accuracy and usability. （c） It has a better semantic explanation and makes adaptation more personalized and more precise.
文摘Modern shared-memory multi-core processors typically have shared Level 2(L2)or Level 3(L3)caches.Cache bottlenecks and replacement strategies are the main problems of such architectures,where multiple cores try to access the shared cache simultaneously.The main problem in improving memory performance is the shared cache architecture and cache replacement.This paper documents the implementation of a Dual-Port Content Addressable Memory(DPCAM)and a modified Near-Far Access Replacement Algorithm(NFRA),which was previously proposed as a shared L2 cache layer in a multi-core processor.Standard Performance Evaluation Corporation(SPEC)Central Processing Unit(CPU)2006 benchmark workloads are used to evaluate the benefit of the shared L2 cache layer.Results show improved performance of the multicore processor’s DPCAM and NFRA algorithms,corresponding to a higher number of concurrent accesses to shared memory.The new architecture significantly increases system throughput and records performance improvements of up to 8.7%on various types of SPEC 2006 benchmarks.The miss rate is also improved by about 13%,with some exceptions in the sphinx3 and bzip2 benchmarks.These results could open a new window for solving the long-standing problems with shared cache in multi-core processors.
文摘【目的】针对目前车载社交网络(Vehicular Social Network,VSN)中存在的缓存冗余大、效率低等问题,提出适用于动态VSN的缓存决策策略和缓存替换策略。【文献范围】文章重点调研国内外对于信息中心网络(Information-Centric Networking,ICN)的架构、ICN缓存、VSN的缓存机制,以及对于两者相结合的研究。【方法】本文首先以缓存内容流行度和节点间朋友关系度为指标判断是否缓存内容。然后将内容存储库进行划分,以增加缓存的多样性。最后基于节点的重要程度制定缓存替换策略。【结果】本文设计的缓存策略明显提高了兴趣包的响应效率,避免了由于频繁切换带来的损失,同时在保证包投递率的前提下,大大减少了网络开销。【局限】由于现实的局限性,使得无法在真实环境下进行实验,导致实验结果过于理想化。【结论】将ICN技术应用于VSN中,利用其内容和位置分离能更好支持终端移动性的特点,以及网内缓存机制的优势,可以降低网络延迟,实现快速的内容交付。
