共查询到20条相似文献,搜索用时 62 毫秒
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她看上去像是一个再平常不过的邻家女孩,也让人觉得她是那种从小抱着洋娃娃、坐在童话书堆里长大的女孩。可她偏偏形容自己“很怪,怪到不能再怪”,“我只记得小时候马桶旁边的橱子里放过几本童话,”她说。 相似文献
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Paulo Sérgio Almeida Carlos Baquero Nuno Preguiça 《Information Processing Letters》2007,101(6):255-261
Bloom filters provide space-efficient storage of sets at the cost of a probability of false positives on membership queries. The size of the filter must be defined a priori based on the number of elements to store and the desired false positive probability, being impossible to store extra elements without increasing the false positive probability. This leads typically to a conservative assumption regarding maximum set size, possibly by orders of magnitude, and a consequent space waste. This paper proposes Scalable Bloom Filters, a variant of Bloom filters that can adapt dynamically to the number of elements stored, while assuring a maximum false positive probability. 相似文献
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Guo Deke Wu Jie Chen Honghui Yuan Ye Luo Xueshan 《Knowledge and Data Engineering, IEEE Transactions on》2010,22(1):120-133
A Bloom filter is an effective, space-efficient data structure for concisely representing a set, and supporting approximate membership queries. Traditionally, the Bloom filter and its variants just focus on how to represent a static set and decrease the false positive probability to a sufficiently low level. By investigating mainstream applications based on the Bloom filter, we reveal that dynamic data sets are more common and important than static sets. However, existing variants of the Bloom filter cannot support dynamic data sets well. To address this issue, we propose dynamic Bloom filters to represent dynamic sets, as well as static sets and design necessary item insertion, membership query, item deletion, and filter union algorithms. The dynamic Bloom filter can control the false positive probability at a low level by expanding its capacity as the set cardinality increases. Through comprehensive mathematical analysis, we show that the dynamic Bloom filter uses less expected memory than the Bloom filter when representing dynamic sets with an upper bound on set cardinality, and also that the dynamic Bloom filter is more stable than the Bloom filter due to infrequent reconstruction when addressing dynamic sets without an upper bound on set cardinality. Moreover, the analysis results hold in stand-alone applications, as well as distributed applications. 相似文献
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On the false-positive rate of Bloom filters 总被引:1,自引:0,他引:1
Prosenjit Bose Hua Guo Anil Maheshwari Jason Morrison Yihui Tang 《Information Processing Letters》2008,108(4):210-213
Bloom filters are a randomized data structure for membership queries dating back to 1970. Bloom filters sometimes give erroneous answers to queries, called false positives. Bloom analyzed the probability of such erroneous answers, called the false-positive rate, and Bloom's analysis has appeared in many publications throughout the years. We show that Bloom's analysis is incorrect and give a correct analysis. 相似文献
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本文提出一种基于多层次结构的树形布鲁姆过滤器TBF。多层次结构是近年来布鲁姆过滤器及相关数据结构研究的热点。这一结构使得多层次的存储方式得以实现,减轻了片上存储的负担,而且也加快了片上查找的速度。TBF是针对BloomingTree算法存在的缺陷所改进的一种更高效的算法,它能够在低于CBF的空间需求的条件下实现与CBF相同的功能。实验证明:与BloomingTree算法相比,TBF能够有效地解决BloomingTree算法在逻辑索引时的错误问题,而且比BloomingTree算法时间上更加高效:在层数不变假阳性相同条件下,查询时间平均提高13.4%;在假阳性不变层数相同条件下,插入时间平均提高17.9%,删除时间平均提高12%。 相似文献
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偏态数据流中的Bloom Filters自适应机制研究 总被引:1,自引:0,他引:1
针对Count Bloom Filters(CBF)在对偏态分布的网络数据流进行频度检测时,其使用的固定位数的计数器容易溢出的不足,提出了一种自适应性Bloom Filters(Adaptive Bloom Filters ABF),ABF使用可扩展的逻辑计数器替代CBF中大小固定的物理计数器进行计数,逻辑计数器由数目动态变化的若干个物理计数器组成,初始状态逻辑计数器等同于物理计数器,但逻辑计数器在频度数值上溢时会自适应扩展,覆盖其外部的物理计数器,增加数值容量,保证数值的测量准确性.实验表明ABF能够更好地适应检测频度的变化,并且不显著增加误判率,在对数据偏态分布的频度测量场合比其它Count Bloom Filters更具有优势. 相似文献
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Invertible Bloom Lookup Tables (IBLTs) have been recently introduced as an extension of traditional Bloom filters. IBLTs store key-value pairs. Unlike traditional Bloom filters, IBLTs support both a lookup operation (given a key, return a value) and an operation that lists out all the key-value pairs stored. One issue with IBLTs is that there is a probability that a lookup operation will return “not found” for a key. In this paper, a technique to reduce this probability without affecting the storage requirement and only moderately increasing the search time is presented and evaluated. The results show that it can significantly reduce the probability of not returning a value that is actually stored in the IBLT. The overhead of the modified search procedure, compared to the standard IBLT search procedure, is small and has little impact on the average search time. 相似文献