共查询到19条相似文献,搜索用时 203 毫秒
1.
基于滑动窗口的数据流连续J-A查询的处理方法 总被引:3,自引:0,他引:3
数据流滑动窗口连接聚集连续查询(简记J-A查询)是经常使用的一类查询.这类查询的直观处理方法是创建查询操作树,以流水线的方式计算查询结果.这种方法需要在主存中保存滑动窗口连接的结果,查询处理的主存空间开销为O(α×β),其中(,(为参加连接两个滑动窗口的大小.在数据流的查询处理中,内存是最重要的计算资源.提出了两种滑动窗口J-A连续查询处理算法--IC算法和TC算法,使得查询处理的空间开销降为Ο(α+β).理论分析和实验结果表明,所提出的算法具有更高的效率. 相似文献
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一种时间复杂度最优的精确串匹配算法 总被引:14,自引:2,他引:12
现有的串匹配算法通常以模式长度作为滑动窗口大小.在窗口移动后,往往会丢弃掉一些已扫描正文的信息.提出了LDM(linear DAWG matching)串匹配算法,该算法将正文分为[n/m]个相互重叠、大小为2m-1的扫描窗口.在每个扫描窗口内,算法批量地尝试m个可能位置,首先使用反向后缀自动机从窗口中间位置向前扫描模式前缀;若成功,则再使用正向有限状态自动机从中间位置向后扫描剩余的模式后缀.分析证明,LDM算法的最差、最好、平均时间复杂度分别达到了理论最好结果:O(n),O(n/m),O(n(1ogσm)/m).实际性能测试也验证了平均时间复杂度最优这一理论结果.而且,对于在较大字母表下查找短模式的情况,LDM算法速度在被测试算法中最快.总之,LDM算法不但适合进行离线模式匹配,而且还特别适合需要进行在线高速匹配的应用. 相似文献
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模糊聚类计算的最佳算法 总被引:14,自引:0,他引:14
给出模糊关系传递闭包在对应模糊图上的几何意义,并提出一个基于图连通分支计算的模糊聚类最佳算法.对任给的n个样本,新算法最坏情况下的时间复杂性函数T(n)满足O(n)≤T(n)≤O(n2).与经典的基于模糊传递闭包计算的模糊聚类算法的O(n3logn)计算时间相比,新算法至少降低了O(n相似文献
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分布式存储的并行串匹配算法的设计与分析 总被引:7,自引:0,他引:7
并行串匹配算法的研究大都集中在PRAM(parallel random access machine)模型上,其他更为实际的模型上的并行串匹配算法的研究相对要薄弱得多.该文采用将最优串行算法并行化的技术,利用模式串的周期性质,巧妙地将改进的KMP(Knuth-Morris-Pratt)算法并行化,提出了一个简便、高效且具有良好可扩放性的分布式串匹配算法,其计算复杂度为O(n/p+m),通信复杂度为O(ulogp相似文献
7.
分别在两种重要并行计算模型中给出计算有向基因组排列的反转距离新的并行算法.基于Hannenhalli和Pevzner理论,分3个主要部分设计并行算法:构建断点图、计算断点图中圈数、计算断点图中障碍的数目.在CREW-PRAM模型上,算法使用O(n2)处理器,时间复杂度为O(log2n);在基于流水光总线的可重构线性阵列系统(linear array with a reconfigurable pipelined bus system, LARPBS)模型上,算法使用O(n3)处理器,计算时间复杂度为O(logn). 相似文献
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基于嵌入二维数组的迁移聚集树的数据流突变检测算法 总被引:1,自引:0,他引:1
数据流突变检测技术由于在金融、医疗服务、电信等重要领域有广泛应用而受到国内外科研学者更多关注。为了能够检测正数据流、负数据流以及正负交错数据流的突变,提出了嵌入二维数组的迁移聚集树的数据流突变检测算法。该算法能够检测单调聚集函数和非单调聚集函数的突变,能够在较少时间内完成数据流突变检测的任务。实验证明本算法有良好的性能和效率,更适合检测突变的数据流。 相似文献
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将串行动态二表算法应用于并行三表算法的设计中,提出一种求解背包、精确的可满足性和集覆盖等背包类NP完全问题的并行三表六子表算法.基于EREW-PRAM模型,该算法可使用O(2n/8)的处理机在O(27n/16)的时间和O(213n/48)的空间求解n维背包类问题,其时间-空间-处理机折衷为O(25n/6).与现有文献的性能对比分析表明,该算法极大地提高了并行求解背包类问题的时间-空间-处理机折衷性能.由于该算法能够破解更高维数的背包类公钥和数字水印系统,其结论在密钥分析领域具有一定的理论和实际意义. 相似文献
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Hua-Fu Li 《Multimedia Tools and Applications》2009,41(2):287-304
Mining of music data is one of the most important problems in multimedia data mining. In this paper, two research issues of
mining music data, i.e., online mining of music query streams and change detection of music query streams, are discussed.
First, we proposed an efficient online algorithm, FTP-stream (Frequent Temporal Pattern mining of streams), to mine all frequent melody structures over sliding windows of music melody sequence streams. An effective bit-sequence
representation is used in the proposed algorithm to reduce the time and memory needed to slide the windows. An effective list
structure is developed in the FTP-stream algorithm to overcome the performance bottleneck of 2-candidate generation. Experiments
show that the proposed algorithm FTP-stream only needs a half of memory requirement of original melody sequence data, and
just scans the music query stream once. After mining frequent melody structures, we developed a simple online algorithm, MQS-change
(changes of Music Query Streams), to detect the changes of frequent melody structures in current user-centered music query streams. Two music melody
structures (set of chord-sets and string of chord-sets) are maintained and four melody structure changes (positive burst,
negative burst, increasing change and decreasing change) are monitored in a new summary data structure, MSC-list (a list of Music Structure Changes). Experiments show that the MQS-change algorithm is an effective online method to detect the changes of music melody
structures over continuous music query streams.
相似文献
Hua-Fu LiEmail: |
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复杂网络大数据中重叠社区检测算法 总被引:3,自引:1,他引:2
大数据时代互联网用户数量呈爆炸性增长,社交网络、电商交易网络等复杂网络规模快速发展,准确有效地检测复杂网络大数据中重叠社区结构对用户兴趣点推荐和热点传播具有重要意义。提出一种新的面向复杂网络大数据的重叠社区检测算法DOC(Detecting Overlapping Communities over complex network big data),时间复杂度为O(nlog2(n)),算法基于模块度聚类和图计算思想应用新的节点和边的更新方法,利用平衡二叉树对模块度增量建立索引,基于模块度最优的思想设计一种新的重叠社区检测算法。相对于传统重叠节点检测算法,对每个节点分析的频率大大降低,可以在较低的算法运行时间下获得较高的识别准确率。复杂网络大数据集上的算法测试结果表明:DOC算法能够有效地检测出网络重叠社区,社区识别准确率较高,在大规模LFR基准数据集上其重叠社区检测标准化互信息指标NMI最高能达到0.97,重叠节点检测指标F-score的平均值在0.91以上,且复杂网络大数据下的运行时间明显优于传统算法。 相似文献
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Geodesic offset curves are important for many industrial applications, such as solid modeling, robot-path planning, the generation of tool paths for NC machining, etc. Although the offset problem is well studied in classical differential geometry and computer-aided design, where the underlying surface is sufficiently smooth, very few algorithms are available for computing geodesic offsets on discrete representation, in which the input is typically a polyline curve restricted on a piecewise linear mesh. In this paper, we propose an efficient and exact algorithm to compute the geodesic offsets on triangle meshes by extending the Xin–Wang algorithm of discrete geodesics. We define a new data structure called parallel-source windows, and extend both the “one angle one split” and the filtering theorem to maintain the window tree. Similar to the original Xin–Wang algorithm, our extended algorithm has an O(n) space complexity and an O(n2logn) asymptotic time complexity, where n is the number of vertices on the input mesh. We tested our algorithm on numerous real-world models and showed that our algorithm is exact, efficient and robust, and can be applied to large scale models with complicated geometry and topology. 相似文献
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Detecting duplicates in data streams is an important problem that has a wide range of applications. In general,precisely detecting duplicates in an unbounded data stream is not feasible in most streaming scenarios,and,on the other hand,the elements in data streams are always time sensitive. These make it particular significant approximately detecting duplicates among newly arrived elements of a data stream within a fixed time frame. In this paper,we present a novel data structure,Decaying Bloom Filter(DBF),as an extension of the Counting Bloom Filter,that effectively removes stale elements as new elements continuously arrive over sliding windows. On the DBF basis we present an efficient algorithm to approximately detect duplicates over sliding windows. Our algorithm may produce false positive errors,but not false negative errors as in many previous results. We analyze the time complexity and detection accuracy,and give a tight upper bound of false positive rate. For a given space G bits and sliding window size W,our algorithm has an amortized time complexity of O((G/W))~(1/2). Both analytical and experimental results on synthetic data demonstrate that our algorithm is superior in both execution time and detection accuracy to the previous results. 相似文献
16.
《Advanced Robotics》2013,27(8):703-715
This article describes an efficient recursive algorithm for the computation of the operational space inertia matrix of an n-link branching robotic mechanism with multiple (m) operational points. The proposed algorithm achieves the complexity of O(nm + m 3). Since m can be considered as a small constant in practice, as the number of links increases, this algorithm performs significantly better than the existing O(n 3 + m 3) symbolic method. The experimental results of this algorithm are presented using real-time dynamic simulation. 相似文献
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We propose two fast algorithms for abrupt change detection in streaming data that can operate on arbitrary unknown data distributions
before and after the change. The first algorithm,
MB-GT\textsf{MB-GT}
, computes efficiently the average Euclidean distance between all pairs of data points before and after the hypothesized change.
The second algorithm,
MB-CUSUM\textsf{MB-CUSUM}
, computes the log-likelihood ratio statistic for the data distributions before and after the change, similarly to the classical
CUSUM algorithm, but unlike that algorithm,
MB-CUSUM\textsf{MB-CUSUM}
does not need to know the exact distributions, and uses kernel density estimates instead. Although a straightforward computation
of the two change statistics would have computational complexity of O(N
4) with respect to the size N of the streaming data buffer, the proposed algorithms are able to use the computational structure of these statistics to
achieve a computational complexity of only O(N
2) and memory requirement of O(N). Furthermore, the algorithms perform surprisingly well on dependent observations generated by underlying dynamical systems,
unlike traditional change detection algorithms. 相似文献
18.
We propose a simple and efficient general algorithm for determining both rotational and involutional symmetries of polyhedra. It requiresO(m
2) time and usesO(m) space, wherem is the number of edges of the polyhedron. As this is the lower bound of the symmetry detection problem for the considered output form, our algorithm is optimal. We show that a slight modification of our symmetry detection algorithm can be used to solve the related conguity problem of polyhedra. 相似文献
19.
Shortest path problems can be solved very efficiently when a directed graph is nearly acyclic. Earlier results defined a graph decomposition, now called the 1-dominator set, which consists of a unique collection of acyclic structures with each single acyclic structure dominated by a single associated trigger vertex. In this framework, a specialised shortest path algorithm only spends delete-min operations on trigger vertices, thereby making the computation of shortest paths through non-trigger vertices easier. A previously presented algorithm computed the 1-dominator set in O(mn) worst-case time, which allowed it to be integrated as part of an O(mn+nrlogr) time all-pairs algorithm. Here m and n respectively denote the number of edges and vertices in the graph, while r denotes the number of trigger vertices. A new algorithm presented in this paper computes the 1-dominator set in just O(m) time. This can be integrated as part of the O(m+rlogr) time spent solving single-source, improving on the value of r obtained by the earlier tree-decomposition single-source algorithm. In addition, a new bidirectional form of 1-dominator set is presented, which further improves the value of r by defining acyclic structures in both directions over edges in the graph. The bidirectional 1-dominator set can similarly be computed in O(m) time and included as part of the O(m+rlogr) time spent computing single-source. This paper also presents a new all-pairs algorithm under the more general framework where r is defined as the size of any predetermined feedback vertex set of the graph, improving the previous all-pairs time complexity from O(mn+nr2) to O(mn+r3). 相似文献