Results 11  20
of
30
Efficient Algorithms for LargeScale Temporal Aggregation
 IEEE TRANS. ON KNOWLEDGE AND DATA ENGINEERING
, 2003
"... The ability to model timevarying natures is essential to many database applications such as data warehousing and mining. However, the temporal aspects provide many unique characteristics and challenges for query processing and optimization. Among the challenges is computing temporal aggregates, whi ..."
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Cited by 13 (2 self)
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The ability to model timevarying natures is essential to many database applications such as data warehousing and mining. However, the temporal aspects provide many unique characteristics and challenges for query processing and optimization. Among the challenges is computing temporal aggregates, which is complicated by having to compute temporal grouping. In this paper, we introduce a variety of temporal aggregation algorithms that overcome major drawbacks of previous work. First, for smallscale aggregations, both the worstcase and averagecase processing time have been improved significantly. Second, for largescale aggregations, the proposed algorithms can deal with a database that is substantially larger than the size of available memory. Third, the parallel algorithm designed on a sharednothing architecture achieves scalable performance by delivering nearly linear scaleup and speedup, even at the presence of data skew. The contributions made in this paper are particularly important because the rate of increase in database size and response time requirements has outpaced advancements in processor and mass storage technology.
DataFlow Frameworks for WorstCase Execution Time Analysis
 RealTime Systems
, 2000
"... The purpose of this paper is to introduce frameworks based on dataflow equations which provide for estimating the worstcase execution time (WCET) of (realtime) programs. These frameworks allow several different WCET analysis techniques, which range from nave approaches to exact analysis, provided ..."
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Cited by 12 (8 self)
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The purpose of this paper is to introduce frameworks based on dataflow equations which provide for estimating the worstcase execution time (WCET) of (realtime) programs. These frameworks allow several different WCET analysis techniques, which range from nave approaches to exact analysis, provided exact knowledge on the program behaviour is available. However, dataflow frameworks can also be used for symbolic analysis based on information derived automatically from the source code of the program. As a byproduct we show that slightly modified elimination methods can be employed for solving WCET dataflow equations, while iteration algorithms cannot be used for this purpose.
Efficient Search in Unbalanced, Randomized PeerToPeer Search Trees
 Ecole Polytechnique Fédérale de Lausanne (EPFL
, 2002
"... Scalable mechanisms to support efficient keybased search in distributed systems are an important part of the infrastructure of peertopeer systems and global information systems. They received substantial attention both in information and communication systems research. A particularly important cl ..."
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Cited by 11 (9 self)
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Scalable mechanisms to support efficient keybased search in distributed systems are an important part of the infrastructure of peertopeer systems and global information systems. They received substantial attention both in information and communication systems research. A particularly important class of approaches is based on a principle of scalable distribution of binary search trees that has been introduced by Plaxton [9]. When adapting the shape of such a tree search structure to the data distribution in order to obtain load balancing, the search trees may become highly unbalanced. We show that for PGrid, a Plaxtonlike distributed search structure that we first introduced in [1], the expected communication cost for searches is strictly limited by where is the number of peers. This result is completely independent of the shape of the underlying tree. The approach exploits the randomization principle of the PGrid structure by virtue of its decentralized and randomized construction process. 1
Pointerless Implementation of Hierarchical Simplicial Meshes and Efficient Neighbor Finding in Arbitrary Dimensions
 In Proc. International Meshing Roundtable (IMR 2004
, 2004
"... We describe a pointerless representation of hierarchical regular simplicial meshes, based on a bisection approach proposed by Maubach. We introduce a new labeling scheme, called an LPT code, that uniquely encodes each simplex of the hierarchy. We present rules to efficiently compute the neighbors ..."
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Cited by 8 (2 self)
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We describe a pointerless representation of hierarchical regular simplicial meshes, based on a bisection approach proposed by Maubach. We introduce a new labeling scheme, called an LPT code, that uniquely encodes each simplex of the hierarchy. We present rules to efficiently compute the neighbors of a given simplex through the use of these codes. In addition, we show how to traverse the associated tree and how to answer point location and interpolation queries.Our system works in arbitrary dimensions.
Simple and efficient algorithm for large scale molecular dynamics simulation in hard disk systems
 Int. J. Mod. Phys. C
, 1999
"... A simple and efficient algorithm of the moleculardynamics simulation of the hard disk system based on the EventDriven method is developed. From the analysis of algorithm, the complexity isO(log N) per 1 event, and the constant coefficient of the complexity is smaller than conventional efficient al ..."
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Cited by 4 (0 self)
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A simple and efficient algorithm of the moleculardynamics simulation of the hard disk system based on the EventDriven method is developed. From the analysis of algorithm, the complexity isO(log N) per 1 event, and the constant coefficient of the complexity is smaller than conventional efficient algorithm based on the concept of CellCrossing Event. The maximum performance of more than 460 millions of collisions per CPUhour on the Alpha600 compatible in a 2500 particle system is achieved. An extension to the infinitespace system based on this algorithm is also proposed. Keywords: EventDriven Molecular Dynamics; Hard Disk System; Algorithm. 1.
A Survey of Algorithms and Data Structures for Range Searching
 ACM Computing Surveys
, 1979
"... An important problem in database systems is answering queries quickly. This paper surveys a number of algorithms for efficiently answering range queries. First a set of “loGical structures ” is described and ‘then their implementation in primary and secondary memories is discussed. The algorithms in ..."
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Cited by 3 (1 self)
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An important problem in database systems is answering queries quickly. This paper surveys a number of algorithms for efficiently answering range queries. First a set of “loGical structures ” is described and ‘then their implementation in primary and secondary memories is discussed. The algorithms included are of both “practical ” and “theoretical ” interest. Although some new results are presented, the primary purpose of this paper is to collect together the known results on range searching and to present them in a common terminology.
Optimal Independent Spanning Trees on Hypercubes
, 2004
"... Two spanning trees rooted at some vertex r in a graph G are said to be independent if for each vertex v of G, v ≠ r, the paths from r to v in two trees are vertexdisjoint. A set of spanning trees of G is said to be independent if they are pairwise independent. A set of independent spanning trees is ..."
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Cited by 3 (1 self)
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Two spanning trees rooted at some vertex r in a graph G are said to be independent if for each vertex v of G, v ≠ r, the paths from r to v in two trees are vertexdisjoint. A set of spanning trees of G is said to be independent if they are pairwise independent. A set of independent spanning trees is optimal if the average path length of the trees is the minimum. Any kdimensional hypercube has k independent spanning trees rooted at an arbitrary vertex. In this paper, an O(kn) time algorithm is proposed to construct k optimal independent spanning trees on a kdimensional hypercube, where n = 2 k is the number of vertices in a hypercube.
A method of vector processing for shared symbolic data
 Parallel Computing
, 1993
"... Conventional processing techniques for pipelined vector processors such as the CrayXMP, or dataparallel
computers, such as the Connection Machines, are generally applied only to independent
multiple data processing. This paper describes a vector processing method for multiple processings
including ..."
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Cited by 1 (0 self)
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Conventional processing techniques for pipelined vector processors such as the CrayXMP, or dataparallel
computers, such as the Connection Machines, are generally applied only to independent
multiple data processing. This paper describes a vector processing method for multiple processings
including parallel rewriting of dynamic data structures with shared elements, and for multiple processings
that may rewrite the same data item multiple times. This method enables vector processing when
entering multiple data items into a hash table, address calculation sorting, and many other algorithms
that handle lists, trees, graphs and other types of symbolic data structures. This method is applied to
several algorithms; consequently, the performance is improved by a factor of ten on a Hitachi S810.
Discrete Pattern Matching Over Sequences And Interval Sets
, 1993
"... Finding matches, both exact and approximate, between a sequence of symbols A and a pattern P has long been an active area of research in algorithm design. Some of the more wellknown byproducts from that research are the diff program and grep family of programs. These problems form a subdomain of a ..."
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Cited by 1 (0 self)
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Finding matches, both exact and approximate, between a sequence of symbols A and a pattern P has long been an active area of research in algorithm design. Some of the more wellknown byproducts from that research are the diff program and grep family of programs. These problems form a subdomain of a larger areas of problems called discrete pattern matching which has been developed recently to characterise the wide range of pattern matching problems. This dissertation presents new algorithms for discrete pattern matching over sequences and develops a new subdomain of problems called discrete pattern matching over interval sets. The problems and algorithms presented here are characterised by pattern matching over interval sets. The problems and al
Enumerative Aspects of Certain Subclasses of Perfect Graphs
"... We investigate the enumerative aspects of various classes of perfect graphs like cographs, split graphs, trivially perfect graphs and threshold graphs. For subclasses of permutation graphs like cographs and threshold graphs we also determine the number of permutations ß of f1; 2; : : : ; ng such tha ..."
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Cited by 1 (0 self)
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We investigate the enumerative aspects of various classes of perfect graphs like cographs, split graphs, trivially perfect graphs and threshold graphs. For subclasses of permutation graphs like cographs and threshold graphs we also determine the number of permutations ß of f1; 2; : : : ; ng such that the permutation graph G[ß] belongs to that class. We establish an interesting bijection between permutations whose permutation graphs are cographs (P4 free graphs) and permutations that are obtainable using an outputrestricted deque [9] and thereby enumerate such permutations. We also prove that the asymptotic number of permutations of f1; 2; : : : ; ng whose permutation graphs are split graphs is \Theta(4 n = p n). We also introduce a new class of graphs called C5 split graphs, characterize and enumerate them. C5 split graphs form a superclass of split graphs and are not necessarily perfect. All the classes of graphs that we enumerate have a finite family of small forbidden induc...