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Viceroy: A Scalable and Dynamic Emulation of the Butterfly
, 2002
"... We propose a family of constantdegree routing networks of logarithmic diameter, with the additional property that the addition or removal of a node to the network requires no global coordination, only a constant number of linkage changes in expectation, and a logarithmic number with high probabilit ..."
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Cited by 316 (16 self)
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We propose a family of constantdegree routing networks of logarithmic diameter, with the additional property that the addition or removal of a node to the network requires no global coordination, only a constant number of linkage changes in expectation, and a logarithmic number with high probability. Our randomized construction improves upon existing solutions, such as balanced search trees, by ensuring that the congestion of the network is always within a logarithmic factor of the optimum with high probability. Our construction derives from recent advances in the study of peertopeer lookup networks, where rapid changes require e#cient and distributed maintenance, and where the lookup e#ciency is impacted both by the lengths of paths to requested data and the presence or elimination of bottlenecks in the network.
Relaxed balanced redblack trees
 In Proc. 3rd Italian Conference on Algorithms and Complexity
, 1997
"... Abstract. Relaxed balancing means that, in a dictionary stored as a balanced tree, the necessary rebalancing after updates may be delayed. This is in contrast to strict balancing meaning that rebalancing is performed immediately after the update. Relaxed balancing is important for efficiency in high ..."
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Cited by 14 (2 self)
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Abstract. Relaxed balancing means that, in a dictionary stored as a balanced tree, the necessary rebalancing after updates may be delayed. This is in contrast to strict balancing meaning that rebalancing is performed immediately after the update. Relaxed balancing is important for efficiency in highly dynamic applications where updates can occur in bursts. The rebalancing tasks can be performed gradually after all urgent updates, allowing the concurrent use of the dictionary even though the underlying tree structure is not completely in balance. In this paper we propose a new scheme of how to make known rebalancing techniques relaxed in an efficient way. The idea is applied to the redblack trees, but can be applied to any class of balanced trees. The key idea is to accumulate insertions and deletions such that they can be settled in arbitrary order using the same rebalancing operations as for standard balanced search trees. As a result it can be shown that the number of needed rebalancing operations known from the strict balancing scheme carry over to relaxed balancing. 1
Binary Search Trees of Almost Optimal Height
 ACTA INFORMATICA
, 1990
"... First we present a generalization of symmetric binary Btrees, SBB(k) trees. The obtained structure has a height of only \Sigma (1 + 1k) log(n + 1)\Upsilon, where k may be chosen to be any positive integer. The maintenance algorithms require only a constant number of rotations per updating operati ..."
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Cited by 11 (1 self)
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First we present a generalization of symmetric binary Btrees, SBB(k) trees. The obtained structure has a height of only \Sigma (1 + 1k) log(n + 1)\Upsilon, where k may be chosen to be any positive integer. The maintenance algorithms require only a constant number of rotations per updating operation in the worst case. These properties together with the fact that the structure is relatively simple to implement makes it a useful alternative to other search trees in practical applications. Then, by using an SBB(k)tree with a varying k we achieve a structure with a logarithmic amortized cost per update and a height of log n + o(log n). This result is an improvement of the upper bound on the height of a dynamic binary search tree. By maintaining two trees simultaneously the amortized cost is transformed into a worstcase cost. Thus, we have improved the worstcase complexity of the dictionary problem.
Adaptive Heuristics for Binary Search Trees and Constant Linkage Cost
 In Proc. of the 2nd ACMSIAM Symposium on Discrete Algorithms
, 1995
"... We present lower and upper bounds on adaptive heuristics for maintaining binary search trees using a constant number of link or pointer changes for each operation (constant linkage cost (CLC)). We show that no adaptive heuristic with an amortized linkage cost of o(log n) can be competitive. In part ..."
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Cited by 8 (0 self)
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We present lower and upper bounds on adaptive heuristics for maintaining binary search trees using a constant number of link or pointer changes for each operation (constant linkage cost (CLC)). We show that no adaptive heuristic with an amortized linkage cost of o(log n) can be competitive. In particular, we show that any heuristic that performs f(n) = o(log n) promotions (rotations) amortized over each access has a competitive ratio of at least \Omega\Gammaast n=f(n)) against an oblivious adversary, and any heuristic that performs f(n) = o(log n) pointer changes amortized over each access has a competitive ratio of at least\Omega\Gamma log n f(n) log(log n=f(n)) ) against an adaptive online adversary. In our investigation of upper bounds we present four adaptive heuristics: ffl A randomized, worstcaseCLC heuristic (R2P) whose expected search time is within a constant factor of the search time using an optimal tree; that is, it is statically competitive ffl A randomized, expecte...
Relaxed Balancing Made Simple
, 1995
"... Relaxed balancing means that, in a dictionary stored as a balanced tree, the necessary rebalancing after updates may be delayed. This is in contrast to strict balancing meaning that rebalancing is performed immediately after the update. Relaxed balancing is important for efficiency in highly dyn ..."
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Cited by 6 (0 self)
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Relaxed balancing means that, in a dictionary stored as a balanced tree, the necessary rebalancing after updates may be delayed. This is in contrast to strict balancing meaning that rebalancing is performed immediately after the update. Relaxed balancing is important for efficiency in highly dynamic applications where updates can occur in bursts. The rebalancing tasks can be performed gradually after all urgent updates, allowing the concurrent use of the dictionary even though the underlying tree structure is not completely in balance. The contribution of the present paper is that we introduce a new scheme for relaxed balancing, which is obtained by a simple generalization of strict balancing. Our approach implies a simple proof of the fact that the number of the needed rebalancing operations (to put the tree in balance) for relaxed balancing is the same as for strict balancing. 1 Introduction A dictionary is a scheme for storing a set of data such that the operations sea...
Viceroy: Scalable Emulation of Butterfly Networks for Distributed Hash Tables
, 2003
"... We propose and analyze a randomized variant of the Butterfly network that is amenable to decentralized construction and modification as nodes join and leave a network. The proposed networks have constant outdegree, and maintain a logarithmic diameter and nearly optimal congestion with high proba ..."
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Cited by 2 (0 self)
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We propose and analyze a randomized variant of the Butterfly network that is amenable to decentralized construction and modification as nodes join and leave a network. The proposed networks have constant outdegree, and maintain a logarithmic diameter and nearly optimal congestion with high probability. In expectation, only a constant number of links are changed during a modification, and a logarithmic number with high probability. These properties make our construction particularly suitable for distributed hash tables (DHTs), which have been heavily promoted as a building block for internetscale distributed services.
ABSTRACT Viceroy: A Scalable and Dynamic Emulation of the Butterfly
"... We propose a family of constantdegree routing networks of logarithmic diameter, with the additional property that the addition or removal of a node to the network requires no global coordination, only a constant number of linkage changes in expectation, and a logarithmic number with high probabilit ..."
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We propose a family of constantdegree routing networks of logarithmic diameter, with the additional property that the addition or removal of a node to the network requires no global coordination, only a constant number of linkage changes in expectation, and a logarithmic number with high probability. Our randomized construction improves upon existing solutions, such as balanced search trees, by ensuring that the congestion of the network is always within a logarithmic factor of the optimum with high probability. Our construction derives from recent advances in the study of peertopeer lookup networks, where rapid changes require efficient and distributed maintenance, and where the lookup efficiency is impacted both by the lengths of paths to requested data and the presence or elimination of bottlenecks in the network. 1.
Complexity of Layered Binary Search Trees with Relaxed Balance
, 1999
"... When search trees are made relaxed, balance constraints are weakened such that updates can be made without immediate rebalancing. This can lead to a speedup in some circumstances. However, the weakened balance constraints also make it more challenging to prove complexity results for relaxed str ..."
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When search trees are made relaxed, balance constraints are weakened such that updates can be made without immediate rebalancing. This can lead to a speedup in some circumstances. However, the weakened balance constraints also make it more challenging to prove complexity results for relaxed structures. In our opinion, one of the simplest and most intuitive presentations of balanced search trees has been given via layered trees. We show that relaxed layered trees are among the best of the relaxed structures. More precisely, rebalancing is worstcase logarithmic and amortized constant per update, and restructuring is worstcase constant per update. Introduction Usually, updating in a balanced search tree is carried out as follows: First, a search is carried out in order to determine the location of the update. Second, the update is performed. Third, local balance constraints are reconsidered. Supported in part by the Danish Natural Sciences Research Council (SNF). y Depart...
Maintaining alphabalanced Trees by Partial Rebuilding
"... The balance criterion defining the class of ffbalanced trees states that the ratio between the shortest and longest paths from a node to a leaf be at least ff. We show that a straightforward use of partial rebuilding for maintenance of ffbalanced trees requires an amortized cost of \Omega (pn) p ..."
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The balance criterion defining the class of ffbalanced trees states that the ratio between the shortest and longest paths from a node to a leaf be at least ff. We show that a straightforward use of partial rebuilding for maintenance of ffbalanced trees requires an amortized cost of \Omega (pn) per update. By slight modifications of the maintenance algorithms the cost can be reduced to O(log n) for any value of ff, 0! ff! 1.