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Parallel Algorithms with Optimal Speedup for Bounded Treewidth
 Proceedings 22nd International Colloquium on Automata, Languages and Programming
, 1995
"... We describe the first parallel algorithm with optimal speedup for constructing minimumwidth tree decompositions of graphs of bounded treewidth. On nvertex input graphs, the algorithm works in O((logn)^2) time using O(n) operations on the EREW PRAM. We also give faster parallel algorithms with opti ..."
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Cited by 33 (10 self)
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We describe the first parallel algorithm with optimal speedup for constructing minimumwidth tree decompositions of graphs of bounded treewidth. On nvertex input graphs, the algorithm works in O((logn)^2) time using O(n) operations on the EREW PRAM. We also give faster parallel algorithms with optimal speedup for the problem of deciding whether the treewidth of an input graph is bounded by a given constant and for a variety of problems on graphs of bounded treewidth, including all decision problems expressible in monadic secondorder logic. On nvertex input graphs, the algorithms use O(n) operations together with O(log n log n) time on the EREW PRAM, or O(log n) time on the CRCW PRAM.
Structured Parallel Computation in Structured Documents
 Journal of Universal Computer Science
, 1995
"... Document archives contain large amounts of data to which sophisticated queries are applied. The size of archives and the complexity of evaluating queries makes the use of parallelism attractive. The use of semanticallybased markup such as SGML makes it possible to represent documents and document ..."
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Cited by 6 (2 self)
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Document archives contain large amounts of data to which sophisticated queries are applied. The size of archives and the complexity of evaluating queries makes the use of parallelism attractive. The use of semanticallybased markup such as SGML makes it possible to represent documents and document archives as data types. We present a theory of trees and tree homomorphisms, modelling structured text archives and operations on them, from which it can be seen that: ffl many apparentlyunrelated tree operations are homomorphisms; ffl homomorphisms can be described in a simple parameterised way that gives standard sequential and parallel implementations for them; ffl special classes of homomorphisms have parallel implementations of practical interest. In particular, we develop an implementation for path expression search, a novel powerful query facility for structured text, that takes time logarithmic in the text size. Keywords: structured text, categorical data type, software developme...
An Effective Load Balancing Policy for Geometric Decaying Algorithms
"... Parallel algorithms are often first designed as a sequence of rounds, where each round includes any number of independent constant time operations. This socalled worktime presentation is then followed by a processor scheduling implementation ona more concrete computational model. Many parallel alg ..."
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Cited by 3 (3 self)
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Parallel algorithms are often first designed as a sequence of rounds, where each round includes any number of independent constant time operations. This socalled worktime presentation is then followed by a processor scheduling implementation ona more concrete computational model. Many parallel algorithms are geometricdecaying in the sense that the sequence of work loads is upper bounded by a decreasing geometric series. A standard scheduling implementation of such algorithms consists of a repeated application of load balancing. We present a more effective, yet as simple, policy for the utilization of load balancing in geometric decaying algorithms. By making a more careful choice of when and how often load balancing should be employed, and by using a simple amortization argument, we showthat the number of required applications of load balancing should be nearlyconstant. The policy is not restricted to any particular model of parallel computation, and, up to a constant factor, it is the best possible.
Parallel Algorithm for Shortest Pairs of EdgeDisjoint Paths
"... Let G = (V , E) be a directed graph having a nonnegative cost associated with each edge. Let s 2 V be a special vertex called the source and W V be a set of other vertices called sinks in G. In this paper, a parallel algorithm is proposed for nding a pair of edgedisjoint paths from s to each p ..."
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Cited by 1 (0 self)
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Let G = (V , E) be a directed graph having a nonnegative cost associated with each edge. Let s 2 V be a special vertex called the source and W V be a set of other vertices called sinks in G. In this paper, a parallel algorithm is proposed for nding a pair of edgedisjoint paths from s to each possible sink t 2 W such that the sum of the costs of the two paths is minimized. This algorithm has processor and time complexities same as those needed to nd shortest paths from s to all sinks t 2 W , i.e., n 3 = log n processors and O(log 2 n) time. 1