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Minimizing Broadcast Costs under Edge Reductions in Tree Networks
 In 7th International Symposium on Spatial and Temporal Databases (SSTD 2001
, 1998
"... We study the broadcasting of messages in tree networks under edge reductions. When an edge is reduced, its cost becomes zero. Edge reductions model the decrease or elimination of broadcasting costs between adjacent nodes in the network. Let T be an nvertex tree and B be a target broadcast cost. We ..."
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Cited by 6 (4 self)
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We study the broadcasting of messages in tree networks under edge reductions. When an edge is reduced, its cost becomes zero. Edge reductions model the decrease or elimination of broadcasting costs between adjacent nodes in the network. Let T be an nvertex tree and B be a target broadcast cost. We present an O(n) time algorithm for determining the minimum number of edges of T to reduce so that a broadcast cost of B can be achieved. We present an O(n log n) time algorithm to determine the minimum number of edges to reduce so that a broadcast initiated at an arbitrary vertex of T costs at most B. Characterizations of where edge reductions are placed underly both algorithms and imply that reduced edges can be centrally located. Keywords: Analysis of algorithms; message broadcasting; blocking communication model; tree networks. Research supported in part by DARPA under contract DABT6392C0022ONR. The views and conclusions contained in this paper are those of the authors and should not...
Improving Spanning Trees by Upgrading Nodes
 PROCEEDINGS OF THE 24TH INTERNATIONAL COLLOQUIUM ON AUTOMATA, LANGUAGES AND PROGRAMMING (ICALP'97
, 1997
"... We study bottleneck constrained network upgrading problems.We are given an edge weighted graph G =(V;E) where node v 2 V can be upgraded at a cost of c(v). This upgrade reduces the delayofeach link emanating from v. The goal is to #nd a minimum cost set of nodes to be upgraded so that the resulting ..."
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Cited by 5 (4 self)
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We study bottleneck constrained network upgrading problems.We are given an edge weighted graph G =(V;E) where node v 2 V can be upgraded at a cost of c(v). This upgrade reduces the delayofeach link emanating from v. The goal is to #nd a minimum cost set of nodes to be upgraded so that the resulting network has a good performance. The performance is measured by the bottleneckweightof a minimum spanning tree. We give a polynomial time appoximation algorithm with logarithmic performance guarantee, which is tight within a small constant factor as shown by our hardness results.
On BudgetConstrained Flow Improvement
, 1998
"... This paper investigates the complexity of budgetconstrained flow improvement problems. We are given a directed graph with capacities on the edges which can be increased at linear costs up to some upper bounds. The problem is to increase the capacities within budget restrictions such that the flow ..."
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Cited by 2 (1 self)
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This paper investigates the complexity of budgetconstrained flow improvement problems. We are given a directed graph with capacities on the edges which can be increased at linear costs up to some upper bounds. The problem is to increase the capacities within budget restrictions such that the flow from the source to the sink vertex is maximized. We show that the problem can be solved in polynomial time even if the improvement strategy is required to be integral. On the other hand, if the capacity of an edge must either be increased to the upper bound or left unchanged, then the problem turns NPhard even on seriesparallel graphs and strongly NPhard on bipartite graphs. For the class seriesparallel graphs we provide a fully polynomial approximation scheme for this problem.
Improving minimum cost spanning trees by upgrading nodes
 Journal of Algorithms
, 1999
"... * A preliminary version of this paper appeared as KM 97. ..."
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Cited by 2 (0 self)
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* A preliminary version of this paper appeared as KM 97.
Downgrading the 1median in the plane with Manhattan metric ∗
, 2008
"... This paper deals with changing parameters of the 1median problem in the plane with Manhattan metric within certain bounds such that the optimal objective value of the 1median problem with respect to the new values of the parameters is maximized. An O(n log 2 n) time algorithm is suggested that is ..."
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This paper deals with changing parameters of the 1median problem in the plane with Manhattan metric within certain bounds such that the optimal objective value of the 1median problem with respect to the new values of the parameters is maximized. An O(n log 2 n) time algorithm is suggested that is mainly based on a fast search and prune procedure. 1