We study variants of the capacitated vehicle routing problem. In the multiple depot capacitated k-travelling repairmen problem (MD-CkTRP), we have a collection of clients to be served by one vehicle in a fleet of k id...
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The graph orientation problem calls for orienting the edges of an undirected graph so as to maximize the number of pre-specified source-target vertex pairs that admit a directed path from the source to the target. Mos...
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Certain answers are a widely accepted semantics of query answering over incomplete databases. Since their computation is a coNP-hard problem, recent research has focused on developing evaluation algorithms with correc...
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Certain answers are a widely accepted semantics of query answering over incomplete databases. Since their computation is a coNP-hard problem, recent research has focused on developing evaluation algorithms with correctness guarantees, that is, techniques computing a sound but possibly incomplete set of certain answers. In this paper, we show how novel evaluation algorithms with correctness guarantees can be developed leveraging conditional tables and the conditional evaluation of queries, while retaining polynomial time data complexity.
We propose an approximation algorithm for the general max-min resource sharing problem with M nonnegative concave constraints on a convex set B. The algorithm is based on a Lagrangian decomposition method and it uses ...
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ISBN:
(纸本)3540223398
We propose an approximation algorithm for the general max-min resource sharing problem with M nonnegative concave constraints on a convex set B. The algorithm is based on a Lagrangian decomposition method and it uses a c - approximation algorithm (called approximate block solver) for a simpler maximization problem over the convex set B. We show that our algorithm achieves within O(M(ln M + epsilon(-2) ln epsilon(-1))) iterations or calls to the approximate block solver a solution for the general max-min resource sharing problem with approximation ratio c/(1 - epsilon). The algorithm is faster and simpler than the previous known approximation algorithms for the problem.
Structural balance theory is an important theory in signed graphs. We consider the optimization problems: given a signed graph, the maximum number of edges that needed to be kept to make it balanced is called K(G). We...
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It is known that one-dimensional variable-sized bin packing problem and network optimization problem are classical combinatorial optimization problems. Inspired by this, we consider a new problem of variable-sized mat...
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We study the generalization of covering problems to partial covering. Here we wish to cover only a desired number of elements, rather than covering all elements as in standard covering problems. For example, in k-set ...
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ISBN:
(纸本)3540422870
We study the generalization of covering problems to partial covering. Here we wish to cover only a desired number of elements, rather than covering all elements as in standard covering problems. For example, in k-set cover, we wish to choose a minimum number of sets to cover at least k elements. For k-set cover, if each element occurs in at most f sets, then we derive a primal-dual f-approximation algorithm (thus implying a 2-approximation for k-vertex cover) in polynomial time. In addition to its simplicity, this algorithm has the advantage of being parallelizable. For instances where each set has cardinality at most three, we obtain an approximation of 4/3. We also present better-than-2-approximation algorithms for k-vertex cover on bounded degree graphs, and for vertex cover on expanders of bounded average degree. We obtain a polynomial-time approximation scheme for k-vertex cover on planar graphs, and for covering points in R-d by disks.
Given a rectangular boundary partitioned into rectangles, the MLC-R problem is to find a Minimum Edge-Length Corridor that visits at least one point from the boundary of every rectangle and from the rectangular bounda...
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Given a rectangular boundary partitioned into rectangles, the MLC-R problem is to find a Minimum Edge-Length Corridor that visits at least one point from the boundary of every rectangle and from the rectangular boundary. We present the first polynomial time constant ratio approximation algorithm for the MLC-R problem, which has been shown to be NP-hard [5].
The problem of traversing a set of points in the order that minimizes the total distance traveled (traveling salesman problem) is one of the most famous and well-studied problems in combinatorial optimization. In this...
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Modern distributed telecommunication networks have widely extended the possibilities of the telecommunication industry for offering a wide variety of services, directly or indirectly by facilitating them for other ser...
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