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Approximation algorithms for the Maximum Induced Planar and Outerplanar Subgraph problems
 J. Graph Algorithms Appl
"... The task of finding the largest subset of vertices of a graph that induces a planar subgraph is known as the Maximum Induced Planar Subgraph problem (MIPS). In this paper, some new approximation algorithms for MIPS are introduced. The results of an extensive study of the performance of these and exi ..."
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The task of finding the largest subset of vertices of a graph that induces a planar subgraph is known as the Maximum Induced Planar Subgraph problem (MIPS). In this paper, some new approximation algorithms for MIPS are introduced. The results of an extensive study of the performance of these and existing MIPS approximation algorithms on randomly generated graphs are presented. Efficient algorithms for finding large induced outerplanar graphs are also given. One of these algorithms is shown to find an induced outerplanar subgraph with at least 3n/(d + 5/3) vertices. The results presented in this paper indicate that most existing algorithms perform substantially better than the existing lower bounds indicate. 1
Apptopinv  user’s guide
, 2003
"... The maximum planar subgraph, maximum outerplanar subgraph, the thickness and outerthickness of a graph are all NPcomplete optimization problems. Apptopinv is a program that contains different heuristic algorithms for these four problems: algorithms based on HopcroftTarjan planarity testing algorit ..."
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The maximum planar subgraph, maximum outerplanar subgraph, the thickness and outerthickness of a graph are all NPcomplete optimization problems. Apptopinv is a program that contains different heuristic algorithms for these four problems: algorithms based on HopcroftTarjan planarity testing algorithm, the spanningtree heuristic and various algorithms based on the cactustree heuristic. Apptopinv contains also a simulated annealing algorithm that can be used to improve the solutions obtained from other heuristics. Most of the heuristics have also a greedy version. We have implemented graph generators for complete graphs, complete kpartite graphs, complete hypercubes, random graphs, random maximum planar and outerplanar graphs and random regular graphs. Apptopinv supports three different graph file formats. Apptopinv is written in C++ programming language for Linuxplatform and GCC 2.95.3 compiler. To compile the program, a commercial LEDA algorithm
Optimal NodeDegree Bounds for the Complexity of Nonplanarity Parameters
 IN PROC. TENTH ANNUAL ACMSIAM SYMPOSIUM ON DISCRETE ALGORITHMS, SODA'99
, 1999
"... We prove that both the NPcompleteness of the nonplanar deletion decision problem and the Max SNPhardness of the nonplanar deletion problem remain true even for cubic graphs. We prove that the class of graphs with splitting number less than or equal to a fixed k is minor closed, which implies the e ..."
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We prove that both the NPcompleteness of the nonplanar deletion decision problem and the Max SNPhardness of the nonplanar deletion problem remain true even for cubic graphs. We prove that the class of graphs with splitting number less than or equal to a fixed k is minor closed, which implies the existence of a corresponding polynomialtime recognition algorithm.
Crossing Numbers and Cutwidths
 JOURNAL OF GRAPH ALGORITHMS AND APPLICATIONS
, 2003
"... The crossing number of a graph G =(V,E), denoted by cr(G), is the smallest number of edge crossings in any drawing of G in the plane. ..."
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The crossing number of a graph G =(V,E), denoted by cr(G), is the smallest number of edge crossings in any drawing of G in the plane.
Two New Approximation Algorithms for the Maximum Planar Subgraph Problem
, 2006
"... The maximum planar subgraph problem (MPS) is defined as follows: given a graph G, find a largest planar subgraph of G. The problem is NPhard and it has applications in graph drawing and resource location optimization. Călinescu et al. [J. Alg. 27, 269302 (1998)] presented the first approximation a ..."
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The maximum planar subgraph problem (MPS) is defined as follows: given a graph G, find a largest planar subgraph of G. The problem is NPhard and it has applications in graph drawing and resource location optimization. Călinescu et al. [J. Alg. 27, 269302 (1998)] presented the first approximation algorithms for MPS with nontrivial performance ratios. Two algorithms were given, a simple algorithm which runs in linear time for boundeddegree graphs with a ratio 7/18 and a more complicated algorithm with a ratio 4/9. Both algorithms produce outerplanar subgraphs. In this article we present two new versions of the simpler algorithm. The first new algorithm still runs in the same time, produces outerplanar subgraphs, has at least the same performance ratio as the original algorithm, but in practice it finds larger planar subgraphs than the original algorithm. The second new algorithm has similar properties to the first algorithm, but it produces only planar subgraphs. We conjecture that the performance ratios of our algorithms are at least 4/9 for MPS. We experimentally compare the new algorithms against the original simple algorithm. We also apply the new algorithms for approximating the thickness and outerthickness of a graph. Experiments show that the new algorithms produce clearly better approximations than the original simple algorithm by Călinescu et al.
Planarity Testing and Embedding
, 2004
"... Testing the planarity of a graph and possibly drawing it without intersections is one of the most fascinating and intriguing problems of the graph drawing and graph theory areas. Although the problem per se can be easily stated, and a complete characterization of planar graphs was available since 19 ..."
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Testing the planarity of a graph and possibly drawing it without intersections is one of the most fascinating and intriguing problems of the graph drawing and graph theory areas. Although the problem per se can be easily stated, and a complete characterization of planar graphs was available since 1930, an efficient solution to it was found only in the seventies of the last century. Planar graphs play an important role both in the graph theory and in the graph drawing areas. In fact, planar graphs have several interesting properties: for example they are sparse, fourcolorable, allow a number of operations to be performed efficiently, and their structure can be elegantly described by an SPQRtree (see Section 3.1.2). From the information visualization perspective, instead, as edge crossings turn out to be the main culprit for reducing readability, planar drawings of graphs are considered clear and comprehensible. As a matter of fact, the study of planarity has motivated much of the development of graph theory. In this chapter we review the number of alternative algorithms available in the literature for efficiently testing planarity and computing planar embeddings. Some of these algorithms
Spatiotemporal Multicast And Partitionable Group Membership Service
, 2003
"... The recent advent of wireless mobile ad hoc networks and sensor networks creates many opportunities and challenges. This thesis explores some of them. In light of new application requirements in such environments, it proposes a new multicast paradigm called spatiotemporal multicast for supporting ..."
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The recent advent of wireless mobile ad hoc networks and sensor networks creates many opportunities and challenges. This thesis explores some of them. In light of new application requirements in such environments, it proposes a new multicast paradigm called spatiotemporal multicast for supporting ad hoc network applications which require both spatial and temporal coordination. With a focus on a special case of spatiotemporal multicast, called mobicast, this work proposes several novel protocols and analyzes their performances. This dissertation also investigates implications of mobility on the classical group membership problem in distributed computing, proposes a new specification for a partitionable group membership service catering to applications on wireless mobile ad hoc networks, and provides a mobilityaware algorithm and middleware for this service. The results of this work bring new insights into the design and analysis of spatiotemporal communication protocols and faulttolerant computing in wireless mobile ad hoc networks.
Displaying Centrality of a Network using Orbital Layout
"... Network analysis uses centralities as a method to order the actors and the links between them according to their importance based on the structural properties of the given network. In mathematical terms a network can be modelled as an instance of the abstract object graph, where the actors of the ne ..."
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Network analysis uses centralities as a method to order the actors and the links between them according to their importance based on the structural properties of the given network. In mathematical terms a network can be modelled as an instance of the abstract object graph, where the actors of the network are vertices and the links are represented by edges. An intuitive form of visualization of a centrality is placing its vertices on concentric circles. Vertices with a higher centrality value are situated close to the center. With decreasing importance vertices are placed on circles further away from the center. We extended the already existing radial and circular layout and defined the term orbital layout, where both interorbit and intraorbit edges are allowed. To be able to produce a conceptional drawing, visual complexity needs to be reduced. The first approach is based on crossing minimization to achieve a good readability. Two heuristics are presented, the first one is based on string matching and the second heuristic is an extension of the radial sifting algorithm to orbital layout. A second idea, based on planarization, is to first planarize the input graph and then reinsert the deleted edges. We introduce three greedy algorithms based on