72 Search Results for "Hong, Sok-Hee"

Volume

LIPIcs, Volume 64

27th International Symposium on Algorithms and Computation (ISAAC 2016)

ISAAC 2016, December 12-14, 2016, Sydney, Australia

Editors: Seok-Hee Hong

Document
Invited Talk
DOI: 10.4230/LIPIcs.ISAAC.2023.2
Faithful Graph Drawing (Invited Talk)

Authors: Seok-Hee Hong

Published in: LIPIcs, Volume 283, 34th International Symposium on Algorithms and Computation (ISAAC 2023)

Abstract
Graph drawing aims to compute good geometric representations of graphs in two or three dimensions. It has wide applications in network visualisation, such as social networks and biological networks, arising from many other disciplines. This talk will review fundamental theoretical results as well as recent advances in graph drawing, including symmetric graph drawing, generalisation of the Tutte’s barycenter theorem, Steinitz’s theorem, and Fáry’s theorem, and the so-called beyond planar graphs such as k-planar graphs. I will conclude my talk with recent progress in visualization of big complex graphs, including sublinear-time graph drawing algorithms and faithful graph drawing.
Cite as

Seok-Hee Hong. Faithful Graph Drawing (Invited Talk). In 34th International Symposium on Algorithms and Computation (ISAAC 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 283, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{hong:LIPIcs.ISAAC.2023.2,
  author =	{Hong, Seok-Hee},
  title =	{{Faithful Graph Drawing}},
  booktitle =	{34th International Symposium on Algorithms and Computation (ISAAC 2023)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-289-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{283},
  editor =	{Iwata, Satoru and Kakimura, Naonori},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2023.2},
  URN =		{urn:nbn:de:0030-drops-193044},
  doi =		{10.4230/LIPIcs.ISAAC.2023.2},
  annote =	{Keywords: Graph drawing, Planar graphs, Beyond planar graphs, Tutte’s barycenter theorem, Steinitz’s theorem, F\'{a}ry’s theorem, Sublinear-time graph drawing algorithm, Faithful graph drawing, Symmetric graph drawing}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2021.8
Self-Improving Voronoi Construction for a Hidden Mixture of Product Distributions

Authors: Siu-Wing Cheng and Man Ting Wong

Published in: LIPIcs, Volume 212, 32nd International Symposium on Algorithms and Computation (ISAAC 2021)

Abstract
We propose a self-improving algorithm for computing Voronoi diagrams under a given convex distance function with constant description complexity. The n input points are drawn from a hidden mixture of product distributions; we are only given an upper bound m = o(√n) on the number of distributions in the mixture, and the property that for each distribution, an input instance is drawn from it with a probability of Ω(1/n). For any ε ∈ (0,1), after spending O(mn log^O(1)(mn) + m^ε n^(1+ε) log(mn)) time in a training phase, our algorithm achieves an O(1/ε n log m + 1/ε n 2^O(log^* n) + 1/ε H) expected running time with probability at least 1 - O(1/n), where H is the entropy of the distribution of the Voronoi diagram output. The expectation is taken over the input distribution and the randomized decisions of the algorithm. For the Euclidean metric, the expected running time improves to O(1/ε n log m + 1/ε H).
Cite as

Siu-Wing Cheng and Man Ting Wong. Self-Improving Voronoi Construction for a Hidden Mixture of Product Distributions. In 32nd International Symposium on Algorithms and Computation (ISAAC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 212, pp. 8:1-8:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{cheng_et_al:LIPIcs.ISAAC.2021.8,
  author =	{Cheng, Siu-Wing and Wong, Man Ting},
  title =	{{Self-Improving Voronoi Construction for a Hidden Mixture of Product Distributions}},
  booktitle =	{32nd International Symposium on Algorithms and Computation (ISAAC 2021)},
  pages =	{8:1--8:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-214-3},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{212},
  editor =	{Ahn, Hee-Kap and Sadakane, Kunihiko},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2021.8},
  URN =		{urn:nbn:de:0030-drops-154418},
  doi =		{10.4230/LIPIcs.ISAAC.2021.8},
  annote =	{Keywords: entropy, Voronoi diagram, convex distance function, hidden mixture of product distributions}
}
Document
DOI: 10.4230/DagRep.9.2.123
Beyond-Planar Graphs: Combinatorics, Models and Algorithms (Dagstuhl Seminar 19092)

Authors: Seok-Hee Hong, Michael Kaufmann, János Pach, and Csaba D. Tóth

Published in: Dagstuhl Reports, Volume 9, Issue 2 (2019)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 19092 "Beyond-Planar Graphs: Combinatorics, Models and Algorithms" which brought together 36 researchers in the areas of graph theory, combinatorics, computational geometry, and graph drawing. This seminar continued the work initiated in Dagstuhl Seminar 16452 "Beyond-Planar Graphs: Algorithmics and Combinatorics" and focused on the exploration of structural properties and the development of algorithms for so-called beyond-planar graphs, i.e., non-planar graphs that admit a drawing with topological constraints such as specific types of crossings, or with some forbidden crossing patterns. The seminar began with four talks about the results of scientific collaborations originating from the previous Dagstuhl seminar. Next we discussed open research problems about beyond planar graphs, such as their combinatorial structures (e.g., book thickness, queue number), their topology (e.g., simultaneous embeddability, gap planarity, quasi-quasiplanarity), their geometric representations (e.g., representations on few segments or arcs), and applications (e.g., manipulation of graph drawings by untangling operations). Six working groups were formed that investigated several of the open research questions. In addition, talks on related subjects and recent conference contributions were presented in the morning opening sessions. Abstracts of all talks and a report from each working group are included in this report.
Cite as

Seok-Hee Hong, Michael Kaufmann, János Pach, and Csaba D. Tóth. Beyond-Planar Graphs: Combinatorics, Models and Algorithms (Dagstuhl Seminar 19092). In Dagstuhl Reports, Volume 9, Issue 2, pp. 123-156, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@Article{hong_et_al:DagRep.9.2.123,
  author =	{Hong, Seok-Hee and Kaufmann, Michael and Pach, J\'{a}nos and T\'{o}th, Csaba D.},
  title =	{{Beyond-Planar Graphs: Combinatorics, Models and Algorithms (Dagstuhl Seminar 19092)}},
  pages =	{123--156},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2019},
  volume =	{9},
  number =	{2},
  editor =	{Hong, Seok-Hee and Kaufmann, Michael and Pach, J\'{a}nos and T\'{o}th, Csaba D.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagRep.9.2.123},
  URN =		{urn:nbn:de:0030-drops-108634},
  doi =		{10.4230/DagRep.9.2.123},
  annote =	{Keywords: combinatorial geometry, geometric algorithms, graph algorithms, graph drawing, graph theory, network visualization}
}
Document
Short Paper
DOI: 10.4230/LIPIcs.GISCIENCE.2018.24
Evaluating Efficiency of Spatial Analysis in Cloud Computing Platforms (Short Paper)

Authors: Changlock Choi, Yelin Kim, Youngho Lee, and Seong-Yun Hong

Published in: LIPIcs, Volume 114, 10th International Conference on Geographic Information Science (GIScience 2018)

Abstract
The increase of high-resolution spatial data and methodological developments in recent years has enabled a detailed analysis of individuals' experience in space and over time. However, despite the increasing availability of data and technological advances, such individual-level analysis is not always possible in practice because of its computing requirements. To overcome this limitation, there has been a considerable amount of research on the use of high-performance, public cloud computing platforms for spatial analysis and simulation. In this paper, we aim to evaluate the efficiency of spatial analysis in cloud computing platforms. We compared the computing speed for calculating the Moran's I index between a local machine and spot instances on clouds, and our results demonstrated that there could be significant improvements in terms of computing time when the analysis was performed parallel on clouds.
Cite as

Changlock Choi, Yelin Kim, Youngho Lee, and Seong-Yun Hong. Evaluating Efficiency of Spatial Analysis in Cloud Computing Platforms (Short Paper). In 10th International Conference on Geographic Information Science (GIScience 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 114, pp. 24:1-24:5, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{choi_et_al:LIPIcs.GISCIENCE.2018.24,
  author =	{Choi, Changlock and Kim, Yelin and Lee, Youngho and Hong, Seong-Yun},
  title =	{{Evaluating Efficiency of Spatial Analysis in Cloud Computing Platforms}},
  booktitle =	{10th International Conference on Geographic Information Science (GIScience 2018)},
  pages =	{24:1--24:5},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-083-5},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{114},
  editor =	{Winter, Stephan and Griffin, Amy and Sester, Monika},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.GISCIENCE.2018.24},
  URN =		{urn:nbn:de:0030-drops-93521},
  doi =		{10.4230/LIPIcs.GISCIENCE.2018.24},
  annote =	{Keywords: spatial analysis, parallel computing, cloud services}
}
Document
DOI: 10.4230/DagRep.6.11.35
Beyond-Planar Graphs: Algorithmics and Combinatorics (Dagstuhl Seminar 16452)

Authors: Sok-Hee Hong, Michael Kaufmann, Stephen G. Kobourov, and János Pach

Published in: Dagstuhl Reports, Volume 6, Issue 11 (2017)

Abstract
This report summarizes Dagstuhl Seminar 16452 "Beyond-Planar Graphs: Algorithmics and Combinatorics'' and documents the talks and discussions. The seminar brought together 29 researchers in the areas of graph theory, combinatorics, computational geometry, and graph drawing. The common interest was in the exploration of structural properties and the development of algorithms for so-called beyond-planar graphs, i.e., non-planar graphs with topological constraints such as specific types of crossings, or with some forbidden crossing patterns. The seminar began with three introductory talks by experts in the different fields. Abstracts of these talks are collected in this report. Next we discussed and grouped together open research problems about beyond planar graphs, such as their combinatorial structures (e.g, thickness, crossing number, coloring), their topology (e.g., string graph representation), their geometric representations (e.g., straight-line drawing, visibility representation, contact representation), and applications (e.g., algorithms for real-world network visualization). Four working groups were formed and a report from each group is included here.
Cite as

Sok-Hee Hong, Michael Kaufmann, Stephen G. Kobourov, and János Pach. Beyond-Planar Graphs: Algorithmics and Combinatorics (Dagstuhl Seminar 16452). In Dagstuhl Reports, Volume 6, Issue 11, pp. 35-62, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@Article{hong_et_al:DagRep.6.11.35,
  author =	{Hong, Sok-Hee and Kaufmann, Michael and Kobourov, Stephen G. and Pach, J\'{a}nos},
  title =	{{Beyond-Planar Graphs: Algorithmics and Combinatorics (Dagstuhl Seminar 16452)}},
  pages =	{35--62},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2017},
  volume =	{6},
  number =	{11},
  editor =	{Hong, Sok-Hee and Kaufmann, Michael and Kobourov, Stephen G. and Pach, J\'{a}nos},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagRep.6.11.35},
  URN =		{urn:nbn:de:0030-drops-70385},
  doi =		{10.4230/DagRep.6.11.35},
  annote =	{Keywords: graph drawing, graph algorithms, graph theory, geometric algorithms, combinatorial geometry, visualization}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.ISAAC.2016
LIPIcs, Volume 64, ISAAC'16, Complete Volume

Authors: Seok-Hee Hong

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
LIPIcs, Volume 64, ISAAC'16, Complete Volume
Cite as

27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@Proceedings{hong:LIPIcs.ISAAC.2016,
  title =	{{LIPIcs, Volume 64, ISAAC'16, Complete Volume}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016},
  URN =		{urn:nbn:de:0030-drops-69067},
  doi =		{10.4230/LIPIcs.ISAAC.2016},
  annote =	{Keywords: Data Structures, Nonnumerical Algorithms and Problems, Optimization, Discrete Mathematics, Mathematical Software, Algorithms Problem Solving, Control Methods, and Search, Computational Geometry and Object Modeling}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.ISAAC.2016.0
Front Matter, Table of Contents, Preface, Program Committee, External Reviewers

Authors: Seok-Hee Hong

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
Front Matter, Table of Contents, Preface, Program Committee, External Reviewers
Cite as

27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, pp. 0:i-0:xiv, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{hong:LIPIcs.ISAAC.2016.0,
  author =	{Hong, Seok-Hee},
  title =	{{Front Matter, Table of Contents, Preface, Program Committee, External Reviewers}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{0:i--0:xiv},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.0},
  URN =		{urn:nbn:de:0030-drops-67728},
  doi =		{10.4230/LIPIcs.ISAAC.2016.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Program Committee, External Reviewers}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.ISAAC.2016.1
Towards Processing of Big Graphs: from Theory, Algorithm to System (Invited Talk)

Authors: Xuemin Lin

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
Graphs are very important parts of Big Data and widely used for modelling complex structured data with a broad spectrum of applications such as bioinformatics, web search, social network, road network, etc. Over the last decade, tremendous research efforts have been devoted to many fundamental problems in managing and analysing graph data. In this talk, I will present some of our recent research efforts in processing big graphs including scalable processing theory and techniques, distributed computation, and system framework.
Cite as

Xuemin Lin. Towards Processing of Big Graphs: from Theory, Algorithm to System (Invited Talk). In 27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{lin:LIPIcs.ISAAC.2016.1,
  author =	{Lin, Xuemin},
  title =	{{Towards Processing of Big Graphs: from Theory, Algorithm to System}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.1},
  URN =		{urn:nbn:de:0030-drops-68346},
  doi =		{10.4230/LIPIcs.ISAAC.2016.1},
  annote =	{Keywords: Graph Processing, Big Data, Cloud Computing}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.ISAAC.2016.2
Compressed and Searchable Indexes for Highly Similar Strings (Invited Talk)

Authors: Kunsoo Park

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
The collection indexing problem is defined as follows: Given a collection of highly similar strings, build a compressed index for the collection of strings, and when a pattern is given, find all occurrences of the pattern in the given strings. Since the index is compressed, we also need a separate operation which retrieves a specified substring of one of the given strings. Such a collection of highly similar strings can be found in genome sequences of a species and in documents stored in a version control system. Many indexes for the collection indexing problem have been developed, most of which use classical compression schemes such as run-length encoding and Lempel-Ziv compressions to exploit the similarity of the given strings. We introduce a new index for highly similar strings, called FM index of alignment. We start by finding common regions and non-common regions of highly similar strings. We need not find a multiple alignment of non-common regions. Finding common and non-common regions is much easier and simpler than finding a multiple alignment. Then we make a transformed alignment of the given strings, where gaps in a non-common region are put together into one gap. We define a suffix array of alignment on the transformed alignment, and the FM index of alignment is an FM index of this suffix array of alignment. The FM index of alignment supports the LF mapping and backward search, the key functionalities of the FM index. The FM index of alignment takes less space than other indexes and its pattern search is also fast.
Cite as

Kunsoo Park. Compressed and Searchable Indexes for Highly Similar Strings (Invited Talk). In 27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{park:LIPIcs.ISAAC.2016.2,
  author =	{Park, Kunsoo},
  title =	{{Compressed and Searchable Indexes for Highly Similar Strings}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.2},
  URN =		{urn:nbn:de:0030-drops-68359},
  doi =		{10.4230/LIPIcs.ISAAC.2016.2},
  annote =	{Keywords: Index for similar strings, FM index, Suffix array, Alignment}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2016.3
Streaming Verification of Graph Properties

Authors: Amirali Abdullah, Samira Daruki, Chitradeep Dutta Roy, and Suresh Venkatasubramanian

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
Streaming interactive proofs (SIPs) are a framework for outsourced computation. A computationally limited streaming client (the verifier) hands over a large data set to an untrusted server (the prover) in the cloud and the two parties run a protocol to confirm the correctness of result with high probability. SIPs are particularly interesting for problems that are hard to solve (or even approximate) well in a streaming setting. The most notable of these problems is finding maximum matchings, which has received intense interest in recent years but has strong lower bounds even for constant factor approximations. In this paper, we present efficient streaming interactive proofs that can verify maximum matchings exactly. Our results cover all flavors of matchings (bipartite/non-bipartite and weighted). In addition, we also present streaming verifiers for approximate metric TSP. In particular, these are the first efficient results for weighted matchings and for metric TSP in any streaming verification model.
Cite as

Amirali Abdullah, Samira Daruki, Chitradeep Dutta Roy, and Suresh Venkatasubramanian. Streaming Verification of Graph Properties. In 27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, pp. 3:1-3:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{abdullah_et_al:LIPIcs.ISAAC.2016.3,
  author =	{Abdullah, Amirali and Daruki, Samira and Roy, Chitradeep Dutta and Venkatasubramanian, Suresh},
  title =	{{Streaming Verification of Graph Properties}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{3:1--3:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.3},
  URN =		{urn:nbn:de:0030-drops-67730},
  doi =		{10.4230/LIPIcs.ISAAC.2016.3},
  annote =	{Keywords: streaming interactive proofs, verification, matching, travelling salesman problem, graph algorithms}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2016.4
Building Clusters with Lower-Bounded Sizes

Authors: Faisal Abu-Khzam, Cristina Bazgan, Katrin Casel, and Henning Fernau

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
Classical clustering problems search for a partition of objects into a fixed number of clusters. In many scenarios however the number of clusters is not known or necessarily fixed. Further, clusters are sometimes only considered to be of significance if they have a certain size. We discuss clustering into sets of minimum cardinality k without a fixed number of sets and present a general model for these types of problems. This general framework allows the comparison of different measures to assess the quality of a clustering. We specifically consider nine quality-measures and classify the complexity of the resulting problems with respect to k. Further, we derive some polynomial-time solvable cases for k = 2 with connections to matching-type problems which, among other graph problems, then are used to compute approximations for larger values of k.
Cite as

Faisal Abu-Khzam, Cristina Bazgan, Katrin Casel, and Henning Fernau. Building Clusters with Lower-Bounded Sizes. In 27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, pp. 4:1-4:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{abukhzam_et_al:LIPIcs.ISAAC.2016.4,
  author =	{Abu-Khzam, Faisal and Bazgan, Cristina and Casel, Katrin and Fernau, Henning},
  title =	{{Building Clusters with Lower-Bounded Sizes}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{4:1--4:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.4},
  URN =		{urn:nbn:de:0030-drops-67742},
  doi =		{10.4230/LIPIcs.ISAAC.2016.4},
  annote =	{Keywords: Clustering, Approximation Algorithms, Complexity, Matching}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2016.5
Simultaneous Feedback Edge Set: A Parameterized Perspective

Authors: Akanksha Agrawal, Fahad Panolan, Saket Saurabh, and Meirav Zehavi

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
In a recent article Agrawal et al. (STACS 2016) studied a simultaneous variant of the classic Feedback Vertex Set problem, called Simultaneous Feedback Vertex Set (Sim-FVS). In this problem the input is an n-vertex graph G, an integer k and a coloring function col : E(G) -> 2^[alpha] , and the objective is to check whether there exists a vertex subset S of cardinality at most k in G such that for all i in [alpha], G_i - S is acyclic. Here, G_i = (V (G), {e in E(G) | i in col(e)}) and [alpha] = {1,...,alpha}. In this paper we consider the edge variant of the problem, namely, Simultaneous Feedback Edge Set (Sim-FES). In this problem, the input is same as the input of Sim-FVS and the objective is to check whether there is an edge subset S of cardinality at most k in G such that for all i in [alpha], G_i - S is acyclic. Unlike the vertex variant of the problem, when alpha = 1, the problem is equivalent to finding a maximal spanning forest and hence it is polynomial time solvable. We show that for alpha = 3 Sim-FES is NP-hard by giving a reduction from Vertex Cover on cubic-graphs. The same reduction shows that the problem does not admit an algorithm of running time O(2^o(k) n^O(1)) unless ETH fails. This hardness result is complimented by an FPT algorithm for Sim-FES running in time O(2^((omega k alpha) + (alpha log k)) n^O(1)), where omega is the exponent in the running time of matrix multiplication. The same algorithm gives a polynomial time algorithm for the case when alpha = 2. We also give a kernel for Sim-FES with (k alpha)^O(alpha) vertices. Finally, we consider the problem Maximum Simultaneous Acyclic Subgraph. Here, the input is a graph G, an integer q and, a coloring function col : E(G) -> 2^[alpha] . The question is whether there is a edge subset F of cardinality at least q in G such that for all i in [alpha], G[F_i] is acyclic. Here, F_i = {e in F | i in col(e)}. We give an FPT algorithm for Maximum Simultaneous Acyclic Subgraph running in time O(2^(omega q alpha) n^O(1) ). All our algorithms are based on parameterized version of the Matroid Parity problem.
Cite as

Akanksha Agrawal, Fahad Panolan, Saket Saurabh, and Meirav Zehavi. Simultaneous Feedback Edge Set: A Parameterized Perspective. In 27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, pp. 5:1-5:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{agrawal_et_al:LIPIcs.ISAAC.2016.5,
  author =	{Agrawal, Akanksha and Panolan, Fahad and Saurabh, Saket and Zehavi, Meirav},
  title =	{{Simultaneous Feedback Edge Set: A Parameterized Perspective}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{5:1--5:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.5},
  URN =		{urn:nbn:de:0030-drops-67767},
  doi =		{10.4230/LIPIcs.ISAAC.2016.5},
  annote =	{Keywords: parameterized complexity, feedback edge set, alpha-matroid parity}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2016.6
Kernels for Deletion to Classes of Acyclic Digraphs

Authors: Akanksha Agrawal, Saket Saurabh, Roohani Sharma, and Meirav Zehavi

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
In the Directed Feedback Vertex Set (DFVS) problem, we are given a digraph D on n vertices and a positive integer k and the objective is to check whether there exists a set of vertices S of size at most k such that F = D - S is a directed acyclic digraph. In a recent paper, Mnich and van Leeuwen [STACS 2016] considered the kernelization complexity of DFVS with an additional restriction on F, namely that F must be an out-forest (Out-Forest Vertex Deletion Set), an out-tree (Out-Tree Vertex Deletion Set), or a (directed) pumpkin (Pumpkin Vertex Deletion Set). Their objective was to shed some light on the kernelization complexity of the DFVS problem, a well known open problem in the area of Parameterized Complexity. In this article, we improve the kernel sizes of Out-Forest Vertex Deletion Set from O(k^3) to O(k^2) and of Pumpkin Vertex Deletion Set from O(k^18) to O(k^3). We also prove that the former kernel size is tight under certain complexity theoretic assumptions.
Cite as

Akanksha Agrawal, Saket Saurabh, Roohani Sharma, and Meirav Zehavi. Kernels for Deletion to Classes of Acyclic Digraphs. In 27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, pp. 6:1-6:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{agrawal_et_al:LIPIcs.ISAAC.2016.6,
  author =	{Agrawal, Akanksha and Saurabh, Saket and Sharma, Roohani and Zehavi, Meirav},
  title =	{{Kernels for Deletion to Classes of Acyclic Digraphs}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{6:1--6:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.6},
  URN =		{urn:nbn:de:0030-drops-67777},
  doi =		{10.4230/LIPIcs.ISAAC.2016.6},
  annote =	{Keywords: out-forest, pumpkin, parameterized complexity, kernelization}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2016.7
An Efficient Algorithm for Placing Electric Vehicle Charging Stations

Authors: Pankaj K. Agarwal, Jiangwei Pan, and Will Victor

Published in: LIPIcs, Volume 64, 27th International Symposium on Algorithms and Computation (ISAAC 2016)

Abstract
Motivated by the increasing popularity of electric vehicles (EV) and a lack of charging stations in the road network, we study the shortest path hitting set (SPHS) problem. Roughly speaking, given an input graph G, the goal is to compute a small-size subset H of vertices of G such that by placing charging stations at vertices in H, every shortest path in G becomes EV-feasible, i.e., an EV can travel between any two vertices of G through the shortest path with a full charge. In this paper, we propose a bi-criteria approximation algorithm with running time near-linear in the size of G that has a logarithmic approximation on |H| and may require the EV to slightly deviate from the shortest path. We also present a data structure for computing an EV-feasible path between two query vertices of G.
Cite as

Pankaj K. Agarwal, Jiangwei Pan, and Will Victor. An Efficient Algorithm for Placing Electric Vehicle Charging Stations. In 27th International Symposium on Algorithms and Computation (ISAAC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 64, pp. 7:1-7:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

Copy BibTex To Clipboard

@InProceedings{agarwal_et_al:LIPIcs.ISAAC.2016.7,
  author =	{Agarwal, Pankaj K. and Pan, Jiangwei and Victor, Will},
  title =	{{An Efficient Algorithm for Placing Electric Vehicle Charging Stations}},
  booktitle =	{27th International Symposium on Algorithms and Computation (ISAAC 2016)},
  pages =	{7:1--7:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-026-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{64},
  editor =	{Hong, Seok-Hee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2016.7},
  URN =		{urn:nbn:de:0030-drops-67782},
  doi =		{10.4230/LIPIcs.ISAAC.2016.7},
  annote =	{Keywords: Shortest path hitting set, Charging station placement, Electric vehicle}
}
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