3 Search Results for "Witkowski, Adam"

Document
DOI: 10.4230/LIPIcs.ISAAC.2021.59
Distributed Approximations of f-Matchings and b-Matchings in Graphs of Sub-Logarithmic Expansion

Authors: Andrzej Czygrinow, Michał Hanćkowiak, and Marcin Witkowski

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

Abstract
We give a distributed algorithm which given ε > 0 finds a (1-ε)-factor approximation of a maximum f-matching in graphs G = (V,E) of sub-logarithmic expansion. Using a similar approach we also give a distributed approximation of a maximum b-matching in the same class of graphs provided the function b: V → ℤ^+ is L-Lipschitz for some constant L. Both algorithms run in O(log^* n) rounds in the LOCAL model, which is optimal.
Cite as

Andrzej Czygrinow, Michał Hanćkowiak, and Marcin Witkowski. Distributed Approximations of f-Matchings and b-Matchings in Graphs of Sub-Logarithmic Expansion. In 32nd International Symposium on Algorithms and Computation (ISAAC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 212, pp. 59:1-59:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{czygrinow_et_al:LIPIcs.ISAAC.2021.59,
  author =	{Czygrinow, Andrzej and Han\'{c}kowiak, Micha{\l} and Witkowski, Marcin},
  title =	{{Distributed Approximations of f-Matchings and b-Matchings in Graphs of Sub-Logarithmic Expansion}},
  booktitle =	{32nd International Symposium on Algorithms and Computation (ISAAC 2021)},
  pages =	{59:1--59:13},
  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.2021.59},
  URN =		{urn:nbn:de:0030-drops-154925},
  doi =		{10.4230/LIPIcs.ISAAC.2021.59},
  annote =	{Keywords: Distributed algorithms, f-matching, b-matching}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2018.22
Distributed Approximation Algorithms for the Minimum Dominating Set in K_h-Minor-Free Graphs

Authors: Andrzej Czygrinow, Michal Hanckowiak, Wojciech Wawrzyniak, and Marcin Witkowski

Published in: LIPIcs, Volume 123, 29th International Symposium on Algorithms and Computation (ISAAC 2018)

Abstract
In this paper we will give two distributed approximation algorithms (in the Local model) for the minimum dominating set problem. First we will give a distributed algorithm which finds a dominating set D of size O(gamma(G)) in a graph G which has no topological copy of K_h. The algorithm runs L_h rounds where L_h is a constant which depends on h only. This procedure can be used to obtain a distributed algorithm which given epsilon>0 finds in a graph G with no K_h-minor a dominating set D of size at most (1+epsilon)gamma(G). The second algorithm runs in O(log^*{|V(G)|}) rounds.
Cite as

Andrzej Czygrinow, Michal Hanckowiak, Wojciech Wawrzyniak, and Marcin Witkowski. Distributed Approximation Algorithms for the Minimum Dominating Set in K_h-Minor-Free Graphs. In 29th International Symposium on Algorithms and Computation (ISAAC 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 123, pp. 22:1-22:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{czygrinow_et_al:LIPIcs.ISAAC.2018.22,
  author =	{Czygrinow, Andrzej and Hanckowiak, Michal and Wawrzyniak, Wojciech and Witkowski, Marcin},
  title =	{{Distributed Approximation Algorithms for the Minimum Dominating Set in K\underlineh-Minor-Free Graphs}},
  booktitle =	{29th International Symposium on Algorithms and Computation (ISAAC 2018)},
  pages =	{22:1--22:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-094-1},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{123},
  editor =	{Hsu, Wen-Lian and Lee, Der-Tsai and Liao, Chung-Shou},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2018.22},
  URN =		{urn:nbn:de:0030-drops-99705},
  doi =		{10.4230/LIPIcs.ISAAC.2018.22},
  annote =	{Keywords: Distributed algorithms, minor-closed family of graphs, MDS}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2018.14
Satisfiability for SCULPT-Schemas for CSV-Like Data

Authors: Johannes Doleschal, Wim Martens, Frank Neven, and Adam Witkowski

Published in: LIPIcs, Volume 98, 21st International Conference on Database Theory (ICDT 2018)

Abstract
SCULPT is a simple schema language inspired by the recent working effort towards a recommendation by the World Wide Web Consortium (W3C) for tabular data and metadata on the Web. In its core, a SCULPT schema consists of a set of rules where left-hand sides select sets of regions in the tabular data and the right-hand sides describe the contents of these regions. A document (divided in cells by row- and column-delimiters) then satisfies a schema if it satisfies every rule. In this paper, we study the satisfiability problem for SCULPT schemas. As SCULPT describes grid-like structures, satisfiability obviously becomes undecidable rather quickly even for very restricted schemas. We define a schema language called L-SCULPT (Lego SCULPT) that restricts the walking power of SCULPT by selecting rectangular shaped areas and only considers tables for which selected regions do not intersect. Depending on the axes used by L-SCULPT, we show that satisfiability is PTIME-complete or undecidable. One of the tractable fragments is practically useful as it extends the structural core of the current W3C proposal for schemas over tabular data. We therefore see how the navigational power of the W3C proposal can be extended while still retaining tractable satisfiability tests.
Cite as

Johannes Doleschal, Wim Martens, Frank Neven, and Adam Witkowski. Satisfiability for SCULPT-Schemas for CSV-Like Data. In 21st International Conference on Database Theory (ICDT 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 98, pp. 14:1-14:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{doleschal_et_al:LIPIcs.ICDT.2018.14,
  author =	{Doleschal, Johannes and Martens, Wim and Neven, Frank and Witkowski, Adam},
  title =	{{Satisfiability for SCULPT-Schemas for CSV-Like Data}},
  booktitle =	{21st International Conference on Database Theory (ICDT 2018)},
  pages =	{14:1--14:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-063-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{98},
  editor =	{Kimelfeld, Benny and Amsterdamer, Yael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2018.14},
  URN =		{urn:nbn:de:0030-drops-85969},
  doi =		{10.4230/LIPIcs.ICDT.2018.14},
  annote =	{Keywords: CSV, schema languages, semi-structured data}
}
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