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Documents authored by Nolin, Alexandre

Document
DOI: 10.4230/LIPIcs.DISC.2024.24
Decentralized Distributed Graph Coloring II: Degree+1-Coloring Virtual Graphs

Authors: Maxime Flin, Magnús M. Halldórsson, and Alexandre Nolin

Published in: LIPIcs, Volume 319, 38th International Symposium on Distributed Computing (DISC 2024)

Abstract
Graph coloring is fundamental to distributed computing. We give the first general treatment of the coloring of virtual graphs, where the graph H to be colored is locally embedded within the communication graph G. Besides generalizing classical distributed graph coloring (where H = G), this captures other previously studied settings, including cluster graphs and power graphs. We find that the complexity of coloring a virtual graph depends linearly on the edge congestion of its embedding. The main question of interest is how fast we can color virtual graphs of constant congestion. We find that, surprisingly, these graphs can be colored nearly as fast as ordinary graphs. Namely, we give a O(log⁴log n)-round algorithm for the deg+1-coloring problem, where each node is assigned more colors than its degree. This can be viewed as a case where a distributed graph problem can be solved even when the operation of each node is decentralized.
Cite as

Maxime Flin, Magnús M. Halldórsson, and Alexandre Nolin. Decentralized Distributed Graph Coloring II: Degree+1-Coloring Virtual Graphs. In 38th International Symposium on Distributed Computing (DISC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 319, pp. 24:1-24:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{flin_et_al:LIPIcs.DISC.2024.24,
  author =	{Flin, Maxime and Halld\'{o}rsson, Magn\'{u}s M. and Nolin, Alexandre},
  title =	{{Decentralized Distributed Graph Coloring II: Degree+1-Coloring Virtual Graphs}},
  booktitle =	{38th International Symposium on Distributed Computing (DISC 2024)},
  pages =	{24:1--24:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-352-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{319},
  editor =	{Alistarh, Dan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2024.24},
  URN =		{urn:nbn:de:0030-drops-212502},
  doi =		{10.4230/LIPIcs.DISC.2024.24},
  annote =	{Keywords: Graph Coloring, Distributed Algorithms, Virtual Graphs, Congestion, Dilation}
}
Document
DOI: 10.4230/LIPIcs.DISC.2024.26
Content-Oblivious Leader Election on Rings

Authors: Fabian Frei, Ran Gelles, Ahmed Ghazy, and Alexandre Nolin

Published in: LIPIcs, Volume 319, 38th International Symposium on Distributed Computing (DISC 2024)

Abstract
In content-oblivious computation, n nodes wish to compute a given task over an asynchronous network that suffers from an extremely harsh type of noise, which corrupts the content of all messages across all channels. In a recent work, Censor-Hillel, Cohen, Gelles, and Sela (Distributed Computing, 2023) showed how to perform arbitrary computations in a content-oblivious way in 2-edge connected networks but only if the network has a distinguished node (called root) to initiate the computation. Our goal is to remove this assumption, which was conjectured to be necessary. Achieving this goal essentially reduces to performing a content-oblivious leader election since an elected leader can then serve as the root required to perform arbitrary content-oblivious computations. We focus on ring networks, which are the simplest 2-edge connected graphs. On oriented rings, we obtain a leader election algorithm with message complexity O(n ⋅ ID_max), where ID_max is the maximal assigned ID. As it turns out, this dependency on ID_max is inherent: we show a lower bound of Ω(n log(ID_max/n)) messages for content-oblivious leader election algorithms. We also extend our results to non-oriented rings, where nodes cannot tell which channel leads to which neighbor. In this case, however, the algorithm does not terminate but only reaches quiescence.
Cite as

Fabian Frei, Ran Gelles, Ahmed Ghazy, and Alexandre Nolin. Content-Oblivious Leader Election on Rings. In 38th International Symposium on Distributed Computing (DISC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 319, pp. 26:1-26:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{frei_et_al:LIPIcs.DISC.2024.26,
  author =	{Frei, Fabian and Gelles, Ran and Ghazy, Ahmed and Nolin, Alexandre},
  title =	{{Content-Oblivious Leader Election on Rings}},
  booktitle =	{38th International Symposium on Distributed Computing (DISC 2024)},
  pages =	{26:1--26:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-352-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{319},
  editor =	{Alistarh, Dan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2024.26},
  URN =		{urn:nbn:de:0030-drops-212527},
  doi =		{10.4230/LIPIcs.DISC.2024.26},
  annote =	{Keywords: Content-Oblivious Computation, Faulty Communication, Leader Election, Ring Networks, Ring Orientation}
}
Document
DOI: 10.4230/LIPIcs.DISC.2023.19
Fast Coloring Despite Congested Relays

Authors: Maxime Flin, Magnús M. Halldórsson, and Alexandre Nolin

Published in: LIPIcs, Volume 281, 37th International Symposium on Distributed Computing (DISC 2023)

Abstract
We provide a O(log⁶ log n)-round randomized algorithm for distance-2 coloring in CONGEST with Δ²+1 colors. For Δ≫polylog n, this improves exponentially on the O(logΔ+polylog log n) algorithm of [Halldórsson, Kuhn, Maus, Nolin, DISC'20].
Cite as

Maxime Flin, Magnús M. Halldórsson, and Alexandre Nolin. Fast Coloring Despite Congested Relays. In 37th International Symposium on Distributed Computing (DISC 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 281, pp. 19:1-19:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{flin_et_al:LIPIcs.DISC.2023.19,
  author =	{Flin, Maxime and Halld\'{o}rsson, Magn\'{u}s M. and Nolin, Alexandre},
  title =	{{Fast Coloring Despite Congested Relays}},
  booktitle =	{37th International Symposium on Distributed Computing (DISC 2023)},
  pages =	{19:1--19:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-301-0},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{281},
  editor =	{Oshman, Rotem},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2023.19},
  URN =		{urn:nbn:de:0030-drops-191453},
  doi =		{10.4230/LIPIcs.DISC.2023.19},
  annote =	{Keywords: CONGEST model, distributed graph coloring, power graphs}
}
Document
DOI: 10.4230/LIPIcs.DISC.2022.26
Fast Distributed Vertex Splitting with Applications

Authors: Magnús M. Halldórsson, Yannic Maus, and Alexandre Nolin

Published in: LIPIcs, Volume 246, 36th International Symposium on Distributed Computing (DISC 2022)

Abstract
We present poly log log n-round randomized distributed algorithms to compute vertex splittings, a partition of the vertices of a graph into k parts such that a node of degree d(u) has ≈ d(u)/k neighbors in each part. Our techniques can be seen as the first progress towards general poly log log n-round algorithms for the Lovász Local Lemma. As the main application of our result, we obtain a randomized poly log log n-round CONGEST algorithm for (1+ε)Δ-edge coloring n-node graphs of sufficiently large constant maximum degree Δ, for any ε > 0. Further, our results improve the computation of defective colorings and certain tight list coloring problems. All the results improve the state-of-the-art round complexity exponentially, even in the LOCAL model.
Cite as

Magnús M. Halldórsson, Yannic Maus, and Alexandre Nolin. Fast Distributed Vertex Splitting with Applications. In 36th International Symposium on Distributed Computing (DISC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 246, pp. 26:1-26:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{halldorsson_et_al:LIPIcs.DISC.2022.26,
  author =	{Halld\'{o}rsson, Magn\'{u}s M. and Maus, Yannic and Nolin, Alexandre},
  title =	{{Fast Distributed Vertex Splitting with Applications}},
  booktitle =	{36th International Symposium on Distributed Computing (DISC 2022)},
  pages =	{26:1--26:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-255-6},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{246},
  editor =	{Scheideler, Christian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2022.26},
  URN =		{urn:nbn:de:0030-drops-172176},
  doi =		{10.4230/LIPIcs.DISC.2022.26},
  annote =	{Keywords: Graph problems, Edge coloring, List coloring, Lov\'{a}sz local lemma, LOCAL model, CONGEST model, Distributed computing}
}
Document
DOI: 10.4230/LIPIcs.DISC.2020.39
Coloring Fast Without Learning Your Neighbors' Colors

Authors: Magnús M. Halldórsson, Fabian Kuhn, Yannic Maus, and Alexandre Nolin

Published in: LIPIcs, Volume 179, 34th International Symposium on Distributed Computing (DISC 2020)

Abstract
We give an improved randomized CONGEST algorithm for distance-2 coloring that uses Δ²+1 colors and runs in O(log n) rounds, improving the recent O(log Δ ⋅ log n)-round algorithm in [Halldórsson, Kuhn, Maus; PODC '20]. We then improve the time complexity to O(log Δ) + 2^{O(√{log log n})}.
Cite as

Magnús M. Halldórsson, Fabian Kuhn, Yannic Maus, and Alexandre Nolin. Coloring Fast Without Learning Your Neighbors' Colors. In 34th International Symposium on Distributed Computing (DISC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 179, pp. 39:1-39:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{halldorsson_et_al:LIPIcs.DISC.2020.39,
  author =	{Halld\'{o}rsson, Magn\'{u}s M. and Kuhn, Fabian and Maus, Yannic and Nolin, Alexandre},
  title =	{{Coloring Fast Without Learning Your Neighbors' Colors}},
  booktitle =	{34th International Symposium on Distributed Computing (DISC 2020)},
  pages =	{39:1--39:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-168-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{179},
  editor =	{Attiya, Hagit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2020.39},
  URN =		{urn:nbn:de:0030-drops-131170},
  doi =		{10.4230/LIPIcs.DISC.2020.39},
  annote =	{Keywords: distributed graph coloring, distance 2 coloring, congestion}
}
Document
DOI: 10.4230/LIPIcs.TQC.2016.5
Robust Bell Inequalities from Communication Complexity

Authors: Sophie Laplante, Mathieu Laurière, Alexandre Nolin, Jérémie Roland, and Gabriel Senno

Published in: LIPIcs, Volume 61, 11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016)

Abstract
The question of how large Bell inequality violations can be, for quantum distributions, has been the object of much work in the past several years. We say a Bell inequality is normalized if its absolute value does not exceed 1 for any classical (i.e. local) distribution. Upper and (almost) tight lower bounds have been given in terms of number of outputs of the distribution, number of inputs, and the dimension of the shared quantum states. In this work, we revisit normalized Bell inequalities together with another family: inefficiency-resistant Bell inequalities. To be inefficiency-resistant, the Bell value must not exceed 1 for any local distribution, including those that can abort. Both these families of Bell inequalities are closely related to communication complexity lower bounds. We show how to derive large violations from any gap between classical and quantum communication complexity, provided the lower bound on classical communication is proven using these lower bounds. This leads to inefficiency-resistant violations that can be exponential in the size of the inputs. Finally, we study resistance to noise and inefficiency for these Bell inequalities.
Cite as

Sophie Laplante, Mathieu Laurière, Alexandre Nolin, Jérémie Roland, and Gabriel Senno. Robust Bell Inequalities from Communication Complexity. In 11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 61, pp. 5:1-5:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{laplante_et_al:LIPIcs.TQC.2016.5,
  author =	{Laplante, Sophie and Lauri\`{e}re, Mathieu and Nolin, Alexandre and Roland, J\'{e}r\'{e}mie and Senno, Gabriel},
  title =	{{Robust Bell Inequalities from Communication Complexity}},
  booktitle =	{11th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2016)},
  pages =	{5:1--5:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-019-4},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{61},
  editor =	{Broadbent, Anne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2016.5},
  URN =		{urn:nbn:de:0030-drops-66867},
  doi =		{10.4230/LIPIcs.TQC.2016.5},
  annote =	{Keywords: Communication complexity, Bell inequalities, nonlocality, detector efficiency}
}
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