8 Search Results for "Davies, Peter"

Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2023.46
Optimal (Degree+1)-Coloring in Congested Clique

Authors: Sam Coy, Artur Czumaj, Peter Davies, and Gopinath Mishra

Published in: LIPIcs, Volume 261, 50th International Colloquium on Automata, Languages, and Programming (ICALP 2023)

Abstract
We consider the distributed complexity of the (degree+1)-list coloring problem, in which each node u of degree d(u) is assigned a palette of d(u)+1 colors, and the goal is to find a proper coloring using these color palettes. The (degree+1)-list coloring problem is a natural generalization of the classical (Δ+1)-coloring and (Δ+1)-list coloring problems, both being benchmark problems extensively studied in distributed and parallel computing. In this paper we settle the complexity of the (degree+1)-list coloring problem in the Congested Clique model by showing that it can be solved deterministically in a constant number of rounds.
Cite as

Sam Coy, Artur Czumaj, Peter Davies, and Gopinath Mishra. Optimal (Degree+1)-Coloring in Congested Clique. In 50th International Colloquium on Automata, Languages, and Programming (ICALP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 261, pp. 46:1-46:20, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)

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@InProceedings{coy_et_al:LIPIcs.ICALP.2023.46,
  author =	{Coy, Sam and Czumaj, Artur and Davies, Peter and Mishra, Gopinath},
  title =	{{Optimal (Degree+1)-Coloring in Congested Clique}},
  booktitle =	{50th International Colloquium on Automata, Languages, and Programming (ICALP 2023)},
  pages =	{46:1--46:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-278-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{261},
  editor =	{Etessami, Kousha and Feige, Uriel and Puppis, Gabriele},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2023.46},
  URN =		{urn:nbn:de:0030-drops-180987},
  doi =		{10.4230/LIPIcs.ICALP.2023.46},
  annote =	{Keywords: Distributed computing, graph coloring, parallel computing}
}
Document
DOI: 10.4230/LIPIcs.DISC.2022.12
Liveness and Latency of Byzantine State-Machine Replication

Authors: Manuel Bravo, Gregory Chockler, and Alexey Gotsman

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

Abstract
Byzantine state-machine replication (SMR) ensures the consistency of replicated state in the presence of malicious replicas and lies at the heart of the modern blockchain technology. Byzantine SMR protocols often guarantee safety under all circumstances and liveness only under synchrony. However, guaranteeing liveness even under this assumption is nontrivial. So far we have lacked systematic ways of incorporating liveness mechanisms into Byzantine SMR protocols, which often led to subtle bugs. To close this gap, we introduce a modular framework to facilitate the design of provably live and efficient Byzantine SMR protocols. Our framework relies on a view abstraction generated by a special SMR synchronizer primitive to drive the agreement on command ordering. We present a simple formal specification of an SMR synchronizer and its bounded-space implementation under partial synchrony. We also apply our specification to prove liveness and analyze the latency of three Byzantine SMR protocols via a uniform methodology. In particular, one of these results yields what we believe is the first rigorous liveness proof for the algorithmic core of the seminal PBFT protocol.
Cite as

Manuel Bravo, Gregory Chockler, and Alexey Gotsman. Liveness and Latency of Byzantine State-Machine Replication. In 36th International Symposium on Distributed Computing (DISC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 246, pp. 12:1-12:19, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bravo_et_al:LIPIcs.DISC.2022.12,
  author =	{Bravo, Manuel and Chockler, Gregory and Gotsman, Alexey},
  title =	{{Liveness and Latency of Byzantine State-Machine Replication}},
  booktitle =	{36th International Symposium on Distributed Computing (DISC 2022)},
  pages =	{12:1--12:19},
  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.2022.12},
  URN =		{urn:nbn:de:0030-drops-172037},
  doi =		{10.4230/LIPIcs.DISC.2022.12},
  annote =	{Keywords: Replication, blockchain, partial synchrony, liveness}
}
Document
DOI: 10.4230/LIPIcs.DISC.2018.15
Deterministic Blind Radio Networks

Authors: Artur Czumaj and Peter Davies

Published in: LIPIcs, Volume 121, 32nd International Symposium on Distributed Computing (DISC 2018)

Abstract
Ad-hoc radio networks and multiple access channels are classical and well-studied models of distributed systems, with a large body of literature on deterministic algorithms for fundamental communications primitives such as broadcasting and wake-up. However, almost all of these algorithms assume knowledge of the number of participating nodes and the range of possible IDs, and often make the further assumption that the latter is linear in the former. These are very strong assumptions for models which were designed to capture networks of weak devices organized in an ad-hoc manner. It was believed that without this knowledge, deterministic algorithms must necessarily be much less efficient. In this paper we address this fundamental question and show that this is not the case. We present deterministic algorithms for blind networks (in which nodes know only their own IDs), which match or nearly match the running times of the fastest algorithms which assume network knowledge (and even surpass the previous fastest algorithms which assume parameter knowledge but not small labels). Specifically, in multiple access channels with k participating nodes and IDs up to L, we give a wake-up algorithm requiring O((k log L log k)/(log log k)) time, improving dramatically over the O(L^3 log^3 L) time algorithm of De Marco et al. (2007), and a broadcasting algorithm requiring O(k log L log log k) time, improving over the O(L) time algorithm of Gasieniec et al. (2001) in most circumstances. Furthermore, we show how these same algorithms apply directly to multi-hop radio networks, achieving even larger running time improvements.
Cite as

Artur Czumaj and Peter Davies. Deterministic Blind Radio Networks. In 32nd International Symposium on Distributed Computing (DISC 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 121, pp. 15:1-15:17, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)

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@InProceedings{czumaj_et_al:LIPIcs.DISC.2018.15,
  author =	{Czumaj, Artur and Davies, Peter},
  title =	{{Deterministic Blind Radio Networks}},
  booktitle =	{32nd International Symposium on Distributed Computing (DISC 2018)},
  pages =	{15:1--15:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-092-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{121},
  editor =	{Schmid, Ulrich and Widder, Josef},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2018.15},
  URN =		{urn:nbn:de:0030-drops-98047},
  doi =		{10.4230/LIPIcs.DISC.2018.15},
  annote =	{Keywords: Broadcasting, Deterministic Algorithms, Radio Networks}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2018.43
Brief Announcement: Randomized Blind Radio Networks

Authors: Artur Czumaj and Peter Davies

Published in: LIPIcs, Volume 121, 32nd International Symposium on Distributed Computing (DISC 2018)

Abstract
Radio networks are a long-studied model for distributed system of devices which communicate wirelessly. When these devices are mobile or have limited capabilities, the system is best modeled by the ad-hoc variant, in which the devices do not know the structure of the network. Much work has been devoted to designing algorithms for the ad-hoc model, particularly for fundamental communications tasks such as broadcasting. Most of these algorithms, however, assume that devices have some network knowledge (usually bounds on the number of nodes in the network n, and the diameter D), which may not be realistic in systems with weak devices or gradual deployment. Little is known about what can be done without this information. This is the issue we address in this work, by presenting the first randomized broadcasting algorithms for blind networks in which nodes have no prior knowledge whatsoever. We demonstrate that lack of parameter knowledge can be overcome at only a small increase in running time. Specifically, we show that in networks without collision detection, broadcast can be achieved in O(D log n/D log^2 log n/D + log^2 n) time, almost reaching the Omega(D log n/D + log^2 n) lower bound. We also give an even faster algorithm for directed networks with collision detection.
Cite as

Artur Czumaj and Peter Davies. Brief Announcement: Randomized Blind Radio Networks. In 32nd International Symposium on Distributed Computing (DISC 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 121, pp. 43:1-43:3, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)

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@InProceedings{czumaj_et_al:LIPIcs.DISC.2018.43,
  author =	{Czumaj, Artur and Davies, Peter},
  title =	{{Brief Announcement: Randomized Blind Radio Networks}},
  booktitle =	{32nd International Symposium on Distributed Computing (DISC 2018)},
  pages =	{43:1--43:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-092-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{121},
  editor =	{Schmid, Ulrich and Widder, Josef},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2018.43},
  URN =		{urn:nbn:de:0030-drops-98323},
  doi =		{10.4230/LIPIcs.DISC.2018.43},
  annote =	{Keywords: Broadcasting, Randomized Algorithms, Radio Networks}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2015.30
Communicating with Beeps

Authors: Artur Czumaj and Peter Davies

Published in: LIPIcs, Volume 46, 19th International Conference on Principles of Distributed Systems (OPODIS 2015)

Abstract
The beep model is a very weak communications model in which devices in a network can communicate only via beeps and silence. As a result of its weak assumptions, it has broad applicability to many different implementations of communications networks. This comes at the cost of a restrictive environment for algorithm design. Despite being only recently introduced, the beep model has received considerable attention, in part due to its relationship with other communication models such as that of ad-hoc radio networks. However, there has been no definitive published result for several fundamental tasks in the model. We aim to rectify this with our paper. We present algorithms for the tasks of broadcast, gossiping, and multi-broadcast, and also, as intermediary results, means of depth-first search and diameter estimation. Our O(D+log(M)-time algorithm for broadcasting is a simple formalization of a concept known as beep waves, and is asymptotically optimal. We give an O(n*log(L))-time depth-first search procedure, and show how this can be used as the basis for an O(n*log(L*M))-time gossiping algorithm. Finally, we approach the more general problem of multi-broadcast. We differentiate between two variants of this problem: one where nodes must know the origin of all source messages, and another where this information is not required. In the first instance we achieve an algorithm running in time O(k*log((L*M)/k)+D*log(L)), and in the second an O(k*log(M/k)+D*log(L))-time algorithm (or O(M+D*log(L)) when M <= k). We then give corresponding lower bounds: Omega(k*log((L*M)/k)+D) in the case where nodes must know message origins, and Omega(k*log(M/k)+D) and Omega(M+D) in the other case, for M > k and M <= k respectively. These lower bounds demonstrate that our algorithms are optimal except for the D*log(L) additive term. In these running-time expressions, n represents network size, D network diameter, L range of node labels, M range of source messages, and k number of sources. Our algorithms are all explicit, deterministic, and practical, and give efficient means of communication while making arguably the minimum possible assumptions about the network.
Cite as

Artur Czumaj and Peter Davies. Communicating with Beeps. In 19th International Conference on Principles of Distributed Systems (OPODIS 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 46, pp. 30:1-30:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2016)

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@InProceedings{czumaj_et_al:LIPIcs.OPODIS.2015.30,
  author =	{Czumaj, Artur and Davies, Peter},
  title =	{{Communicating with Beeps}},
  booktitle =	{19th International Conference on Principles of Distributed Systems (OPODIS 2015)},
  pages =	{30:1--30:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-98-9},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{46},
  editor =	{Anceaume, Emmanuelle and Cachin, Christian and Potop-Butucaru, Maria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2015.30},
  URN =		{urn:nbn:de:0030-drops-66195},
  doi =		{10.4230/LIPIcs.OPODIS.2015.30},
  annote =	{Keywords: Beep model, Communication networks, Broadcasting, Gossiping, Leader election}
}
Document
DOI: 10.4230/LIPIcs.ICALP.2016.139
Faster Deterministic Communication in Radio Networks

Authors: Artur Czumaj and Peter Davies

Published in: LIPIcs, Volume 55, 43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016)

Abstract
In this paper we improve the deterministic complexity of two fundamental communication primitives in the classical model of ad-hoc radio networks with unknown topology: broadcasting and wake-up. We consider an unknown radio network, in which all nodes have no prior knowledge about network topology, and know only the size of the network n, the maximum in-degree of any node Delta, and the eccentricity of the network D. For such networks, we first give an algorithm for wake-up, in both directed and undirected networks, based on the existence of small universal synchronizers. This algorithm runs in O((min{n,D*Delta}*log(n)*log(Delta))/(log(log(Delta)))) time, improving over the previous best O(n*log^2(n))-time result across all ranges of parameters, but particularly when maximum in-degree is small. Next, we introduce a new combinatorial framework of block synchronizers and prove the existence of such objects of low size. Using this framework, we design a new deterministic algorithm for the fundamental problem of broadcasting, running in O(n*log(D)*log(log((D*Delta)/n))) time. This is the fastest known algorithm for this problems, improving upon the O(n*log(n)*log*log(n))-time algorithm of De Marco (2010) and the O(n*log^2(D))-time algorithm due to Czumaj and Rytter (2003), the previous fastest results for directed networks, and is the first to come within a log-logarithmic factor of the Omega(n*log(D)) lower bound due to Clementi et al. (2003). Our results have also direct implications on the fastest deterministic leader election and clock synchronization algorithms in both directed and undirected radio networks, tasks which are commonly used as building blocks for more complex procedures.
Cite as

Artur Czumaj and Peter Davies. Faster Deterministic Communication in Radio Networks. In 43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 55, pp. 139:1-139:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2016)

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@InProceedings{czumaj_et_al:LIPIcs.ICALP.2016.139,
  author =	{Czumaj, Artur and Davies, Peter},
  title =	{{Faster Deterministic Communication in Radio Networks}},
  booktitle =	{43rd International Colloquium on Automata, Languages, and Programming (ICALP 2016)},
  pages =	{139:1--139:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-013-2},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{55},
  editor =	{Chatzigiannakis, Ioannis and Mitzenmacher, Michael and Rabani, Yuval and Sangiorgi, Davide},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2016.139},
  URN =		{urn:nbn:de:0030-drops-62838},
  doi =		{10.4230/LIPIcs.ICALP.2016.139},
  annote =	{Keywords: Radio networks, Communication networks, Broadcasting, Wake-Up, Deterministic algorithms}
}
Document
DOI: 10.4230/DagSemProc.05181.5
Connecting the Vehicle with the Environment - Trends and Challenges

Authors: Gerrit de Boer and Peter Vogel

Published in: Dagstuhl Seminar Proceedings, Volume 5181, Mobile Computing and Ambient Intelligence: The Challenge of Multimedia (2005)

Abstract
Innovations in automotive electronics have become increasingly complex, resulting in high-end vehicles containing more than 70 electronic control units and offering a variety of functions to the driver. In-vehicle telematics and infotainment systems provide services like digital radio, broadcast services, television, and MP3 audio. Future applications and services will integrate information sources available outside and inside the car, requiring vehicle systems connected with in-vehicle Consumer Electronics devices and the outside world. In order to realized the vision of an intelligent networked car, connected with the environment and providing the driver with information according to his demands, common efforts towards car manufacturer and supplier spanning standards for data exchange are required. The paper discusses possible approaches and future challenges.
Cite as

Gerrit de Boer and Peter Vogel. Connecting the Vehicle with the Environment - Trends and Challenges. In Mobile Computing and Ambient Intelligence: The Challenge of Multimedia. Dagstuhl Seminar Proceedings, Volume 5181, pp. 1-5, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2005)

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@InProceedings{deboer_et_al:DagSemProc.05181.5,
  author =	{de Boer, Gerrit and Vogel, Peter},
  title =	{{Connecting the Vehicle with the Environment - Trends and Challenges}},
  booktitle =	{Mobile Computing and Ambient Intelligence: The Challenge of Multimedia},
  pages =	{1--5},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2005},
  volume =	{5181},
  editor =	{Nigel Davies and Thomas Kirste and Heidrun Schumann},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.05181.5},
  URN =		{urn:nbn:de:0030-drops-3793},
  doi =		{10.4230/DagSemProc.05181.5},
  annote =	{Keywords: Mobile Multimedia, Vehicle Infotainment, Telematics}
}
Document
DOI: 10.4230/DagSemProc.04441.8
04441 Working Group – Towards a Handbook for User-Centred Mobile Application Design

Authors: Susanne Boll, Martin Breunig, Nigel Davies, Christian S. Jensen, Birgitta König-Ries, Rainer Malaka, Florian Matthes, Christoforos Panayiotou, Simonas Saltenis, and Thomas Schwarz

Published in: Dagstuhl Seminar Proceedings, Volume 4441, Mobile Information Management (2005)

Abstract
Why do we have difficulties designing mobile apps? Is there a "Mobile RUP"?
Cite as

Susanne Boll, Martin Breunig, Nigel Davies, Christian S. Jensen, Birgitta König-Ries, Rainer Malaka, Florian Matthes, Christoforos Panayiotou, Simonas Saltenis, and Thomas Schwarz. 04441 Working Group – Towards a Handbook for User-Centred Mobile Application Design. In Mobile Information Management. Dagstuhl Seminar Proceedings, Volume 4441, pp. 1-8, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2005)

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@InProceedings{boll_et_al:DagSemProc.04441.8,
  author =	{Boll, Susanne and Breunig, Martin and Davies, Nigel and Jensen, Christian S. and K\"{o}nig-Ries, Birgitta and Malaka, Rainer and Matthes, Florian and Panayiotou, Christoforos and Saltenis, Simonas and Schwarz, Thomas},
  title =	{{04441 Working Group – Towards a Handbook for User-Centred Mobile Application Design}},
  booktitle =	{Mobile Information Management},
  pages =	{1--8},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2005},
  volume =	{4441},
  editor =	{Margaret H. Dunham and Birgitta K\"{o}nig-Ries and Evaggelia Pitoura and Peter Reiher and Can T\"{u}rker},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.04441.8},
  URN =		{urn:nbn:de:0030-drops-1662},
  doi =		{10.4230/DagSemProc.04441.8},
  annote =	{Keywords: User-Centred Mobile Application Design}
}
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