Volume
LIPIcs, Volume 70
20th International Conference on Principles of Distributed Systems (OPODIS 2016)
Event
OPODIS 2016, December 13-16, 2016, Madrid, SpainEditors
Publication Details
- published at: 2017-04-06
- Publisher: Schloss Dagstuhl – Leibniz-Zentrum für Informatik
- ISBN: 978-3-95977-031-6
- DBLP: db/conf/opodis/opodis2016
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Complete Volume
LIPIcs, Volume 70, OPODIS'16, Complete Volume
Abstract
LIPIcs, Volume 70, OPODIS'16, Complete Volume
Cite as
20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@Proceedings{fatourou_et_al:LIPIcs.OPODIS.2016,
title = {{LIPIcs, Volume 70, OPODIS'16, Complete Volume}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016},
URN = {urn:nbn:de:0030-drops-71111},
doi = {10.4230/LIPIcs.OPODIS.2016},
annote = {Keywords: Distributed Systems, Performance of Systems, Concurrent Programming, Data Structures, Modes of Computation}
}
Document
Front Matter
Front Matter, Table of Contents, Preface, Committees, List of Authors
Abstract
Front Matter, Table of Contents, Preface, Committees, List of Authors
Cite as
20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 0:i-0:xviii, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{fatourou_et_al:LIPIcs.OPODIS.2016.0,
author = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
title = {{Front Matter, Table of Contents, Preface, Committees, List of Authors}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {0:i--0:xviii},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.0},
URN = {urn:nbn:de:0030-drops-70699},
doi = {10.4230/LIPIcs.OPODIS.2016.0},
annote = {Keywords: Front Matter, Table of Contents, Preface, Committees, List of Authors}
}
Document
Keynote Abstract
High Throughput Connectomics (Keynote Abstract)
Abstract
Connectomics is an emerging field of neurobiology that uses cutting edge machine learning and image processing to extract brain connectivity graphs from electron microscopy images. It has long been assumed that the processing of connectomics data will require mass storage and farms of CPUs and GPUs and will take months if not years. This talk will discuss the feasibility of designing a high-throughput connectomics-on-demand system that runs on a multicore machine with less than 100 cores and extracts connectomes at the terabyte per hour pace of modern electron microscopes. Building this system required solving algorithmic and performance engineering issues related to scaling machine learning on multicore architectures, and may have important lessons for other problem spaces in the natural sciences, where until now large distributed server or GPU farms seemed to be the only way to go.
Cite as
Nir Shavit. High Throughput Connectomics (Keynote Abstract). In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{shavit:LIPIcs.OPODIS.2016.1,
author = {Shavit, Nir},
title = {{High Throughput Connectomics}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {1:1--1:1},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.1},
URN = {urn:nbn:de:0030-drops-70705},
doi = {10.4230/LIPIcs.OPODIS.2016.1},
annote = {Keywords: Machine learning, multicore architectures}
}
Document
Keynote Abstract
Blockchain - From the Anarchy of Cryptocurrencies to the Enterprise (Keynote Abstract)
Abstract
A blockchain is a public ledger for recording transactions, maintained by many nodes without central authority through a distributed cryptographic protocol. All nodes validate the information to be appended to the blockchain, and a consensus protocol ensures that the nodes agree on a unique order in which entries are appended. Distributed protocols tolerating faults and adversarial attacks, coupled with cryptographic tools are needed for this. The recent interest in blockchains has revived research on consensus protocols, ranging from the proof-of-work method in Bitcoin's "mining" protocol to classical Byzantine agreement. Going far beyond its use in cryptocurrencies, blockchain is today viewed as a promising technology to simplify trusted exchanges of data and goods among companies. In this context, the Hyperledger Project has been established in early 2016 as an industry-wide collaborative effort to develop an open-source blockchain. This talk will present an overview of blockchain concepts, cryptographic building blocks and consensus mechanisms. It will also introduce Hyperledger Fabric, an implementation of blockchain technology intended for enterprise applications. Being one of the key partners in the Hyperledger Project, IBM is actively involved in the development of this blockchain platform.
Cite as
Christian Cachin. Blockchain - From the Anarchy of Cryptocurrencies to the Enterprise (Keynote Abstract). In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{cachin:LIPIcs.OPODIS.2016.2,
author = {Cachin, Christian},
title = {{Blockchain - From the Anarchy of Cryptocurrencies to the Enterprise}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {2:1--2:1},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.2},
URN = {urn:nbn:de:0030-drops-70719},
doi = {10.4230/LIPIcs.OPODIS.2016.2},
annote = {Keywords: consensus, cryptographic, distributed protocols}
}
Document
Keynote Abstract
Really Big Data: Analytics on Graphs with Trillions of Edges (Keynote Abstract)
Abstract
Big graphs occur naturally in many applications, most obviously in social networks, but also in many other areas such as biology and forensics. Current approaches to processing large graphs use either supercomputers or very large clusters. In both cases the entire graph must reside in memory before it can be processed. We are pursuing an alternative approach, processing graphs from secondary storage. While this comes with a performance penalty, it makes analytics on very large graphs feasible on a small number of commodity machines. We have developed two systems, one for a single machine and one for a cluster of machines. X-Stream, the single machine solution, aims to make all secondary storage access sequential. It uses two techniques to achieve this goal, edge-centric processing and streaming partitions. Chaos, the cluster solution, starts from the observation that there is little benefit to locality when accessing data from secondary storage over a high-speed network. As a result, Chaos spreads graph data uniformly randomly over storage devices, and uses randomized access to achieve I/O balance. Chaos furthermore uses work stealing to achieve computational load balance. By using these techniques, it avoids the need for expensive partitioning during pre-processing, while still achieving good scaling behavior. With Chaos we have been able to process an 8-trillion-edge graph on 32 machines, a new milestone for graph size on a small cluster. I will describe both systems and their performance on a number of benchmarks and in comparison to state-of-the-art alternatives. This is joint work with Laurent Bindschaedler (EPFL), Jasmina Malicevic (EPFL) and Amitabha Roy (Intel Labs).
Cite as
Willy Zwaenepoel. Really Big Data: Analytics on Graphs with Trillions of Edges (Keynote Abstract). In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, p. 3:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{zwaenepoel:LIPIcs.OPODIS.2016.3,
author = {Zwaenepoel, Willy},
title = {{Really Big Data: Analytics on Graphs with Trillions of Edges}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {3:1--3:1},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.3},
URN = {urn:nbn:de:0030-drops-70724},
doi = {10.4230/LIPIcs.OPODIS.2016.3},
annote = {Keywords: large graphs}
}
Document
Keynote Abstract
Participating Sets, Simulations, and the Consensus Hierarchy (Keynote Abstract)
Abstract
The participating set problem can be solved in an asynchronous system using only registers. I will gently explain this problem and its solution, followed by a new extension, called consistent ordered partition. Next, I will present a wait-free simulation by f + 1 processes of any setconsensus algorithm that tolerates f faults. I will also describe how to extend this simulation using consistent ordered partition. Finally, I will discuss how this extension can be used to prove that, within every level m > 1 of the consensus hierarchy, there is an infinite sequence of increasingly more powerful deterministic objects.
Cite as
Faith Ellen. Participating Sets, Simulations, and the Consensus Hierarchy (Keynote Abstract). In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, p. 4:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{ellen:LIPIcs.OPODIS.2016.4,
author = {Ellen, Faith},
title = {{Participating Sets, Simulations, and the Consensus Hierarchy}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {4:1--4:1},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.4},
URN = {urn:nbn:de:0030-drops-70736},
doi = {10.4230/LIPIcs.OPODIS.2016.4},
annote = {Keywords: Consensus, shared-memory systems}
}
Document
Bounded Disagreement
Abstract
A well-known generalization of the consensus problem, namely, set agreement (SA), limits the number of distinct decision values that processes decide. In some settings, it may be more important to limit the number of "disagreers". Thus, we introduce another natural generalization of the consensus problem, namely, bounded disagreement (BD), which limits the number of processes that decide differently from the plurality. More precisely, in a system with n processes, the (n, l)-BD task has the following requirement: there is a value v such that at most l processes (the disagreers) decide a value other than v. Despite their apparent similarities, the results described below show that bounded disagreement, consensus, and set agreement are in fact fundamentally different problems.
We investigate the relationship between bounded disagreement, consensus, and set agreement. In particular, we determine the consensus number for every instance of the BD task. We also determine values of n, l, m, and k such that the (n, l)-BD task can solve the (m, k)-SA task (where m processes can decide at most k distinct values). Using our results and a previously known impossibility result for set agreement, we prove that for all n >= 2, there is a BD task (and a corresponding BD object) that has consensus number n but can not be solved using n-consensus and registers. Prior to our paper, the only objects known to have this unusual characteristic for n >= 2 (which shows that the consensus number of an object is not sufficient to fully capture its power) were artificial objects crafted solely for the purpose of exhibiting this behaviour.
Cite as
David Yu Cheng Chan, Vassos Hadzilacos, and Sam Toueg. Bounded Disagreement. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 5:1-5:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{yuchengchan_et_al:LIPIcs.OPODIS.2016.5,
author = {Yu Cheng Chan, David and Hadzilacos, Vassos and Toueg, Sam},
title = {{Bounded Disagreement}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {5:1--5:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.5},
URN = {urn:nbn:de:0030-drops-70742},
doi = {10.4230/LIPIcs.OPODIS.2016.5},
annote = {Keywords: Consensus, Set Agreement, Asynchronous System, Distributed Algorithms, Shared Memory}
}
Document
Read-Write Memory and k-Set Consensus as an Affine Task
Abstract
The wait-free read-write memory model has been characterized as an iterated Immediate Snapshot (IS) task. The IS task is affine — it can be defined as a (sub)set of simplices of the standard chromatic subdivision. In this paper, we highlight the phenomenon of a "natural" model that can be captured by an iterated affine task and, thus, by a subset of runs of the iterated immediate snapshot model. We show that the read-write memory model in which, additionally, k-set-consensus objects can be used is "natural" by presenting the corresponding simple affine task captured by a subset of 2-round IS runs. As an "unnatural" example, the model using the abstraction of Weak Symmetry Breaking (WSB) cannot be captured by a set of IS runs and, thus, cannot be represented as an affine task. Our results imply the first combinatorial characterization of models equipped with abstractions other than read-write memory that applies to generic tasks.
Cite as
Eli Gafni, Yuan He, Petr Kuznetsov, and Thibault Rieutord. Read-Write Memory and k-Set Consensus as an Affine Task. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 6:1-6:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{gafni_et_al:LIPIcs.OPODIS.2016.6,
author = {Gafni, Eli and He, Yuan and Kuznetsov, Petr and Rieutord, Thibault},
title = {{Read-Write Memory and k-Set Consensus as an Affine Task}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {6:1--6:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.6},
URN = {urn:nbn:de:0030-drops-70759},
doi = {10.4230/LIPIcs.OPODIS.2016.6},
annote = {Keywords: iterated affine tasks, k-set consensus, k-concurrency, simplicial complexes, immediate snapshot}
}
Document
Set-Consensus Collections are Decidable
Abstract
A natural way to measure the power of a distributed-computing model is to characterize the set of tasks that can be solved in it. In general, however, the question of whether a given task can be solved in a given model is undecidable, even if we only consider the wait-free shared-memory model. In this paper, we address this question for restricted classes of models and tasks. We show that the question of whether a collection C of (l, j)-set consensus objects, for various l (the number of processes that can invoke the object) and j (the number of distinct outputs the object returns), can be used by n processes to solve wait-free k-set consensus is decidable. Moreover, we provide a simple O(n^2) decision algorithm, based on a dynamic programming solution to the Knapsack optimization problem. We then present an adaptive wait-free set-consensus algorithm that, for each set of participating processes, achieves the best level of agreement that is possible to achieve using C. Overall, this gives us a complete characterization of a read-write model defined by a collection of set-consensus objects through its set-consensus power.
Cite as
Carole Delporte-Gallet, Hugues Fauconnier, Eli Gafni, and Petr Kuznetsov. Set-Consensus Collections are Decidable. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 7:1-7:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{delportegallet_et_al:LIPIcs.OPODIS.2016.7,
author = {Delporte-Gallet, Carole and Fauconnier, Hugues and Gafni, Eli and Kuznetsov, Petr},
title = {{Set-Consensus Collections are Decidable}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {7:1--7:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.7},
URN = {urn:nbn:de:0030-drops-70761},
doi = {10.4230/LIPIcs.OPODIS.2016.7},
annote = {Keywords: Decidability, distributed tasks, set consensus, Knapsack problem}
}
Document
k-Set Agreement in Communication Networks with Omission Faults
Abstract
We consider an arbitrary communication network G where at most f messages can be lost at each round, and consider the classical k-set agreement problem in this setting. We characterize exactly for which f the k-set agreement problem can be solved on G.
The case with k = 1, that is the Consensus problem, has first been introduced by Santoro and Widmayer in 1989, the characterization is already known from [Coulouma/Godard/Peters, TCS, 2015]. As a first contribution, we present a detailed and complete characterization for the 2-set problem. The proof of the impossibility result uses topological methods. We introduce a new subdivision approach for these topological methods that is of independent interest.
In the second part, we show how to extend to the general case with k in N. This characterization is the first complete characterization for this kind of synchronous message passing model, a model that is a subclass of the family of oblivious message adversaries.
Cite as
Emmanuel Godard and Eloi Perdereau. k-Set Agreement in Communication Networks with Omission Faults. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 8:1-8:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{godard_et_al:LIPIcs.OPODIS.2016.8,
author = {Godard, Emmanuel and Perdereau, Eloi},
title = {{k-Set Agreement in Communication Networks with Omission Faults}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {8:1--8:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.8},
URN = {urn:nbn:de:0030-drops-70775},
doi = {10.4230/LIPIcs.OPODIS.2016.8},
annote = {Keywords: k-set agreement, message passing, dynamic networks, message adversary, omission faults}
}
Document
Using Read-k Inequalities to Analyze a Distributed MIS Algorithm
Abstract
Until recently, the fastest distributed MIS algorithm, even for simple graph classes such as unoriented trees that can contain large independent sets within neighborhoods, has been the simple randomized algorithm discovered independently by several researchers in the late 80s. This algorithm (commonly called Luby’s algorithm) computes an MIS of an n-node graph in O(log n) communication rounds (with high probability). This situation changed when Lenzen and Wattenhofer (PODC 2011) presented a distributed (randomized) MIS algorithm for unoriented treesrunning in O( sqrt (log n * log log n)) rounds. This algorithm was slightly improved by Barenboim et al. (FOCS 2012), resulting in an O( sqrt (log n * log log n))-round (randomized) MIS algorithm for trees. At their core, these algorithms still run Luby's algorithm, but only up to the point at which the graph has been "shattered" into small connected components that can be independently processed in parallel.
The analyses of these tree MIS algorithms critically depends on "near independence" among probabilistic events, a feature that arises from the tree structure of the network. In their paper, Lenzen and Wattenhofer express hope that their algorithm and analysis could be extended to graphs with bounded arboricity. We show how to do this in the current paper. By using a new tail inequality for read-k families of random variables due to Gavinsky et al. (Random Struct Algorithms, 2015), we show how to deal with dependencies induced by the recent tree MIS algorithms when they are executed on bounded arboricity graphs. Specifically, we analyze a version of the tree MIS algorithm of Barenboim et al. and show that it runs in O(poly(a) * sqrt ( log n * log log n)) rounds in the CONGEST model for graphs with arboricity a.
While the main thrust of this paper is the new probabilistic analysis via read-k inequalities, we point out that for small values of a, this algorithm is faster than the MIS algorithm of Barenboim et al. specifically designed for bounded arboricity graphs. In this context, it should be noted that recently (in SODA 2016) Ghaffari presented a novel distributed MIS algorithm for general graphs that runs in O (log d) + 2^O(sqrt(log log n)) rounds and a corollary of this algorithm is an O(log d + sqrt (log n))-round MIS algorithm on graphs with arboricity a.
Cite as
Sriram Pemmaraju and Talal Riaz. Using Read-k Inequalities to Analyze a Distributed MIS Algorithm. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 9:1-9:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{pemmaraju_et_al:LIPIcs.OPODIS.2016.9,
author = {Pemmaraju, Sriram and Riaz, Talal},
title = {{Using Read-k Inequalities to Analyze a Distributed MIS Algorithm}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {9:1--9:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.9},
URN = {urn:nbn:de:0030-drops-70784},
doi = {10.4230/LIPIcs.OPODIS.2016.9},
annote = {Keywords: Bounded Arboricity Graphs, CONGEST model, Luby’s Algorithm, Maximal Independent Set, Read-k Inequality}
}
Document
Self-Stabilizing Disconnected Components Detection and Rooted Shortest-Path Tree Maintenance in Polynomial Steps
Abstract
We deal with the problem of maintaining a shortest-path tree rooted at some process r in a network that may be disconnected after topological changes. The goal is then to maintain a shortest-path tree rooted at r in its connected component, V_r, and make all processes of other components detecting that r is not part of their connected component. We propose, in the composite atomicity model, a silent self-stabilizing algorithm for this problem working in semi-anonymous networks under the distributed unfair daemon (the most general daemon) without requiring any a priori knowledge about global parameters of the network. This is the first algorithm for this problem that is proven to achieve a polynomial stabilization time in steps. Namely, we exhibit a bound in O(W_{max} * n_{maxCC}^3 * n), where W_{max} is the maximum weight of an edge, n_{maxCC} is the maximum number of non-root processes in a connected component, and n is the number of processes. The stabilization time in rounds is at most 3n_{maxCC} + D, where D is the hop-diameter of V_r.
Cite as
Stéphane Devismes, David Ilcinkas, and Colette Johnen. Self-Stabilizing Disconnected Components Detection and Rooted Shortest-Path Tree Maintenance in Polynomial Steps. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 10:1-10:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{devismes_et_al:LIPIcs.OPODIS.2016.10,
author = {Devismes, St\'{e}phane and Ilcinkas, David and Johnen, Colette},
title = {{Self-Stabilizing Disconnected Components Detection and Rooted Shortest-Path Tree Maintenance in Polynomial Steps}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {10:1--10:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.10},
URN = {urn:nbn:de:0030-drops-70792},
doi = {10.4230/LIPIcs.OPODIS.2016.10},
annote = {Keywords: distributed algorithm, self-stabilization, routing algorithm, shortest path, disconnected network, shortest-path tree}
}
Document
Polynomial Self-Stabilizing Maximum Matching Algorithm with Approximation Ratio 2/3
Abstract
We present the first polynomial self-stabilizing algorithm for finding a (2/3)-approximation of a maximum matching in a general graph. The previous best known algorithm has been presented by Manne et al. and has a sub-exponential time complexity under the distributed adversarial daemon. Our new algorithm is an adaptation of the Manne et al. algorithm and works under the same daemon, but with a time complexity in O(n^3) moves. Moreover, our algorithm only needs one more boolean variable than the previous one, thus as in the Manne et al. algorithm, it only requires a constant amount of memory space (three identifiers and two booleans per node).
Cite as
Johanne Cohen, Khaled Maâmra, George Manoussakis, and Laurence Pilard. Polynomial Self-Stabilizing Maximum Matching Algorithm with Approximation Ratio 2/3. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 11:1-11:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{cohen_et_al:LIPIcs.OPODIS.2016.11,
author = {Cohen, Johanne and Ma\^{a}mra, Khaled and Manoussakis, George and Pilard, Laurence},
title = {{Polynomial Self-Stabilizing Maximum Matching Algorithm with Approximation Ratio 2/3}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {11:1--11:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.11},
URN = {urn:nbn:de:0030-drops-70808},
doi = {10.4230/LIPIcs.OPODIS.2016.11},
annote = {Keywords: Self-Stabilization, Distributed Algorithm, Fault Tolerance, Matching}
}
Document
Distributed Stable Matching with Similar Preference Lists
Abstract
Consider a complete bipartite graph of 2n nodes with n nodes on each side. In a round, each node can either send at most one message to a neighbor or receive at most one message from a neighbor. Each node has a preference list that ranks all its neighbors in a strict order from 1 to n. We introduce a non-negative similarity parameter D < n for the preference lists of nodes on one side only. For D = 0, these preference lists are same and for D = n-1, they can be completely arbitrary. There is no restriction on the preference lists of the other side. We show that each node can compute its partner in a stable matching by receiving O(n(D + 1)) messages of size O(log n) each. We also show that this is optimal (up to a logarithmic factor) if D is constant.
Cite as
Pankaj Khanchandani and Roger Wattenhofer. Distributed Stable Matching with Similar Preference Lists. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 12:1-12:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{khanchandani_et_al:LIPIcs.OPODIS.2016.12,
author = {Khanchandani, Pankaj and Wattenhofer, Roger},
title = {{Distributed Stable Matching with Similar Preference Lists}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {12:1--12:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.12},
URN = {urn:nbn:de:0030-drops-70811},
doi = {10.4230/LIPIcs.OPODIS.2016.12},
annote = {Keywords: distributed stable matching, similar preference lists, stable matching, stable marriage}
}
Document
Time and Space Optimal Counting in Population Protocols
Abstract
This work concerns the general issue of combined optimality in terms of time and space complexity. In this context, we study the problem of (exact) counting resource-limited and passively mobile nodes in the model of population protocols, in which the space complexity is crucial. The counted nodes are memory-limited anonymous devices (called agents) communicating asynchronously in pairs (according to a fairness condition). Moreover, we assume that these agents are prone to failures so that they cannot be correctly initialized.
This study considers two classical fairness conditions, and for each we investigate the issue of time optimality of counting given the optimal space per agent. In the case of randomly interacting agents (probabilistic fairness), as usual, the convergence time is measured in terms of parallel time (or parallel interactions), which is defined as the number of pairwise interactions until convergence, divided by n (the number of agents). In case of weak fairness, where it is only required that every pair of agents interacts infinitely often, the convergence time is defined in terms of non-null transitions, i.e, the transitions that affect the states of the interacting agents.
First, assuming probabilistic fairness, we present a "non-guessing" time optimal protocol of O(n log n) expected time given an optimal space of only one bit, and we prove the time optimality of this protocol. Then, for weak fairness, we show that a space optimal (semi-uniform) solution cannot converge faster than in big-omega (2^n) time (non-null transitions). This result, together with the time complexity analysis of an already known space optimal protocol, shows that it is also optimal in time (given the optimal space constrains).
Cite as
James Aspnes, Joffroy Beauquier, Janna Burman, and Devan Sohier. Time and Space Optimal Counting in Population Protocols. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 13:1-13:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{aspnes_et_al:LIPIcs.OPODIS.2016.13,
author = {Aspnes, James and Beauquier, Joffroy and Burman, Janna and Sohier, Devan},
title = {{Time and Space Optimal Counting in Population Protocols}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {13:1--13:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.13},
URN = {urn:nbn:de:0030-drops-70828},
doi = {10.4230/LIPIcs.OPODIS.2016.13},
annote = {Keywords: networks of passively mobile agents/sensors, population protocols, counting, anonymous non-initialized agents, time and space complexity, lower bounds}
}
Document
Deterministic Population Protocols for Exact Majority and Plurality
Abstract
In this paper we study space-efficient deterministic population protocols for several variants of the majority problem including plurality consensus. We focus on space efficient majority protocols in populations with an arbitrary number of colours C represented by k-bit labels, where k = ceiling (log C). In particular, we present asymptotically space-optimal (with respect to the adopted k-bit representation of colours) protocols for (1) the absolute majority problem, i.e., a protocol which decides whether a single colour dominates all other colours considered together, and (2) the relative majority problem, also known in the literature as plurality consensus, in which colours declare their volume superiority versus other individual colours.
The new population protocols proposed in this paper rely on a dynamic formulation of the majority problem in which the colours originally present in the population can be changed by an external force during the communication process. The considered dynamic formulation is based on the concepts studied by D. Angluin et al. and O. Michail et al. about stabilizing inputs and composition of population protocols. Also, the protocols presented in this paper use a composition of some known protocols for static and dynamic majority.
Cite as
Leszek Gasieniec, David Hamilton, Russell Martin, Paul G. Spirakis, and Grzegorz Stachowiak. Deterministic Population Protocols for Exact Majority and Plurality. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 14:1-14:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{gasieniec_et_al:LIPIcs.OPODIS.2016.14,
author = {Gasieniec, Leszek and Hamilton, David and Martin, Russell and Spirakis, Paul G. and Stachowiak, Grzegorz},
title = {{Deterministic Population Protocols for Exact Majority and Plurality}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {14:1--14:14},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.14},
URN = {urn:nbn:de:0030-drops-70837},
doi = {10.4230/LIPIcs.OPODIS.2016.14},
annote = {Keywords: Deterministic population protocols, majority, plurality consenus}
}
Document
Design Patterns in Beeping Algorithms
Abstract
We consider networks of processes which interact with beeps. In the basic model defined by Cornejo and Kuhn, which we refer to as the BL variant, processes can choose in each round either to beep or to listen. Those who beep are unable to detect simultaneous beeps. Those who listen can only distinguish between silence and the presence of at least one beep. Stronger variants exist where the nodes can also detect collision while they are beeping (B_{cd}L) or listening (BL_{cd}), or both (B_{cd}L_{cd}). Beeping models are weak in essence and even simple tasks are difficult or unfeasible with them.
This paper starts with a discussion on generic building blocks (design patterns) which seem to occur frequently in the design of beeping algorithms. They include multi-slot phases: the fact of dividing the main loop into a number of specialised slots; exclusive beeps: having a single node beep at a time in a neighbourhood (within one or two hops); adaptive probability: increasing or decreasing the probability of beeping to produce more exclusive beeps; internal (resp. peripheral) collision detection: for detecting collision while beeping (resp. listening); and emulation of collision detection: for enabling this feature when it is not available as a primitive.
We then provide algorithms for a number of basic problems, including colouring, 2-hop colouring, degree computation, 2-hop MIS, and collision detection (in BL). Using the patterns, we formulate these algorithms in a rather concise and elegant way. Their analyses (in the full version) are more technical, e.g. one of them relies on a Martingale technique with non-independent variables; another improves that of the MIS algorithm (P. Jeavons et al.) by getting rid of a gigantic constant (the asymptotic order was already optimal).
Finally, we study the relative power of several variants of beeping models. In particular, we explain how every Las Vegas algorithm with collision detection can be converted, through emulation, into a Monte Carlo algorithm without, at the cost of a logarithmic slowdown. We prove that this slowdown is optimal up to a constant factor by giving a matching lower bound.
Cite as
Arnaud Casteigts, Yves Métivier, John Michael Robson, and Akka Zemmari. Design Patterns in Beeping Algorithms. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 15:1-15:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{casteigts_et_al:LIPIcs.OPODIS.2016.15,
author = {Casteigts, Arnaud and M\'{e}tivier, Yves and Robson, John Michael and Zemmari, Akka},
title = {{Design Patterns in Beeping Algorithms}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {15:1--15:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.15},
URN = {urn:nbn:de:0030-drops-70840},
doi = {10.4230/LIPIcs.OPODIS.2016.15},
annote = {Keywords: Beeping models, Design patterns, Collision detection, Colouring, 2-hop colouring, Degree computation, Emulation}
}
Document
Collision-Free Pattern Formation
Abstract
Shoals of small fishes can change their collective shape and form a specific pattern. They do so efficiently (in parallel) and without collision.
In this paper, we study the analog problem of distributed pattern formation. A set of processes needs to move from a set of initial positions to a set of final positions. The processes are oblivious (no internal memory) and must preserve, at any time, a minimal distance between them.
A naive solution would be to move the processes one by one, but this would take too long. The difficulty here is to move the processes simultaneously in clearly delimited phases, no matter how unfavorable the initial configuration may be. We solve this by treating the problem "dimension by dimension": the processes first form 1D trails, then gather into a 2D shape (this technique can be generalized to higher dimensions).
We present an optimal algorithm which time complexity depends linearly on the radius of the smallest circle containing both initial and final positions. The algorithm is self-stabilizing, as the processes are oblivious and the initial positions are arbitrary.
Cite as
Rachid Guerraoui and Alexandre Maurer. Collision-Free Pattern Formation. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 16:1-16:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{guerraoui_et_al:LIPIcs.OPODIS.2016.16,
author = {Guerraoui, Rachid and Maurer, Alexandre},
title = {{Collision-Free Pattern Formation}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {16:1--16:13},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.16},
URN = {urn:nbn:de:0030-drops-70856},
doi = {10.4230/LIPIcs.OPODIS.2016.16},
annote = {Keywords: Pattern formation, Collision, Landmarks}
}
Document
Predicate Detection for Parallel Computations with Locking Constraints
Abstract
The happened-before model (or the poset model) has been widely used for modeling the computations (execution traces) of parallel programs and detecting predicates (user-specified conditions). This model captures potential causality as well as locking constraints among the executed events of computations using Lamport's happened-before relation. The detection of a predicate in a computation is performed by checking if the predicate could become true in any reachable global state of the computation. In this paper, we argue that locking constraints are fundamentally different from potential causality. Hence, a poset is not an appropriate model for debugging purposes when the computations contain locking constraints. We present a model called Locking Poset, or a Loset, that generalizes the poset model for locking constraints. Just as a poset captures possibly an exponential number of total orders, a loset captures possibly an exponential number of posets. Therefore, detecting a predicate in a loset is equivalent to detecting the predicate in all corresponding posets. Since determining if a global state is reachable in a computation is a fundamental problem for detecting predicates, this paper first studies the reachability problem in the loset model. We show that the problem is NP-complete. Afterwards, we introduce a subset of reachable global states called lock-free feasible global states such that we can check whether a global state is lock-free feasible in polynomial time. Moreover, we show that lock-free feasible global states can act as "reset" points for reachability and be used to drastically reduce the time for determining the reachability of other global states. We also introduce strongly feasible global states that contain all reachable global states and show that the strong feasibility of a global state can be checked in polynomial time. We show that strong feasibility provides an effective approximation of reachability for many practical applications.
Cite as
Yen-Jung Chang and Vijay K. Garg. Predicate Detection for Parallel Computations with Locking Constraints. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 17:1-17:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{chang_et_al:LIPIcs.OPODIS.2016.17,
author = {Chang, Yen-Jung and Garg, Vijay K.},
title = {{Predicate Detection for Parallel Computations with Locking Constraints}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {17:1--17:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.17},
URN = {urn:nbn:de:0030-drops-70867},
doi = {10.4230/LIPIcs.OPODIS.2016.17},
annote = {Keywords: predicate detection, parallel computations, reachable global states, locking constraints, happened-before relation}
}
Document
WNetKAT: A Weighted SDN Programming and Verification Language
Abstract
Programmability and verifiability lie at the heart of the software-defined networking paradigm. While OpenFlow and its match-action concept provide primitive operations to manipulate hardware configurations, over the last years, several more expressive network programming languages have been developed. This paper presents WNetKAT, the first network programming language accounting for the fact that networks are inherently weighted, and communications subject to capacity constraints (e.g., in terms of bandwidth) and costs (e.g., latency or monetary costs). WNetKAT is based on a syntactic and semantic extension of the NetKAT algebra. We demonstrate several relevant applications for WNetKAT, including cost and capacity-aware reachability, as well as quality-of-service and fairness aspects. These applications do not only apply to classic, splittable and unsplittable (s,t)-flows, but also generalize to more complex (and stateful) network functions and service chains. For example, WNetKAT allows to model flows which need to traverse certain waypoint functions, which can change the traffic rate. This paper also shows the relationship between the equivalence problem of WNetKAT and the equivalence problem of the weighted finite automata, which implies undecidability of the former. However, this paper also shows the decidability of whether an expression equals to 0, which is sufficient in many practical scenarios, and we initiate the discussion of decidable subsets of the whole language.
Cite as
Kim G. Larsen, Stefan Schmid, and Bingtian Xue. WNetKAT: A Weighted SDN Programming and Verification Language. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 18:1-18:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{larsen_et_al:LIPIcs.OPODIS.2016.18,
author = {Larsen, Kim G. and Schmid, Stefan and Xue, Bingtian},
title = {{WNetKAT: A Weighted SDN Programming and Verification Language}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {18:1--18:18},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.18},
URN = {urn:nbn:de:0030-drops-70870},
doi = {10.4230/LIPIcs.OPODIS.2016.18},
annote = {Keywords: Software-Defined Networking, Verification, Reachability, Stateful Processing, Service Chains, Weighted Automata, Decidability, NetKAT}
}
Document
Deadline-Budget constrained Scheduling Algorithm for Scientific Workflows in a Cloud Environment
Abstract
Recently cloud computing has gained popularity among e-Science environments as a high performance computing platform. From the viewpoint of the system, applications can be submitted by users at any moment in time and with distinct QoS requirements. To achieve higher rates of successful applications attending to their QoS demands, an effective resource allocation (scheduling) strategy between workflow's tasks and available resources is required. Several algorithms have been proposed for QoS workflow scheduling, but most of them use search-based strategies that generally have a higher time complexity, making them less useful in realistic scenarios. In this paper, we present a heuristic scheduling algorithm with quadratic time complexity that considers two important constraints for QoS-based workflow scheduling, time and cost, named Deadline-Budget Workflow Scheduling (DBWS) for cloud environments. Performance evaluation of some well-known scientific workflows shows that the DBWS algorithm accomplishes both constraints with higher success rate in comparison to the current state-of-the-art heuristic-based approaches.
Cite as
Mozhgan Ghasemzadeh, Hamid Arabnejad, and Jorge G. Barbosa. Deadline-Budget constrained Scheduling Algorithm for Scientific Workflows in a Cloud Environment. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 19:1-19:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{ghasemzadeh_et_al:LIPIcs.OPODIS.2016.19,
author = {Ghasemzadeh, Mozhgan and Arabnejad, Hamid and Barbosa, Jorge G.},
title = {{Deadline-Budget constrained Scheduling Algorithm for Scientific Workflows in a Cloud Environment}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {19:1--19:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.19},
URN = {urn:nbn:de:0030-drops-70888},
doi = {10.4230/LIPIcs.OPODIS.2016.19},
annote = {Keywords: Resource management, QoS scheduling, scientific workflow applications, deadline-constrained, budget-constrained}
}
Document
Moving Participants Turtle Consensus
Abstract
We present Moving Participants Turtle Consensus (MPTC), an asynchronous consensus protocol for crash and Byzantine-tolerant distributed systems. MPTC uses various moving target defense strategies to tolerate certain Denial-of-Service (DoS) attacks issued by an adversary capable of compromising a bounded portion of the system. MPTC supports on the fly reconfiguration of the consensus strategy as well as of the processes executing this strategy when solving the problem of agreement. It uses existing cryptographic techniques to ensure that reconfiguration takes place in an unpredictable fashion thus eliminating the adversary’s advantage on predicting protocol and execution-specific information that can be used against the protocol.
We implement MPTC as well as a State Machine Replication protocol and evaluate our design under different attack scenarios. Our evaluation shows that MPTC approximates best case scenario performance even under a well-coordinated DoS attack.
Cite as
Stavros Nikolaou and Robbert van Renesse. Moving Participants Turtle Consensus. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 20:1-20:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{nikolaou_et_al:LIPIcs.OPODIS.2016.20,
author = {Nikolaou, Stavros and van Renesse, Robbert},
title = {{Moving Participants Turtle Consensus}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {20:1--20:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.20},
URN = {urn:nbn:de:0030-drops-70895},
doi = {10.4230/LIPIcs.OPODIS.2016.20},
annote = {Keywords: Consensus, adaptation, moving target defense}
}
Document
Kleinberg’s Grid Reloaded
Abstract
One of the key features of small-worlds is the ability to route messages with few hops only using local knowledge of the topology. In 2000, Kleinberg proposed a model based on an augmented grid that asymptotically exhibits such property.
In this paper, we propose to revisit the original model from a simulation-based perspective. Our approach is fueled by a new algorithm that uses dynamic rejection sampling to draw augmenting links. The speed gain offered by the algorithm enables a detailed numerical evaluation. We show for example that in practice, the augmented scheme proposed by Kleinberg is more robust than predicted by the asymptotic behavior, even for very large finite grids. We also propose tighter bounds on the performance of Kleinberg's routing algorithm. At last, we show that fed with realistic parameters, the model gives results in line with real-life experiments.
Cite as
Fabien Mathieu. Kleinberg’s Grid Reloaded. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 21:1-21:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{mathieu:LIPIcs.OPODIS.2016.21,
author = {Mathieu, Fabien},
title = {{Kleinberg’s Grid Reloaded}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {21:1--21:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.21},
URN = {urn:nbn:de:0030-drops-70908},
doi = {10.4230/LIPIcs.OPODIS.2016.21},
annote = {Keywords: Small-World Routing,Kleinberg’s Grid, Simulation, Rejection Sampling}
}
Document
Generalized Selectors and Locally Thin Families with Applications to Conflict Resolution in Multiple Access Channels Supporting Simultaneous Successful Transmissions
Abstract
We consider the Conflict Resolution Problem in the context of a multiple-access system in which several stations can transmit their messages simultaneously to the channel. We assume that there are n stations and that at most k, k <= n, stations are active at the same time, i.e, are willing to transmit a message over the channel. If in a certain instant at most d, d <= k, active stations transmit to the channel then their messages are successfully transmitted, whereas if more than d active stations transmit simultaneously then their messages are lost. In this latter case we say that a conflict occurs. The present paper investigates non-adaptive conflict resolution algorithms working under the assumption that active stations receive a feedback from the channel that informs them on whether their messages have been successfully transmitted. If a station becomes aware that its message has been correctly sent over the channel then it becomes immediately inactive, that is, stops transmitting. The measure to optimize is the number of time slots needed to solve conflicts among all active stations. The fundamental question is how much this measure decreases with the number d of messages that can be simultaneously transmitted with success. In this paper we prove that it is possible to achieve a speedup linear in d by providing a conflict resolution algorithm that uses a 1/d ratio of the number of time slots used by the optimal conflict resolution algorithm for the particular case d = 1. Moreover, we derive a lower bound on the number of time slots needed to solve conflicts non-adaptively which is within a log(k/d) factor from the upper bound. To the aim of proving these results, we introduce a new combinatorial structure that consists in a generalization of Komlós and Greenberg codes. Constructions of these new codes are obtained via a new kind of selectors, whereas the non-existential result is implied by a non-existential result for a new generalization of the locally thin families. We believe that the combinatorial structures introduced in this paper and the related results may be of independent interest.
Cite as
Annalisa De Bonis. Generalized Selectors and Locally Thin Families with Applications to Conflict Resolution in Multiple Access Channels Supporting Simultaneous Successful Transmissions. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 22:1-22:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{debonis:LIPIcs.OPODIS.2016.22,
author = {De Bonis, Annalisa},
title = {{Generalized Selectors and Locally Thin Families with Applications to Conflict Resolution in Multiple Access Channels Supporting Simultaneous Successful Transmissions}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {22:1--22:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.22},
URN = {urn:nbn:de:0030-drops-70916},
doi = {10.4230/LIPIcs.OPODIS.2016.22},
annote = {Keywords: Multiple-Access channels, Multi Access Communication, Conflict Resolutions, New Combinatorial Structures, Selectors}
}
Document
How Lock-free Data Structures Perform in Dynamic Environments: Models and Analyses
Abstract
In this paper we present two analytical frameworks for calculating the performance of lock-free data structures. Lock-free data structures are based on retry loops and are called by application-specific routines. In contrast to previous work, we consider in this paper lock-free data structures in dynamic environments. The size of each of the retry loops, and the size of the application routines invoked in between, are not constant but may change dynamically. The new frameworks follow two different approaches. The first framework, the simplest one, is based on queuing theory. It introduces an average-based approach that facilitates a more coarse-grained analysis, with the benefit of being ignorant of size distributions. Because of this independence from the distribution nature it covers a set of complicated designs. The second approach, instantiated with an exponential distribution for the size of the application routines, uses Markov chains, and is tighter because it constructs stochastically the execution, step by step.
Both frameworks provide a performance estimate which is close to what we observe in practice. We have validated our analysis on (i) several fundamental lock-free data structures such as stacks, queues, deques and counters, some of them employing helping mechanisms, and (ii) synthetic tests covering a wide range of possible lock-free designs. We show the applicability of our results by introducing new back-off mechanisms, tested in application contexts, and by designing an efficient memory management scheme that typical lock-free algorithms can utilize.
Cite as
Aras Atalar, Paul Renaud-Goud, and Philippas Tsigas. How Lock-free Data Structures Perform in Dynamic Environments: Models and Analyses. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 23:1-23:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{atalar_et_al:LIPIcs.OPODIS.2016.23,
author = {Atalar, Aras and Renaud-Goud, Paul and Tsigas, Philippas},
title = {{How Lock-free Data Structures Perform in Dynamic Environments: Models and Analyses}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {23:1--23:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.23},
URN = {urn:nbn:de:0030-drops-70922},
doi = {10.4230/LIPIcs.OPODIS.2016.23},
annote = {Keywords: Lock-free, Data Structures, Parallel Computing, Performance, Modeling, Analysis}
}
Document
Non-Determinism in Byzantine Fault-Tolerant Replication
Abstract
Service replication distributes an application over many processes for tolerating faults, attacks, and misbehavior among a subset of the processes. With the recent interest in blockchain technologies, distributed execution of one logical application has become a prominent topic. The established state-machine replication paradigm inherently requires the application to be deterministic. This paper distinguishes three models for dealing with non-determinism in replicated services, where some processes are subject to faults and arbitrary behavior (so-called Byzantine faults): first, the modular case that does not require any changes to the potentially non-deterministic application (and neither access to its internal data); second, master-slave solutions, where ties are broken by a leader and the other processes validate the choices of the leader; and finally, applications that use cryptography and secret keys. Cryptographic operations and secrets must be treated specially because they require strong randomness to satisfy their goals.
The paper also introduces two new protocols. First, Protocol Sieve uses the modular approach and filters out non-deterministic operations in an application. It ensures that all correct processes produce the same outputs and that their internal states do not diverge. A second protocol, called Mastercrypt, implements cryptographically secure randomness generation with a verifiable random function and is appropriate for most situations in which cryptographic secrets are involved. All protocols are described in a generic way and do not assume a particular implementation of the underlying consensus primitive.
Cite as
Christian Cachin, Simon Schubert, and Marko Vukolic. Non-Determinism in Byzantine Fault-Tolerant Replication. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 24:1-24:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{cachin_et_al:LIPIcs.OPODIS.2016.24,
author = {Cachin, Christian and Schubert, Simon and Vukolic, Marko},
title = {{Non-Determinism in Byzantine Fault-Tolerant Replication}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {24:1--24:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.24},
URN = {urn:nbn:de:0030-drops-70935},
doi = {10.4230/LIPIcs.OPODIS.2016.24},
annote = {Keywords: Blockchain, atomic broadcast, consensus, distributed cryptography, verifiable random functions}
}
Document
Flexible Paxos: Quorum Intersection Revisited
Abstract
Distributed consensus is integral to modern distributed systems. The widely adopted Paxos algorithm uses two phases, each requiring majority agreement, to reliably reach consensus. In this paper, we demonstrate that Paxos, which lies at the foundation of many production systems, is conservative. Specifically, we observe that each of the phases of Paxos may use non-intersecting quorums. Majority quorums are not necessary as intersection is required only across phases.
Using this weakening of the requirements made in the original formulation, we propose Flexible Paxos, which generalizes over the Paxos algorithm to provide flexible quorums. We show that Flexible Paxos is safe, e cient and easy to utilize in existing distributed systems. We discuss far reaching implications of this result. For example, improved availability results from reducing the size of second phase quorums by one when the system size is even, while keeping majority quorums in the first phase. Another example is improved throughput of replication by using much smaller phase 2 quorums, while increasing the leader election (phase 1) quorums. Finally, non intersecting quorums in either first or second phases may enhance the efficiency of both.
Cite as
Heidi Howard, Dahlia Malkhi, and Alexander Spiegelman. Flexible Paxos: Quorum Intersection Revisited. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 25:1-25:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{howard_et_al:LIPIcs.OPODIS.2016.25,
author = {Howard, Heidi and Malkhi, Dahlia and Spiegelman, Alexander},
title = {{Flexible Paxos: Quorum Intersection Revisited}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {25:1--25:14},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.25},
URN = {urn:nbn:de:0030-drops-70947},
doi = {10.4230/LIPIcs.OPODIS.2016.25},
annote = {Keywords: Paxos, Distributed Consensus, Quorums}
}
Document
Relaxed Byzantine Vector Consensus
Abstract
Byzantine vector consensus requires that non-faulty processes reach agreement on adecision (or output) that is in the convex hull of the inputs at the non-faulty processes. Recent work has shown that, for n processes with up to f Byzantine failures, when the inputs are d-dimensional vectors of reals, n >= max (3f + 1, (d + 1)f + 1) is the tight bound for synchronous systems, and n >= (d + 2)f + 1 is tight for approximate consensus in asynchronous systems.
Due to the dependence of the lower bound on vector dimension d, the number of processes necessary becomes large when the vector dimension is large. With the hope of reducing the lower bound on n, we propose relaxed versions of Byzantine vector consensus: k-relaxed Byzantine vector consensus and (delta, p)-relaxed Byzantine vector consensus. k-relaxed consensus only requires consensus for projections of inputs on every subset of k dimensions. (delta, p)-relaxed consensus requires that the output be within distance d of the convex hull of the non-faulty inputs, where distance is defined using the L_{p}-norm. An input-dependent delta allows the distance from the non-faulty convex hull to be dependent on the maximum distance between the non-faulty inputs.
We show that for k-relaxed consensus with k > 1, and for (delta, p)-relaxed consensus with constant delta >= 0, the bound on n is identical to the bound stated above for the original vector consensus problem. On the other hand, when k = 1 or d depends on the inputs, we show that the bound on n is smaller when d >= 3. Input-dependent delta may be of interest in practice. In essence, input-dependent delta scales with the spread of the inputs.
Cite as
Zhuolun Xiang and Nitin H. Vaidya. Relaxed Byzantine Vector Consensus. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 26:1-26:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{xiang_et_al:LIPIcs.OPODIS.2016.26,
author = {Xiang, Zhuolun and Vaidya, Nitin H.},
title = {{Relaxed Byzantine Vector Consensus}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {26:1--26:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.26},
URN = {urn:nbn:de:0030-drops-70958},
doi = {10.4230/LIPIcs.OPODIS.2016.26},
annote = {Keywords: Byzantine consensus, vector inputs, relaxed validity conditions}
}
Document
m-Consensus Objects Are Pretty Powerful
Abstract
A recent paper by Afek, Ellen, and Gafni introduced a family of deterministic objects O_{m,k}, for m,k >= 2, with consensus numbers m such that, for each k >= 2, O_{m,k} is computationally less powerful than O_{m,k+1} in systems with at least mk+m+k processes. This paper gives a wait-free implementation of O_{m,k} from (m + 1)-consensus objects and registers in systems with any finite number of processes. In order to do so, it introduces a new family of objects which helps us to understand the power of m-consensus among more than m processes.
Cite as
Ammar Qadri. m-Consensus Objects Are Pretty Powerful. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 27:1-27:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{qadri:LIPIcs.OPODIS.2016.27,
author = {Qadri, Ammar},
title = {{m-Consensus Objects Are Pretty Powerful}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {27:1--27:14},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.27},
URN = {urn:nbn:de:0030-drops-70964},
doi = {10.4230/LIPIcs.OPODIS.2016.27},
annote = {Keywords: Deterministic Consensus Hierarchy, Wait-free Implementation, Tournament}
}
Document
RADON: Repairable Atomic Data Object in Networks
Abstract
Erasure codes offer an efficient way to decrease storage and communication costs while implementing atomic memory service in asynchronous distributed storage systems. In this paper, we provide erasure-code-based algorithms having the additional ability to perform background repair of crashed nodes. A repair operation of a node in the crashed state is triggered externally, and is carried out by the concerned node via message exchanges with other active nodes in the system. Upon completion of repair, the node re-enters active state, and resumes participation in ongoing and future read, write, and repair operations. To guarantee liveness and atomicity simultaneously, existing works assume either the presence of nodes with stable storage, or presence of nodes that never crash during the execution. We demand neither of these; instead we consider a natural, yet practical network stability condition N1 that only restricts the number of nodes in the crashed/repair state during broadcast of any message.
We present an erasure-code based algorithm RADON_{C} that is always live, and guarantees atomicity as long as condition N1 holds. In situations when the number of concurrent writes is limited, RADON_{C} has significantly improved storage and communication cost over a replication-based algorithm RADON_{R}, which also works under N1. We further show how a slightly stronger network stability condition N2 can be used to construct algorithms that never violate atomicity. The guarantee of atomicity comes at the expense of having an additional phase during the read and write operations.
Cite as
Kishori M. Konwar, N. Prakash, Nancy A. Lynch, and Muriel Médard. RADON: Repairable Atomic Data Object in Networks. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 28:1-28:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{konwar_et_al:LIPIcs.OPODIS.2016.28,
author = {Konwar, Kishori M. and Prakash, N. and Lynch, Nancy A. and M\'{e}dard, Muriel},
title = {{RADON: Repairable Atomic Data Object in Networks}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {28:1--28:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.28},
URN = {urn:nbn:de:0030-drops-70970},
doi = {10.4230/LIPIcs.OPODIS.2016.28},
annote = {Keywords: Atomicity, repair, fault-tolerance, storage cost, erasure codes}
}
Document
Computationally Light "Multi-Speed" Atomic Memory
Abstract
Communication demands are usually the leading factor that defines the efficiency of operations on a read/write shared memory emulation in the message-passing environment. In the quest for minimizing the communication demands, the algorithms proposed either require restrictions in the system or incur high computation demands. As a result, such solutions may be not suitable to be used in practice.
In this paper we focus on the practicality of implementations of atomic read/write shared memory emulation in the message-passing environment. In particular we investigate implementations that reduce both communication and computation demands. We first examine the shortcomings of the best two (in terms of communication demands) known algorithms that implement atomic single-writer multiple-reader (SWMR) atomic memory. The algorithm ccFast proposed by A. Fernández et al., achieves optimal communication by allowing each operation to complete in one round trip, with light computation requirements. Unfortunately, it relies on strict limitations on the number of readers. On the other hand, algorithm OhSam, imposes no restrictions on the system, but provides operations that require one and a half communication rounds. In the light of these shortcomings, we present two algorithms that implement multi-speed operations with light computation, and without imposing any restriction on the system. In particular, algorithm ccHybrid adopts the fast (one-round) writes and makes clients to switch to a slow (two-round) mode whenever the system is congested. On the other hand, algorithm OhFast, pushes the responsibility of deciding for the speed switch to the servers. This allows the algorithm to utilize the fast operations, and the slow one-and-a-half-rounds operations of the algorithm presented by T. Hadjistasi et al., whenever is necessary. We prove that both new algorithms preserve atomicity. To evaluate the new algorithms we implement five different atomic memory algorithms in the NS3 simulator, and we compare their performance in terms of operation latency, and ratio of slow over fast operations performed. We test the algorithms over different: (i) topologies, and (ii) operation loads. Our results support that the newly presented algorithms increase the practicality of atomic read/write atomic shared memory implementations in the message-passing, asynchronous environment.
Cite as
Antonio Fernández Anta, Theophanis Hadjistasi, and Nicolas Nicolaou. Computationally Light "Multi-Speed" Atomic Memory. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 29:1-29:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{fernandezanta_et_al:LIPIcs.OPODIS.2016.29,
author = {Fern\'{a}ndez Anta, Antonio and Hadjistasi, Theophanis and Nicolaou, Nicolas},
title = {{Computationally Light "Multi-Speed" Atomic Memory}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {29:1--29:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.29},
URN = {urn:nbn:de:0030-drops-70980},
doi = {10.4230/LIPIcs.OPODIS.2016.29},
annote = {Keywords: atomicity, read/write objects, shared memory, operation latency}
}
Document
Exploring Key-Value Stores in Multi-Writer Byzantine-Resilient Register Emulations
Abstract
Resilient register emulation is a fundamental technique to implement dependable storage and distributed systems. In data-centric models, where servers are modeled as fail-prone base objects, classical solutions achieve resilience by using fault-tolerant quorums of read-write registers or read-modify-write objects. Recently, this model has attracted renewed interest due to the popularity of cloud storage providers (e.g., Amazon S3), that can be modeled as key-value stores (KVSs) and combined for providing secure and dependable multi-cloud storage services. In this paper we present three novel wait-free multi-writer multi-reader regular register emulations on top of Byzantine-prone KVSs. We implemented and evaluated these constructions using five existing cloud storage services and show that their performance matches or surpasses existing data-centric register emulations.
Cite as
Tiago Oliveira, Ricardo Mendes, and Alysson Bessani. Exploring Key-Value Stores in Multi-Writer Byzantine-Resilient Register Emulations. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 30:1-30:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{oliveira_et_al:LIPIcs.OPODIS.2016.30,
author = {Oliveira, Tiago and Mendes, Ricardo and Bessani, Alysson},
title = {{Exploring Key-Value Stores in Multi-Writer Byzantine-Resilient Register Emulations}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {30:1--30:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.30},
URN = {urn:nbn:de:0030-drops-70999},
doi = {10.4230/LIPIcs.OPODIS.2016.30},
annote = {Keywords: Byzantine fault tolerance, register emulation, multi-writer, key-value store, data-centric algorithms}
}
Document
The Case for Reconfiguration without Consensus: Comparing Algorithms for Atomic Storage
Abstract
We compare different algorithms for reconfigurable atomic storage in the data-centric model. We present the first experimental evaluation of two recently proposed algorithms for reconfiguration without consensus and compare them to established algorithms for reconfiguration both with and without consensus.
Our evaluation reveals that the new algorithms offer a significant improvement in terms of latency and overhead for reconfiguration without consensus. Our evaluation also shows that reconfiguration without consensus, can obtain similar results to that of consensus-based reconfiguration, which relies on a stable leader. Moreover, the new algorithms also substantially reduces the overhead compared to consensus-based reconfiguration without a leader.
While our analysis confirms our intuition that batching reconfiguration requests serves to reduce the overhead of reconfigurations, our evaluation also shows that it is equally important to separate reconfigurations from read and write operations. Specifically, we found that using read and write operations to assist in completing concurrent reconfigurations is in fact detrimental to the reconfiguration performance.
Cite as
Leander Jehl and Hein Meling. The Case for Reconfiguration without Consensus: Comparing Algorithms for Atomic Storage. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 31:1-31:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{jehl_et_al:LIPIcs.OPODIS.2016.31,
author = {Jehl, Leander and Meling, Hein},
title = {{The Case for Reconfiguration without Consensus: Comparing Algorithms for Atomic Storage}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {31:1--31:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.31},
URN = {urn:nbn:de:0030-drops-71006},
doi = {10.4230/LIPIcs.OPODIS.2016.31},
annote = {Keywords: atomic storage, reconfiguration, data-centric model}
}
Document
Step Optimal Implementations of Large Single-Writer Registers
Abstract
We present two wait-free algorithms for simulating an l-bit single-writer register from k-bit single-writer registers, for any k >= 1. Our first algorithm has big-theta(l/k) step complexity for both Read and Write and uses big-theta (4^(l-k)) registers. An interesting feature of the algorithm is that Read operations do not write to shared variables. Our second algorithm has big-theta (l/k + (log n)/k) step complexity for both Read and Write, where n is the number of readers, but uses only big-theta (nl/k + n(log n)/k) registers. Combining both algorithms gives an implementation with big-theta (l/k) step complexity using big-theta (nl/k) space for any 1 <= k < l.
We also prove that any implementation with big-O (l/k) step complexity for Read requires big-omega (l/k) step complexity for Write. Since reading l-bits requires at least ceiling(l/k) reads of k-bit registers, our lower bound shows that our implementation is step optimal.
Cite as
Tian Ze Chen and Yuanhao Wei. Step Optimal Implementations of Large Single-Writer Registers. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 32:1-32:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{chen_et_al:LIPIcs.OPODIS.2016.32,
author = {Chen, Tian Ze and Wei, Yuanhao},
title = {{Step Optimal Implementations of Large Single-Writer Registers}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {32:1--32:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.32},
URN = {urn:nbn:de:0030-drops-71010},
doi = {10.4230/LIPIcs.OPODIS.2016.32},
annote = {Keywords: atomic register, regular register, wait-free implementation, single writer, optimal}
}
Document
Dynamic Atomic Snapshots
Abstract
Snapshots are useful tools for monitoring big distributed and parallel systems. In this paper, we adapt the well-known atomic snapshot abstraction to dynamic models with an unbounded number of participating processes. Our dynamic snapshot specification extends the API to allow changing the set of processes whose values should be returned from a scan operation. We introduce the ephemeral memory model, which consists of a dynamically changing set of nodes; when a node is removed, its memory can be immediately reclaimed. In this model, we present an algorithm for wait-free dynamic atomic snapshots.
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Alexander Spiegelman and Idit Keidar. Dynamic Atomic Snapshots. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 33:1-33:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{spiegelman_et_al:LIPIcs.OPODIS.2016.33,
author = {Spiegelman, Alexander and Keidar, Idit},
title = {{Dynamic Atomic Snapshots}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {33:1--33:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.33},
URN = {urn:nbn:de:0030-drops-71028},
doi = {10.4230/LIPIcs.OPODIS.2016.33},
annote = {Keywords: snapshots, shared memory, dynamic, ephemeral memory}
}
Document
Deletion without Rebalancing in Non-Blocking Binary Search Trees
Abstract
We present a provably linearizable and lock-free relaxed AVL tree called the non-blocking ravl tree. At any time, the height of a non-blocking ravl tree is upper bounded by log_d (2m) + c, where d is the golden ratio, m is the total number of successful INSERT operations performed so far and c is the number of active concurrent processes that have inserted new keys and are still rebalancing the tree at this time. The most significant feature of the non-blocking ravl tree is that it does not rebalance itself after DELETE operations. Instead, it performs rebalancing only after INSERT operations. Thus, the non-blocking ravl tree is much simpler to implement than other self-balancing concurrent binary search trees (BSTs) which typically introduce a large number of rebalancing cases after DELETE operations, while still providing a provable non-trivial bound on its height. We further conduct experimental studies to compare our solution with other state-of-the-art concurrent BSTs using randomly generated data sequences under uniform distributions, and find that our solution achieves the best performance among concurrent self-balancing BSTs. As the keys in access sequences are likely to be partially sorted in system software, we also conduct experiments using data sequences with various degrees of presortedness to better simulate applications in practice. Our experimental results show that, when there are enough degrees of presortedness, our solution achieves the best performance among all the concurrent BSTs used in our studies, including those that perform self-balancing operations and those that do not, and thus is potentially the best candidate for many real-world applications.
Cite as
Meng He and Mengdu Li. Deletion without Rebalancing in Non-Blocking Binary Search Trees. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 34:1-34:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{he_et_al:LIPIcs.OPODIS.2016.34,
author = {He, Meng and Li, Mengdu},
title = {{Deletion without Rebalancing in Non-Blocking Binary Search Trees}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {34:1--34:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.34},
URN = {urn:nbn:de:0030-drops-71032},
doi = {10.4230/LIPIcs.OPODIS.2016.34},
annote = {Keywords: concurrent data structures, non-blocking data structures, lock-free data structures, self-balancing binary search trees, relaxed AVL trees}
}
Document
Proving Opacity of a Pessimistic STM
Abstract
Transactional Memory (TM) is a high-level programming abstraction for concurrency control that provides programmers with the illusion of atomically executing blocks of code, called transactions. TMs come in two categories, optimistic and pessimistic, where in the latter transactions never abort. While this simplifies the programming model, high-performing pessimistic TMs can be complex. In this paper, we present the first formal verification of a pessimistic software TM algorithm, namely, an algorithm proposed by Matveev and Shavit. The correctness criterion used is opacity, formalising the transactional atomicity guarantees. We prove that this pessimistic TM is a refinement of an intermediate opaque I/O-automaton, known as TMS2. To this end, we develop a rely-guarantee approach for reducing the complexity of the proof. Proofs are mechanised in the interactive prover Isabelle.
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Simon Doherty, Brijesh Dongol, John Derrick, Gerhard Schellhorn, and Heike Wehrheim. Proving Opacity of a Pessimistic STM. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 35:1-35:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)
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@InProceedings{doherty_et_al:LIPIcs.OPODIS.2016.35,
author = {Doherty, Simon and Dongol, Brijesh and Derrick, John and Schellhorn, Gerhard and Wehrheim, Heike},
title = {{Proving Opacity of a Pessimistic STM}},
booktitle = {20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
pages = {35:1--35:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-031-6},
ISSN = {1868-8969},
year = {2017},
volume = {70},
editor = {Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.35},
URN = {urn:nbn:de:0030-drops-71040},
doi = {10.4230/LIPIcs.OPODIS.2016.35},
annote = {Keywords: Pessimistic STMs, Opacity, Verification, Isabelle, Simulation, TMS2}
}