41 Search Results for "Palmieri, Roberto"

Volume

LIPIcs, Volume 253

26th International Conference on Principles of Distributed Systems (OPODIS 2022)

OPODIS 2022, December 13-15, 2022, Brussels, Belgium

Editors: Eshcar Hillel, Roberto Palmieri, and Etienne Rivière

Document
DOI: 10.4230/LIPIcs.DISC.2025.35
PIPQ: Strict Insert-Optimized Concurrent Priority Queue

Authors: Olivia Grimes, Ahmed Hassan, Panagiota Fatourou, and Roberto Palmieri

Published in: LIPIcs, Volume 356, 39th International Symposium on Distributed Computing (DISC 2025)

Abstract
This paper presents PIPQ, a strict and linearizable concurrent priority queue whose design differs from existing solutions in literature because it focuses on enabling parallelism of insert operations as opposed to accelerating delete-min operations, as traditionally done. In a nutshell, PIPQ’s structure includes two levels: the worker level and the leader level. The worker level provides per-thread data structures enabling fast and parallel insertions. The leader level contains the highest priority elements in the priority queue and can thus serve delete-min operations. Our evaluation, which includes an exploration of different data access patterns, operation mixes, runtime settings, and an integration into a graph-based application, shows that PIPQ outperforms competitors in a variety of cases, especially with insert-dominant workloads.
Cite as

Olivia Grimes, Ahmed Hassan, Panagiota Fatourou, and Roberto Palmieri. PIPQ: Strict Insert-Optimized Concurrent Priority Queue. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 35:1-35:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{grimes_et_al:LIPIcs.DISC.2025.35,
  author =	{Grimes, Olivia and Hassan, Ahmed and Fatourou, Panagiota and Palmieri, Roberto},
  title =	{{PIPQ: Strict Insert-Optimized Concurrent Priority Queue}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{35:1--35:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-402-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{356},
  editor =	{Kowalski, Dariusz R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2025.35},
  URN =		{urn:nbn:de:0030-drops-248525},
  doi =		{10.4230/LIPIcs.DISC.2025.35},
  annote =	{Keywords: Priority Queue, Concurrent Data Structures, Synchronization}
}
Artifact
Software
DOI: 10.4230/artifacts.24906
PIPQ Priority Queue

Authors: Olivia Grimes, Ahmed Hassan, Panagiota Fatourou, and Roberto Palmieri

Abstract
Cite as

Olivia Grimes, Ahmed Hassan, Panagiota Fatourou, Roberto Palmieri. PIPQ Priority Queue (Software, Source Code). Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@misc{dagstuhl-artifact-24906,
   title = {{PIPQ Priority Queue}}, 
   author = {Grimes, Olivia and Hassan, Ahmed and Fatourou, Panagiota and Palmieri, Roberto},
   note = {Software (visited on 2025-10-22)},
   url = {https://github.com/sss-lehigh/pipq},
   doi = {10.4230/artifacts.24906},
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.8
Optimal Multilevel Slashing for Blockchains

Authors: Kenan Wood, Hammurabi Mendes, and Jonad Pulaj

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
We present the notion of multilevel slashing, where proof-of-stake blockchain validators can obtain gradual levels of assurance that a certain block is bound to be finalized in a global consensus procedure, unless an increasing and optimally large number of Byzantine processes have their staked assets slashed - that is, deducted - due to provably incorrect behavior. Our construction is a highly parameterized generalization of combinatorial intersection systems based on finite projective spaces, with asymptotic high availability and optimal slashing properties. Even under weak conditions, we show that our construction has asymptotically optimal slashing properties with respect to message complexity and validator load; this result also illustrates a fundamental trade off between message complexity, load, and slashing. In addition, we show that any intersection system whose ground elements are disjoint subsets of nodes (e.g. "committees" in committee-based consensus protocols) has asymptotic high availability under similarly weak conditions. Finally, our multilevel construction gives the flexibility to blockchain validators to decide how many "levels" of finalization assurance they wish to obtain. This functionality can be seen either as (i) a form of an early, slashing-based block finalization; or (ii) a service to support reorg tolerance.
Cite as

Kenan Wood, Hammurabi Mendes, and Jonad Pulaj. Optimal Multilevel Slashing for Blockchains. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{wood_et_al:LIPIcs.OPODIS.2024.8,
  author =	{Wood, Kenan and Mendes, Hammurabi and Pulaj, Jonad},
  title =	{{Optimal Multilevel Slashing for Blockchains}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{8:1--8:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.8},
  URN =		{urn:nbn:de:0030-drops-225445},
  doi =		{10.4230/LIPIcs.OPODIS.2024.8},
  annote =	{Keywords: Blockchains, Finality, Slashablility, Committees, Availability}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.13
Symmetry Preservation in Swarms of Oblivious Robots with Limited Visibility

Authors: Raphael Gerlach, Sören von der Gracht, Christopher Hahn, Jonas Harbig, and Peter Kling

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
In the general pattern formation (GPF) problem, a swarm of simple autonomous, disoriented robots must form a given pattern. The robots' simplicity imply a strong limitation: When the initial configuration is rotationally symmetric, only patterns with a similar symmetry can be formed [Masafumi Yamashita and Ichiro Suzuki, 2010]. The only known algorithm to form large patterns with limited visibility and without memory requires the robots to start in a near-gathering (a swarm of constant diameter) [Christopher Hahn et al., 2024]. However, not only do we not know any near-gathering algorithm guaranteed to preserve symmetry but most natural gathering strategies trivially increase symmetries [Jannik Castenow et al., 2022]. Thus, we study near-gathering without changing the swarm’s rotational symmetry for disoriented, oblivious robots with limited visibility (the OBLOT-model, see [Paola Flocchini et al., 2019]). We introduce a technique based on the theory of dynamical systems to analyze how a given algorithm affects symmetry and provide sufficient conditions for symmetry preservation. Until now, it was unknown whether the considered OBLOT-model allows for any non-trivial algorithm that always preserves symmetry. Our first result shows that a variant of Go-To-The-Average always preserves symmetry but may sometimes lead to multiple, unconnected near-gathering clusters. Our second result is a symmetry-preserving near-gathering algorithm that works on swarms with a convex boundary (the outer boundary of the unit disc graph) and without "holes" (circles of diameter 1 inside the boundary without any robots).
Cite as

Raphael Gerlach, Sören von der Gracht, Christopher Hahn, Jonas Harbig, and Peter Kling. Symmetry Preservation in Swarms of Oblivious Robots with Limited Visibility. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 13:1-13:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gerlach_et_al:LIPIcs.OPODIS.2024.13,
  author =	{Gerlach, Raphael and von der Gracht, S\"{o}ren and Hahn, Christopher and Harbig, Jonas and Kling, Peter},
  title =	{{Symmetry Preservation in Swarms of Oblivious Robots with Limited Visibility}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{13:1--13:28},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.13},
  URN =		{urn:nbn:de:0030-drops-225490},
  doi =		{10.4230/LIPIcs.OPODIS.2024.13},
  annote =	{Keywords: Swarm Algorithm, Swarm Robots, Distributed Algorithm, Pattern Formation, Limited Visibility, Oblivious}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.19
A General Class of Reductions and Extension-Based Proofs

Authors: Yusong Shi and Weidong Liu

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
The concept of extension-based proofs models the idea of a valency argument which is widely used in distributed computing. Extension-based proofs have been shown to be limited in power: there is no extension-based proof of the impossibility of a wait-free protocol for (n,k)-set agreement among n > k ≥ 2 processes. Previous work used a restricted class of reductions to show that there are no extension-based proofs of the impossibility of wait-free protocols for some other distributed computing problems. It is known that for a restricted class of reductions, if a task 𝒯 reduces to 𝒮 and 𝒯 has an augmented extension-based proof that it is impossible to solve in the NIS model, then so does 𝒮. We introduce multiple-instance extension-based proofs and show that, if 𝒯 reduces to multiple instances of 𝒮, instead of just one instance and 𝒯 has an augmented extension-based proof, then 𝒮 has a multiple-instance extension-based proof that it is impossible to solve in the NIIS model. We introduce a new version of extension-based proofs that can further our understanding of extension-based proofs and their limitations.
Cite as

Yusong Shi and Weidong Liu. A General Class of Reductions and Extension-Based Proofs. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 19:1-19:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{shi_et_al:LIPIcs.OPODIS.2024.19,
  author =	{Shi, Yusong and Liu, Weidong},
  title =	{{A General Class of Reductions and Extension-Based Proofs}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{19:1--19:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.19},
  URN =		{urn:nbn:de:0030-drops-225559},
  doi =		{10.4230/LIPIcs.OPODIS.2024.19},
  annote =	{Keywords: Reductions, Impossibility proofs, Extension-based proof}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.32
Distributed Agreement in the Arrovian Framework

Authors: Kenan Wood, Hammurabi Mendes, and Jonad Pulaj

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
Preference aggregation is a fundamental problem in voting theory, in which public input rankings of a set of alternatives (called preferences) must be aggregated into a single preference that satisfies certain soundness properties. The celebrated Arrow Impossibility Theorem is equivalent to a distributed task in a synchronous fault-free system that satisfies properties such as respecting unanimous preferences, maintaining independence of irrelevant alternatives (IIA), and non-dictatorship, along with consensus since only one preference can be decided. In this work, we study a weaker distributed task in which crash faults are introduced, IIA is not required, and the consensus property is relaxed to either k-set agreement or ε-approximate agreement using any metric on the set of preferences. In particular, we prove several novel impossibility results for both of these tasks in both synchronous and asynchronous distributed systems. We additionally show that the impossibility for our ε-approximate agreement task using the Kendall tau or Spearman footrule metrics holds under extremely weak assumptions.
Cite as

Kenan Wood, Hammurabi Mendes, and Jonad Pulaj. Distributed Agreement in the Arrovian Framework. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 32:1-32:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{wood_et_al:LIPIcs.OPODIS.2024.32,
  author =	{Wood, Kenan and Mendes, Hammurabi and Pulaj, Jonad},
  title =	{{Distributed Agreement in the Arrovian Framework}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{32:1--32:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.32},
  URN =		{urn:nbn:de:0030-drops-225686},
  doi =		{10.4230/LIPIcs.OPODIS.2024.32},
  annote =	{Keywords: Approximate Agreement, Set Agreement, Preference Aggregation, Voting Theory, Impossibility}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.OPODIS.2022
LIPIcs, Volume 253, OPODIS 2022, Complete Volume

Authors: Eshcar Hillel, Roberto Palmieri, and Etienne Rivière

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
LIPIcs, Volume 253, OPODIS 2022, Complete Volume
Cite as

26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 1-536, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@Proceedings{hillel_et_al:LIPIcs.OPODIS.2022,
  title =	{{LIPIcs, Volume 253, OPODIS 2022, Complete Volume}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{1--536},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022},
  URN =		{urn:nbn:de:0030-drops-176190},
  doi =		{10.4230/LIPIcs.OPODIS.2022},
  annote =	{Keywords: LIPIcs, Volume 253, OPODIS 2022, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.OPODIS.2022.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Eshcar Hillel, Roberto Palmieri, and Etienne Rivière

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 0:i-0:xiv, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{hillel_et_al:LIPIcs.OPODIS.2022.0,
  author =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{0:i--0:xiv},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.0},
  URN =		{urn:nbn:de:0030-drops-176203},
  doi =		{10.4230/LIPIcs.OPODIS.2022.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2022.1
Theory Meets Practice in the Algorand Blockchain (Invited Talk)

Authors: Victor Luchangco

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Robust and effective distributed systems require good theory and good engineering, not separately but in concert: user requirements and system constraints are not merely implementation details but often must inform the design of algorithms for such systems. Blockchains are an excellent example. The heart of a blockchain is its (Byzantine) consensus protocol, and consensus protocols have been extensively studied in the theory community for decades. But traditional consensus protocols are not directly applicable to blockchains, which have, or hope to have, millions of participants. Furthermore, public blockchains, which allow anyone to participate, must have some mechanism to guarantee the security of the protocol, and traditional fault models do not adequately capture the assumptions of such mechanisms. In this talk, I will discuss these and other ways in which theory and practice meet in the context of the Algorand blockchain, and how Algorand is able to achieve high transaction throughput with low latency.
Cite as

Victor Luchangco. Theory Meets Practice in the Algorand Blockchain (Invited Talk). In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{luchangco:LIPIcs.OPODIS.2022.1,
  author =	{Luchangco, Victor},
  title =	{{Theory Meets Practice in the Algorand Blockchain}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.1},
  URN =		{urn:nbn:de:0030-drops-176219},
  doi =		{10.4230/LIPIcs.OPODIS.2022.1},
  annote =	{Keywords: Theory and practice, Design of distributed systems, Blockchain, Consensus, Algorand}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2022.2
Recoverable Computing (Invited Talk)

Authors: Panagiota Fatourou

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Non-Volatile Memory (NVM) is an emerging memory technology which aims to address the high computational demands of modern applications and support recovery from crashes. Recovery ensures that after a crash every executed operation is able to recover and return a correct response. This talk will shed light on different aspects of the question "How does concurrent computing change in systems with NVM and what will the impact of persistent memory be on the way we compute?". Specifically, this talk addresses the following four main challenges in NVM computing. - Challenge 1: How to appropriately model and abstract fundamental aspects of NVM computing? The talk will provide an overview of the theoretical framework for NVM computing, including a discussion of correctness conditions, progress guarantees, failure types, etc. - Challenge 2: How to compute in a recoverable way at no significant cost? The talk will summarize state-of-the-art generic approaches for deriving recoverable synchronization algorithms, as well as recoverable implementations of many widely-used concurrent data structures on top of them. The collection of data structures includes fundamental structures, such as stacks and queues, but also more complex structures that implement sets, such as linked-lists and trees. - Challenge 3: How to analyze the cost of recoverable algorithms? The talk will present a way of analyzing the cost of persistence instructions, not by simply counting them but by separating them into categories based on the impact they have on the performance. This analysis reveals that understanding the actual persistence cost of an algorithm in machines with NVM, is more complicated than previously thought, and requires a thorough evaluation, since the performance impact of different persistence instructions may greatly vary. - Challenge 4: When is Recoverable Consensus Harder Than Consensus? The talk will briefly discuss the ability of different shared object types to solve recoverable consensus using NVM when processes crash and recover, and it will compare the difficulty of solving recoverable consensus to the difficulty of solving the standard consensus problem in a system with halting failures. For each of the above challenges, the talk will present main results, provide some of the details of the best-performing techniques, and discuss open problems and directions for further research. Some of the results that will be discussed in detail have appeared in [Attiya et al., 2022; Delporte-Gallet et al., 2022; Fatourou et al., 2022].
Cite as

Panagiota Fatourou. Recoverable Computing (Invited Talk). In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 2:1-2:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{fatourou:LIPIcs.OPODIS.2022.2,
  author =	{Fatourou, Panagiota},
  title =	{{Recoverable Computing}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{2:1--2:2},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.2},
  URN =		{urn:nbn:de:0030-drops-176221},
  doi =		{10.4230/LIPIcs.OPODIS.2022.2},
  annote =	{Keywords: non-volatile memory, persistence, detectability, durability, recoverable algorithms, recoverable data structures, persistent objects, stacks, queues, heaps, synchronization, universal constructions, software combining, lock-freedom, wait-freedom, persistence cost analysis}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2022.3
Realistic Self-Stabilization (Invited Talk)

Authors: Sébastien Tixeuil

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
It is almost fifty years since Dijkstra coined the term "self-stabilization" to denote a distributed system able to recover correct behavior starting from any arbitrary (even unreachable) configuration. His seminal paper triggered many works since then, exploring over the years new variants of the original concept, new application domains, and new complexity results. While the huge majority of those contributions relates to theory, considering computability and worst case complexity issues, this talk revisits old and recent contributions from the prism of "realistic" distributed systems, aiming to address the following question: is self-stabilization relevant in practice for distributed systems?
Cite as

Sébastien Tixeuil. Realistic Self-Stabilization (Invited Talk). In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, p. 3:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{tixeuil:LIPIcs.OPODIS.2022.3,
  author =	{Tixeuil, S\'{e}bastien},
  title =	{{Realistic Self-Stabilization}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{3:1--3:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.3},
  URN =		{urn:nbn:de:0030-drops-176232},
  doi =		{10.4230/LIPIcs.OPODIS.2022.3},
  annote =	{Keywords: Self-stabilization, Distributed systems, Probable stabilization, Performance evaluation, Asynchronous message passing, Multi-tolerance}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2022.4
Efficient Wait-Free Queue Algorithms with Multiple Enqueuers and Multiple Dequeuers

Authors: Colette Johnen, Adnane Khattabi, and Alessia Milani

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Despite the widespread usage of FIFO queues in distributed applications, designing efficient wait-free implementations of queues remains a challenge. The majority of wait-free queue implementations restrict either the number of dequeuers or the number of enqueuers that can operate on the queue, even when they use strong synchronization primitives, like the Compare&Swap. If we do not limit the number of processes that can perform enqueue and dequeue operations, the best-known upper bound on the worst case step complexity for a wait-free queue is given by [Khanchandani and Wattenhofer, 2018]. In particular, they present an implementation of a multiple dequeuer multiple enqueuer wait-free queue whose worst case step complexity is in O(√n), where n is the number of processes. In this work, we investigate whether it is possible to improve this bound. In particular, we present a wait-free FIFO queue implementation that supports n enqueuers and k dequeuers where the worst case step complexity of an Enqueue operation is in O(log n) and of a Dequeue operation is in O(k log n). Then, we show that if the semantics of the queue can be relaxed, by allowing concurrent Dequeue operations to retrieve the same element, then we can achieve O(log n) worst-case step complexity for both the Enqueue and Dequeue operations.
Cite as

Colette Johnen, Adnane Khattabi, and Alessia Milani. Efficient Wait-Free Queue Algorithms with Multiple Enqueuers and Multiple Dequeuers. In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 4:1-4:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{johnen_et_al:LIPIcs.OPODIS.2022.4,
  author =	{Johnen, Colette and Khattabi, Adnane and Milani, Alessia},
  title =	{{Efficient Wait-Free Queue Algorithms with Multiple Enqueuers and Multiple Dequeuers}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{4:1--4:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.4},
  URN =		{urn:nbn:de:0030-drops-176240},
  doi =		{10.4230/LIPIcs.OPODIS.2022.4},
  annote =	{Keywords: Distributed computing, distributed algorithms, FIFO queue, shared memory, fault tolerance, concurrent data structures, relaxed specifications, complexity}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2022.5
EEMARQ: Efficient Lock-Free Range Queries with Memory Reclamation

Authors: Gali Sheffi, Pedro Ramalhete, and Erez Petrank

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Multi-Version Concurrency Control (MVCC) is a common mechanism for achieving linearizable range queries in database systems and concurrent data-structures. The core idea is to keep previous versions of nodes to serve range queries, while still providing atomic reads and updates. Existing concurrent data-structure implementations, that support linearizable range queries, are either slow, use locks, or rely on blocking reclamation schemes. We present EEMARQ, the first scheme that uses MVCC with lock-free memory reclamation to obtain a fully lock-free data-structure supporting linearizable inserts, deletes, contains, and range queries. Evaluation shows that EEMARQ outperforms existing solutions across most workloads, with lower space overhead and while providing full lock freedom.
Cite as

Gali Sheffi, Pedro Ramalhete, and Erez Petrank. EEMARQ: Efficient Lock-Free Range Queries with Memory Reclamation. In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 5:1-5:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{sheffi_et_al:LIPIcs.OPODIS.2022.5,
  author =	{Sheffi, Gali and Ramalhete, Pedro and Petrank, Erez},
  title =	{{EEMARQ: Efficient Lock-Free Range Queries with Memory Reclamation}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{5:1--5:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.5},
  URN =		{urn:nbn:de:0030-drops-176253},
  doi =		{10.4230/LIPIcs.OPODIS.2022.5},
  annote =	{Keywords: safe memory reclamation, lock-freedom, snapshot, concurrency, range query}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2022.6
The Step Complexity of Multidimensional Approximate Agreement

Authors: Hagit Attiya and Faith Ellen

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Approximate agreement allows a set of n processes to obtain outputs that are within a specified distance ε > 0 of one another and within the convex hull of the inputs. When the inputs are real numbers, there is a wait-free shared-memory approximate agreement algorithm [Moran, 1995] whose step complexity is in O(n log(S/ε)), where S, the spread of the inputs, is the maximal distance between inputs. There is another wait-free algorithm [Schenk, 1995] that avoids the dependence on n and achieves O(log(M/ε)) step complexity where M, the magnitude of the inputs, is the absolute value of the maximal input. This paper considers whether it is possible to obtain an approximate agreement algorithm whose step complexity depends on neither n nor the magnitude of the inputs, which can be much larger than their spread. On the negative side, we prove that Ω(min{(log M)/(log log M), (√log n)/(log log n)}) is a lower bound on the step complexity of approximate agreement, even when the inputs are real numbers. On the positive side, we prove that a polylogarithmic dependence on n and S/ε can be achieved, by presenting an approximate agreement algorithm with O(log n (log n + log(S/ε))) step complexity. Our algorithm works for multidimensional domains. The step complexity can be further restricted to be in O(min{log n (log n + log (S/ε)), log(M/ε)}) when the inputs are real numbers.
Cite as

Hagit Attiya and Faith Ellen. The Step Complexity of Multidimensional Approximate Agreement. In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 6:1-6:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{attiya_et_al:LIPIcs.OPODIS.2022.6,
  author =	{Attiya, Hagit and Ellen, Faith},
  title =	{{The Step Complexity of Multidimensional Approximate Agreement}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{6:1--6:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.6},
  URN =		{urn:nbn:de:0030-drops-176261},
  doi =		{10.4230/LIPIcs.OPODIS.2022.6},
  annote =	{Keywords: approximate agreement, conflict detection, shared memory, wait-freedom, step complexity}
}
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