7 Search Results for "Hellings, Jelle"

Document
DOI: 10.4230/LIPIcs.DISC.2025.2
On the Efficiency of Dynamic Transaction Scheduling in Blockchain Sharding

Authors: Ramesh Adhikari, Costas Busch, and Miroslav Popovic

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

Abstract
Sharding is a technique to speed up transaction processing in blockchains, where the n processing nodes in the blockchain are divided into s disjoint groups (shards) that can process transactions in parallel. We study dynamic scheduling problems on a shard graph G_s where transactions arrive online over time and are not known in advance. Each transaction may access at most k shards, and we denote by d the worst distance between a transaction and its accessing (destination) shards (the parameter d is unknown to the shards). To handle different values of d, we assume a locality sensitive decomposition of G_s into clusters of shards, where every cluster has a leader shard that schedules transactions for the cluster. We first examine the simpler case of the stateless model, where leaders are not aware of the current state of the transaction accounts, and we prove a O(d log² s ⋅ min{k, √s}) competitive ratio for latency. We then consider the stateful model, where leader shards gather the current state of accounts, and we prove a O(log s⋅ min{k, √s}+log² s) competitive ratio for latency. Each leader calculates the schedule in polynomial time for each transaction that it processes. We show that for any ε > 0, approximating the optimal schedule within a (min{k, √s})^{1 -ε} factor is NP-hard. Hence, our bound for the stateful model is within a poly-log factor from the best possibly achievable. To the best of our knowledge, this is the first work to establish provably efficient dynamic scheduling algorithms for blockchain sharding systems.
Cite as

Ramesh Adhikari, Costas Busch, and Miroslav Popovic. On the Efficiency of Dynamic Transaction Scheduling in Blockchain Sharding. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 2:1-2:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{adhikari_et_al:LIPIcs.DISC.2025.2,
  author =	{Adhikari, Ramesh and Busch, Costas and Popovic, Miroslav},
  title =	{{On the Efficiency of Dynamic Transaction Scheduling in Blockchain Sharding}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{2:1--2:23},
  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.2025.2},
  URN =		{urn:nbn:de:0030-drops-248191},
  doi =		{10.4230/LIPIcs.DISC.2025.2},
  annote =	{Keywords: Blockchain, Blockchain Sharding, Dynamic Transaction Scheduling}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2025.59
Brief Announcement: Carry the Tail in Consensus Protocols

Authors: Suyash Gupta, Dakai Kang, Dahlia Malkhi, and Mohammad Sadoghi

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

Abstract
We present Carry-the-Tail, the first deterministic atomic broadcast protocol in partial synchrony that, after GST, simultaneously guarantees two desirable properties: (i) a constant fraction of commits are proposed by non-faulty leaders against tail-forking attacks, and (ii) optimal, worst-case quadratic communication under a cascade of faulty leaders. The solution also guarantees linear amortized communication, i.e., the steady-state is linear. Combining these two desirable properties was not simultaneously achieved previously: on one hand, prior atomic broadcast solutions achieve per-view linear word communication complexity. However, they face a significant degradation in throughput under tail-forking attack. On the other hand, existing solutions to tail-forking attacks require either quadratic communication steps or computationally-prohibitive SNARK generation. The key technical contribution is Carry, a practical drop-in mechanism for streamlined protocols in the HotStuff family. Carry guarantees good performance against tail-forking and removes most leader-induced stalls, while retaining linear traffic and protocol simplicity. Carry-the-Tail implements the Carry mechanism on HotStuff-2.
Cite as

Suyash Gupta, Dakai Kang, Dahlia Malkhi, and Mohammad Sadoghi. Brief Announcement: Carry the Tail in Consensus Protocols. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 59:1-59:7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{gupta_et_al:LIPIcs.DISC.2025.59,
  author =	{Gupta, Suyash and Kang, Dakai and Malkhi, Dahlia and Sadoghi, Mohammad},
  title =	{{Brief Announcement: Carry the Tail in Consensus Protocols}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{59:1--59:7},
  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.2025.59},
  URN =		{urn:nbn:de:0030-drops-248759},
  doi =		{10.4230/LIPIcs.DISC.2025.59},
  annote =	{Keywords: Consensus, Blockchain, BFT}
}
Document
DOI: 10.4230/LIPIcs.CSL.2025.14
Finite Variable Counting Logics with Restricted Requantification

Authors: Simon Raßmann, Georg Schindling, and Pascal Schweitzer

Published in: LIPIcs, Volume 326, 33rd EACSL Annual Conference on Computer Science Logic (CSL 2025)

Abstract
Counting logics with a bounded number of variables form one of the central concepts in descriptive complexity theory. Although they restrict the number of variables that a formula can contain, the variables can be nested within scopes of quantified occurrences of themselves. In other words, the variables can be requantified. We study the fragments obtained from counting logics by restricting requantification for some but not necessarily all the variables. Similar to the logics without limitation on requantification, we develop tools to investigate the restricted variants. Specifically, we introduce a bijective pebble game in which certain pebbles can only be placed once and for all, and a corresponding two-parametric family of Weisfeiler-Leman algorithms. We show close correspondences between the three concepts. By using a suitable cops-and-robber game and adaptations of the Cai-Fürer-Immerman construction, we completely clarify the relative expressive power of the new logics. We show that the restriction of requantification has beneficial algorithmic implications in terms of graph identification. Indeed, we argue that with regard to space complexity, non-requantifiable variables only incur an additive polynomial factor when testing for equivalence. In contrast, for all we know, requantifiable variables incur a multiplicative linear factor. Finally, we observe that graphs of bounded tree-depth and 3-connected planar graphs can be identified using no, respectively, only a very limited number of requantifiable variables.
Cite as

Simon Raßmann, Georg Schindling, and Pascal Schweitzer. Finite Variable Counting Logics with Restricted Requantification. In 33rd EACSL Annual Conference on Computer Science Logic (CSL 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 326, pp. 14:1-14:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{ramann_et_al:LIPIcs.CSL.2025.14,
  author =	{Ra{\ss}mann, Simon and Schindling, Georg and Schweitzer, Pascal},
  title =	{{Finite Variable Counting Logics with Restricted Requantification}},
  booktitle =	{33rd EACSL Annual Conference on Computer Science Logic (CSL 2025)},
  pages =	{14:1--14:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-362-1},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{326},
  editor =	{Endrullis, J\"{o}rg and Schmitz, Sylvain},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2025.14},
  URN =		{urn:nbn:de:0030-drops-227716},
  doi =		{10.4230/LIPIcs.CSL.2025.14},
  annote =	{Keywords: Requantification, Finite variable counting logics, Weisfeiler-Leman algorithm}
}
Document
DOI: 10.4230/LIPIcs.TIME.2020.18
Stab-Forests: Dynamic Data Structures for Efficient Temporal Query Processing

Authors: Jelle Hellings and Yuqing Wu

Published in: LIPIcs, Volume 178, 27th International Symposium on Temporal Representation and Reasoning (TIME 2020)

Abstract
Many sources of data have temporal start and end attributes or are created in a time-ordered manner. Hence, it is only natural to consider joining datasets based on these temporal attributes. To do so efficiently, several internal-memory temporal join algorithms have recently been proposed. Unfortunately, these join algorithms are designed to join entire datasets and cannot efficiently join skewed datasets in which only few events participate in the join result. To support high-performance internal-memory temporal joins of skewed datasets, we propose the skip-join algorithm, which operates on stab-forests. The stab-forest is a novel dynamic data structure for indexing temporal data that allows efficient updates when events are appended in a time-based order. Our stab-forests efficiently support not only traditional temporal stab-queries, but also more general multi-stab-queries. We conducted an experimental evaluation to compare the skip-join algorithm with state-of-the-art techniques using real-world datasets. We observed that the skip-join algorithm outperforms other techniques by an order of magnitude when joining skewed datasets and delivers comparable performance to other techniques on non-skewed datasets.
Cite as

Jelle Hellings and Yuqing Wu. Stab-Forests: Dynamic Data Structures for Efficient Temporal Query Processing. In 27th International Symposium on Temporal Representation and Reasoning (TIME 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 178, pp. 18:1-18:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{hellings_et_al:LIPIcs.TIME.2020.18,
  author =	{Hellings, Jelle and Wu, Yuqing},
  title =	{{Stab-Forests: Dynamic Data Structures for Efficient Temporal Query Processing}},
  booktitle =	{27th International Symposium on Temporal Representation and Reasoning (TIME 2020)},
  pages =	{18:1--18:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-167-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{178},
  editor =	{Mu\~{n}oz-Velasco, Emilio and Ozaki, Ana and Theobald, Martin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TIME.2020.18},
  URN =		{urn:nbn:de:0030-drops-129869},
  doi =		{10.4230/LIPIcs.TIME.2020.18},
  annote =	{Keywords: Cache-friendly temporal joins, temporal data, skewed data, stab-queries, temporal indices}
}
Document
DOI: 10.4230/LIPIcs.ICDT.2020.17
Coordination-Free Byzantine Replication with Minimal Communication Costs

Authors: Jelle Hellings and Mohammad Sadoghi

Published in: LIPIcs, Volume 155, 23rd International Conference on Database Theory (ICDT 2020)

Abstract
State-of-the-art fault-tolerant and federated data management systems rely on fully-replicated designs in which all participants have equivalent roles. Consequently, these systems have only limited scalability and are ill-suited for high-performance data management. As an alternative, we propose a hierarchical design in which a Byzantine cluster manages data, while an arbitrary number of learners can reliable learn these updates and use the corresponding data. To realize our design, we propose the delayed-replication algorithm, an efficient solution to the Byzantine learner problem that is central to our design. The delayed-replication algorithm is coordination-free, scalable, and has minimal communication cost for all participants involved. In doing so, the delayed-broadcast algorithm opens the door to new high-performance fault-tolerant and federated data management systems. To illustrate this, we show that the delayed-replication algorithm is not only useful to support specialized learners, but can also be used to reduce the overall communication cost of permissioned blockchains and to improve their storage scalability.
Cite as

Jelle Hellings and Mohammad Sadoghi. Coordination-Free Byzantine Replication with Minimal Communication Costs. In 23rd International Conference on Database Theory (ICDT 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 155, pp. 17:1-17:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{hellings_et_al:LIPIcs.ICDT.2020.17,
  author =	{Hellings, Jelle and Sadoghi, Mohammad},
  title =	{{Coordination-Free Byzantine Replication with Minimal Communication Costs}},
  booktitle =	{23rd International Conference on Database Theory (ICDT 2020)},
  pages =	{17:1--17:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-139-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{155},
  editor =	{Lutz, Carsten and Jung, Jean Christoph},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2020.17},
  URN =		{urn:nbn:de:0030-drops-119418},
  doi =		{10.4230/LIPIcs.ICDT.2020.17},
  annote =	{Keywords: Byzantine learner, coordination-free checkpoint protocol, delayed-replication, information dispersal, consensus}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2019.44
Brief Announcement: Revisiting Consensus Protocols through Wait-Free Parallelization

Authors: Suyash Gupta, Jelle Hellings, and Mohammad Sadoghi

Published in: LIPIcs, Volume 146, 33rd International Symposium on Distributed Computing (DISC 2019)

Abstract
In this brief announcement, we propose a protocol-agnostic approach to improve the design of primary-backup consensus protocols. At the core of our approach is a novel wait-free design of running several instances of the underlying consensus protocol in parallel. To yield a high-performance parallelized design, we present coordination-free techniques to order operations across parallel instances, deal with instance failures, and assign clients to specific instances. Consequently, the design we present is able to reduce the load on individual instances and primaries, while also reducing the adverse effects of any malicious replicas. Our design is fine-tuned such that the instances coordinated by non-faulty replicas are wait-free: they can continuously make consensus decisions, independent of the behavior of any other instances.
Cite as

Suyash Gupta, Jelle Hellings, and Mohammad Sadoghi. Brief Announcement: Revisiting Consensus Protocols through Wait-Free Parallelization. In 33rd International Symposium on Distributed Computing (DISC 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 146, pp. 44:1-44:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{gupta_et_al:LIPIcs.DISC.2019.44,
  author =	{Gupta, Suyash and Hellings, Jelle and Sadoghi, Mohammad},
  title =	{{Brief Announcement: Revisiting Consensus Protocols through Wait-Free Parallelization}},
  booktitle =	{33rd International Symposium on Distributed Computing (DISC 2019)},
  pages =	{44:1--44:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-126-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{146},
  editor =	{Suomela, Jukka},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2019.44},
  URN =		{urn:nbn:de:0030-drops-113514},
  doi =		{10.4230/LIPIcs.DISC.2019.44},
  annote =	{Keywords: Consensus, primary-backup, high-performance, wait-free parallelization}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2019.45
Brief Announcement: The Fault-Tolerant Cluster-Sending Problem

Authors: Jelle Hellings and Mohammad Sadoghi

Published in: LIPIcs, Volume 146, 33rd International Symposium on Distributed Computing (DISC 2019)

Abstract
The development of fault-tolerant distributed systems that can tolerate Byzantine behavior has traditionally been focused on consensus protocols, which support fully-replicated designs. For the development of more sophisticated high-performance Byzantine distributed systems, more specialized fault-tolerant communication primitives are necessary, however. In this brief announcement, we identify the cluster-sending problem - the problem of sending a message from one Byzantine cluster to another Byzantine cluster in a reliable manner - as such an essential communication primitive. We not only formalize this fundamental problem, but also establish lower bounds on the complexity of this problem under crash failures and Byzantine failures. Furthermore, we develop practical cluster-sending protocols that meet these lower bounds and, hence, have optimal complexity. As such, our work provides a strong foundation for the further exploration of novel designs that address challenges encountered in fault-tolerant distributed systems.
Cite as

Jelle Hellings and Mohammad Sadoghi. Brief Announcement: The Fault-Tolerant Cluster-Sending Problem. In 33rd International Symposium on Distributed Computing (DISC 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 146, pp. 45:1-45:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{hellings_et_al:LIPIcs.DISC.2019.45,
  author =	{Hellings, Jelle and Sadoghi, Mohammad},
  title =	{{Brief Announcement: The Fault-Tolerant Cluster-Sending Problem}},
  booktitle =	{33rd International Symposium on Distributed Computing (DISC 2019)},
  pages =	{45:1--45:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-126-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{146},
  editor =	{Suomela, Jukka},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2019.45},
  URN =		{urn:nbn:de:0030-drops-113528},
  doi =		{10.4230/LIPIcs.DISC.2019.45},
  annote =	{Keywords: Byzantine clusters, message sending, lower bound, optimal protocol}
}
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