34 Search Results for "Anderson, James H."

Document
DOI: 10.4230/LIPIcs.DISC.2024.17
Breaking Through the Ω(n)-Space Barrier: Population Protocols Decide Double-Exponential Thresholds

Authors: Philipp Czerner

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

Abstract
Population protocols are a model of distributed computation in which finite-state agents interact randomly in pairs. A protocol decides for any initial configuration whether it satisfies a fixed property, specified as a predicate on the set of configurations. A family of protocols deciding predicates φ_n is succinct if it uses 𝒪(|φ_n|) states, where φ_n is encoded as quantifier-free Presburger formula with coefficients in binary. (All predicates decidable by population protocols can be encoded in this manner.) While it is known that succinct protocols exist for all predicates, it is open whether protocols with o(|φ_n|) states exist for any family of predicates φ_n. We answer this affirmatively, by constructing protocols with 𝒪(log|φ_n|) states for some family of threshold predicates φ_n(x) ⇔ x ≥ k_n, with k₁,k₂,... ∈ ℕ. (In other words, protocols with 𝒪(n) states that decide x ≥ k for a k ≥ 2^2ⁿ.) This matches a known lower bound. Moreover, our construction for threshold predicates is the first that is not 1-aware, and it is almost self-stabilising.
Cite as

Philipp Czerner. Breaking Through the Ω(n)-Space Barrier: Population Protocols Decide Double-Exponential Thresholds. In 38th International Symposium on Distributed Computing (DISC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 319, pp. 17:1-17:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{czerner:LIPIcs.DISC.2024.17,
  author =	{Czerner, Philipp},
  title =	{{Breaking Through the \Omega(n)-Space Barrier: Population Protocols Decide Double-Exponential Thresholds}},
  booktitle =	{38th International Symposium on Distributed Computing (DISC 2024)},
  pages =	{17:1--17:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-352-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{319},
  editor =	{Alistarh, Dan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2024.17},
  URN =		{urn:nbn:de:0030-drops-212438},
  doi =		{10.4230/LIPIcs.DISC.2024.17},
  annote =	{Keywords: Distributed computing, population protocols, state complexity}
}
Document
DOI: 10.4230/LIPIcs.DISC.2024.39
The Power of Abstract MAC Layer: A Fault-Tolerance Perspective

Authors: Qinzi Zhang and Lewis Tseng

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

Abstract
This paper studies the power of the "abstract MAC layer" model in a single-hop asynchronous network. The model captures primitive properties of modern wireless MAC protocols. In this model, Newport [PODC '14] proves that it is impossible to achieve deterministic consensus when nodes may crash. Subsequently, Newport and Robinson [DISC '18] present randomized consensus algorithms that terminate with O(n³ log n) expected broadcasts in a system of n nodes. We are not aware of any results on other fault-tolerant distributed tasks in this model. We first study the computability aspect of the abstract MAC layer. We present a wait-free algorithm that implements an atomic register. Furthermore, we show that in general, k-set consensus is impossible. Second, we aim to minimize storage complexity. Existing algorithms require Ω(n log n) bits. We propose two wait-free approximate consensus and two wait-free randomized binary consensus algorithms that only need constant storage complexity (except for the phase index). One randomized algorithm terminates with O(n log n) expected broadcasts. All our algorithms are anonymous, meaning that at the algorithm level, nodes do not need to have a unique identifier.
Cite as

Qinzi Zhang and Lewis Tseng. The Power of Abstract MAC Layer: A Fault-Tolerance Perspective. In 38th International Symposium on Distributed Computing (DISC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 319, pp. 39:1-39:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{zhang_et_al:LIPIcs.DISC.2024.39,
  author =	{Zhang, Qinzi and Tseng, Lewis},
  title =	{{The Power of Abstract MAC Layer: A Fault-Tolerance Perspective}},
  booktitle =	{38th International Symposium on Distributed Computing (DISC 2024)},
  pages =	{39:1--39:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-352-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{319},
  editor =	{Alistarh, Dan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2024.39},
  URN =		{urn:nbn:de:0030-drops-212677},
  doi =		{10.4230/LIPIcs.DISC.2024.39},
  annote =	{Keywords: Abstract MAC Layer, Computation Power, Consensus}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2024.15
Rose: Composable Autodiff for the Interactive Web

Authors: Sam Estep, Wode Ni, Raven Rothkopf, and Joshua Sunshine

Published in: LIPIcs, Volume 313, 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
Reverse-mode automatic differentiation (autodiff) has been popularized by deep learning, but its ability to compute gradients is also valuable for interactive use cases such as bidirectional computer-aided design, embedded physics simulations, visualizing causal inference, and more. Unfortunately, the web is ill-served by existing autodiff frameworks, which use autodiff strategies that perform poorly on dynamic scalar programs, and pull in heavy dependencies that would result in unacceptable webpage sizes. This work introduces Rose, a lightweight autodiff framework for the web using a new hybrid approach to reverse-mode autodiff, blending conventional tracing and transformation techniques in a way that uses the host language for metaprogramming while also allowing the programmer to explicitly define reusable functions that comprise a larger differentiable computation. We demonstrate the value of the Rose design by porting two differentiable physics simulations, and evaluate its performance on an optimization-based diagramming application, showing Rose outperforming the state-of-the-art in web-based autodiff by multiple orders of magnitude.
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Sam Estep, Wode Ni, Raven Rothkopf, and Joshua Sunshine. Rose: Composable Autodiff for the Interactive Web. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 15:1-15:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{estep_et_al:LIPIcs.ECOOP.2024.15,
  author =	{Estep, Sam and Ni, Wode and Rothkopf, Raven and Sunshine, Joshua},
  title =	{{Rose: Composable Autodiff for the Interactive Web}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{15:1--15:27},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-341-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{313},
  editor =	{Aldrich, Jonathan and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2024.15},
  URN =		{urn:nbn:de:0030-drops-208642},
  doi =		{10.4230/LIPIcs.ECOOP.2024.15},
  annote =	{Keywords: Automatic differentiation, differentiable programming, compilers, web}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2024.42
Failure Transparency in Stateful Dataflow Systems

Authors: Aleksey Veresov, Jonas Spenger, Paris Carbone, and Philipp Haller

Published in: LIPIcs, Volume 313, 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
Failure transparency enables users to reason about distributed systems at a higher level of abstraction, where complex failure-handling logic is hidden. This is especially true for stateful dataflow systems, which are the backbone of many cloud applications. In particular, this paper focuses on proving failure transparency in Apache Flink, a popular stateful dataflow system. Even though failure transparency is a critical aspect of Apache Flink, to date it has not been formally proven. Showing that the failure transparency mechanism is correct, however, is challenging due to the complexity of the mechanism itself. Nevertheless, this complexity can be effectively hidden behind a failure transparent programming interface. To show that Apache Flink is failure transparent, we model it in small-step operational semantics. Next, we provide a novel definition of failure transparency based on observational explainability, a concept which relates executions according to their observations. Finally, we provide a formal proof of failure transparency for the implementation model; i.e., we prove that the failure-free model correctly abstracts from the failure-related details of the implementation model. We also show liveness of the implementation model under a fair execution assumption. These results are a first step towards a verified stack for stateful dataflow systems.
Cite as

Aleksey Veresov, Jonas Spenger, Paris Carbone, and Philipp Haller. Failure Transparency in Stateful Dataflow Systems. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 42:1-42:31, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{veresov_et_al:LIPIcs.ECOOP.2024.42,
  author =	{Veresov, Aleksey and Spenger, Jonas and Carbone, Paris and Haller, Philipp},
  title =	{{Failure Transparency in Stateful Dataflow Systems}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{42:1--42:31},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-341-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{313},
  editor =	{Aldrich, Jonathan and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2024.42},
  URN =		{urn:nbn:de:0030-drops-208911},
  doi =		{10.4230/LIPIcs.ECOOP.2024.42},
  annote =	{Keywords: Failure transparency, stateful dataflow, operational semantics, checkpoint recovery}
}
Document
DOI: 10.4230/LIPIcs.WABI.2024.19
RNA Inverse Folding Can Be Solved in Linear Time for Structures Without Isolated Stacks or Base Pairs

Authors: Théo Boury, Laurent Bulteau, and Yann Ponty

Published in: LIPIcs, Volume 312, 24th International Workshop on Algorithms in Bioinformatics (WABI 2024)

Abstract
Inverse folding is a classic instance of negative RNA design which consists in finding a sequence that uniquely folds into a target secondary structure with respect to energy minimization. A breakthrough result of Bonnet et al. shows that, even in simple base pairs-based (BP) models, the decision version of a mildly constrained version of inverse folding is NP-hard. In this work, we show that inverse folding can be solved in linear time for a large collection of targets, including every structure that contains no isolated BP and no isolated stack (or, equivalently, when all helices consist of 3^{+} base pairs). For structures featuring shorter helices, our linear algorithm is no longer guaranteed to produce a solution, but still does so for a large proportion of instances. Our approach introduces a notion of modulo m-separability, generalizing a property pioneered by Hales et al. Separability is a sufficient condition for the existence of a solution to the inverse folding problem. We show that, for any input secondary structure of length n, a modulo m-separated sequence can be produced in time 𝒪(n 2^m) anytime such a sequence exists. Meanwhile, we show that any structure consisting of 3^{+} base pairs is either trivially non-designable, or always admits a modulo-2 separated solution (m = 2). Solution sequences can thus be produced in linear time, and even be uniformly generated within the set of modulo-2 separable sequences.
Cite as

Théo Boury, Laurent Bulteau, and Yann Ponty. RNA Inverse Folding Can Be Solved in Linear Time for Structures Without Isolated Stacks or Base Pairs. In 24th International Workshop on Algorithms in Bioinformatics (WABI 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 312, pp. 19:1-19:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{boury_et_al:LIPIcs.WABI.2024.19,
  author =	{Boury, Th\'{e}o and Bulteau, Laurent and Ponty, Yann},
  title =	{{RNA Inverse Folding Can Be Solved in Linear Time for Structures Without Isolated Stacks or Base Pairs}},
  booktitle =	{24th International Workshop on Algorithms in Bioinformatics (WABI 2024)},
  pages =	{19:1--19:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-340-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{312},
  editor =	{Pissis, Solon P. and Sung, Wing-Kin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.WABI.2024.19},
  URN =		{urn:nbn:de:0030-drops-206632},
  doi =		{10.4230/LIPIcs.WABI.2024.19},
  annote =	{Keywords: RNA structure, String Design, Parameterized Complexity, Uniform Sampling}
}
Document
DOI: 10.4230/LIPIcs.WABI.2024.20
The Path-Label Reconciliation (PLR) Dissimilarity Measure for Gene Trees

Authors: Alitzel López Sánchez, José Antonio Ramírez-Rafael, Alejandro Flores-Lamas, Maribel Hernández-Rosales, and Manuel Lafond

Published in: LIPIcs, Volume 312, 24th International Workshop on Algorithms in Bioinformatics (WABI 2024)

Abstract
In this study, we investigate the problem of comparing gene trees reconciled with the same species tree using a novel semi-metric, called the Path-Label Reconciliation (PLR) dissimilarity measure. This approach not only quantifies differences in the topology of reconciled gene trees, but also considers discrepancies in predicted ancestral gene-species maps and speciation/duplication events, offering a refinement of existing metrics such as Robinson-Foulds (RF) and their labeled extensions LRF and ELRF. A tunable parameter α also allows users to adjust the balance between its species map and event labeling components. We show that PLR can be computed in linear time and that it is a semi-metric. We also discuss the diameters of reconciled gene tree measures, which are important in practice for normalization, and provide initial bounds on PLR, LRF, and ELRF. To validate PLR, we simulate reconciliations and perform comparisons with LRF and ELRF. The results show that PLR provides a more evenly distributed range of distances, making it less susceptible to overestimating differences in the presence of small topological changes, while at the same time being computationally efficient. Our findings suggest that the theoretical diameter is rarely reached in practice. The PLR measure advances phylogenetic reconciliation by combining theoretical rigor with practical applicability. Future research will refine its mathematical properties, explore its performance on different tree types, and integrate it with existing bioinformatics tools for large-scale evolutionary analyses. The open source code is available at: https://pypi.org/project/parle/.
Cite as

Alitzel López Sánchez, José Antonio Ramírez-Rafael, Alejandro Flores-Lamas, Maribel Hernández-Rosales, and Manuel Lafond. The Path-Label Reconciliation (PLR) Dissimilarity Measure for Gene Trees. In 24th International Workshop on Algorithms in Bioinformatics (WABI 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 312, pp. 20:1-20:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{lopezsanchez_et_al:LIPIcs.WABI.2024.20,
  author =	{L\'{o}pez S\'{a}nchez, Alitzel and Ram{\'\i}rez-Rafael, Jos\'{e} Antonio and Flores-Lamas, Alejandro and Hern\'{a}ndez-Rosales, Maribel and Lafond, Manuel},
  title =	{{The Path-Label Reconciliation (PLR) Dissimilarity Measure for Gene Trees}},
  booktitle =	{24th International Workshop on Algorithms in Bioinformatics (WABI 2024)},
  pages =	{20:1--20:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-340-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{312},
  editor =	{Pissis, Solon P. and Sung, Wing-Kin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.WABI.2024.20},
  URN =		{urn:nbn:de:0030-drops-206645},
  doi =		{10.4230/LIPIcs.WABI.2024.20},
  annote =	{Keywords: Reconciliation, gene trees, species trees, evolutionary scenarios}
}
Document
DOI: 10.4230/LIPIcs.TQC.2024.2
Stochastic Error Cancellation in Analog Quantum Simulation

Authors: Yiyi Cai, Yu Tong, and John Preskill

Published in: LIPIcs, Volume 310, 19th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2024)

Abstract
Analog quantum simulation is a promising path towards solving classically intractable problems in many-body physics on near-term quantum devices. However, the presence of noise limits the size of the system and the length of time that can be simulated. In our work, we consider an error model in which the actual Hamiltonian of the simulator differs from the target Hamiltonian we want to simulate by small local perturbations, which are assumed to be random and unbiased. We analyze the error accumulated in observables in this setting and show that, due to stochastic error cancellation, with high probability the error scales as the square root of the number of qubits instead of linearly. We explore the concentration phenomenon of this error as well as its implications for local observables in the thermodynamic limit. Moreover, we show that stochastic error cancellation also manifests in the fidelity between the target state at the end of time-evolution and the actual state we obtain in the presence of noise. This indicates that, to reach a certain fidelity, more noise can be tolerated than implied by the worst-case bound if the noise comes from many statistically independent sources.
Cite as

Yiyi Cai, Yu Tong, and John Preskill. Stochastic Error Cancellation in Analog Quantum Simulation. In 19th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 310, pp. 2:1-2:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{cai_et_al:LIPIcs.TQC.2024.2,
  author =	{Cai, Yiyi and Tong, Yu and Preskill, John},
  title =	{{Stochastic Error Cancellation in Analog Quantum Simulation}},
  booktitle =	{19th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2024)},
  pages =	{2:1--2:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-328-7},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{310},
  editor =	{Magniez, Fr\'{e}d\'{e}ric and Grilo, Alex Bredariol},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TQC.2024.2},
  URN =		{urn:nbn:de:0030-drops-206720},
  doi =		{10.4230/LIPIcs.TQC.2024.2},
  annote =	{Keywords: Analog quantum simulation, error cancellation, concentration of measure}
}
Document
Invited Paper
DOI: 10.4230/OASIcs.WCET.2024.3
Invited Paper: Assessing Unchecked Factors for Certification: An Experimental Approach for GPU Cache Parameters

Authors: Cédric Cazanove, Benjamin Lesage, Frédéric Boniol, and Jérôme Ermont

Published in: OASIcs, Volume 121, 22nd International Workshop on Worst-Case Execution Time Analysis (WCET 2024)

Abstract
The certification objectives for airborne electronic hardware defined in AMC20-152A [EASA, 2021] and in AMC20-193 [EASA, 2020] capture some of the activities required for an applicant to embed a hardware platform in a safety-critical avionic system. For COTS (Commercially available Off-The-Shelf) platforms in particular, these objectives require applicants to identify functions, configuration settings, and resources present on the platform, and assess their use by the system. AMC20-152A however recognizes that documentation regarding the behavior of a COTS may be incomplete. There is thus a strong push for applicants to the certification of a COTS to demonstrate their mastery of the platform, to highlight relevant factors (functions, settings, resources, etc.), and their use in their system. We outline in the following a standard approach to the exploration of unchecked factors of a platform, considering existing approaches in the literature, to build such a mastery. Our approach incrementally incorporates and validates knowledge of various factors by including them in micro-simulations compared to experimental ground truth.
Cite as

Cédric Cazanove, Benjamin Lesage, Frédéric Boniol, and Jérôme Ermont. Invited Paper: Assessing Unchecked Factors for Certification: An Experimental Approach for GPU Cache Parameters. In 22nd International Workshop on Worst-Case Execution Time Analysis (WCET 2024). Open Access Series in Informatics (OASIcs), Volume 121, pp. 3:1-3:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{cazanove_et_al:OASIcs.WCET.2024.3,
  author =	{Cazanove, C\'{e}dric and Lesage, Benjamin and Boniol, Fr\'{e}d\'{e}ric and Ermont, J\'{e}r\^{o}me},
  title =	{{Invited Paper: Assessing Unchecked Factors for Certification: An Experimental Approach for GPU Cache Parameters}},
  booktitle =	{22nd International Workshop on Worst-Case Execution Time Analysis (WCET 2024)},
  pages =	{3:1--3:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-346-1},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{121},
  editor =	{Carle, Thomas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.WCET.2024.3},
  URN =		{urn:nbn:de:0030-drops-204719},
  doi =		{10.4230/OASIcs.WCET.2024.3},
  annote =	{Keywords: GPU, benchmarks, simulation, certification}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.2
SlackCheck: A Linux Kernel Module to Verify Temporal Properties of a Task Schedule

Authors: Michele Castrovilli and Enrico Bini

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
The Linux Kernel offers several scheduling classes. From SCHED_DEADLINE down to SCHED_FIFO, SCHED_RR and SCHED_OTHER, the scheduling classes can provide different responsiveness to very diverse user workloads. Still, Linux does not offer any mechanism to take some action upon the violation of temporal constraints at runtime. The lack of such a feature is also due to the difficulty of extending the established notion of deadline to workloads which are not releasing periodic/sporadic jobs. Exploiting the notion of supply functions for any resource schedule, we implemented SlackCheck, a kernel module which is capable to verify at runtime if a given task is assigned a desired amount of resource or not. SlackCheck adds a constant-time check at every scheduling decision and leverages the recent availability of a Runtime Verification engine in the kernel.
Cite as

Michele Castrovilli and Enrico Bini. SlackCheck: A Linux Kernel Module to Verify Temporal Properties of a Task Schedule. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 2:1-2:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{castrovilli_et_al:LIPIcs.ECRTS.2024.2,
  author =	{Castrovilli, Michele and Bini, Enrico},
  title =	{{SlackCheck: A Linux Kernel Module to Verify Temporal Properties of a Task Schedule}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{2:1--2:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.2},
  URN =		{urn:nbn:de:0030-drops-203054},
  doi =		{10.4230/LIPIcs.ECRTS.2024.2},
  annote =	{Keywords: Linux scheduler, Runtime verification, bounded-delay resource partition, supply function, service curve, real-time calculus, network calculus}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.4
Tighter Worst-Case Response Time Bounds for Jitter-Based Self-Suspension Analysis

Authors: Mario Günzel, Georg von der Brüggen, and Jian-Jia Chen

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
Tasks are called self-suspending if they can yield their ready state (specifically, releasing the processor while having highest priority) despite being incomplete, for instance, to offload computation to an external device or when waiting on access rights for shared resources or data. This self-suspending behavior requires special treatment when applying analytical results to compute worst-case response time bounds. One typical treatment is modeling self-suspension as release jitter in a so-called jitter-based analysis. The state of the art, when considering task-level fixed-priority scheduling, individually quantifies the jitter term of each higher-priority task by its worst-case response time minus its worst-case execution time. This work tightens the jitter term by taking the execution behavior of the other higher-priority tasks into account. Our improved jitter-based analysis analytically dominates the previous jitter-based analysis. Moreover, an evaluation for synthetically generated sporadic tasks demonstrates that this jitter term results in tighter worst-case response time bounds for self-suspending tasks. We observe an improvement for up to 55.89 % of the tasksets compared to the previous jitter-based analysis.
Cite as

Mario Günzel, Georg von der Brüggen, and Jian-Jia Chen. Tighter Worst-Case Response Time Bounds for Jitter-Based Self-Suspension Analysis. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 4:1-4:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gunzel_et_al:LIPIcs.ECRTS.2024.4,
  author =	{G\"{u}nzel, Mario and von der Br\"{u}ggen, Georg and Chen, Jian-Jia},
  title =	{{Tighter Worst-Case Response Time Bounds for Jitter-Based Self-Suspension Analysis}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{4:1--4:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.4},
  URN =		{urn:nbn:de:0030-drops-203074},
  doi =		{10.4230/LIPIcs.ECRTS.2024.4},
  annote =	{Keywords: Worst-Case Response Time, WCRT, Jitter, Self-Suspension, Analysis}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.10
Crêpe: Clock-Reconfiguration-Aware Preemption Control in Real-Time Systems with Devices

Authors: Eva Dengler and Peter Wägemann

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
The domain of energy-constrained real-time systems that are operated on modern embedded system-on-chip (SoC) platforms brings numerous novel challenges for optimal resource minimization. These modern hardware platforms offer a heterogeneous variety of features to configure the tradeoff between temporal performance and energy efficiency, which goes beyond the state-of-the-art of existing dynamic-voltage-frequency-scaling (DVFS) scheduling schemes. The control center for configuring this tradeoff on platforms are complex clock subsystems that are intertwined with requirements of the SoC’s components (e.g., transceiver/memory/sensor devices). That is, several devices have precedence constraints with respect to specific clock sources and their settings. The challenge of dynamically adapting the various clock sources to select resource-optimal configurations becomes especially challenging in the presence of asynchronous preemptions, which are inherent to systems that use devices. In this paper, we present Crêpe, an approach to clock-reconfiguration-aware preemption control: Crêpe has an understanding of the target platform’s clock subsystem, its sleep states, and penalties to reconfigure clock sources for adapting clock frequencies. Crêpe’s hardware model is combined with an awareness of the application’s device requirements for each executed task, as well as possible interrupts that cause preemptions during runtime. Using these software/hardware constraints, Crêpe employs, in its offline phase, a mathematical formalization in order to select energy-minimal configurations while meeting given deadlines. This optimizing formalization, processed by standard mathematical solver tools, accounts for potentially occurring interrupts and the respective clock reconfigurations, which are then forwarded as alternative schedules to Crêpe’s runtime system. During runtime, the dispatcher assesses these offline-determined alternative schedules and reconfigures the clock sources for energy minimization. We developed an implementation based on a widely-used SoC platform (i.e., ESP32-C3) and an automated testbed for comprehensive energy-consumption evaluations to validate Crêpe’s claim of selecting resource-optimal settings under worst-case considerations.
Cite as

Eva Dengler and Peter Wägemann. Crêpe: Clock-Reconfiguration-Aware Preemption Control in Real-Time Systems with Devices. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 10:1-10:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dengler_et_al:LIPIcs.ECRTS.2024.10,
  author =	{Dengler, Eva and W\"{a}gemann, Peter},
  title =	{{Cr\^{e}pe: Clock-Reconfiguration-Aware Preemption Control in Real-Time Systems with Devices}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{10:1--10:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.10},
  URN =		{urn:nbn:de:0030-drops-203135},
  doi =		{10.4230/LIPIcs.ECRTS.2024.10},
  annote =	{Keywords: energy-constrained real-time systems, time/energy tradeoff, system-on-chip, energy-aware real-time scheduling, resource minimization, preemption control, worst-case energy consumption (WCEC), worst-case execution time (WCET), static whole-system analysis}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.11
Open Problem Resolved: The "Two" in Existing Multiprocessor PI-Blocking Bounds Is Fundamental

Authors: Shareef Ahmed and James H. Anderson

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
The goal of a real-time locking protocol is to reduce any priority-inversion blocking (pi-blocking) a task may incur while waiting to access a shared resource. For mutual-exclusion sharing on an m-processor platform, the best existing lower bound on per-task pi-blocking under suspension-oblivious analysis is a (trivial) lower bound of (m-1) request lengths under any job-level fixed-priority (JLFP) scheduler. Surprisingly, most asymptotically optimal locking protocols achieve a per-task pi-blocking upper bound of (2m-1) request lengths under JLFP scheduling, even though a range of very different mechanisms are used in these protocols. This paper closes the gap between these existing lower and upper bounds by establishing a lower bound of (2m-2) request lengths under global fixed-priority (G-FP) and global earliest-deadline-first (G-EDF) scheduling. This paper also shows that worst-case per-task pi-blocking can be arbitrarily close to (2m-1) request lengths for locking protocols that satisfy a certain property that is met by most (if not all) existing locking protocols. These results imply that most known asymptotically optimal locking protocols are almost truly optimal (not just asymptotic) under G-FP and G-EDF scheduling.
Cite as

Shareef Ahmed and James H. Anderson. Open Problem Resolved: The "Two" in Existing Multiprocessor PI-Blocking Bounds Is Fundamental. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 11:1-11:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ahmed_et_al:LIPIcs.ECRTS.2024.11,
  author =	{Ahmed, Shareef and Anderson, James H.},
  title =	{{Open Problem Resolved: The "Two" in Existing Multiprocessor PI-Blocking Bounds Is Fundamental}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{11:1--11:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.11},
  URN =		{urn:nbn:de:0030-drops-203145},
  doi =		{10.4230/LIPIcs.ECRTS.2024.11},
  annote =	{Keywords: Real-Time Systems, Real-Time Synchronization, Multiprocessors}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.12
Autonomy Today: Many Delay-Prone Black Boxes

Authors: Sizhe Liu, Rohan Wagle, James H. Anderson, Ming Yang, Chi Zhang, and Yunhua Li

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
Machine-learning (ML) technology has been a key enabler in the push towards realizing ever more sophisticated autonomous-driving features. In deploying such technology, the automotive industry has relied heavily on using "black-box" software and hardware components that were originally intended for non-safety-critical contexts, without a full understanding of their real-time capabilities. A prime example of such a component is CUDA, which is fundamental to the acceleration of ML algorithms using NVIDIA GPUs. In this paper, evidence is presented demonstrating that CUDA can cause unbounded task delays. Such delays are the result of CUDA’s usage of synchronization mechanisms in the POSIX thread (pthread) library, so the latter is implicated as a delay-prone component as well. Such synchronization delays are shown to be the source of a system failure that occurred in an actual autonomous vehicle system during testing at WeRide. Motivated by these findings, a broader experimental study is presented that demonstrates several real-time deficiencies in CUDA, the glibc pthread library, Linux, and the POSIX interface of the safety-certified QNX Operating System for Safety. Partial mitigations for these deficiencies are presented and further actions are proposed for real-time researchers and developers to integrate more complete mitigations.
Cite as

Sizhe Liu, Rohan Wagle, James H. Anderson, Ming Yang, Chi Zhang, and Yunhua Li. Autonomy Today: Many Delay-Prone Black Boxes. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 12:1-12:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{liu_et_al:LIPIcs.ECRTS.2024.12,
  author =	{Liu, Sizhe and Wagle, Rohan and Anderson, James H. and Yang, Ming and Zhang, Chi and Li, Yunhua},
  title =	{{Autonomy Today: Many Delay-Prone Black Boxes}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{12:1--12:27},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.12},
  URN =		{urn:nbn:de:0030-drops-203152},
  doi =		{10.4230/LIPIcs.ECRTS.2024.12},
  annote =	{Keywords: autonomous driving, CUDA programming, locking protocols, POSIX thread, operating systems, machine learning systems, real-time systems}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.14
GCAPS: GPU Context-Aware Preemptive Priority-Based Scheduling for Real-Time Tasks

Authors: Yidi Wang, Cong Liu, Daniel Wong, and Hyoseung Kim

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
Scheduling real-time tasks that utilize GPUs with analyzable guarantees poses a significant challenge due to the intricate interaction between CPU and GPU resources, as well as the complex GPU hardware and software stack. While much research has been conducted in the real-time research community, several limitations persist, including the absence or limited availability of GPU-level preemption, extended blocking times, and/or the need for extensive modifications to program code. In this paper, we propose GCAPS, a GPU Context-Aware Preemptive Scheduling approach for real-time GPU tasks. Our approach exerts control over GPU context scheduling at the device driver level and enables preemption of GPU execution based on task priorities by simply adding one-line macros to GPU segment boundaries. In addition, we provide a comprehensive response time analysis of GPU-using tasks for both our proposed approach as well as the default Nvidia GPU driver scheduling that follows a work-conserving round-robin policy. Through empirical evaluations and case studies, we demonstrate the effectiveness of the proposed approaches in improving taskset schedulability and response time. The results highlight significant improvements over prior work as well as the default scheduling approach, with up to 40% higher schedulability, while also achieving predictable worst-case behavior on Nvidia Jetson embedded platforms.
Cite as

Yidi Wang, Cong Liu, Daniel Wong, and Hyoseung Kim. GCAPS: GPU Context-Aware Preemptive Priority-Based Scheduling for Real-Time Tasks. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 14:1-14:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{wang_et_al:LIPIcs.ECRTS.2024.14,
  author =	{Wang, Yidi and Liu, Cong and Wong, Daniel and Kim, Hyoseung},
  title =	{{GCAPS: GPU Context-Aware Preemptive Priority-Based Scheduling for Real-Time Tasks}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{14:1--14:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.14},
  URN =		{urn:nbn:de:0030-drops-203170},
  doi =		{10.4230/LIPIcs.ECRTS.2024.14},
  annote =	{Keywords: Real-time systems, GPU scheduling}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.15
Predictable GPU Sharing in Component-Based Real-Time Systems

Authors: Syed W. Ali, Zelin Tong, Joseph Goh, and James H. Anderson

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
This paper presents a real-time locking protocol whose design was motivated by the goal of enabling safe GPU sharing in time-sliced component-based systems. This locking protocol enables a GPU to be shared concurrently across, and utilized within, isolated components with predictable execution times. It relies on a novel resizing technique where GPU work is dimensioned on-the-fly to run on partitions of an NVIDIA GPU. This technique can be applied to any component that internally utilizes global CPU scheduling. The proposed locking protocol enables increased GPU parallelism and reduces GPU capacity loss with analytically provable benefits.
Cite as

Syed W. Ali, Zelin Tong, Joseph Goh, and James H. Anderson. Predictable GPU Sharing in Component-Based Real-Time Systems. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 15:1-15:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ali_et_al:LIPIcs.ECRTS.2024.15,
  author =	{Ali, Syed W. and Tong, Zelin and Goh, Joseph and Anderson, James H.},
  title =	{{Predictable GPU Sharing in Component-Based Real-Time Systems}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{15:1--15:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.15},
  URN =		{urn:nbn:de:0030-drops-203183},
  doi =		{10.4230/LIPIcs.ECRTS.2024.15},
  annote =	{Keywords: GPU locking protocols, real-time locking protocols, priority-inversion blocking, component-based systems}
}
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