8 Search Results for "Agrawal, Kunal"

Document
DOI: 10.4230/LIPIcs.ITP.2024.13
Completeness of Asynchronous Session Tree Subtyping in Coq

Authors: Burak Ekici and Nobuko Yoshida

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract
Multiparty session types (MPST) serve as a foundational framework for formally specifying and verifying message passing protocols. Asynchronous subtyping in MPST allows for typing optimised programs preserving type safety and deadlock freedom under asynchronous interactions where the message order is preserved and sending is non-blocking. The optimisation is obtained by message reordering, which allows for sending messages earlier or receiving them later. Sound subtyping algorithms have been extensively studied and implemented as part of various programming languages and tools including C, Rust and C-MPI. However, formalising all such permutations under sequencing, selection, branching and recursion in session types is an intricate task. Additionally, checking asynchronous subtyping has been proven to be undecidable. This paper introduces the first formalisation of asynchronous subtyping in MPST within the Coq proof assistant. We first decompose session types into session trees that do not involve branching and selection, and then establish a coinductive refinement relation over them to govern subtyping. To showcase our formalisation, we prove example subtyping schemas that appear in the literature, all of which cannot be verified, at the same time, by any of the existing decidable sound algorithms. Additionally, we take the (inductive) negation of the refinement relation from a prior work by Ghilezan et al. [Ghilezan et al., 2023] and re-implement it, significantly reducing the number of rules (from eighteen to eight). We establish the completeness of subtyping with respect to its negation in Coq, addressing the issues concerning the negation rules outlined in the previous work [Ghilezan et al., 2023]. In the formalisation, we use the greatest fixed point of the least fixed point technique, facilitated by the paco library, to define coinductive predicates. We employ parametrised coinduction to prove their properties. The formalisation consists of roughly 10K lines of Coq code, accessible at: https://github.com/ekiciburak/sessionTreeST/tree/itp2024.
Cite as

Burak Ekici and Nobuko Yoshida. Completeness of Asynchronous Session Tree Subtyping in Coq. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 13:1-13:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ekici_et_al:LIPIcs.ITP.2024.13,
  author =	{Ekici, Burak and Yoshida, Nobuko},
  title =	{{Completeness of Asynchronous Session Tree Subtyping in Coq}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{13:1--13:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.13},
  URN =		{urn:nbn:de:0030-drops-207418},
  doi =		{10.4230/LIPIcs.ITP.2024.13},
  annote =	{Keywords: asynchronous multiparty session types, session trees, subtyping, Coq}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2023.3
The Safe and Effective Use of Low-Assurance Predictions in Safety-Critical Systems

Authors: Kunal Agrawal, Sanjoy Baruah, Michael A. Bender, and Alberto Marchetti-Spaccamela

Published in: LIPIcs, Volume 262, 35th Euromicro Conference on Real-Time Systems (ECRTS 2023)

Abstract
The algorithm-design paradigm of algorithms using predictions is explored as a means of incorporating the computations of lower-assurance components (such as machine-learning based ones) into safety-critical systems that must have their correctness validated to very high levels of assurance. The paradigm is applied to two simple example applications that are relevant to the real-time systems community: energy-aware scheduling, and classification using ML-based classifiers in conjunction with more reliable but slower deterministic classifiers. It is shown how algorithms using predictions achieve much-improved performance when the low-assurance computations are correct, at a cost of no more than a slight performance degradation even when they turn out to be completely wrong.
Cite as

Kunal Agrawal, Sanjoy Baruah, Michael A. Bender, and Alberto Marchetti-Spaccamela. The Safe and Effective Use of Low-Assurance Predictions in Safety-Critical Systems. In 35th Euromicro Conference on Real-Time Systems (ECRTS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 262, pp. 3:1-3:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{agrawal_et_al:LIPIcs.ECRTS.2023.3,
  author =	{Agrawal, Kunal and Baruah, Sanjoy and Bender, Michael A. and Marchetti-Spaccamela, Alberto},
  title =	{{The Safe and Effective Use of Low-Assurance Predictions in Safety-Critical Systems}},
  booktitle =	{35th Euromicro Conference on Real-Time Systems (ECRTS 2023)},
  pages =	{3:1--3:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-280-8},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{262},
  editor =	{Papadopoulos, Alessandro V.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2023.3},
  URN =		{urn:nbn:de:0030-drops-180323},
  doi =		{10.4230/LIPIcs.ECRTS.2023.3},
  annote =	{Keywords: Algorithms using predictions, robust scheduling, energy minimization, classification, on-line scheduling}
}
Document
DOI: 10.4230/LIPIcs.FUN.2021.7
1 X 1 Rush Hour with Fixed Blocks Is PSPACE-Complete

Authors: Josh Brunner, Lily Chung, Erik D. Demaine, Dylan Hendrickson, Adam Hesterberg, Adam Suhl, and Avi Zeff

Published in: LIPIcs, Volume 157, 10th International Conference on Fun with Algorithms (FUN 2021) (2020)

Abstract
Consider n²-1 unit-square blocks in an n × n square board, where each block is labeled as movable horizontally (only), movable vertically (only), or immovable - a variation of Rush Hour with only 1 × 1 cars and fixed blocks. We prove that it is PSPACE-complete to decide whether a given block can reach the left edge of the board, by reduction from Nondeterministic Constraint Logic via 2-color oriented Subway Shuffle. By contrast, polynomial-time algorithms are known for deciding whether a given block can be moved by one space, or when each block either is immovable or can move both horizontally and vertically. Our result answers a 15-year-old open problem by Tromp and Cilibrasi, and strengthens previous PSPACE-completeness results for Rush Hour with vertical 1 × 2 and horizontal 2 × 1 movable blocks and 4-color Subway Shuffle.
Cite as

Josh Brunner, Lily Chung, Erik D. Demaine, Dylan Hendrickson, Adam Hesterberg, Adam Suhl, and Avi Zeff. 1 X 1 Rush Hour with Fixed Blocks Is PSPACE-Complete. In 10th International Conference on Fun with Algorithms (FUN 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 157, pp. 7:1-7:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{brunner_et_al:LIPIcs.FUN.2021.7,
  author =	{Brunner, Josh and Chung, Lily and Demaine, Erik D. and Hendrickson, Dylan and Hesterberg, Adam and Suhl, Adam and Zeff, Avi},
  title =	{{1 X 1 Rush Hour with Fixed Blocks Is PSPACE-Complete}},
  booktitle =	{10th International Conference on Fun with Algorithms (FUN 2021)},
  pages =	{7:1--7:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-145-0},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{157},
  editor =	{Farach-Colton, Martin and Prencipe, Giuseppe and Uehara, Ryuhei},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FUN.2021.7},
  URN =		{urn:nbn:de:0030-drops-127681},
  doi =		{10.4230/LIPIcs.FUN.2021.7},
  annote =	{Keywords: puzzles, sliding blocks, PSPACE-hardness}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2020.7
The Safe and Effective Use of Learning-Enabled Components in Safety-Critical Systems

Authors: Kunal Agrawal, Sanjoy Baruah, and Alan Burns

Published in: LIPIcs, Volume 165, 32nd Euromicro Conference on Real-Time Systems (ECRTS 2020)

Abstract
Autonomous systems increasingly use components that incorporate machine learning and other AI-based techniques in order to achieve improved performance. The problem of assuring correctness in safety-critical systems that use such components is considered. A model is proposed in which components are characterized according to both their worst-case and their typical behaviors; it is argued that while safety must be assured under all circumstances, it is reasonable to be concerned with providing a high degree of performance for typical behaviors only. The problem of assuring safety while providing such improved performance is formulated as an optimization problem in which performance under typical circumstances is the objective function to be optimized while safety is a hard constraint that must be satisfied. Algorithmic techniques are applied to derive an optimal solution to this optimization problem. This optimal solution is compared with an alternative approach that optimizes for performance under worst-case conditions, as well as some common-sense heuristics, via simulation experiments on synthetically-generated workloads.
Cite as

Kunal Agrawal, Sanjoy Baruah, and Alan Burns. The Safe and Effective Use of Learning-Enabled Components in Safety-Critical Systems. In 32nd Euromicro Conference on Real-Time Systems (ECRTS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 165, pp. 7:1-7:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{agrawal_et_al:LIPIcs.ECRTS.2020.7,
  author =	{Agrawal, Kunal and Baruah, Sanjoy and Burns, Alan},
  title =	{{The Safe and Effective Use of Learning-Enabled Components in Safety-Critical Systems}},
  booktitle =	{32nd Euromicro Conference on Real-Time Systems (ECRTS 2020)},
  pages =	{7:1--7:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-152-8},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{165},
  editor =	{V\"{o}lp, Marcus},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2020.7},
  URN =		{urn:nbn:de:0030-drops-123704},
  doi =		{10.4230/LIPIcs.ECRTS.2020.7},
  annote =	{Keywords: Learning-enabled components (LECs), Safety-critical systems, Typical analysis, Performance optimization, Run-time monitoring}
}
Document
DOI: 10.4230/DagRep.9.3.1
Analysis, Design, and Control of Predictable Interconnected Systems (Dagstuhl Seminar 19101)

Authors: Kunal Agrawal, Enrico Bini, and Giovanni Stea

Published in: Dagstuhl Reports, Volume 9, Issue 3 (2019)

Abstract
We call "Interconnected Systems" any collection of systems distributed over a metric space whose behavior is influenced by its neighborhood. Examples of interconnected systems exist at very different scales: different cores over the same silicon, different sub-systems in vehicles, communicating nodes over either a physical (e.g., optical) network, or - more recently - virtualized network. Examples also exist in contexts which are not related to computing or communication. Smart Grids (of energy production, distribution, and consumption) and Intelligent Transportation Systems are just two notable examples. The common characteristic among all these examples is the presence of a spatially distributed demand of resources (energy, computing, communication bandwidth, etc.) which needs to be matched with a spatially distributed supply. Often times demands and availability of resources of different types (e.g., computing and link bandwidth in virtualized network environments) need to be matched simultaneously. Time predictability is a key requirement for above systems. Despite this, the strong market pressure has often led to ``quick and dirty'' best-effort solutions, which make it extremely challenging to predict the behavior of such systems. Research communities have developed formal theories for predictability which are specialized to each application domain or type of resource (e.g., schedulability analysis for real-time systems or network calculus for communication systems). However, the emerging application domains (virtualized networks, cyber-physical systems, etc.) clearly require a unified, holistic approach. By leveraging the expertise, vision and interactions of scientists that have addressed predictability in different areas, the proposed seminar aims at constructing a common ground for the theory supporting the analysis, the design, and the control of predictable interconnected systems.
Cite as

Kunal Agrawal, Enrico Bini, and Giovanni Stea. Analysis, Design, and Control of Predictable Interconnected Systems (Dagstuhl Seminar 19101). In Dagstuhl Reports, Volume 9, Issue 3, pp. 1-15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@Article{agrawal_et_al:DagRep.9.3.1,
  author =	{Agrawal, Kunal and Bini, Enrico and Stea, Giovanni},
  title =	{{Analysis, Design, and Control of Predictable Interconnected Systems (Dagstuhl Seminar 19101)}},
  pages =	{1--15},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2019},
  volume =	{9},
  number =	{3},
  editor =	{Agrawal, Kunal and Bini, Enrico and Stea, Giovanni},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.9.3.1},
  URN =		{urn:nbn:de:0030-drops-112882},
  doi =		{10.4230/DagRep.9.3.1},
  annote =	{Keywords: distributed resource management, network calculus, real-time systems}
}
Document
DOI: 10.4230/LITES-v006-i001-a005
Elastic Scheduling for Parallel Real-Time Systems

Authors: James Orr, Chris Gill, Kunal Agrawal, Jing Li, and Sanjoy Baruah

Published in: LITES, Volume 6, Issue 1 (2019). Leibniz Transactions on Embedded Systems, Volume 6, Issue 1

Abstract
The elastic task model was introduced by Buttazzo et al.~in order to represent recurrent real-time workloads executing upon uniprocessor platforms that are somewhat flexible with regards to timing constraints.  In this work, we propose an extension of this model and apply it to represent recurrent real-time workloads that exhibit internal parallelism and are executed on multiprocessor platforms. In our proposed extension, the elasticity coefficient - the quantitative measure of a task's elasticity that was introduced in the model proposed by Buttazzo et al. - is interpreted in the same manner as in the original (sequential) model. Hence, system developers who are familiar with the elastic task model in the uniprocessor context may use our more general model as they had previously done, now for real-time tasks whose computational demands require them to utilize more than one processor.
Cite as

James Orr, Chris Gill, Kunal Agrawal, Jing Li, and Sanjoy Baruah. Elastic Scheduling for Parallel Real-Time Systems. In LITES, Volume 6, Issue 1 (2019). Leibniz Transactions on Embedded Systems, Volume 6, Issue 1, pp. 05:1-05:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@Article{orr_et_al:LITES-v006-i001-a005,
  author =	{Orr, James and Gill, Chris and Agrawal, Kunal and Li, Jing and Baruah, Sanjoy},
  title =	{{Elastic Scheduling for Parallel Real-Time Systems}},
  journal =	{Leibniz Transactions on Embedded Systems},
  pages =	{05:1--05:14},
  ISSN =	{2199-2002},
  year =	{2019},
  volume =	{6},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES-v006-i001-a005},
  doi =		{10.4230/LITES-v006-i001-a005},
  annote =	{Keywords: Parallel real-time tasks, multiprocessor federated scheduling, elasticity coefficient}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2018.5
A Measurement-Based Model for Parallel Real-Time Tasks

Authors: Kunal Agrawal and Sanjoy Baruah

Published in: LIPIcs, Volume 106, 30th Euromicro Conference on Real-Time Systems (ECRTS 2018)

Abstract
Under the federated paradigm of multiprocessor scheduling, a set of processors is reserved for the exclusive use of each real-time task. If tasks are characterized very conservatively (as is typical in safety-critical systems), it is likely that most invocations of the task will have computational demand far below the worst-case characterization, and could have been scheduled correctly upon far fewer processors than were assigned to it assuming the worst-case characterization of its run-time behavior. Provided we could safely determine during run-time when all the processors are going to be needed, for the rest of the time the unneeded processors could be idled in low-energy "sleep" mode, or used for executing non-real time work in the background. In this paper we propose a model for representing parallelizable real-time tasks in a manner that permits us to do so. Our model does not require us to have fine-grained knowledge of the internal structure of the code represented by the task; rather, it characterizes each task by a few parameters that are obtained by repeatedly executing the code under different conditions and measuring the run-times.
Cite as

Kunal Agrawal and Sanjoy Baruah. A Measurement-Based Model for Parallel Real-Time Tasks. In 30th Euromicro Conference on Real-Time Systems (ECRTS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 106, pp. 5:1-5:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{agrawal_et_al:LIPIcs.ECRTS.2018.5,
  author =	{Agrawal, Kunal and Baruah, Sanjoy},
  title =	{{A Measurement-Based Model for Parallel Real-Time Tasks}},
  booktitle =	{30th Euromicro Conference on Real-Time Systems (ECRTS 2018)},
  pages =	{5:1--5:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-075-0},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{106},
  editor =	{Altmeyer, Sebastian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2018.5},
  URN =		{urn:nbn:de:0030-drops-89999},
  doi =		{10.4230/LIPIcs.ECRTS.2018.5},
  annote =	{Keywords: multiprocessor federated scheduling, parallel tasks, work and span, mixed criticality}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2018.11
Intractability Issues in Mixed-Criticality Scheduling

Authors: Kunal Agrawal and Sanjoy Baruah

Published in: LIPIcs, Volume 106, 30th Euromicro Conference on Real-Time Systems (ECRTS 2018)

Abstract
In seeking to develop mixed-criticality scheduling algorithms, one encounters challenges arising from two sources. First, mixed-criticality scheduling is an inherently an on-line problem in that scheduling decisions must be made without access to all the information that is needed to make such decisions optimally - such information is only revealed over time. Second, many fundamental mixed-criticality schedulability analysis problems are computationally intractable - NP-hard in the strong sense - but we desire to solve these problems using algorithms with polynomial or pseudo-polynomial running time. While these two aspects of intractability are traditionally studied separately in the theoretical computer science literature, they have been considered in an integrated fashion in mixed-criticality scheduling theory. In this work we seek to separate out the effects of being inherently on-line, and being computationally intractable, on the overall intractability of mixed-criticality scheduling problems. Speedup factor is widely used as quantitative metric of the effectiveness of mixed-criticality scheduling algorithms; there has recently been a bit of a debate regarding the appropriateness of doing so. We provide here some additional perspective on this matter: we seek to better understand its appropriateness as well as its limitations in this regard by examining separately how the on-line nature of some mixed-criticality problems, and their computational complexity, contribute to the speedup factors of two widely-studied mixed-criticality scheduling algorithms.
Cite as

Kunal Agrawal and Sanjoy Baruah. Intractability Issues in Mixed-Criticality Scheduling. In 30th Euromicro Conference on Real-Time Systems (ECRTS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 106, pp. 11:1-11:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{agrawal_et_al:LIPIcs.ECRTS.2018.11,
  author =	{Agrawal, Kunal and Baruah, Sanjoy},
  title =	{{Intractability Issues in Mixed-Criticality Scheduling}},
  booktitle =	{30th Euromicro Conference on Real-Time Systems (ECRTS 2018)},
  pages =	{11:1--11:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-075-0},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{106},
  editor =	{Altmeyer, Sebastian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2018.11},
  URN =		{urn:nbn:de:0030-drops-89925},
  doi =		{10.4230/LIPIcs.ECRTS.2018.11},
  annote =	{Keywords: mixed-criticality scheduling, speedup factor, competitive ratio, approximation ratio, NP-completeness results, sporadic tasks}
}
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