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Documents authored by Das, Ankush

Document
DOI: 10.4230/LIPIcs.CONCUR.2020.13
Session Types with Arithmetic Refinements

Authors: Ankush Das and Frank Pfenning

Published in: LIPIcs, Volume 171, 31st International Conference on Concurrency Theory (CONCUR 2020)

Abstract
Session types statically prescribe bidirectional communication protocols for message-passing processes. However, simple session types cannot specify properties beyond the type of exchanged messages. In this paper we extend the type system by using index refinements from linear arithmetic capturing intrinsic attributes of data structures and algorithms. We show that, despite the decidability of Presburger arithmetic, type equality and therefore also subtyping and type checking are now undecidable, which stands in contrast to analogous dependent refinement type systems from functional languages. We also present a practical, but incomplete algorithm for type equality, which we have used in our implementation of Rast, a concurrent session-typed language with arithmetic index refinements as well as ergometric and temporal types. Moreover, if necessary, the programmer can propose additional type bisimulations that are smoothly integrated into the type equality algorithm.
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Ankush Das and Frank Pfenning. Session Types with Arithmetic Refinements. In 31st International Conference on Concurrency Theory (CONCUR 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 171, pp. 13:1-13:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{das_et_al:LIPIcs.CONCUR.2020.13,
  author =	{Das, Ankush and Pfenning, Frank},
  title =	{{Session Types with Arithmetic Refinements}},
  booktitle =	{31st International Conference on Concurrency Theory (CONCUR 2020)},
  pages =	{13:1--13:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-160-3},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{171},
  editor =	{Konnov, Igor and Kov\'{a}cs, Laura},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2020.13},
  URN =		{urn:nbn:de:0030-drops-128252},
  doi =		{10.4230/LIPIcs.CONCUR.2020.13},
  annote =	{Keywords: Session Types, Refinement Types, Type Equality}
}
Document
System Description
DOI: 10.4230/LIPIcs.FSCD.2020.33
Rast: Resource-Aware Session Types with Arithmetic Refinements (System Description)

Authors: Ankush Das and Frank Pfenning

Published in: LIPIcs, Volume 167, 5th International Conference on Formal Structures for Computation and Deduction (FSCD 2020)

Abstract
Traditional session types prescribe bidirectional communication protocols for concurrent computations, where well-typed programs are guaranteed to adhere to the protocols. Recent work has extended session types with refinements from linear arithmetic, capturing intrinsic properties of processes and data. These refinements then play a central role in describing sequential and parallel complexity bounds on session-typed programs. The Rast language and system provide an open-source implementation of session-typed concurrent programs extended with arithmetic refinements as well as ergometric and temporal types to capture work and span of program execution. Type checking relies on Cooper’s algorithm for quantifier elimination in Presburger arithmetic with a few significant optimizations, and a heuristic extension to nonlinear constraints. Rast furthermore includes a reconstruction engine so that most program constructs pertaining the layers of refinements and resources are inserted automatically. We provide a variety of examples to demonstrate the expressivity of the language.
Cite as

Ankush Das and Frank Pfenning. Rast: Resource-Aware Session Types with Arithmetic Refinements (System Description). In 5th International Conference on Formal Structures for Computation and Deduction (FSCD 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 167, pp. 33:1-33:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{das_et_al:LIPIcs.FSCD.2020.33,
  author =	{Das, Ankush and Pfenning, Frank},
  title =	{{Rast: Resource-Aware Session Types with Arithmetic Refinements}},
  booktitle =	{5th International Conference on Formal Structures for Computation and Deduction (FSCD 2020)},
  pages =	{33:1--33:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-155-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{167},
  editor =	{Ariola, Zena M.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2020.33},
  URN =		{urn:nbn:de:0030-drops-123558},
  doi =		{10.4230/LIPIcs.FSCD.2020.33},
  annote =	{Keywords: Session Types, Resource Analysis, Refinement Types}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2017.40
On Petri Nets with Hierarchical Special Arcs

Authors: S. Akshay, Supratik Chakraborty, Ankush Das, Vishal Jagannath, and Sai Sandeep

Published in: LIPIcs, Volume 85, 28th International Conference on Concurrency Theory (CONCUR 2017)

Abstract
We investigate the decidability of termination, reachability, coverability and deadlock-freeness of Petri nets endowed with a hierarchy of places, and with inhibitor arcs, reset arcs and transfer arcs that respect this hierarchy. We also investigate what happens when we have a mix of these special arcs, some of which respect the hierarchy, while others do not. We settle the decidability status of the above four problems for all combinations of hierarchy, inhibitor, reset and transfer arcs, except the termination problem for two combinations. For both these combinations, we show that deciding termination is as hard as deciding the positivity problem on linear recurrence sequences -- a long-standing open problem.
Cite as

S. Akshay, Supratik Chakraborty, Ankush Das, Vishal Jagannath, and Sai Sandeep. On Petri Nets with Hierarchical Special Arcs. In 28th International Conference on Concurrency Theory (CONCUR 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 85, pp. 40:1-40:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{akshay_et_al:LIPIcs.CONCUR.2017.40,
  author =	{Akshay, S. and Chakraborty, Supratik and Das, Ankush and Jagannath, Vishal and Sandeep, Sai},
  title =	{{On Petri Nets with Hierarchical Special Arcs}},
  booktitle =	{28th International Conference on Concurrency Theory (CONCUR 2017)},
  pages =	{40:1--40:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-048-4},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{85},
  editor =	{Meyer, Roland and Nestmann, Uwe},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2017.40},
  URN =		{urn:nbn:de:0030-drops-78026},
  doi =		{10.4230/LIPIcs.CONCUR.2017.40},
  annote =	{Keywords: Petri Nets, Hierarchy, Reachability, Coverability, Termination, Positivity}
}
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