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Documents authored by Wrigstad, Tobias

Document
Artifact
DOI: 10.4230/DARTS.6.2.19
Implementation of SHAPES Case Studies (Artifact)

Authors: Alexandros Tasos, Juliana Franco, Sophia Drossopoulou, Tobias Wrigstad, and Susan Eisenbach

Published in: DARTS, Volume 6, Issue 2, Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
Our main paper presents {SHAPES}, a language extension which offers developers fine-grained control over the placement of data in memory, whilst retaining both memory safety and object abstraction via pooling and clustering. As part of the development of {SHAPES}, we wanted to investigate the usefulness of the concepts {SHAPES} brings to the table. To that extent, we implemented five such case studies. This publication provides the corresponding code and instructions on how to run these case studies and derive the results we provide.
Cite as

Alexandros Tasos, Juliana Franco, Sophia Drossopoulou, Tobias Wrigstad, and Susan Eisenbach. Implementation of SHAPES Case Studies (Artifact). In Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020). Dagstuhl Artifacts Series (DARTS), Volume 6, Issue 2, pp. 19:1-19:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@Article{tasos_et_al:DARTS.6.2.19,
  author =	{Tasos, Alexandros and Franco, Juliana and Drossopoulou, Sophia and Wrigstad, Tobias and Eisenbach, Susan},
  title =	{{Implementation of SHAPES Case Studies (Artifact)}},
  pages =	{19:1--19:3},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2020},
  volume =	{6},
  number =	{2},
  editor =	{Tasos, Alexandros and Franco, Juliana and Drossopoulou, Sophia and Wrigstad, Tobias and Eisenbach, Susan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.6.2.19},
  URN =		{urn:nbn:de:0030-drops-132167},
  doi =		{10.4230/DARTS.6.2.19},
  annote =	{Keywords: Cache utilisation, Data representation, Memory safety}
}
Document
SCICO Journal-first
DOI: 10.4230/LIPIcs.ECOOP.2020.31
Reshape Your Layouts, Not Your Programs: A Safe Language Extension for Better Cache Locality (SCICO Journal-first)

Authors: Alexandros Tasos, Juliana Franco, Sophia Drossopoulou, Tobias Wrigstad, and Susan Eisenbach

Published in: LIPIcs, Volume 166, 34th European Conference on Object-Oriented Programming (ECOOP 2020)

Abstract
The vast gap between CPU and RAM speed means that on modern architectures, developers need to carefully consider data placement in memory to exploit spatial and temporal cache locality and use CPU caches effectively. To that extent, developers have devised various strategies regarding data placement; for objects that should be close in memory, a contiguous pool of objects is allocated and then new instances are constructed inside it; an array of objects is clustered into multiple arrays, each holding the values of a specific field of the objects. Such data placements, however, have to be performed manually, hence readability, maintainability, memory safety, and key OO concepts such as encapsulation and object identity need to be sacrificed and the business logic needs to be modified accordingly. We propose a language extension, SHAPES, which aims to offer developers high-level fine-grained control over data placement, whilst retaining memory safety and the look-and-feel of OO. SHAPES extends an OO language with the concepts of pools and layouts: Developers declare pools that contain objects of a specific type and specify the pool’s layout. A layout specifies how objects in a pool are laid out in memory. That is, it dictates how the values of the fields of the pool’s objects are grouped together into clusters. Objects stored in pools behave identically to ordinary, standalone objects; the type system allows the code to be oblivious to the layout being used. This means that the business logic is completely decoupled from any placement concerns and the developer need not deviate from the spirit of OO to better utilise the cache. In this paper, we present the features of SHAPES, as well as the design rationale behind each feature. We then showcase the merit of SHAPES through a sequence of case studies; we claim that, compared to the manual pooling and clustering of objects, we can observe improvement in readability and maintainability, and comparable (i.e., on par or better) performance. We also present SHAPES^h, an OO calculus which models the SHAPES ideas, we formalise the type system, and prove soundness. The SHAPES^h type system uses ideas from Ownership Types [Clarke et al., 2013] and Java Generics [Gosling et al., 2014]: In SHAPES^h, pools are part of the types; SHAPES^h class and type definitions are enriched with pool parameters. Moreover, class pool parameters are enriched with bounds, which is what allows the business logic of SHAPES to be oblivious to the layout being used. SHAPES^h types also enforce pool uniformity and homogeneity. A pool is uniform if it contains objects of the same class only; a pool is homogeneous if the corresponding fields of all its objects point to objects in the same pool. These properties allow for more efficient implementation. For performance considerations, we also designed SHAPES^l, an untyped, unsafe low-level language with no explicit support for objects or pools. We argue that it is possible to translate SHAPES^l into existing low-level intermediate representations, such as LLVM [Lattner and Adve, 2004], present the translation of SHAPES^h into SHAPES^l, and show its soundness. Thus, we expect SHAPES to offer developers more fine-grained control over data placement, without sacrificing memory safety or the OO look-and-feel.
Cite as

Alexandros Tasos, Juliana Franco, Sophia Drossopoulou, Tobias Wrigstad, and Susan Eisenbach. Reshape Your Layouts, Not Your Programs: A Safe Language Extension for Better Cache Locality (SCICO Journal-first). In 34th European Conference on Object-Oriented Programming (ECOOP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 166, pp. 31:1-31:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{tasos_et_al:LIPIcs.ECOOP.2020.31,
  author =	{Tasos, Alexandros and Franco, Juliana and Drossopoulou, Sophia and Wrigstad, Tobias and Eisenbach, Susan},
  title =	{{Reshape Your Layouts, Not Your Programs: A Safe Language Extension for Better Cache Locality}},
  booktitle =	{34th European Conference on Object-Oriented Programming (ECOOP 2020)},
  pages =	{31:1--31:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-154-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{166},
  editor =	{Hirschfeld, Robert and Pape, Tobias},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2020.31},
  URN =		{urn:nbn:de:0030-drops-131887},
  doi =		{10.4230/LIPIcs.ECOOP.2020.31},
  annote =	{Keywords: Cache utilisation, Data representation, Memory safety}
}
Document
Artifact
DOI: 10.4230/DARTS.5.2.1
Godot: All the Benefits of Implicit and Explicit Futures (Artifact)

Authors: Kiko Fernandez-Reyes, Dave Clarke, Ludovic Henrio, Einar Broch Johnsen, and Tobias Wrigstad

Published in: DARTS, Volume 5, Issue 2, Special Issue of the 33rd European Conference on Object-Oriented Programming (ECOOP 2019)

Abstract
This artifact contains an implementation of data-flow futures in terms of control-flow futures, in the Scala language. In the implementation, we show microbenchmarks that solve the three identified problems from the paper: 1) The Type Proliferation Problem, 2) The Fulfilment Observation Problem, and 3) The Future Proliferation Problem There are also detailed instructions on design decisions that differ from the formal semantics and restrictions on the limits of how much can be encoded in the Scala language. We provide examples, e.g., creation of a proxy service using data-flow futures, as well as tests that exercise different parts of the type system.
Cite as

Kiko Fernandez-Reyes, Dave Clarke, Ludovic Henrio, Einar Broch Johnsen, and Tobias Wrigstad. Godot: All the Benefits of Implicit and Explicit Futures (Artifact). In Special Issue of the 33rd European Conference on Object-Oriented Programming (ECOOP 2019). Dagstuhl Artifacts Series (DARTS), Volume 5, Issue 2, pp. 1:1-1:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@Article{fernandezreyes_et_al:DARTS.5.2.1,
  author =	{Fernandez-Reyes, Kiko and Clarke, Dave and Henrio, Ludovic and Johnsen, Einar Broch and Wrigstad, Tobias},
  title =	{{Godot: All the Benefits of Implicit and Explicit Futures}},
  pages =	{1:1--1:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2019},
  volume =	{5},
  number =	{2},
  editor =	{Fernandez-Reyes, Kiko and Clarke, Dave and Henrio, Ludovic and Johnsen, Einar Broch and Wrigstad, Tobias},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.5.2.1},
  URN =		{urn:nbn:de:0030-drops-107786},
  doi =		{10.4230/DARTS.5.2.1},
  annote =	{Keywords: Futures, Concurrency, Type Systems, Formal Semantics}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2019.2
Godot: All the Benefits of Implicit and Explicit Futures

Authors: Kiko Fernandez-Reyes, Dave Clarke, Ludovic Henrio, Einar Broch Johnsen, and Tobias Wrigstad

Published in: LIPIcs, Volume 134, 33rd European Conference on Object-Oriented Programming (ECOOP 2019)

Abstract
Concurrent programs often make use of futures, handles to the results of asynchronous operations. Futures provide means to communicate not yet computed results, and simplify the implementation of operations that synchronise on the result of such asynchronous operations. Futures can be characterised as implicit or explicit, depending on the typing discipline used to type them. Current future implementations suffer from "future proliferation", either at the type-level or at run-time. The former adds future type wrappers, which hinders subtype polymorphism and exposes the client to the internal asynchronous communication architecture. The latter increases latency, by traversing nested future structures at run-time. Many languages suffer both kinds. Previous work offer partial solutions to the future proliferation problems; in this paper we show how these solutions can be integrated in an elegant and coherent way, which is more expressive than either system in isolation. We describe our proposal formally, and state and prove its key properties, in two related calculi, based on the two possible families of future constructs (data-flow futures and control-flow futures). The former relies on static type information to avoid unwanted future creation, and the latter uses an algebraic data type with dynamic checks. We also discuss how to implement our new system efficiently.
Cite as

Kiko Fernandez-Reyes, Dave Clarke, Ludovic Henrio, Einar Broch Johnsen, and Tobias Wrigstad. Godot: All the Benefits of Implicit and Explicit Futures. In 33rd European Conference on Object-Oriented Programming (ECOOP 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 134, pp. 2:1-2:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{fernandezreyes_et_al:LIPIcs.ECOOP.2019.2,
  author =	{Fernandez-Reyes, Kiko and Clarke, Dave and Henrio, Ludovic and Johnsen, Einar Broch and Wrigstad, Tobias},
  title =	{{Godot: All the Benefits of Implicit and Explicit Futures}},
  booktitle =	{33rd European Conference on Object-Oriented Programming (ECOOP 2019)},
  pages =	{2:1--2:28},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-111-5},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{134},
  editor =	{Donaldson, Alastair F.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2019.2},
  URN =		{urn:nbn:de:0030-drops-107949},
  doi =		{10.4230/LIPIcs.ECOOP.2019.2},
  annote =	{Keywords: Futures, Concurrency, Type Systems, Formal Semantics}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2017.6
Relaxed Linear References for Lock-free Data Structures

Authors: Elias Castegren and Tobias Wrigstad

Published in: LIPIcs, Volume 74, 31st European Conference on Object-Oriented Programming (ECOOP 2017)

Abstract
Linear references are guaranteed to be free from aliases. This is a strong property that simplifies reasoning about programs and enables powerful optimisations, but it is also a property that is too strong for many applications. Notably, lock-free algorithms, which implement protocols that ensure safe, non-blocking concurrent access to data structures, are generally not typable with linear references because they rely on aliasing to achieve lock-freedom. This paper presents LOLCAT, a type system with a relaxed notion of linearity that allows an unbounded number of aliases to an object as long as at most one alias at a time owns the right to access the contents of the object. This ownership can be transferred between aliases, but can never be duplicated. types are powerful enough to type several lock-free data structures and give a compile-time guarantee of absence of data-races when accessing owned data. In particular, LOLCAT is able to assign types to the CAS (compare and swap) primitive that precisely describe how ownership is transferred across aliases, possibly across different threads. The paper introduces LOLCAT through a sound core procedural calculus, and shows how LOLCAT can be applied to three fundamental lock-free data structures. It also discusses a prototype implementation which integrates LOLCAT with an object-oriented programming language.
Cite as

Elias Castegren and Tobias Wrigstad. Relaxed Linear References for Lock-free Data Structures. In 31st European Conference on Object-Oriented Programming (ECOOP 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 74, pp. 6:1-6:32, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{castegren_et_al:LIPIcs.ECOOP.2017.6,
  author =	{Castegren, Elias and Wrigstad, Tobias},
  title =	{{Relaxed Linear References for Lock-free Data Structures}},
  booktitle =	{31st European Conference on Object-Oriented Programming (ECOOP 2017)},
  pages =	{6:1--6:32},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-035-4},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{74},
  editor =	{M\"{u}ller, Peter},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2017.6},
  URN =		{urn:nbn:de:0030-drops-72670},
  doi =		{10.4230/LIPIcs.ECOOP.2017.6},
  annote =	{Keywords: Type systems, Concurrency, Lock-free programming}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2016.5
Reference Capabilities for Concurrency Control

Authors: Elias Castegren and Tobias Wrigstad

Published in: LIPIcs, Volume 56, 30th European Conference on Object-Oriented Programming (ECOOP 2016)

Abstract
The proliferation of shared mutable state in object-oriented programming complicates software development as two seemingly unrelated operations may interact via an alias and produce unexpected results. In concurrent programming this manifests itself as data-races. Concurrent object-oriented programming further suffers from the fact that code that warrants synchronisation cannot easily be distinguished from code that does not. The burden is placed solely on the programmer to reason about alias freedom, sharing across threads and side-effects to deduce where and when to apply concurrency control, without inadvertently blocking parallelism. This paper presents a reference capability approach to concurrent and parallel object-oriented programming where all uses of aliases are guaranteed to be data-race free. The static type of an alias describes its possible sharing without using explicit ownership or effect annotations. Type information can express non-interfering deterministic parallelism without dynamic concurrency control, thread-locality, lock-based schemes, and guarded-by relations giving multi-object atomicity to nested data structures. Unification of capabilities and traits allows trait-based reuse across multiple concurrency scenarios with minimal code duplication. The resulting system brings together features from a wide range of prior work in a unified way.
Cite as

Elias Castegren and Tobias Wrigstad. Reference Capabilities for Concurrency Control. In 30th European Conference on Object-Oriented Programming (ECOOP 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 56, pp. 5:1-5:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{castegren_et_al:LIPIcs.ECOOP.2016.5,
  author =	{Castegren, Elias and Wrigstad, Tobias},
  title =	{{Reference Capabilities for Concurrency Control}},
  booktitle =	{30th European Conference on Object-Oriented Programming (ECOOP 2016)},
  pages =	{5:1--5:26},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-014-9},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{56},
  editor =	{Krishnamurthi, Shriram and Lerner, Benjamin S.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2016.5},
  URN =		{urn:nbn:de:0030-drops-60998},
  doi =		{10.4230/LIPIcs.ECOOP.2016.5},
  annote =	{Keywords: Type systems, Capabilities, Traits, Concurrency, Object-Oriented}
}
Document
DOI: 10.4230/DagSemProc.09301.3
Minimal Ownership for Active Objects

Authors: David Clarke, Tobias Wrigstad, Johan Ostlund, and Einar Broch Johnsen

Published in: Dagstuhl Seminar Proceedings, Volume 9301, Typing, Analysis and Verification of Heap-Manipulating Programs (2010)

Abstract
Active objects offer a structured approach to concurrency, encapsulating both unshared state and a thread of control. For efficient data transfer, data should be passed by reference whenever possible, but this introduces aliasing and undermines the validity of the active objects. This paper proposes a minimal variant of ownership types that preserves the required race freedom invariant yet enables data transfer by reference between active objects (that is, without copying) in many cases, and a cheap clone operation where copying is necessary. Our approach is general and should be adaptable to several existing active object systems.
Cite as

David Clarke, Tobias Wrigstad, Johan Ostlund, and Einar Broch Johnsen. Minimal Ownership for Active Objects. In Typing, Analysis and Verification of Heap-Manipulating Programs. Dagstuhl Seminar Proceedings, Volume 9301, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2010)

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@InProceedings{clarke_et_al:DagSemProc.09301.3,
  author =	{Clarke, David and Wrigstad, Tobias and Ostlund, Johan and Johnsen, Einar Broch},
  title =	{{Minimal Ownership for Active Objects}},
  booktitle =	{Typing, Analysis and Verification of Heap-Manipulating Programs},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2010},
  volume =	{9301},
  editor =	{Peter O'Hearn and Arnd Poetzsch-Heffter and Mooly Sagiv},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.09301.3},
  URN =		{urn:nbn:de:0030-drops-24379},
  doi =		{10.4230/DagSemProc.09301.3},
  annote =	{Keywords: Ownership, concurrency, uniqueness, active objects}
}
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