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Language Constructs for Safe Parallel Programming on Multi-Cores
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The last decade has seen the transition from single-core processors to multi-cores and many-cores. This move has by and large shifted the responsibility from chip manufacturers to programmers to keep up with ever-increasing expectations on performance. In the single-core era, improvements in hardware capacity could immediately be leveraged by an application: faster machine - faster program. In the age of the multi-cores, this is no longer the case. Programs must be written in specific ways to utilize available parallel hardware resources.

Programming language support for concurrent and parallel programming is poor in most popular object-oriented programming languages. Shared memory, threads and locks is the most common concurrency model provided. Threads and locks are hard to understand, error-prone and inflexible; they break encapsulation - the very foundation of the object-oriented approach. This makes it hard to break large complex problems into smaller pieces which can be solved independently and composed to make a whole. Ubiquitous parallelism and object-orientation, seemingly, do not match.

Actors, or active objects, have been proposed as a concurrency model better fit for object-oriented programming than threads and locks. Asynchronous message passing between actors each with a logical thread of control preserves encapsulation as objects themselves decide when messages are executed. Unfortunately most implementations of active objects do not prevent sharing of mutable objects across actors. Sharing, whether on purpose or by accident, exposes objects to multiple threads of control, destroying object encapsulation.

In this thesis we show techniques for compiler-enforced isolation of active objects, while allowing sharing and zero-copy communication of mutable data in the cases where it is safe to do so. We also show how the same techniques that enforce isolation can be utilized internal to an active object to allow data race-free parallel message processing and data race-free structured parallel computations. This overcomes the coarse-grained nature of active object parallelism without compromising safety.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. , 105 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1319
Keyword [en]
Programming Languages, Type Systems, Ownership Types, Concurrency, Parallelism, Actors, Active Objects, Structured Parallelism, Data Race-Freedom, Immutability, Uniqueness
National Category
Computer Science
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:uu:diva-266795ISBN: 978-91-554-9413-1 (print)OAI: oai:DiVA.org:uu-266795DiVA: diva2:872118
Public defence
2016-01-18, 2446, ITC, Lägerhyddsvägen 2, hus 2, Uppsala, 13:00 (English)
Opponent
Supervisors
Projects
UPMARC
Available from: 2015-12-17 Created: 2015-11-10 Last updated: 2016-04-18Bibliographically approved
List of papers
1. Ownership, Uniqueness, and Immutability
Open this publication in new window or tab >>Ownership, Uniqueness, and Immutability
2008 (English)In: Lecture Notes in Business Information Processing, ISSN 1865-1348Article in journal (Refereed) Published
Abstract [en]

Programming in an object-oriented language demands a fine balance between flexibility and control. At one level, objects need to interact freely to achieve our implementation goals. At a higher level, architectural constraints that ensure the system can be understood by new developers and can evolve as requirements change must be met. To resolve this tension, researchers have developed type systems expressing ownership and behavioural restrictions such as immutability. This work reports on our consolidation of the resulting discoveries into a single programming language. Our language, Joe 3 , imposes little additional syntactic overhead, yet can encode powerful patterns such as fractional permissions and the reference modes of Flexible Alias Protection.

National Category
Computer Science
Identifiers
urn:nbn:se:uu:diva-266671 (URN)10.1007/978-3-540-69824-1_11 (DOI)
Conference
46th International Conference, TOOLS EUROPE 2008, Zurich, Switzerland, June 30 - July 4, 2008.
Available from: 2015-11-10 Created: 2015-11-10 Last updated: 2016-01-13
2. Minimal Ownership for Active Objects
Open this publication in new window or tab >>Minimal Ownership for Active Objects
2008 (English)In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Computer Science
Identifiers
urn:nbn:se:uu:diva-266793 (URN)10.1007/978-3-540-89330-1_11 (DOI)
Conference
6th Asian Symposium, APLAS 2008, Bangalore, India, December 9-11, 2008
Projects
EU project IST-33826 CREDO
Available from: 2015-11-10 Created: 2015-11-10 Last updated: 2016-04-25
3. Welterweight Java
Open this publication in new window or tab >>Welterweight Java
2010 (English)In: Objects, Models, Components, Patterns / [ed] Vitek, Jan, Berlin: Springer-Verlag , 2010, 97-116 p.Conference paper, (Refereed)
Place, publisher, year, edition, pages
Berlin: Springer-Verlag, 2010
Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 6141
National Category
Computer Science
Identifiers
urn:nbn:se:uu:diva-130897 (URN)10.1007/978-3-642-13953-6_6 (DOI)000286162000006 ()978-3-642-13952-9 (ISBN)
Conference
48th International Conference, TOOLS 2010
Projects
UPMARCFacilitating Concurrent and Parallel Programming in Mainstream Programming Languages
Available from: 2010-09-17 Created: 2010-09-17 Last updated: 2016-01-13Bibliographically approved
4. Multiple Aggregate Entry Points for Ownership Types
Open this publication in new window or tab >>Multiple Aggregate Entry Points for Ownership Types
2012 (English)In: ECOOP 2012 – Object-Oriented Programming, Springer Berlin/Heidelberg, 2012, 156-180 p.Conference paper, (Refereed)
Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2012
Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 7313
National Category
Computer Science
Identifiers
urn:nbn:se:uu:diva-176660 (URN)10.1007/978-3-642-31057-7_8 (DOI)978-3-642-31056-0 (ISBN)
Conference
26th European Conference on Object-Oriented Programming
Projects
UPMARCFacilitating Concurrent and Parallel Programming in Mainstream Programming Languages
Available from: 2012-06-28 Created: 2012-06-21 Last updated: 2016-01-13Bibliographically approved
5. Refined Ownership: Fine-grained controlled internal sharing
Open this publication in new window or tab >>Refined Ownership: Fine-grained controlled internal sharing
2015 (English)In: Formal Methods for Multicore Programming, 2015, Vol. 9104, 179-210 p.Conference paper, (Refereed)
Abstract [en]

Ownership type systems give a strong notion of separation between aggregates. Objects belonging to different owners cannot be aliased, and thus a mutating operation internal to one object is guaranteed to be invisible to another. This naturally facilitates reasoning about correctness on a local scale, but also proves beneficial for coarse-grained parallelism as noninterference between statements touching different objects is easily established. For fine-grained parallelism, ownership types fall short as owner-based disjointness only allows separation of the innards of different aggregates, which is very coarse-grained. Concretely: ownership types can reason about the disjointness of two different data structures, but cannot reason about the internal structure or disjointness within the data structure, without resorting to static and overly constraining measures. For similar reasons, ownership fails to determine internal disjointness of external pointers to objects that share a common owner. In this paper, we introduce the novel notion of refined ownership which overcomes these limitations by allowing precise local reasoning about a group of objects even though they belong to the same external owner. Using refined ownership, we can statically check determinism of parallel operations on tree-shaped substructures of a data structure, including operations on values external to the structure, without imposing any non-local alias restrictions.

Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 9104
National Category
Computer Science
Identifiers
urn:nbn:se:uu:diva-266673 (URN)10.1007/978-3-319-18941-3_5 (DOI)000362511600005 ()978-3-319-18941-3 (ISBN)978-3-319-18940-6 (ISBN)
Conference
15th International School on Formal Methods for the Design of Computer, Communication, and Software Systems; SFM 2015, June 15–19, Bertinoro, Italy
Projects
UPMARCUPSCALE
Available from: 2015-05-07 Created: 2015-11-10 Last updated: 2016-01-13Bibliographically approved

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