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Efficient logic variables for distributed computing
Swedish Institute of Computer Science.ORCID iD: 0000-0002-6718-0144
Dept. of Comp. Sci. and Engineering, Univ. Catholique de Louvain.
Swedish Institute of Computer Science.
German Research Center For Artifcial Intelligence.
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1999 (English)In: ACM Transactions on Programming Languages and Systems, ISSN 0164-0925, E-ISSN 1558-4593, Vol. 21, no 3, 569-626 p.Article in journal (Refereed) Published
Abstract [en]

We define a practical algorithm for distributed rational tree unification and prove its correctness in both the off-line and on-line cases. We derive the distributed algorithm from a centralized one, showing clearly the trade-offs between local and distributed execution. The algorithm is used to realize logic variables in the Mozart Programming System, which implements the Oz language (see Oz appears to the programmer as a concurrent object-oriented language with dataflow synchronization Logic variables implement the dataflow behavior. We show that logic variables can easily be added to the more restricted models of Java and ML, thus providing an alternative way to do concurrent programming in these languages. We present common distributed programming idioms in a network-transparent way using logic variables. We show that in common cases the algorithm maintains the same message latency as explicit message passing. In addition, it is able to handle uncommon cases that arise from the properties of latency tolerance and third-party independence. This is evidence that using logic variables in distributed computing is beneficial at both the system and language levels. At the system level, they improve latency tolerance and third-party independence. At the language level, they help make network-transparent distribution practical.

Place, publisher, year, edition, pages
1999. Vol. 21, no 3, 569-626 p.
Keyword [en]
algorithms, languages, theory, distributed algorithms, Oz, Mozart
National Category
Computer and Information Science
URN: urn:nbn:se:kth:diva-24876ISI: 000083593400005OAI: diva2:353700
QC 20100928Available from: 2010-09-28 Created: 2010-09-28 Last updated: 2010-09-28Bibliographically approved
In thesis
1. The design philosophy of distributed programming systems: the Mozart experience
Open this publication in new window or tab >>The design philosophy of distributed programming systems: the Mozart experience
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Distributed programming is usually considered both difficult and inherently different from concurrent centralized programming. It is thought that the distributed programming systems that we ultimately deploy, in the future, when we've worked out all the details, will require a very different programming model and will even need to be evaluated by new criteria.

The Mozart Programming System, described in this thesis, demonstrates that this need not be the case. It is shown that, with a good system design, distributed programming can be seen as an extended form of concurrent programming. This is from the programmer's point-of-view; under the hood the design and implementation will necessarily be more complex. We relate the Mozart system with the classical transparencies of distributed systems. We show that some of these are inherently on the application level, while as Mozart demonstrates, others can and should be dealt with on the language/system level.

The extensions to the programming model, given the right concurrent programming base, are mainly concerned with non-functional properties of programs. The models and tuning facilities for failure and performance need to take latency, bandwidth, and partial failure into account. Other than that there need not be any difference between concurrent programming and distributed programming.

The Mozart Programming System is based on the concurrent programming language Oz, which integrates, in a coherent way, all three known concurrency or thread-interaction models. These are message-passing (like Erlang), shared objects (like Java with threads) and shared data-flow variables. The Mozart design philosophy is thus applicable over the entire range of concurrent programming languages/systems. We have extracted from the experience with Mozart a number of principles and properties that are applicable to the design and implementation of all (general-purpose) distributed programming systems.

The full range of the design and implementation issues behind Mozart are presented. This includes a description of the consistency protocols that make transparency possible for the full language, including distributed objects and distributed data-flow variables.

Mozart is extensively compared with other approaches to distributed programming, in general, and to other language-based distributed programming systems, in particular

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 347 p.
Trita-IMIT. LECS, ISSN 1651-4076 ; 05:04
National Category
Computer and Information Science
urn:nbn:se:kth:diva-232 (URN)
Public defence
2005-06-03, Sal C1, KTH-Electrum, Kista, 13:00
QC 20100928Available from: 2005-05-30 Created: 2005-05-30 Last updated: 2010-09-28Bibliographically approved

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