An Implementation of the Object-Oriented Concurrent Programming Language SINA

SINA is an object-oriented language for distributed and concurrent programming. The primary focus of this paper is on the object-oriented concurrent programming mechanisms of SINA and their implementation. This paper presents the SINA constructs for concurrent programming and inter-object communication, some illustrative examples and a message-based implementation model for SINA that we have used in our current implementation

Practical Condition Synchronization for Transactional Memory

Few transactional memory implementations allow for condition synchronization among transactions. The problems are many, most notably the lack of consensus about a single appropriate linguistic construct, and the lack of mechanisms that are compatible with hardware transactional memory. In this thesis, we introduce a broadly useful mechanism for supporting condition synchronization among transactions. Our mechanism supports a number of linguistic constructs for coordinating transactions, and does so without introducing overhead on in-flight hardware transactions. Experiments show that our mechanisms work well, and that the diversity of linguistic constructs allows programmers to chose the technique that is best suited to a particular application

Klassische Kommunikations- und Koordinationsmodelle

Bei der Betrachtung von Multi-Agenten-Systemen (MAS) als Teilbereich der Verteilten Künstlichen Intelligenz treten Probleme zutage, die der klassischen Informatik nicht unbekannt sind. Im folgenden werden bekannte klassische Verfahren zur Kommunikation und Koordination in Verteilten Systemen wie sie in Verteilten Betriebssystemen, in Verteilten Programmiersprachen und in Verteilten Datenbanksystemen zur Anwendung kommen, vorgestellt. Die Verwendbarkeit dieser Methoden im Rahmen der Aufgabenstellung des Projektes AKA-MOD wird allgemein untersucht und am Beispiel eines dort verwendeten Szenarios von Transportunternehmen, des sog. Speditions-Szenarios, veranschaulicht

Nested pessimistic transactions for both atomicity and synchronization in concurrent software

Existing atomic section interface proposals, thus far, have tended to only isolate transactions from each other. Less considered is the coordination of threads performing transactions with respect to one another. Synchronization of nested sections is typically relegated to outside of and among the top-level flattened sections. However existing models do not permit the composition of even simple synchronization constructs such as barriers. The proposed model integrates synchronization as a first-class construct in a truly nested atomic block implementation. The implementation is evaluated on quantitative benchmarks, with qualitative examples of the atomic section interface’s expressive power compared with conventional transactional memory implementations.1 yea

Distributed Concurrent Persistent Languages: An Experimental Design and Implementation

A universal persistent object store is a logical space of persistent objects whose localities span over machines reachable over networks. It provides a conceptual framework in which, on one hand, the distribution of data is transparent to application programmers and, on the other, store semantics of conventional languages is preserved. This means the manipulation of persistent objects on remote machines is both syntactically and semantically the same as in the case of local data. Consequently, many aspects of distributed programming in which computation tasks cooperate over different processors and different stores can be addressed within the confines of persistent programming. The work reported in this thesis is a logical generalization of the notion of persistence in the context of distribution. The concept of a universal persistent store is founded upon a universal addressing mechanism which augments existing addressing mechanisms. The universal addressing mechanism is realized based upon remote pointers which although containing more locality information than ordinary pointers, do not require architectural changes. Moreover, these remote pointers are transparent to the programmers. A language, Distributed PS-algol, is designed to experiment with this idea. The novel features of the language include: lightweight processes with a flavour of distribution, mutexes as the store-based synchronization primitive, and a remote procedure call mechanism as the message-based interprocess communication mechanism. Furthermore, the advantages of shared store programming and network architecture are obtained with the introduction of the programming concept of locality in an unobtrusive manner. A characteristic of the underlying addressing mechanism is that data are never copied to satisfy remote demands except where efficiency can be attained without compromising the semantics of data. A remote store operation model is described to effect remote updates. It is argued that such a choice is the most natural given that remote store operations resemble remote procedure calls

Concurrency in C∀

C∀ is a modern, non-object-oriented extension of the C programming language. This thesis serves as a definition and an implementation for the concurrency and parallelism C∀ offers. These features are created from scratch due to the lack of concurrency in ISO C. Lightweight threads are introduced into the language. In addition, monitors are introduced as a high-level tool for control-flow based synchronization and mutual-exclusion. The main contributions of this thesis are two-fold: it extends the existing semantics of monitors introduce by [37] to handle monitors in groups and also details the engineering effort needed to introduce these features as core language features. Indeed, these features are added with respect to expectations of C programmers, and integrate with the C∀ type-system and other language features

The exploitation of parallelism on shared memory multiprocessors

PhD ThesisWith the arrival of many general purpose shared memory multiple processor (multiprocessor) computers into the commercial arena during the mid-1980's, a rift has opened between the raw processing power offered by the emerging hardware and the relative inability of its operating software to effectively deliver this power to potential users. This rift stems from the fact that, currently, no computational model with the capability to elegantly express parallel activity is mature enough to be universally accepted, and used as the basis for programming languages to exploit the parallelism that multiprocessors offer. To add to this, there is a lack of software tools to assist programmers in the processes of designing and debugging parallel programs. Although much research has been done in the field of programming languages, no undisputed candidate for the most appropriate language for programming shared memory multiprocessors has yet been found. This thesis examines why this state of affairs has arisen and proposes programming language constructs, together with a programming methodology and environment, to close the ever widening hardware to software gap. The novel programming constructs described in this thesis are intended for use in imperative languages even though they make use of the synchronisation inherent in the dataflow model by using the semantics of single assignment when operating on shared data, so giving rise to the term shared values. As there are several distinct parallel programming paradigms, matching flavours of shared value are developed to permit the concise expression of these paradigms.The Science and Engineering Research Council

High Level Concurrency in C∀

Concurrent programs are notoriously hard to write and even harder to debug. Furthermore concurrent programs must be performant, as the introduction of concurrency into a program is often done to achieve some form of speedup. This thesis presents a suite of high-level concurrent-language features in the new programming language C∀, all of which are implemented with the aim of improving the performance, productivity, and safety of concurrent programs. C∀ is a non-object-oriented programming language that extends C. The foundation for concurrency in C∀ was laid by Thierry Delisle [15], who implemented coroutines, user-level threads, and monitors. This thesis builds upon that work and introduces a suite of new concurrent features as its main contribution. The features include a mutex statement (similar to a C++ scoped lock or Java synchronized statement), Go-like channels and select statement, and an actor system. The root ideas behind these features are not new, but the C∀ implementations extends the original ideas in performance, productivity, and safety