Rendezvous Mechanism Research Articles

An abstract execution model for basic LOTOS

This paper presents some techniques that can be used for translating a LOTOS (Language Of Temporal Orfering Specification) specification into an efficient implementation. In particular, the paper focuses attention on basic LOTOS, the control aprt of LOTOS, and presents a simple algorithm to derive an abstract machnine based on a set of labelled transition systems from a basic LOTOS specification. The transition systems define interacting processes. The problem of the unbounded number of states is considered and solved, by allowing dynamic creation and destruction of processes and by adopting an appropriate consturction procedure for the transition systems. The synchronisation of the processes, according to the LOTOS multi-way rendezvous mechanism, is obtained by means of a procedure based on message transfers among the processes, thus enabling a distributed implementation.

An SR approach to multiway rendezvous

This paper presents a new approach to programming multiway rendezvous problems in the SR language. The approach uses SR's concurrent invocation statement and rendezvous mechanism to coordinate the interacting processes. This approach is compared with one that suggested an extension to SR's rendezvous mechanism. The two approaches result in differing program structure. The new approach is shown to lead to simpler and cleaner interfaces between the main process and the worker processes, and uses only existing language mechanisms. The results are of importance to both programmers and designers of concurrent program languages.

Concurrent programming in the Ada® language: The polling bias

AbstractThe rendezvous is an important concept in concurrent programming—two processes need to synchronize, i.e. rendezvous, to exchange information. The Ada programming language is the first programming language to use the rendezvous as the basis of its concurrent programming facilities.Our experience with rendezvous facilities in the Ada language shows that these facilities lead to and encourage the design of programs that poll. Polling is generally, but not always, undesirable because it is wasteful of system resources.We illustrate and examine the reasons for polling bias in the Ada language. We give suggestions on how to avoid polling programs, and suggest changes to the rendezvous facilities to eliminate the polling bias. The ramifications of these changes to the implementation of the Ada language are also discussed.Although we have focused on the rendezvous facilities in the Ada language our analysis is also applicable to other languages. A polling bias can occur in any concurrent programming language based on the rendezvous mechanism if it does not provide appropriate facilities.

Some experiences of implementing the ada concurrency facilities on a distributed multiprocessor computer system

The paper first identifies the concurrency requirements for a high-level concurrent programming language, and then discusses how the concurrency primitives proposed for the programming language Ada meet these requirements. This is followed by a description of an actual implementation of the Ada tasking constructs on a distributed multiprocessor computer system comprising a number of multiprocessor-shared memory stations linked by a serial communications network. A brief description of the system and the overheads involved when implementing the rendezvous mechanism on this architecture is presented, and also the implications of processing interrupts by mapping them into external entry calls to high-level service tasks are discussed

Axioms and proof rules for Ada tasks

An axiomatic proof system is developed for use in proving partial correctness and absence of deadlock in Ada tasks. Axioms for the Ada tasking primitives in isolation are presented, and then rules proposed that describe the logical interaction of tasks through the rendezvous mechanism. These axioms and rules are then used to present partial correctness proofs of parallel-processing examples written in Ada. The system is extended to deal with questions of blocking and detection of deadlock and, finally, the problems of task termination and exception handling are discussed.

Erratum: Distributed mailbox arrangement which facilitates task communication in a multimicroprocessor system

A distributed mailbox facility that could minimise the memory conflicts arising out of busy wait synchronisation operations is described. A mapping of the Ada rendezvous mechanism is suggested as an application.

Distributed mailbox arrangement which facilitates task communication in a multimicroprocessor system

A distributed mailbox facility that could minimise the memory conflicts arising out of busy wait synchronisation operations is described. A mapping of the Ada rendezvous mechanism is suggested as an application.