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We present the Esterel programming language which is especially designed to program reactive systems, that is systems which maintain a permanent interaction with their environment: real-time process controllers, communication protocols, man-machine interface drivers, etc. We present the design of CRP, its semantics, a translation into classical process calculi for program verificatio. CRP faithfully extends both Esterel and CSP and adds new possibilities such as precise local watchdogs on rendezvous.
![multiclock multiclock](https://i.pinimg.com/originals/c0/ce/a1/c0cea1a898d05e66002cd821434288f3.jpg)
A CRP program consists of independent locally reactive Esterel nodes that communicate with each other by CSP rendezvous.
![multiclock multiclock](https://thumbs.static-thomann.de/thumb/orig/pics/bdb/369156/10191946_800.jpg)
Complex applications such as process or robot control require to couple both forms of concurrency, which is the object of CRP. The Esterel synchronous language is dedicated to reactive systems its processes are tightly coupled and deterministic, communication being realized by instantaneous broadcasting. Asynchronous languages such as CSP, Occam, or Ada are well-suited for distributed algorithms their processes are loosely coupled and communication takes time. We present a new programming paradigm called Communicating Reactive Processes or CRP that unifies the capabilities of asynchronous and synchronous concurrent programming languages. We have implemented approximate synchrony as a part of a model checker and used it to verify models of the Best Master Clock (BMC) algorithm, the core component of the IEEE 1588 precision time protocol, as well as the time-synchronized channel hopping protocol that is part of the IEEE 802.15.4e standard. Moreover, we show how approximate synchrony also provides a useful strategy to guide state-space exploration. We provide an algorithmic approach for constructing this abstraction for symmetric, almost-synchronous systems, a subclass of almost-synchronous systems.
#Multiclock verification#
We show how approximate synchrony can be used for verification of both time synchronization protocols and applications running on top of them. Abstractions used for modeling and verification of such systems should accurately capture these imperfections that cause the system to only be “almost synchronized.” In this paper, we present approximate synchrony, a sound and tunable abstraction for verification of almost-synchronous systems. However, these protocols synchronize the distributed clocks only within a certain tolerance, and there are transient phases while synchronization is still being achieved. Thus, recent advances in clock synchronization protocols and their adoption hold promise for system design. This provides a general-purpose framework that simplifies multi-rate FRP systems and can be used for game development, media applications, GUIs and embedded systems, through a flexible API with many reusable components.įorms of synchrony can greatly simplify modeling, design, and verification of distributed systems. Diverse reactive subsystems can be combined in a coherent, declarative data-flow framework, while correct interoperability of data at different rates is guaranteed by type-level clocks. Concurrent communication is encapsulated safely. It separates the aspects of clocking, scheduling and resampling from each other, and ensures clock-safety at the type level. Rhine is a clock-safe library for synchronous and asynchronous Functional Reactive Programming (FRP). Techniques to avoid clock errors, such as type-level clocks and deterministic scheduling, exist in the field of synchronous programming, but are not implemented in general-purpose languages like Haskell. Many of these problems are clock errors, where data at different rates is combined incorrectly. Buffering problems, lags, and concurrency issues often occur.
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Processing data at different rates is generally a hard problem in reactive programming.