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Implementing mixed-criticality synchronous reactive programs upon uniprocessor platforms

REAL-TIME SYSTEMS 2014年第3期50卷 317-341页

作者： Baruah, Sanjoy Univ N Carolina Chapel Hill NC 27599 USA

Model-based design methodologies based on the synchrony assumption are widely used in many safety-critical application domains. The synchrony assumption asserts that actions (such as the execution of code) occur instantaneously;however, physical platforms obviously do not possess this property. This paper considers the problem of obtaining resource-efficient implementations of programs that are written under the synchrony assumption on actual platforms, such that these implementations execute in a manner that is semantically consistent with the execution sequences that would occur if the synchrony assumption were to hold.

关键词： synchronous programming Mixed-criticality systems Scheduling

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Operational semantics of a domain specific language for real time musician-computer interaction

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DISCRETE EVENT DYNAMIC SYSTEMS-THEORY AND APPLICATIONS 2013年第4期23卷 343-383页

作者： Echeveste, Jose Cont, Arshia Giavitto, Jean-Louis Jacquemard, Florent UPMC STMS Lab IRCAM CNRSINRIARepMus Mutant Team F-75004 Paris France

With the advent and availability of powerful personal computing, the computer music research and industry have been focusing on real-time musical interactions between musicians and computers;delegating human-like actions to computers who interact with a musical environment. One common use-case of this kind is Automatic Accompaniment where the system is comprised of a real-time machine listening system that in reaction to recognition of events in a score from a human performer, launches necessary actions for the accompaniment section. While the real-time detection of score events out of live musicians' performance has been widely addressed in the literature, score accompaniment (or the reactive part of the process) has been rarely discussed. This paper deals with this missing component in the literature from a formal language perspective. We show how language considerations would enable better authoring of time and interaction during programming/composing and how it addresses critical aspects of a musical performance (such as errors) in real-time. We sketch the real-time features required by automatic musical accompaniment seen as a reactive system. We formalize the timing strategies for musical events taking into account the various temporal scales used in music. Various strategies for the handling of synchronization constraints and the handling of errors are presented. We give a formal semantics to model the possible behaviors of the system in terms of Parametric Timed Automata.

关键词： Computer music Score following Automatic musical accompaniment synchronous programming synchronous language Error handling

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Constructive polychronous systems

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SCIENCE OF COMPUTER programming 2014年第Part3期96卷 377-394页

作者： Talpin, Jean-Pierre Brandt, Jens Gemuende, Mike Schneider, Klaus Shukla, Sandeep INRIA F-35042 Rennes France Univ Kaiserslautern D-67663 Kaiserslautern Germany Virginia Tech Blacksburg VA USA

The synchronous paradigm provides a logical abstraction of time for reactive system design which allows automatic synthesis of embedded systems that behave in a predictable, timely, and reactive manner. According to the synchrony hypothesis, a synchronous model reacts to inputs by generating outputs that are immediately made available to the environment. While synchrony greatly simplifies the design of complex systems in general, it can sometimes lead to causal cycles. In these cases, constructiveness is a key property to guarantee that the output of each reaction can still be always algorithmically determined. Polychrony deviates from perfect synchrony by using a partially ordered, i.e., a relational model of time. It encompasses the behaviors of (implicitly) multi-clocked data-flow networks of synchronous modules and can analyze and synthesize them as GALS systems or Kahn process networks (KPNs). In this paper, we present a unified constructive semantic framework using structured operational semantics, which encompasses both the constructive behavior of synchronous modules and the multi-clocked behavior of polychronous networks. Along the way, we define the very first executable operational semantics of the polychronous language SIGNAL. (C) 2014 Elsevier B.V. All rights reserved.

关键词： synchronous programming Operational semantics Constructive systems Fixpoint theory Program verification

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User-level Threading: Have Your Cake and Eat It Too

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PROCEEDINGS OF THE ACM ON MEASUREMENT AND ANALYSIS OF COMPUTING SYSTEMS 2020年第1期4卷 1–30页

作者： Karsten, Martin Barghi, Saman Univ Waterloo Waterloo ON Canada

An important class of computer software, such as network servers, exhibits concurrency through many loosely coupled and potentially long-running communication sessions. For these applications, a long-standing open question is whether thread-per-session programming can deliver comparable performance to event-driven programming. This paper clearly demonstrates, for the first time, that it is possible to employ user-level threading for building thread-per-session applications without compromising functionality, efficiency, performance, or scalability. We present the design and implementation of a general-purpose, yet nimble, user-level M:N threading runtime that is built from scratch to accomplish these objectives. Its key components are efficient and effective load balancing and user-level I/O blocking. While no other runtime exists with comparable characteristics, an important fundamental finding of this work is that building this runtime does not require particularly intricate data structures or algorithms. The runtime is thus a straightforward existence proof for user-level threading without performance compromises and can serve as a reference platform for future research. It is evaluated in comparison to event-driven software, system-level threading, and several other user-level threading runtimes. An experimental evaluation is conducted using benchmark programs, as well as the popular Memcached application. We demonstrate that our user-level runtime outperforms other threading runtimes and enables thread-per-session programming at high levels of concurrency and hardware parallelism without sacrificing performance.

关键词： synchronous programming user-level runtime network server

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A Constructive State-based Semantics and Interpreter for a synchronous Data-flow Language with State Machines

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ACM TRANSACTIONS ON EMBEDDED COMPUTING SYSTEMS 2023年第5期22卷 1-26页

作者： Colaco, Jean-Louis Mendler, Michael Pauget, Baptiste Pouzet, Marc Ansys SBU Pk Ave Batiment Emeraude 19 Rue Michel Labrous F-31100 Toulouse France Univ Bamberg Fac Informat Syst & Appl Comp Sci Gutenbergstr 13 D-96050 Bamberg Germany INRIA 2 Rue Simone IFF F-75012 Paris France PSL DIENS ENS 45 rue Ulm F-75230 Paris France

Scade is a domain-specific synchronous functional language used to implement safety-critical real-time software for more than twenty years. Two main approaches have been considered for its semantics: (i) an indirect collapsing semantics based on a source-to-source translation of high-level constructs into a data-flow core language whose semantics is precisely specified and is the entry for code generation;a relational synchronous semantics, akin to Esterel, that applies directly to the source. It defines what is a valid synchronous reaction but hides, on purpose, if a semantics exists, is unique and can be computed;hence, it is not executable. This paper presents, for the first time, an executable, state-based semantics for a language that has the key constructs of Scade all together, in particular the arbitrary combination of data-flow equations and hierarchical state machines. It can apply directly to the source language before static checks and compilation steps. It is constructive in the sense that the language in which the semantics is defined is a statically typed functional language with call-by-value and strong normalization, e.g., it is expressible in a proof-assistant where all functions terminate. It leads to a reference, purely functional, interpreter. This semantics is modular and can account for possible errors, allowing to establish what property is ensured by each static verification performed by the compiler. It also clarifies how causality is treated in Scade compared with Esterel. This semantics can serve as an oracle for compiler testing and validation;to prototype novel language constructs before they are implemented, to execute possibly unfinishedmodels or that are correct but rejected by the compiler;to prove the correctness of compilation steps. The semantics given in the paper is implemented as an interpreter in a purely functional style, in OCaml.

关键词： programming language dynamic semantics synchronous programming embedded software

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Integrating discrete controller synthesis into a reactive programming language compiler

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DISCRETE EVENT DYNAMIC SYSTEMS-THEORY AND APPLICATIONS 2013年第4期23卷 385-418页

作者： Delaval, Gwenael Rutten, Eric Marchand, Herve Univ Grenoble LIG Grenoble France INRIA LIG Grenoble France INRIA Rennes France

We define a mixed imperative/declarative programming language: declarative contracts are enforced upon imperatively described behaviors. This paper describes the semantics of the language, making use of the notion of Discrete Controller Synthesis (DCS). We target the application domain of adaptive and reconfigurable systems: our language can serve programming closed-loop adaptation controllers, enabling flexible execution of functionalities w.r.t. changing resource and environment conditions. DCS is integrated into a1 programming language compiler, which facilitates its use by users and programmers, performing executable code generation. The tool is concretely built upon the basis of a reactive programming language compiler, where the nodes describe behaviors that can be modeled in terms of transition systems. Our compiler integrates this with a DCS tool, making it a new environment for formal methods. We define the trace semantics of our contracts language, describe its compilation and establish its correctness, and discuss implementation and examples.

关键词： Reactive systems synchronous programming Discrete control synthesis Compilation Behavioral contracts Adaptive/reconfigurable systems

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Static Analysis of synchronous Programs in Signal for Efficient Design of Multi-Clocked Embedded Systems 11

Static Analysis of Synchronous Programs in Signal for Effici...

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ACM SIGPLAN/SIGBED Conference on Languages Compilers, Tools, and Theory for Embedded Systems (LCTES 2011)

作者： Gamatie, Abdoulaye Gonnord, Laure LIFL UMR CNRS Lille1 8022 F-59650 Villeneuve Dascq France

ISBN: (纸本)9781450305556

In this paper, we propose a sound abstraction for an efficient static analysis of synchronous programs describing multi-clock embedded systems in SIGNAL. This abstraction combines the Boolean theory and numeric interval approximation to adequately address clock relations defined as combinations of logical and numerical expressions. Through a few examples, we show how the proposed solution is used to determine absence of reaction captured by empty clocks;mutual exclusion captured by two or more clocks whose associated signals never occur at the same time;or hierarchical control of component activations via clock inclusion. We also show this analysis improves the quality of the code generated automatically by the SIGNAL compiler, e.g., a code with smaller footprint, or a code executed more efficiently thanks to optimizations enabled by the new abstraction.

关键词： Embedded systems static analysis abstraction abstract clocks synchronous programming compilation

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Contracts for Modular Discrete Controller Synthesis 10

Contracts for Modular Discrete Controller Synthesis

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ACM SIGPLAN/SIGBED Conference on Languages, Compilers and Tool for Embedded Systems

作者： Delaval, Gwenael Marchand, Herve Rutten, Eric INRIA Grenoble France INRIA Rennes France

ISBN: (纸本)9781605589534

We describe the extension of a reactive programming language with a behavioral contract construct. It is dedicated to the programming of reactive control of applications in embedded systems, and involves principles of the supervisory control of discrete event systems. Our contribution is in a language approach where modular discrete controller synthesis (DCS) is integrated, and it is concretized in the encapsulation of DCS into a compilation process. From transition system specifications of possible behaviors, DCS automatically produces controllers that make the controlled system satisfy the property given as objective. Our language features and compiling technique provide correctness-by-construction in that sense, and enhance reliability and verifiability. Our application domain is adaptive and reconfigurable systems: closed-loop adaptation mechanisms enable flexible execution of functionalities w.r.t. changing resource and environment conditions. Our language can serve programming such adaption controllers. This paper particularly describes the compilation of the language. We present a method for the modular application of discrete controller synthesis on synchronous programs, and its integration in the BZR language. We consider structured programs, as a composition of nodes, and first apply DCS on particular nodes of the program, in order to reduce the complexity of the controller computation;then, we allow the abstraction of parts of the program for this computation;and finally, we show how to recompose the different controllers computed from different abstractions for their correct co-execution with the initial program. Our work is illustrated with examples, and we present quantitative results about its implementation.

关键词： Design Languages Reliability Verification Discrete controller synthesis modularity components contracts reactive systems synchronous programming adaptive and reconfigurable systems

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Scheduling synchronous Tutoring Sessions in Learning Activities 21st

Scheduling Synchronous Tutoring Sessions in Learning Activit...

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21st International Conference on Interactive Collaborative Learning (ICL) / 47th IGIP International Conference on Engineering Pedagogy - Teaching and Learning in a Digital World

作者： Gueye, Amadou Dahirou Faye, Pape Mamadou Djidiack Gueye, Bounama Lishou, Claude Alioune Diop Univ Bambey Senegal Virtual Univ Dakar Senegal Cheikh Anta Diop Univ Dakar Senegal

ISBN: (纸本)9783030119324;9783030119317

This paper deals with a solution allowing digital universities or distance learning structures to extend the functionalities of their distance learning platform to improve not only the management of course session activities but also the organization and synchronous scheduling of these sessions. Indeed, the major problem that is often encountered at the level of distance learning platforms is the management of course hours. This paper proposes a solution for the FOAD Moodle platform to develop a plugin offering teachers the possibility to dynamically choose their course availability and learners the possibility to visualize in real time the week's schedules. The developed plugin is integrated as a new educational resource into the Moodle platform to extend its functionality. This plugin which constitutes the originality of this paper bears the name of Planning.

关键词： Distance learning platform synchronous programming Plugin development Planning

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Semantics-preserving multitask implementation of synchronous programs

Semantics-preserving multitask implementation of synchronous...

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2nd Embedded Systems Week

作者： Caspi, Paul Scaife, Norman Sofronis, Christos Tripakis, Stavros Verimag Lab Ctr Equat F-38610 Gieres France Verimag & Cadence Res Labs Berkeley CA 94704 USA

We study the implementation of a synchronous program as a set of multiple tasks running on the same computer, and scheduled by a real-time operating system using some preemptive scheduling policy, such as fixed priority or earliest-deadline first. Multitask implementations are necessary, for instance, in multiperiodic applications, when the worst-case execution time of the program is larger than its smallest period. In this case, a single-task implementation violates the schedulability assumption and, therefore, the synchrony hypothesis does not hold. We are aiming at semantics-preserving implementations, where, for a given input sequence, the output sequence produced by the implementation is the same as that produced by the original synchronous program, and this under all possible executions of the implementation. Straightforward implementation techniques are not semantics-preserving. We present an intertask communication protocol, called DBP, that is semantics-preserving and memory-optimal. DBP guarantees semantical preservation under all possible triggering patterns of the synchronous program: thus, it is applicable not only to time-, but also event-triggered applications. DBP works under both fixed priority and earliest-deadline first scheduling. DBP is a nonblocking protocol based on the use of intermediate buffers and manipulations of write-to/read-from pointers to these buffers: these manipulations happen upon arrivals, rather than executions of tasks, which is a distinguishing feature of DBP. DBP is memory-optimal in the sense that it uses as few buffers as needed, for any given triggering pattern. In the worst case, DBP requires, at most, N + 2 buffers for each writer, where N is the number of readers for this writer.

关键词： Embedded software Model-based design Optimality Preemptive scheduling Process communication Semantical preservation synchronous programming

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