35 research outputs found
Reconciling Repeatable Timing with Pipelining and Memory Hierarchy
This paper argues that repeatable timing is more important and more achievable than predictable timing. It describes microarchitecture approaches to pipelining and memory hierarchy that deliver repeatable timing and promise comparable or better performance compared to established techniques. Specifically, threads are interleaved in a pipeline to eliminate pipeline hazards, and a hierarchical memory architecture is outlined that hides memory latencies
DesafĂos en el diseño de sistemas Ciber-FĂsicos
Los sistemas cyber-fĂsicos ─Cyber-Physical Systems CPS─ es un proceso que integra la computaciĂłn con los procesos fĂsicos. Los computadores embebidos, el monitoreo de redes y el control de procesos fĂsicos, usualmente tienen ciclos de retroalimentaciĂłn en los que los procesos fĂsicos afectan los cálculos, y viceversa. En este artĂculo se examinan los desafĂos en el diseño de estos sistemas, y se plantea la cuestiĂłn de si la informática y las tecnologĂas de redes actuales proporcionan una base adecuada para ellos. La conclusiĂłn es que para mejorar los procesos de diseño de estos sistemas no será suficiente con elevar el nivel de abstracciĂłn o verificar, formalmente o no, los diseños en los que se basan las abstracciones de hoy. El potencial social y econĂłmico de los CPS es mucho mayor de lo que hasta el momento se ha pensado; en todo el mundo se están realizando grandes inversiones para desarrollar esta tecnologĂa, pero los retos son considerables. Para aprovechar todo el potencial de los CPS se tendrán que reconstruir los procesos de las abstracciones informáticas y de las redes, y los procesos se deberán acoger en pleno a los principios de las dinámicas fĂsicas y de la computaciĂłn
An Introduction to Pervasive Interface Automata
Pervasive systems are often context-dependent, component based systems in which components expose interfaces and offer one or more services. These systems may evolve in unpredictable ways, often through component replacement. We present pervasive interface automata as a formalism for modelling components and their composition. Pervasive interface automata are based on the interface automata of Henzinger et al, with several significant differences. We expand their notion of input and output actions to combinations of input, output actions, and callable methods and method calls. Whereas interfaces automata have a refinement relation, we argue the crucial relation in pervasive systems is component replacement, which must include consideration of the services offered by a component and assumptions about the environment. We illustrate pervasive interface autmotata and component replacement with a small case study of a pervasive application for sports predictions
Region Type Checking for Core-Java
Region-based memory management offers several important advantages over garbage-collected heap, including real-time performance, better data locality and efficient use of limited memory. The concept of regions was first introduced for a call-by-value functional language by Tofte and Talpin, and has since been advocated for imperative and object-oriented languages. Scope memory, a lexical variant of regions, is now a core feature in a recent proposal on Real-Time Specification for Java (RTSJ). In this paper, we propose a region-based memory management system for a core subset of Java. Our region type analysis can completely prevent dangling references and thus is ready to cater for the no-dangling requirement in RTSJ. Our system also supports modular compilation, which is an important feature for Java, but was missing in recent related work.Singapore-MIT Alliance (SMA
From dataflow specification to multiprocessor partitioned time-triggered real-time implementation
We consider deterministic functional specifications provided by means of synchronous data-flow models with multiple modes and multiple relative periods. These specifications are extended to include a real-time characterization defining task periods, release dates, and deadlines. Task deadlines can be longer than the period to allow a faithful representation of complex end-to-end flow requirements. We also extend our specifications with partitioning and allocation constraints. Then, we provide algorithms for the off-line scheduling of these specifications onto partitioned time-triggered architectures Ă la ARINC 653. Allocation of time slots/windows to partitions can be fully or partially provided, or synthesized by our tool. Our algorithms allow the automatic allocation and scheduling onto multi-processor (distributed) systems with a global time base, taking into account communication costs. We demonstrate our technique on a model of space flight software system with strong real-time determinism requirements
From Dataflow Specification to Multiprocessor Partitioned Time-triggered Real-time Implementation *
International audienceOur objective is to facilitate the development of complex time-triggered systems by automating the allocation and scheduling steps. We show that full automation is possible while taking into account the elements of complexity needed by a complex embedded control system. More precisely, we consider deterministic functional specifications provided (as often in an industrial setting) by means of synchronous data-flow models with multiple modes and multiple relative periods. We first extend this functional model with an original real-time characterization that takes advantage of our time-triggered framework to provide a simpler representation of complex end-to-end flow requirements. We also extend our specifications with additional non-functional properties specifying partitioning, allocation , and preemptability constraints. Then, weprovide novel algorithms for the off-line scheduling of these extended specifications onto partitioned time-triggered architectures Ă la ARINC 653. The main originality of our work is that it takes into account at the same time multiple complexity elements: various types of non-functional properties (real-time, partitioning, allocation, preemptability) and functional specifications with conditional execution and multiple modes. Allocation of time slots/windows to partitions can be fullyor partially provided, or synthesized by our tool. Our algorithms allow the automatic allocation and scheduling onto multi-processor (distributed) sys-tems with a global time base, taking into account communication costs. We demonstrate our technique on a model of space flight software systemwith strong real-time determinism requirements
Multi-Facets Contract for Modeling and Verifying Heterogeneous Systems
Critical and cyber-physical systems (CPS) that exist in large industries,
such as nuclear power plants, railway, automotive or aeronautical industries
are complex heterogeneous systems. They are complex because they are open,
perimeter-less, often built by assembling various heterogeneous and interacting
components which are frequently reconfigured due to requirements. Consequently,
the modeling and analysis of such systems is a challenge in software
engineering. We introduce a new method for modeling and verifying heterogeneous
systems. The method consists in: equipping individual components with
generalized contract, ordering these contracts according to given facets,
composing these components and verifying the resulting system with respect to
the facets. We illustrate the use of the method by a case study. The proposed
method may be extended to cover more facets, and by strengthening assistance
tool through proactive aspects in modelling and property verification