1,721,080 research outputs found
Understanding Shared Memory Bank Access Interference in Multi-Core Avionics
Get PDFDeployment of multi-core platforms in safety-critical applications requires reliable estimation of worst-case response time (WCRT) for critical processes. Determination of WCRT needs to accurately estimate and measure the interferences arising from multiple processes and multiple cores. Earlier works have proposed frameworks in which CPU, shared cache, and shared memory (DRAM) interferences can be estimated using some application and platform-dependent parameters. In this work we examine a recent work in which single core equivalent (SCE) worst case execution time is used as a basis for deriving WCRT. We describe the specific requirements in an avionics context including the sharing of memory banks by multiple processes on multiple cores, and adapt the SCE framework to account for them. We present the needed adaptations to a real-time operating system to enforce the requirements, and present a methodology for validating the theoretical WCRT through measurements on the resulting platform. The work reveals that the framework indeed creates a (pessimistic) bound on the WCRT. It also discloses that the maximum interference for memory accesses does not arise when all cores share the same memory bank
Anomaly detection and mitigation for disaster area networks
No full textOne of the most challenging applications of wireless networking are in disaster area networks where lack of infrastructure, limited energy resources, need for common operational picture and thereby reliable dissemination are prevalent.In this paper we address anomaly detection in intermittently connected mobile ad hoc networks in which there is little or no knowledge about the actors on the scene, and opportunistic contacts together with a store-and-forward mechanism are used to overcome temporary partitions. The approach uses a statistical method for detecting anomalies when running a manycast protocol for dissemination of important messages to k receivers. Simulation of the random walk gossip (RWG) protocol combined with detection and mitigation mechanisms is used to illustrate that resilience can be built into a network in a fully distributed and attack-agnostic manner, at a modest cost in terms of drop in delivery ratio and additional transmissions. The approach is evaluated with attacks by adversaries that behave in a similar manner to fair nodes when invoking protocol actions.The original publication is available at www.springerlink.com: Jordi Cucurull, Simin Nadjm-Tehrani and Mikael Asplund, Anomaly detection and mitigation for disaster area networks, 2010, Lecture Notes in Computer Science: RAID 2010, 339-359. http://dx.doi.org/10.1007/978-3-642-15512-3_18 Copyright: Springer Verlag http://www.springerlink.com/</p
Towards real-time systems education with PBL
No full textIn this report the plans for the spring term of the third year of the Information Technology M.Sc. program in engineering at Linkping university is described. The adopted pedagogical form is inspired by the idea of Problem-Based Learning (PBL). Major ingredients in PBL are self-directed learning, and group discussions based on realistic examples. This induces a higher degree of integration among topics than is usual in traditional curricula. The spring term which is reported upon is organized around four themes of study integrating the traditional topics of concurrent programming, operating systems, real-time systems, automatic control, discrete time circuit theory, linear algebra, transform theory, and ethics. A team of several teachers from four departments of the university are involved in the implementation of this term's education. 1 Background Education in computer science and engineering in Sweden has been confronted with a number of challenges in the last decade. There are cl..
Towards real-time systems education with PBL
No full textIn this report the plans for the spring term of the third year of the Information Technology M.Sc. program in engineering at Linkping university is described. The adopted pedagogical form is inspired by the idea of Problem-Based Learning (PBL). Major ingredients in PBL are self-directed learning, and group discussions based on realistic examples. This induces a higher degree of integration among topics than is usual in traditional curricula. The spring term which is reported upon is organized around four themes of study integrating the traditional topics of concurrent programming, operating systems, real-time systems, automatic control, discrete time circuit theory, linear algebra, transform theory, and ethics. A team of several teachers from four departments of the university are involved in the implementation of this term's education. 1 Background Education in computer science and engineering in Sweden has been confronted with a number of challenges in the last decade. There are cl..
Reactive Systems in Physical Environments
No full text. In this paper we propose an architecture as a framework for decomposition and analysis of hybrid systems. We represent a computer system's behaviour in interaction with its physical environment using modular models and the combination of discrete and continuous modelling techniques. To this end, a modular extention of timed transition systems, Hybrid Transition Systems, are presented. For this formalism a parallel composition operator and an operational semantics is provided. Two novel aspects of the formalism are separation of the input and state variables, and adoption of algebraic equations for description of the change in the value for some continuous variables. The paper includes a brief description of example applications and a discussion of hybrid transition systems without a run. 1. Introduction This paper addresses modelling of reactive programs which are embedded in physical environments, and which perform a combination of symbolic and numeric computations. The motivation..
Debugging Prolog Programs Declaratively
No full textTraditional declarative debuggers, despite their theoretical attractions are not considered to be practical tools for debugging of many Prolog programs. This is partly due to the fact that the basic declarative debugging system (Shapiro 83) only dealt with pure Prolog programs, and partly due to practical limitations of the suggested methods and algorithms. Our aim has been to study the applicability of declarative debugging methods to a wider range of Prolog programs. Earlier we have reported on improvements to methods and algorithms for declarative debugging of logic programs. In this paper we discuss extention of our algorithms for dealing with some Prolog constructs. In particular, negation of composed goals, unsafe uses of negation, the built-in setof predicate, and the if-then-else construct are elaborated upon. We also report on experiments with a sample of non-trivial Prolog programs, using our prototype system. Practical problems such as multiplicity of "irrelevant" user inter..
Integration of Analog and Discrete Synchronous Design
No full text. The synchronous family of languages (Lustre, Esterel, Signal, Statecharts) provide a great deal of support for verifying a control program at the design and compilation stage. However, a common aspect of embedded systems is that significant properties of the system can not be verified by formally analysing the controller (software) on its own. To analyse the system one requires to state and document assumptions on the environment. Furthermore, proving timeliness properties necessitates justifying a sampling interval and relating the synchronous step to metric time. Support for these activities is generally missing from current formal methods tools. In this paper we exploit simulation models -- based on physical modelling of the environment -- together with theorem proving, to prove properties of a closed loop system. We report on the work in progress on a case study provided by Saab Aerospace where deductive tools such as NP-Tools and simulation environments such as MATRIXx-SystemBui..
Tool support for incremental failure mode and effects analysis of component-based systems
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