Interpreted graph models

A model class called an Interpreted Graph Model (IGM) is defined. This class includes a large number of graph-based models that are used in asynchronous circuit design and other applications of concurrecy. The defining characteristic of this model class is an underlying static graph-like structure where behavioural semantics are attached using additional entities, such as tokens or node/arc states. The similarities in notation and expressive power allow a number of operations on these formalisms, such as visualisation, interactive simulation, serialisation, schematic entry and model conversion to be generalised. A software framework called Workcraft was developed to take advantage of these properties of IGMs. Workcraft provides an environment for rapid prototyping of graph-like models and related tools. It provides a large set of standardised functions that considerably facilitate the task of providing tool support for any IGM. The concept of Interpreted Graph Models is the result of research on methods of application of lower level models, such as Petri nets, as a back-end for simulation and verification of higher level models that are more easily manipulated. The goal is to achieve a high degree of automation of this process. In particular, a method for verification of speed-independence of asynchronous circuits is presented. Using this method, the circuit is specified as a gate netlist and its environment is specified as a Signal Transition Graph. The circuit is then automatically translated into a behaviourally equivalent Petri net model. This model is then composed with the specification of the environment. A number of important properties can be established on this compound model, such as the absence of deadlocks and hazards. If a trace is found that violates the required property, it is automatically interpreted in terms of switching of the gates in the original gate-level circuit specification and may be presented visually to the circuit designer. A similar technique is also used for the verification of a model called Static Data Flow Structure (SDFS). This high level model describes the behaviour of an asynchronous data path. SDFS is particularly interesting because it models complex behaviours such as preemption, early evaluation and speculation. Preemption is a technique which allows to destroy data objects in a computation pipeline if the result of computation is no longer needed, reducing the power consumption. Early evaluation allows a circuit to compute the output using a subset of its inputs and preempting the inputs which are not needed. In speculation, all conflicting branches of computation run concurrently without waiting for the selecting condition; once the selecting condition is computed the unneeded branches are preempted. The automated Petri net based verification technique is especially useful in this case because of the complex nature of these features. As a result of this work, a number of cases are presented where the concept of IGMs and the Workcraft tool were instrumental. These include the design of two different types of arbiter circuits, the design and debugging of the SDFS model, synthesis of asynchronous circuits from the Conditional Partial Order Graph model and the modification of the workflow of Balsa asynchronous circuit synthesis system.EThOS - Electronic Theses Online ServiceEPSRCGBUnited Kingdo

Modelling parallel and distributed virtual reality systems for performance analysis and comparison

Most Virtual Reality systems employ some form of parallel processing, making use of multiple processors which are often distributed over large areas geographically, and which communicate via various forms of message passing. The approaches to parallel decomposition differ for each system, as do the performance implications of each approach. Previous comparisons have only identified and categorized the different approaches. None have examined the performance issues involved in the different parallel decompositions. Performance measurement for a Virtual Reality system differs from that of other parallel systems in that some measure of the delays involved with the interaction of the separate components is required, in addition to the measure of the throughput of the system. Existing performance analysis approaches are typically not well suited to providing both these measures. This thesis describes the development of a performance analysis technique that is able to provide measures of both interaction latency and cycle time for a model of a Virtual Reality system. This technique allows performance measures to be generated as symbolic expressions describing the relationships between the delays in the model. It automatically generates constraint regions, specifying the values of the system parameters for which performance characteristics change. The performance analysis technique shows strong agreement with values measured from implementation of three common decomposition strategies on two message passing architectures. The technique is successfully applied to a range of parallel decomposition strategies found in Parallel and Distributed Virtual Reality systems. For each system, the primary decomposition techniques are isolated and analysed to determine their performance characteristics. This analysis allows a comparison of the various decomposition techniques, and in many cases reveals trends in their behaviour that would have gone unnoticed with alternative analysis techniques. The work described in this thesis supports the Performance Analysis and Comparison of Parallel and Distributed Virtual Reality systems. In addition it acts as a reference, describing the performance characteristics of decomposition strategies used in Virtual Reality systems

Embedded System Design

A unique feature of this open access textbook is to provide a comprehensive introduction to the fundamental knowledge in embedded systems, with applications in cyber-physical systems and the Internet of things. It starts with an introduction to the field and a survey of specification models and languages for embedded and cyber-physical systems. It provides a brief overview of hardware devices used for such systems and presents the essentials of system software for embedded systems, including real-time operating systems. The author also discusses evaluation and validation techniques for embedded systems and provides an overview of techniques for mapping applications to execution platforms, including multi-core platforms. Embedded systems have to operate under tight constraints and, hence, the book also contains a selected set of optimization techniques, including software optimization techniques. The book closes with a brief survey on testing. This fourth edition has been updated and revised to reflect new trends and technologies, such as the importance of cyber-physical systems (CPS) and the Internet of things (IoT), the evolution of single-core processors to multi-core processors, and the increased importance of energy efficiency and thermal issues

Developing Globally-Asynchronous Locally- Synchronous Systems through the IOPT-Flow Framework

Throughout the years, synchronous circuits have increased in size and com-plexity, consequently, distributing a global clock signal has become a laborious task. Globally-Asynchronous Locally-Synchronous (GALS) systems emerge as a possible solution; however, these new systems require new tools. The DS-Pnet language formalism and the IOPT-Flow framework aim to support and accelerate the development of cyber-physical systems. To do so it offers a tool chain that comprises a graphical editor, a simulator and code gener-ation tools capable of generating C, JavaScript and VHDL code. However, DS-Pnets and IOPT-Flow are not yet tuned to handle GALS systems, allowing for partial specification, but not a complete one. This dissertation proposes extensions to the DS-Pnet language and the IOPT-Flow framework in order to allow development of GALS systems. Addi-tionally, some asynchronous components were created, these form interfaces that allow synchronous blocks within a GALS system to communicate with each other