A Methodology for Transforming Java Applications Towards Real-Time Performance

The development of real-time systems has traditionally been based on low-level programming languages, such as C and C++, as these provide a fine-grained control of the applications temporal behavior. However, the usage of such programming languages suffers from increased complexity and high error rates compared to high-level languages such as Java. The Java programming language provides many benefits to software development such as automatic memory management and platform independence. However, Java is unable to provide any real-time guarantees, as the high-level benefits come at the cost of unpredictable temporal behavior.This thesis investigates the temporal characteristics of the Java language and analyses several possibilities for introducing real-time guarantees, including official language extensions and commercial runtime environments. Based on this analysis a new methodology is proposed for Transforming Java Applications towards Real-time Performance (TJARP). This method motivates a clear definition of timing requirements, followed by an analysis of the system through use of the formal modeling languageVDM-RT. Finally, the method provides a set of structured guidelines to facilitate the choice of strategy for obtaining real-time performance using Java. To further support this choice, an analysis is presented of available solutions, supported by a simple case study and a series of benchmarks.Furthermore, this thesis applies the TJARP method to a complex industrialcase study provided by a leading supplier of mission critical systems. Thecase study proves how the TJARP method is able to analyze an existing and complex system, and successfully introduce hard real-time guaranteesin critical sub-components

High-level real-time programming in Java

Real-time systems have reached a level of complexity beyond the scaling capability of the low-level or restricted languages traditionally used for real-time programming. While Metronome garbage collection has made it practical to use Java to implement real-time systems, many challenges remain for the construction of complex real-time systems, some specic to the use of Java and others simply due to the change in scale of such systems. The goal of our research is the creation of a comprehensive Java-based programming environment and methodology for the creation of complex real-time systems. Our goals include construction of a provably correct real-time garbage collec-tor capable of providing worst case latencies of 100 s, capa-ble of scaling from sensor nodes up to large multiprocessors; specialized programming constructs that retain the safety and simplicity of Java, and yet provide sub-microsecond la-tencies; the extension of Java's \write once, run anywhere" principle from functional correctness to timing behavior; on-line analysis and visualization that aids in the understanding of complex behaviors; and a principled probabilistic analy-sis methodology for bounding the behavior of the resulting systems. While much remains to be done, this paper describes the progress we have made towards these goals

Execution level Java software and hardware for the NPS autonomous underwater vehicle

Autonomous underwater vehicles (AUVs) have a great potential use for the United States Marine Corps and United States Navy. When performing amphibious operations, underwater mines present a danger for the forces going ashore. The use of underwater vehicles for the detection of this mines and signaling to the Amphibious Ready Group is very attractive. With advancements in hardware and object oriented language technology, more complicated and robust software can be developed. The Naval Postgraduate School Center for AUV Research has been designing, building, operating, and researching AUVs since 1987. Each generation of vehicles has provided substantially increased in operational capabilities and level of sophistication in the hardware and software respectively. With the advancement in real-time computer languages support, object oriented technology, and cost efficient and high performance hardware, this thesis lays the foundations to develop a software system for the execution level using the Java language. We look into the Java Real-Time specifications and extension to familiarize with the capabilities of Java for realtime support, and study Java boards and its application for embedded real-time systems. We developed an object-oriented design for the execution level control software and implemented the design in Java. A testing phase is still under work.http://archive.org/details/executionlevelja109455509Captain, United States Marine CorpsApproved for public release; distribution is unlimited

Actor-Oriented Programming for Resource Constrained Multiprocessor Networks on Chip

Multiprocessor Networks on Chip (MPNoCs) are an attractive architecture for integrated circuits as they can benefit from the improved performance of ever smaller transistors but are not severely constrained by the poor performance of global on-chip wires. As the number of processors increases it becomes ever more expensive to provide coherent shared memory but this is a foundational assumption of thread-level parallelism. Threaded models of concurrency cannot efficiently address architectures where shared memory is not coherent or does not exist. In this thesis an extended actor oriented programming model is proposed to enable the design of complex and general purpose software for highly parallel and decentralised multiprocessor architectures. This model requires the encapsulation of an execution context and state into isolated Machines which may only initiate communication with one another via explicitly named channels. An emphasis on message passing and strong isolation of computation encourages application structures that are congruent with the nature of non-shared memory multiprocessors, and the model also avoids creating dependences on specific hardware topologies. A realisation of the model called Machine Java is presented to demonstrate the applicability of the model to a general purpose programming language. Applications designed with this framework are shown to be capable of scaling to large numbers of processors and remain independent of the hardware targets. Through the use of an efficient compilation technique, Machine Java is demonstrated to be portable across several architectures and viable even in the highly constrained context of an FPGA hosted MPNoC

Model for WCET prediction, scheduling and task allocation for emergent agent-behaviours in real-time scenarios

[ES]Hasta el momento no se conocen modelos de tiempo real específicamente desarrollados para su uso en sistemas abiertos, como las Organizaciones Virtuales de Agentes (OVs). Convencionalmente, los modelos de tiempo real se aplican a sistemas cerrados donde todas las variables se conocen a priori. Esta tesis presenta nuevas contribuciones y la novedosa integración de agentes en tiempo real dentro de OVs. Hasta donde alcanza nuestro conocimiento, éste es el primer modelo específicamente diseñado para su aplicación en OVs con restricciones temporales estrictas. Esta tesis proporciona una nueva perspectiva que combina la apertura y dinamicidad necesarias en una OV con las restricciones de tiempo real. Ésto es una aspecto complicado ya que el primer paradigma no es estricto, como el propio término de sistema abierto indica, sin embargo, el segundo paradigma debe cumplir estrictas restricciones. En resumen, el modelo que se presenta permite definir las acciones que una OV debe llevar a cabo con un plazo concreto, considerando los cambios que pueden ocurrir durante la ejecución de un plan particular. Es una planificación de tiempo real en una OV. Otra de las principales contribuciones de esta tesis es un modelo para el cálculo del tiempo de ejecución en el peor caso (WCET). La propuesta es un modelo efectivo para calcular el peor escenario cuando un agente desea formar parte de una OV y para ello, debe incluir sus tareas o comportamientos dentro del sistema de tiempo real, es decir, se calcula el WCET de comportamientos emergentes en tiempo de ejecución. También se incluye una planificación local para cada nodo de ejecución basada en el algoritmo FPS y una distribución de tareas entre los nodos disponibles en el sistema. Para ambos modelos se usan modelos matemáticos y estadísticos avanzados para crear un mecanismo adaptable, robusto y eficiente para agentes inteligentes en OVs. El desconocimiento, pese al estudio realizado, de una plataforma para sistemas abiertos que soporte agentes con restricciones de tiempo real y los mecanismos necesarios para el control y la gestión de OVs, es la principal motivación para el desarrollo de la plataforma de agentes PANGEA+RT. PANGEA+RT es una innovadora plataforma multi-agente que proporciona soporte para la ejecución de agentes en ambientes de tiempo real. Finalmente, se presenta un caso de estudio donde robots heterogéneos colaboran para realizar tareas de vigilancia. El caso de estudio se ha desarrollado con la plataforma PANGEA+RT donde el modelo propuesto está integrado. Por tanto al final de la tesis, con este caso de estudio se obtienen los resultados y conclusiones que validan el modelo