8 research outputs found

    Relajaciones de ejecución definidas por el usuario para la mejora de la programabilidad en computación paralela de altas prestaciones

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    Tesis de la Universidad Complutense de Madrid, Facultad de Informática, leída el 22-11-2019This thesis proposes the development and implementation of a new programming model basedon execution relaxations, and focused on High-Performance Parallel Computing. Specifically,the main goals of the thesis are:1. Advocate a development methodology in which users define the basic computing units(tasks), together with a set of relaxations in, possibly, multiple dimensions. These relaxationswill be translated, at execution time, into expanded (and complex) scheduling opportunitiesdepending on the underlying architectural features, yielding improvements in termsof desired output metrics (e.g., performance or energy consumption).2. Abstract away users from the complexity of the underlying heterogeneous hardware, delegatingthe proper exploitation of expanded scheduling choices to a system software component(typically referred as a runtime). This piece of software, armed with knowledge fromstatic architectural characteristics and dynamic status of the hardware at execution time,will exploit those combinations considered optimal among those relaxations proposed bythe user for each task ready for execution.3. Extend this abstraction in order to describe both computing systems, by means of executor/ allocator hierarchies that describe the heterogeneous computing architecture, and applications,in terms of sets of interdependent tasks. In addition, the relations between executorsand tasks are categorized into a new task-executor taxonomy, which motivates ambiguityfreeHPC programming frontends based on the STSE, Single Task - Single Executor classification,distinguished from fully-automated runtime backends.4. Propose a new programming model (STEEL) based on previous ideas, that gathers featuresconsidered to be basic for future task-based programming models, namely: performance,composability, expressivity and hard-to-misuse interfaces.5. Specify an API to support the STEEL programming model, and a runtime implementationleveraging techniques and programming paradigms supported by modern C++, illustratingits flexibility, ease of use and performance impact by means of simple use cases and examples.Hence, the proposed methodology stands for a clear and strict separation of concerns betweenthe involved actors in a parallel executions: user / codes and underlying hardware. This kind ofabstractions allows a delegation of the expert knowledge from the user toward the system software(runtime) in a systematic way, and facilitates the integration of mechanisms to automate optimizations,adapting performance to the specificities of the heterogeneous parallel architecture in whichthe code is instantiated and executed.From this perspective, the thesis designs, implements and validates mechanisms to perform aso-called complexity formalization, classifying many actions that are currently done by the userand building a framework in which these complexities can be delegated to the runtime system. Thedelegation of these decisions is already a step forward to next generation of programming modelsseeking performance, expressivity, programmability and portability...La presente tesis doctoral propone el diseño e implementación de un nuevo modelo de programación basado en relajaciones de ejecución y enfocado al ámbito de la Computación Paralela de Altas Prestaciones. Concretamente, los objetivos principales de la tesis son:1. Abogar por una metodología de desarrollo en la que el usuario define las unidades básicas de computo (tareas), junto con un conjunto de relajaciones en, posiblemente, múltiples dimensiones. Estas relajaciones se traducirán, en tiempo de ejecución, en oportunidades expandidas(y complejas) de planificación en función de la arquitectura subyacente, impactando así en métricas como rendimiento o consumo energético.2. Abstraer al usuario de la complejidad del hardware subyacente, delegando la correcta explotación de dichas posibilidades de planificación expandidas a un componente software de sistema (típicamente conocido como runtime). Dicho software, dotado de conocimiento tanto de las características estáticas de la arquitectura subyacente como del estado puntual de la misma en el momento de la ejecución, explotará las combinaciones consideradas optimas de entre las relajaciones propuestas por el usuario para cada tarea lista para set ejecutada.3. Extender dicha abstracción para describir tanto sistemas de cómputo, en forma de jerarquía de ejecutores y alojadores de memoria que en ´ultimo término describen una arquitectura de cómputo heterogénea, como aplicaciones, en forma de un conjunto de tareas interrelacionadas. Además, las relaciones entre ejecutores y tareas son clasificadas en una nueva taxonomía tarea-ejecutor, la cual motiva frontends de programación HPC sin ambigüedad basados en la clasificación STSE, Single Task - Single Executor, separada de backends runtime totalmente automatizados.4. Proponer un nuevo modelo de programación (STEEL) basado en la clasificación STSE que aglutine ciertas características consideradas básicas de cara al éxito de los futuros modelos de programación basados en tareas: rendimiento, facilidad de composición, expresividad e interfaces no permisivos ante fallos.5. Especificar una API que dé soporte al modelo de programación, así como una implementación runtime del mismo aprovechando técnicas y paradigmas soportados en el lenguaje C++ de última generación, e ilustrar su uso, flexibilidad e impacto en el rendimiento a través de ejemplos y casos de uso sencillos .La metodología que se propugna aboga por una clara y estricta separación de conceptos entre los actores básicos que componen una ejecución paralela: usuario / código y hardware subyacente. Este tipo de abstracciones permite delegar el conocimiento experto desde el usuario hacia el software de sistema, proporcionando así mecanismos para mecanizar y automatizar su optimización ,y adaptar su rendimiento a la arquitectura paralela sobre la que se instanciarán los códigos. Desde este punto de vista, la tesis diseña, implementa y valida mecanismos para llevar a cabo una formalización de la complejidad inherente a la programación paralela heterogénea, clasificando aquellas acciones que en la actualidad se llevan a cabo por parte del usuario en el proceso de desarrollo y optimización de código, y proporcionando un marco de trabajo en el que dicha complejidad puede ser delegada, de forma eficiente y consistente, a un runtime...Fac. de InformáticaTRUEunpu

    Model Checking and Model-Based Testing : Improving Their Feasibility by Lazy Techniques, Parallelization, and Other Optimizations

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    This thesis focuses on the lightweight formal method of model-based testing for checking safety properties, and derives a new and more feasible approach. For liveness properties, dynamic testing is impossible, so feasibility is increased by specializing on an important class of properties, livelock freedom, and deriving a more feasible model checking algorithm for it. All mentioned improvements are substantiated by experiments

    Language independent modelling of parallelism

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    To make programs work in parallel contexts without any hazards, programming languages require changes to their structures and compilers. One of the most complicated parts is memory models and how programming languages deal with memory interactions. Different processors provide a different level of safety guarantees (i.e. ARM provides relaxed whereas Intel provides strong guarantees). On the other hand, different programming languages provide different structures for parallel computation and have individual protocols for communicating with parallel processes. Unfortunately, no specific choice is best in all situations. This thesis focuses on memory models of various programming languages and processors highlighting some positive and negative features from the point of view of programmability, performance and portability. In order to give some evidence of problems and performance bottlenecks, some small programs have been developed. This thesis also concentrates on incorrect behaviors, especially on data race conditions in programs, providing suggestions on how to avoid them. Also, some litmus tests on systems featuring different vendors' processors were performed to observe data races on each system. Nowadays programming paradigms also became a big issue. Some of the programming styles support observable non-determinism which is the main reason for incorrect behavior in programs. In this thesis, different programming models are also discussed based on the current state of the available research. Also, the imperative and functional paradigms in different contexts are compared. Finally, a mathematical problem was solved using two different paradigms to provide some practical evidence of the theory

    Proceedings of the 5th International Workshop on Reconfigurable Communication-centric Systems on Chip 2010 - ReCoSoC\u2710 - May 17-19, 2010 Karlsruhe, Germany. (KIT Scientific Reports ; 7551)

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    ReCoSoC is intended to be a periodic annual meeting to expose and discuss gathered expertise as well as state of the art research around SoC related topics through plenary invited papers and posters. The workshop aims to provide a prospective view of tomorrow\u27s challenges in the multibillion transistor era, taking into account the emerging techniques and architectures exploring the synergy between flexible on-chip communication and system reconfigurability

    Static Detection of Livelocks in Ada Multitasking Programs

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    Abstract. In this paper we present algorithms to statically detect livelocks in Ada multitasking programs. Although the algorithms ’ worst-case execution time is exponential, they can be expected to run in polynomial time. Since the problem is strongly connected to finding infinite loops, which is undecidable in general, our algorithms compute only an approximation to the real solution of the problem. As a consequence our algorithms may compute false positives.
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