A static scheduling approach to enable safety-critical OpenMP applications

Parallel computation is fundamental to satisfy the performance requirements of advanced safety-critical systems. OpenMP is a good candidate to exploit the performance opportunities of parallel platforms. However, safety-critical systems are often based on static allocation strategies, whereas current OpenMP implementations are based on dynamic schedulers. This paper proposes two OpenMP-compliant static allocation approaches: an optimal but costly approach based on an ILP formulation, and a sub-optimal but tractable approach that computes a worst-case makespan bound close to the optimal one.This work is funded by the EU projects P-SOCRATES (FP7-ICT-2013-10) and HERCULES (H2020/ICT/2015/688860), and the Spanish Ministry of Science and Innovation under contract TIN2015-65316-P.Peer ReviewedPostprint (author's final draft

A Rat Model of Gambling Behavior and its Extinction: Effects of Win Probability on Choice in a Concurrent-Chains Procedure

Two experiments examined the effects of varying the probability of “wins” within a rat model of gambling. On a concurrent-chains procedure, rats could choose between a “work” lever on which a fixed 20 responses produced a food pellet or a “gamble” lever, where on some trials (“wins”) only one response was required for reinforcement while on other trials 40 responses were required. Despite the fact that the work lever was always associated with the higher overall reinforcement rate, rats frequently chose to respond on the gamble lever. The frequency with which rats chose the gamble lever varied as a function of win probability. Extinction of the gamble choice (i.e., gamble-lever choices no longer resulted in wins) resulted in consistent choice of the work lever. The behavioral baselines reported in the present study may prove useful for investigators interested in employing a rat model of gambling

A time-predictable parallel programing model for real-time systems

The recent technological advancements and market trends are causing an interesting phenomenon towards the convergence of the high-performance and the embedded computing domains. Critical real-time embedded systems are increasingly concerned with providing higher performance to implement advanced functionalities in a predictable way. OpenMP, the de-facto parallel programming model for shared memory architectures in the high-performance computing domain, is gaining the attention to be used in embedded platforms. The reason is that OpenMP is a mature language that allows to efficiently exploit the huge computational capabilities of parallel embedded architectures. Moreover, OpenMP allows to express parallelism on top of the current technologies used in embedded designs (e.g., C/C++ applications). At a lower level, OpenMP provides a powerful task-centric model that allows to define very sophisticated types of regular and irregular parallelism. While OpenMP provides relevant features for embedded systems, both the programming interface and the execution model are completely agnostic to the timing requirements of real-time systems. This thesis evaluates the use of OpenMP to develop future critical real-time embedded systems. The first contribution analyzes the OpenMP specification from a timing perspective. It proposes new features to be incorporated in the OpenMP standard and a set of guidelines to implement critical real-time systems with OpenMP. The second contribution develops new methods to analyze and predict the timing behavior of parallel applications, so that the notion of parallelism can be safely incorporated into critical real-time systems. Finally, the proposed techniques are evaluated with both synthetic applications and real use cases parallelized with OpenMP. With the above contributions, this thesis pushes the limits of the use of task-based parallel programming models in general, and OpenMP in particular, in critical real-time embedded domains.Los recientes avances tecnológicos y tendencias de mercado estan causando un interesante fenómeno hacia la convergencia de dos dominios: la computacion de altas prestaciones y la computacion embebida. Hay cada vez mas interés en que los sistemas embebidos criticos de tiempo real proporcionen un mayor rendimiento para implementar funcionalidades avanzadas de una manera predecible. OpenMP, el modelo de programación paralela estándar para arquitecturas de memoria compartida en el dominio de la computación de altas prestaciones, está ganando atención para ser utilizado en systemas embebidos. La razón es que OpenMP es un lenguaje asentado que permite explotar eficientemente las enormes capacidades computacionales de las arquitecturas paralelas embebidas. Además, OpenMP permite expresar paralelismo sobre las tecnologías actuales utilizadas en los diseños embebidos (por ejemplo, aplicaciones C/C++). A un nivel inferior, OpenMP proporciona un potente modelo centrado en tareas que permite expresar tipos muy sofisticados de paralelismo regular e irregular. Si bien OpenMP proporciona funciones relevantes para los sistemas embebidos, tanto la interfaz de programación como el modelo de ejecución son completamente ajenos a los requisitos temporales de los sistemas de tiempo real. Esta tesis evalúa el uso de OpenMP para desarrollar los futuros sistemas embebidos criticos de timepo real. La primera contribución analiza la especificación de OpenMP desde una perspectiva temporal. Se propone nuevas funcionalidades que podrian ser incorporadas en el estándar de OpenMP y un conjunto de pautas para implementar sistemas críticos de tiempo real con OpenMP. La segunda contribución desarrolla nuevos métodos para analizar y predecir el comportamiento temporal de las aplicaciones paralelas, de modo que la noción de paralelismo se pueda incorporar de manera segura en sistemas críticos de tiempo real. Finalmente, las técnicas propuestas se evaluan con aplicaciones sintéticas y casos de uso reales paralelizados con OpenMP. Con las mencionadas contribuciones, esta tesis amplía los límites en el uso de los modelos de programación paralela basados en tarea en general, y de OpenMP en particular, en dominios embebidos criticos de tiempo real

An Analysis of Lazy and Eager Limited Preemption Approaches under DAG-Based Global Fixed Priority Scheduling

DAG-based scheduling models have been shown to effectively express the parallel execution of current many-core heterogeneous architectures. However, their applicability to real-time settings is limited by the difficulties to find tight estimations of the worst-case timing parameters of tasks that may arbitrarily be preempted/migrated at any instruction. An efficient approach to increase the system predictability is to limit task preemptions to a set of pre-defined points. This limited preemption model supports two different preemption approaches, eager and lazy, which have been analyzed only for sequential task-sets. This paper proposes a new response time analysis that computes an upper bound on the lower priority blocking that each task may incur with eager and lazy preemptions. We evaluate our analysis with both, synthetic DAG-based task-sets and a real case-study from the automotive domain. Results from the analysis demonstrate that, despite the eager approach generates a higher number of priority inversions, the blocking impact is generally smaller than in the lazy approach, leading to a better schedulability performance.This work was funded by the EU projects P-SOCRATES (FP7-ICT-2013-10) and HERCULES (H2020/ICT/2015/688860), and the Spanish Ministry of Science and Innovation under contract TIN2015-65316-P.Peer ReviewedPostprint (author's final draft

Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes

The environmental conditions on the Earth before 4 billion years ago are highly uncertain, largely because of the lack of a substantial rock record from this period. During this time interval, known as the Hadean, the young planet transformed from an uninhabited world to the one capable of supporting, and inhabited by the first living cells. These cells formed in a fluid environment they could not at first control, with homeostatic mechanisms developing only later. It is therefore possible that present-day organisms retain some record of the primordial fluid in which the first cells formed. Here we present new data on the elemental compositions and mineral fingerprints of both Bacteria and Archaea, using these data to constrain the environment in which life formed. The cradle solution that produced this elemental signature was saturated in barite, sphene, chalcedony, apatite, and clay minerals. The presence of these minerals, as well as other chemical features, suggests that the cradle environment of life may have been a weathering fluid interacting with dry-land silicate rocks. The specific mineral assemblage provides evidence for a moderate Hadean climate with dry and wet seasons and a lower atmospheric abundance of CO2 than is present today.Fil: Novoselov, Alexey A.. Universidad de Concepción; ChileFil: Silva, Dailto. Universidade Estadual de Campinas; BrasilFil: Schneider, Jerusa. Universidade Estadual de Campinas; BrasilFil: Abrevaya, Ximena Celeste. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Chaffin, Michael S.. State University Of Colorado Boulder; Estados UnidosFil: Serrano, Paloma. Alfred Wegener Institute Helmholtz Centre For Polar And Marine Research,; AlemaniaFil: Navarro, Margareth Sugano. Universidade Estadual de Campinas; BrasilFil: Conti, Maria Josiane. André Tosello Institute; BrasilFil: Souza Filho, Carlos Roberto de. Universidade Estadual de Campinas; Brasi

Robust program for LLSE data correlation of ternary systems

The existing commercial software packages (like Dechema Data Preparation Package (DPP) and the regression utilities of Chemical Engineering simulators like Chemcad) have been widely used and their extensive capabilities are well-known. Nevertheless, and as long as LLE calculations is concerned, they have been designed for the simplest equilibrium behaviour. For example, for ternary systems it is only possible the correlation of type 1 and type 2 LLE data. None of these applications allows for the correlation of type 0 LLE, type 3 LLLE or type 4 LLSE systems. To enable a possible extension of such software, a robust calculation algorithm to compute phase equilibria among condensed phases for all these more complicated behaviours has been developed.Vicepresidency of Research (University of Alicante) and Generalitat Valenciana (GV/2007/125)

Sensitivity of bile acid transport by organic anion-transporting polypeptides to intracellular pH

AbstractWe investigated the influence of intracellular pH (pHi) on [14C]-glycocholate (GC) uptake by human hepatoblastoma HepG2 cells that express sodium-independent (mainly OATP-A and OATP-8), but not sodium-dependent, GC transporters. Replacement of extracellular sodium by choline (Chol) stimulated GC uptake but did not affect GC efflux from loaded cells. Amiloride or NaCl replacement by tetraethylammonium chloride (TeACl) or sucrose also increased GC uptake. All stimulating circumstances decreased pHi. By contrast, adding to the medium ammonium or imidazole, which increased pHi, had no effect on GC uptake. In Chinese hamster ovary (CHO) cells expressing rat Oatp1, acidification of pHi had the opposite effect on GC uptake, that is, this was reduced. Changes in extracellular pH (pHo) between 7.40 and 7.00 had no effect on GC uptake at pHi 7.30 or 7.45 when pHo<pHi. However, GC uptake was inhibited at pHo 7.40 and 7.80 when pHo>pHi. Inhibition was not proportional to the pHo−pHi difference. Intracellular acidification decreased Vmax, but had no effect on Km. In sum, sodium-independent GC transport can be affected by intracellular acidification, possibly due both to modifications in the driving forces and to the particular response to protonation of carrier proteins involved in this process

Timing characterization of OpenMP4 tasking model

OpenMP is increasingly being supported by the newest high-end embedded many-core processors. Despite the lack of any notion of real-time execution, the latest specification of OpenMP (v4.0) introduces a tasking model that resembles the way real-time embedded applications are modeled and designed, i.e., as a set of periodic task graphs. This makes OpenMP4 a convenient candidate to be adopted in future real-time systems. However, OpenMP4 incorporates as well features to guarantee backward compatibility with previous versions that limit its practical usability in real-time systems. The most notable example is the distinction between tied and untied tasks. Tied tasks force all parts of a task to be executed on the same thread that started the execution, whereas a suspended untied task is allowed to resume execution on a different thread. Moreover, tied tasks are forbidden to be scheduled in threads in which other non-descendant tied tasks are suspended. As a result, the execution model of tied tasks, which is the default model in OpenMP to simplify the coexistence with legacy constructs, clearly restricts the performance and has serious implications on the response time analysis of OpenMP4 applications, making difficult to adopt it in real-time environments. In this paper, we revisit OpenMP design choices, introducing timing predictability as a new and key metric of interest. Our first results confirm that even if tied tasks can be timing analyzed, the quality of the analysis is much worse than with untied tasks. We thus reason about the benefits of using untied tasks, deriving a response time analysis for this model, and so allowing OpenMP4 untied model to be applied to real-time systems

Comparison of the voltammetric behavior of metronidazole at a DNA-modified glassy carbon electrode, a mercury thin film electrode and a glassy carbon electrode

The electroanalytical performance at three electrodes: DNA-modified galssy carbon electrode, mercury thin film electrode and glassy carbon electrode, for the study of the electrochemical reduction of metronidazole is compared. All three electrodes showed a similar trend in the reduction mechanism for metronidazole, depenent on pH in the acid and neutral region and independent in alkaline media, although there was a shift in the peak potentials to more negative values when a bare glassy carbon electrode was used compared to the other two. Besides the advantage of using a solid electrode for the reduction of metronidazole, the DNA-modified galssy carbon electrode enables a lower detection limit of 1.0 muM owing to the preconecentration of the drug on the electrode surface, which is not the case for the mercury thin film or bare glassy carbon electrodes