A Multi-core processor for hard real-time systems

The increasing demand for new functionalities in current and future hard real-time embedded systems, like the ones deployed in automotive and avionics industries, is driving an increment in the performance required in current embedded processors. Multi-core processors represent a good design solution to cope with such higher performance requirements due to their better performance-per-watt ratio while maintaining the core design simple. Moreover, multi-cores also allow executing mixed-criticality level workloads composed of tasks with and without hard real-time requirements, maximizing the utilization of the hardware resources while guaranteeing low cost and low power consumption. Despite those benefits, current multi-core processors are less analyzable than single-core ones due to the interferences between different tasks when accessing hardware shared resources. As a result, estimating a meaningful Worst-Case Execution Time (WCET) estimation - i.e. to compute an upper bound of the application's execution time - becomes extremely difficult, if not even impossible, because the execution time of a task may change depending on the other threads running at the same time. This makes the WCET of a task dependent on the set of inter-task interferences introduced by the co-running tasks. Providing a WCET estimation independent from the other tasks (time composability property) is a key requirement in hard real-time systems. This thesis proposes a new multi-core processor design in which time composability is achieved, hence enabling the use of multi-cores in hard real-time systems. With our proposals the WCET estimation of a HRT is independent from the other co-running tasks. To that end, we design a multi-core processor in which the maximum delay a request from a Hard Real-time Task (HRT), accessing a hardware shared resource can suffer due to other tasks is bounded: our processor guarantees that a request to a shared resource cannot be delayed longer than a given Upper Bound Delay (UBD). In addition, the UBD allows identifying the impact that different processor configurations may have on the WCET by determining the sensitivity of a HRT to different resource allocations. This thesis proposes an off-line task allocation algorithm (called IA3: Interference-Aware Allocation Algorithm), that allocates tasks in a task set based on the HRT's sensitivity to different resource allocations. As a result the hardware shared resources used by HRTs are minimized, by allowing Non Hard Real-time Tasks (NHRTs) to use the rest of resources. Overall, our proposals provide analyzability for the HRTs allowing NHRTs to be executed into the same chip without any effect on the HRTs. The previous first two proposals of this thesis focused on supporting the execution of multi-programmed workloads with mixed-criticality levels (composed of HRTs and NHRTs). Higher performance could be achieved by implementing multi-threaded applications. As a first step towards supporting hard real-time parallel applications, this thesis proposes a new hardware/software approach to guarantee a predictable execution of software pipelined parallel programs. This thesis also investigates a solution to verify the timing correctness of HRTs without requiring any modification in the core design: we design a hardware unit which is interfaced with the processor and integrated into a functional-safety aware methodology. This unit monitors the execution time of a block of instructions and it detects if it exceeds the WCET. Concretely, we show how to handle timing faults on a real industrial automotive platform.La creciente demanda de nuevas funcionalidades en los sistemas empotrados de tiempo real actuales y futuros en industrias como la automovilística y la de aviación, está impulsando un incremento en el rendimiento necesario en los actuales procesadores empotrados. Los procesadores multi-núcleo son una solución eficiente para obtener un mayor rendimiento ya que aumentan el rendimiento por vatio, manteniendo el diseño del núcleo simple. Por otra parte, los procesadores multi-núcleo también permiten ejecutar cargas de trabajo con niveles de tiempo real mixtas (formadas por tareas de tiempo real duro y laxo así como tareas sin requerimientos de tiempo real), maximizando así la utilización de los recursos de procesador y garantizando el bajo consumo de energía. Sin embargo, a pesar los beneficios mencionados anteriormente, los actuales procesadores multi-núcleo son menos analizables que los de un solo núcleo debido a las interferencias surgidas cuando múltiples tareas acceden simultáneamente a los recursos compartidos del procesador. Como resultado, la estimación del peor tiempo de ejecución (conocido como WCET) - es decir, una cota superior del tiempo de ejecución de la aplicación - se convierte en extremadamente difícil, si no imposible, porque el tiempo de ejecución de una tarea puede cambiar dependiendo de las otras tareas que se estén ejecutando concurrentemente. Determinar una estimación del WCET independiente de las otras tareas es un requisito clave en los sistemas empotrados de tiempo real duro. Esta tesis propone un nuevo diseño de procesador multi-núcleo en el que el tiempo de ejecución de las tareas se puede componer, lo que permitirá el uso de procesadores multi-núcleo en los sistemas de tiempo real duro. Para ello, diseñamos un procesador multi-núcleo en el que la máxima demora que puede sufrir una petición de una tarea de tiempo real duro (HRT) para acceder a un recurso hardware compartido debido a otras tareas está acotado, tiene un límite superior (UBD). Además, UBD permite identificar el impacto que las diferentes posibles configuraciones del procesador pueden tener en el WCET, mediante la determinación de la sensibilidad en la variación del tiempo de ejecución de diferentes reservas de recursos del procesador. Esta tesis propone un algoritmo estático de reserva de recursos (llamado IA3), que asigna tareas a núcleos en función de dicha sensibilidad. Como resultado los recursos compartidos del procesador usados por tareas HRT se reducen al mínimo, permitiendo que las tareas sin requerimiento de tiempo real (NHRTs) puedas beneficiarse del resto de recursos. Por lo tanto, las propuestas presentadas en esta tesis permiten el análisis del WCET para tareas HRT, permitiendo así mismo la ejecución de tareas NHRTs en el mismo procesador multi-núcleo, sin que estas tengan ningún efecto sobre las tareas HRT. Las propuestas presentadas anteriormente se centran en el soporte a la ejecución de múltiples cargas de trabajo con diferentes niveles de tiempo real (HRT y NHRTs). Sin embargo, un mayor rendimiento puede lograrse mediante la transformación una tarea en múltiples sub-tareas paralelas. Esta tesis propone una nueva técnica, con soporte del procesador y del sistema operativo, que garantiza una ejecución analizable del modelo de ejecución paralela software pipelining. Esta tesis también investiga una solución para verificar la corrección del WCET de HRT sin necesidad de ninguna modificación en el diseño de la base: un nuevo componente externo al procesador se conecta a este sin necesidad de modificarlo. Esta nueva unidad monitorea el tiempo de ejecución de un bloque de instrucciones y detecta si se excede el WCET. Esta unidad permite detectar fallos de sincronización en sistemas de computación utilizados en automóviles

The influence of estradiol and progesterone on neurocognition during three phases of the menstrual cycle: Modulating factors

This paper is dedicated to the memory of the first professor of Behavioral Endocrinology in the Faculty of Psychology at the University of Granada, Prof. Filomena Molina. We are grateful to Daniel Robert Caldera Jr. for his assistance with the English. This study was supported by the Spanish Ministry of Economy, Industry and Competitiveness (National I + D Plan: PSI2017-89324-C2-1-P and PSI2017-89324C2-2-P). Funding for open access charge: Universidad de Granada/CBUA.Estradiol is an ovarian steroid hormone that peaks shortly before ovulation and significantly affects various brain regions and neurotransmitter systems, with similar and differential effects with progesterone, another ovarian hormone. Studies investigating the neurocognitive processes during the menstrual cycle have focused on the early follicular phase (EFP) characterized by low estradiol and progesterone levels and the mid-luteal phase (MLP) with high estradiol and progesterone levels. However, most studies have failed to include the ovulatory phase, characterized by high estradiol and low progesterone levels. Given the various hormonal changes in the menstrual cycle, we revisited studies suggesting that the menstrual cycle did not affect verbal and spatial abilities and observed that many contain mixed results. Comparing these studies makes it possible to identify relevant modulating factors, such as sample size, participant age, accurate selection of days for testing, asymmetrical practice effects, genetic polymorphisms, and task difficulty. More robust findings are related to improved mental rotation capacity during EFP with challenging tasks and differences in brain activation among menstrual cycle phases during the execution of spatial and verbal tasks. During MLP, less robust findings were observed, possibly modulated by the complex effects of the two hormones on the brain. In conclusion, we propose that it is crucial to include all three menstrual cycle phases and consider these modulating factors to avoid confounding findings.Spanish Ministry of Economy, Industry and Competitiveness PSI2017-89324-C2-1-P PSI2017-89324C2-2-PUniversidad de Granada/CBU

Gender congruency between languages influence second-language comprehension: Behavioral and electrophysiological evidence

In the present study we explore whether gender congruency between languages modulates bilinguals’ access to their second language words presented in isolation. We predicted that accessing L2 words that have a different gender across languages (gender-incongruent) would be more costly and require more effort than accessing same-gender words (gender-congruent) due to language co-activation, even when no access to L1 was required to perform the task. Additionally, we intended to shed some light into the mechanism underlying the gender congruency effect. To these aims, we compared the performance of Spanish native speakers with that of Italian-Spanish bilinguals (Italian native speakers) during a lexical decision task. The participants saw Spanish words that were gender-congruent and gender-incongruent between languages while event related potentials were recorded. Moreover, as an additional manipulation, we selected nouns that in both languages could be ambiguous or unambiguous. With the aim to examine whether the underlying mechanism is activation of multiple information during word processing, we focused on the N400 component, related with the effort to integrate lexical-semantic information: higher N400 amplitudes indicate greater effort. According to our prediction, Italian-Spanish bilinguals produced more errors and evoked larger N400 amplitudes when accessing gender-incongruent than gender-congruent words, while no differences appeared for Spanish native speakers between conditions. These results indicate that gender-incongruent words are harder to integrate compared with gender-congruent words, and that bilinguals automatically activate the grammatical gender of both languages during L2 language comprehension. Nevertheless, the results do not seem to support the assumption of a similar mechanism responsible for the gender congruency and the ambiguity effects. In short, the gender-congruency effect seems to originate due to activation of multiple information at the lexical level which generates difficulties to integrate at the semantic level during word access.This work has been supported by Spanish Ministry of Science, Innovation and Universities (RED2018-102615-T), by Feder Andalucía (A-SEJ-416-UGR20) to D.P., by Spanish Ministry of Science and Innovation (PID2019-111359 GB-I00/AEI/10.13039/501100011033) and by the Universitat Rovira i Virgili to P. F. (2019PFR-URV-B2-32). Funding for open access charge: Universidad de Granada / CBUA

The scope of grammatical gender in Spanish: Transference to the conceptual level

This research was supported by grants, PCIN-2015-165-C02-01 and PSI2017-89324-C2-1 from the Spanish Ministry of Economy and Competitiveness. We want to thank the Jagiellonian University for providing open access, and the anonymous reviewers for their valuable comments.The aim of the present study was to explore under what circumstances we could observe a transference from grammatical gender to the conceptual representation of sex in Spanish, a two-gender language. The participants performed a lexical decision task and a gender decision task in the auditory modality, including words referencing inanimate entities associated with males or females. The sex stereotype could be congruent (falda [skirt], feminine) or incongruent (corbata [tie], feminine) with the grammatical gender. If the transfer from grammatical gender to conceptual information related to sex is settled, we should observed faster access for the congruent words compared with the incongruent ones both in the gender decision task and in the lexical decision task. The results showed a facilitation while processing congruent vs. incongruent words where attention to gender was mandatory during the adapted gender decision task. However, there was a lack of transference during the lexical decision task that might have been caused by the absence of direct conceptual activation by the time the decision was made. Additionally, we found that grammatical gender and sex-related information are closely connected, such as the indexical information about the sex of the speaker primes the activation of information related to sex at the conceptual (sex stereotype) and also at the lexical level (grammatical gender). Altogether, the results indicate that gender congruency effect is magnified by direct gender activation.Spanish Ministry of Economy and Competitiveness PCIN-2015-165-C02-01 PSI2017-89324-C2-

Grammatical Gender Inhibition in Bilinguals

Inhibitory control processes have been recently considered to be involved in interference resolution in bilinguals at the phonological level. In this study we explored if interference resolution is also carried out by this inhibitory mechanism at the grammatical level. Thirty-two bilinguals (Italian-L1 and Spanish-L2) participated. All of them completed two tasks. In the first one they had to name pictures in L2. We manipulated gender congruency between the two languages and the number of presentations of the pictures (1 and 5). Results showed a gender congruency effect with slower naming latencies in the incongruent condition. In the second task, participants were presented with the pictures practiced during the first naming task, but now they were asked to produce the L1 article. Results showed a grammatical gender congruency effect in L1 that increased for those words practiced five times in L2. Our conclusion is that an inhibitory mechanism was involved in the suppression of the native language during a picture naming task. Furthermore, this inhibitory process was also involved in suppressing grammatical gender when it was a source of competition between the languages