A Review on Software Architectures for Heterogeneous Platforms

The increasing demands for computing performance have been a reality regardless of the requirements for smaller and more energy efficient devices. Throughout the years, the strategy adopted by industry was to increase the robustness of a single processor by increasing its clock frequency and mounting more transistors so more calculations could be executed. However, it is known that the physical limits of such processors are being reached, and one way to fulfill such increasing computing demands has been to adopt a strategy based on heterogeneous computing, i.e., using a heterogeneous platform containing more than one type of processor. This way, different types of tasks can be executed by processors that are specialized in them. Heterogeneous computing, however, poses a number of challenges to software engineering, especially in the architecture and deployment phases. In this paper, we conduct an empirical study that aims at discovering the state-of-the-art in software architecture for heterogeneous computing, with focus on deployment. We conduct a systematic mapping study that retrieved 28 studies, which were critically assessed to obtain an overview of the research field. We identified gaps and trends that can be used by both researchers and practitioners as guides to further investigate the topic

Influencia de la habilidad lectora en L1 y competencia lingüística en L2 en la comprensión de lectura en L2

El proceso de lectura tiene como componentes al texto mismo, al lector y al conocimiento del mundo que éste tiene. A pesar de la simplicidad, en cuanto al número de componentes se refiere, es un proceso muy complejo. Ha sido difícil, sino imposible, descifrar hasta el momento el constructo que ayuda al ser humano a comprender un texto. El proceso es dinámico, ya que se efectúa en medio de un vaivén de ideas, predicciones, conceptualizaciones, juicios y prejuicios; es interactivo, puesto que el lector aporta sus ideas y conocimiento para el entendimiento del texto, a la vez que éste proporciona información al lector para que incremente sus conocimientos del medio. Todas estas características son una muestra de la complejidad que envuelve al proceso de lectura

A Process-oriented Approach for Migrating Software to Heterogeneous Platforms

Context: Heterogeneous computing, i.e., computing performed on processors of different types - such as combination of CPUs and GPUs, or CPUs and FPGAs - has shown to be a feasible path towards higher performance and less energy consumption. However, this approach imposes a number of challenges on the software side that must be addressed in order to achieve the aforementioned advantages.Objective: The objective of this thesis is to improve the process of software deployment on heterogeneous platforms. Through a detailed analysis of the state-of-the-art and state-of-the-practice, we aim to provide a reasoning framework for engineers to migrate software to be executed on such platforms.Method: To achieve our goal, we conducted: (i) a literature review in the form of a systematic mapping study on software deployment on heterogeneous platforms; (ii) a multiple case study in industry that highlights the main challenges and concerns in the state-of-the-practice in the area; and (iii) a study in which we propose and evaluate a decision framework to guide engineers in migrating software for execution on heterogeneous platforms, with a case study in the automotive domain.Results: In the mapping study, we provided a thorough classification of the identified concerns and approaches to deploying software on heterogeneous platforms. Among other findings, we discovered a lack of holistic approaches that include development processes, as well as few validation studies in industrial contexts. In the second study, we discovered and analyzed common practices and challenges that companies face when using heterogeneous platforms. One of such challenges is related to the lack of approaches that cover the software development lifecycle. In the third study, we proposed a decision framework that guides engineers in the process of reasoning for migrating software for execution on heterogeneous platforms. It consists of five stages (assessing, re-architecting, developing, deploying, evaluating), each containing a set of aspects to be addressed through the answers to predefined questions.Conclusions: This thesis addresses a gap that was identified in both theory and practice concerning the lack of holistic approaches to migrate software for execution on heterogeneous platforms. Our proposed approach addresses the problem through systematic guidance for engineers.Future work: In the future, we intend to further refine the proposed framework through case studies in domains other than automotive. We will explore its integration with existing software engineering processes in industrial contexts, performing in-depth analysis of the required adaptations and providing detailed solutions within the stages of the framework

Analysis and Design Methodologies for Switched-Capacitor Filter Circuits in Advanced CMOS Technologies

Analog filters are an extremely important block in several electronic systems, such as RF transceivers, data acquisition channels, or sigma-delta modulators. They allow the suppression of unwanted frequencies bands in a signal, improving the system’s performance. These blocks are typically implemented using active RC filters, gm-C filters, or switched-capacitor (SC) filters. In modern deep-submicron CMOS technologies, the transistors intrinsic gain is small and has a large variability, making the design of moderate and high-gain amplifiers, used in the implementation of filter blocks, extremely difficult. To avoid this difficulty, in the case of SC filters, the opamp can be replaced with a voltage buffer or a low-gain amplifier (< 2), simplifying the amplifier’s design and making it easier to achieve higher bandwidths, for the same power. However, due to the loss of the virtual ground node, the circuit becomes sensitive to the effects of parasitic capacitances, which effect needs to be compensated during the design process. This thesis addresses the task of optimizing SC filters (mainly focused on implementations using low-gain amplifiers), helping designers with the complex task of designing high performance SC filters in advanced CMOS technologies. An efficient optimization methodology is introduced, based on hybrid cost functions (equation-based/simulation-based) and using genetic algorithms. The optimization software starts by using equations in the cost function to estimate the filter’s frequency response reducing computation time, when compared with the electrical simulation of the circuit’s impulse response. Using equations, the frequency response can be quickly computed (< 1 s), allowing the use of larger populations in the genetic algorithm (GA) to cover the entire design space. Once the specifications are met, the population size is reduced and the equation-based design is fine-tuned using the more computationally intensive, but more accurate, simulation-based cost function, allowing to accurately compensate the parasitic capacitances, which are harder to estimate using equations. With this hybrid approach, it is possible to obtain the final optimized design within a reasonable amount of computation time. Two methods are described for the estimation of the filter’s frequency response. The first method is hierarchical in nature where, in the first step, the frequency response is optimized using the circuit’s ideal transfer function. The following steps are used to optimize circuits, at transistor level, to replace the ideal blocks (amplifier and switches) used in the first step, while compensating the effects of the circuit’s parasitic capacitances in the ideal design. The second method uses a novel efficient numerical methodology to obtain the frequency response of SC filters, based on the circuit’s first-order differential equations. The methodology uses a non-hierarchical approach, where the non-ideal effects of the transistors (in the amplifier and in the switches) are taken into consideration, allowing the accurate computation of the frequency response, even in the case of incomplete settling in the SC branches. Several design and optimization examples are given to demonstrate the performance of the proposed methods. The prototypes of a second order programmable bandpass SC filter and a 50 Hz notch SC filter have been designed in UMC 130 nm CMOS technology and optimized using the proposed optimization software with a supply voltage of 0.9 V. The bandpass SC filter has a total power consumption of 249 uW. The filter’s central frequency can be tuned between 3.9 kHz and 7.1 kHz, the gain between -6.4 dB and 12.6 dB, and the quality factor between 0.9 and 6.9. Depending on the bit configuration, the circuit’s THD is between -54.7 dB and -61.7 dB. The 50 Hz notch SC filter has a total power consumption of 273 uW. The transient simulation of the circuit’s extracted view (C+CC) shows an attenuation of 52.3 dB in the 50 Hz interference and that the desired 5 kHz signal has a THD of -92.3 dB

Design of switched-capacitor filters using low gain amplifiers

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de ComputadoresAnalog filters are extremely important blocks in several electronic systems such as RF transceivers or sigma delta modulators. They allow selecting between signals with different frequency and eliminating unwanted signals. In modern deep-submicron CMOS technologies the intrinsic gain of the transistors is low and has a large variability, making the design of moderate and high gain amplifiers extremely difficult. The objective of this thesis is to study switched-capacitor (SC) circuits based on the low-pass and band-pass Sallen-Key topologies, since they do not require high gain amplifiers. The strategy used to achieve this objective is to replace the operational amplifier (opamp) with a voltage buffer. Doing this simplifies the design of the amplifier although it also eliminates the virtual ground node from the circuit. Without this node parasitic insensitive SC networks cannot be used. Due to modern parasitic extraction software that can reliably predict the values of parasitic capacitances, the historical disadvantage of parasitic sensitive SC networks (parallel SC) is no longer critical, allowing its influence to be compensated during the design process. Different types of switches were simulated to determine the one with the least nonlinear effects. Two techniques (common mode voltage adjustment and source degeneration) were used to reduce the distortion introduced by the buffers. Low-pass (second and sixth order) and band-pass (second and fourth order) SC filters were simulated in differential configuration in standard 130 nm CMOS technology, having obtained for the low-pass filter a distortion of -62 dB for the biquad section and -54 dB for the sixth-order filter, for a cutoff frequency of 1MHz and when operating at 100 MHz of clock frequency. The total power consumption was 986 W and 5.838 mW, respectively

Setting up a network of agrometeorological stations in East Timor

A developed and sustainable agriculture requires a permanent and reliable monitoring of climatic/ meteorological elements in (agro) meteorological stations which should be located close to agricultural, silvicultural or pastoral activities. An adequate network of meteorological stations is then a necessary condition to support innovation and development in any country. Developing countries, mainly those with a history of frequent conflicts, presents deficient number of weather stations, often poorly composed and improperly distributed within their territories, and without a regular operation that allows continuity of records for a sufficiently long period of time. The objective of this work was to build a network of meteorological and agro-meteorological stations in East Timor. To achieve this goal, the number and location of pre-existing stations, their structure and composition (number and type of sensors, communication system,… ), the administrative division of the country and the available agro-ecological zoning, the agricultural and forestry practices in the country, the existing centres for the agricultural research and the history of the weathers records were taken into account. Several troubles were found (some of the automatic stations were assembled incorrectly, others stations duplicated information regarding the same agricultural area, vast areas with relevant agro-ecological representativeness were not monitored …). It was proposed the elimination of 11 existing stations, the relocation of 7 new stations in places not covered until then, the automation of 3 manual meteorological stations. Two networks were then purposed, a major with 15 agro-meteorological stations (all automatized) and one other secondary composed by 32 weather stations (only two were manual). The set of the 47 stations corresponded to a density of 329 km2/station. The flexibility in the composition of each of the networks was safeguarded and intends to respond effectively to any substantive change in the conditions in a country in constant change. It was also discussed the national coverage by these networks under a “management concept for weather stations”