1,720,957 research outputs found
Energy-aware scheduling for real-time systems: A survey
No full textThis article presents a survey of energy-aware scheduling algorithms proposed for real-time systems. The analysis presents the main results starting from the middle 1990s until today, showing how the proposed solutions evolved to address the evolution of the platform's features and needs. The survey first presents a taxonomy to classify the existing approaches for uniprocessor systems, distinguishing them according to the technology exploited for reducing energy consumption, that is, Dynamic Voltage and Frequency Scaling (DVFS), Dynamic Power Management (DPM), or both. Then, the survey discusses the approaches proposed in the literature to deal with the additional problems related to the evolution of computing platforms toward multicore architectures
On the effectiveness of energy-aware real-time scheduling algorithms on single-core platforms
No full textEnergy-aware scheduling is a challenging problem that has been studied for decades, investigating the trade-off between performance and energy consumption. In early CMOS circuits, Dynamic Voltage and Frequency Scaling (DVFS) techniques allowed drastically reducing the power consumption. Recent technological advancements have decreased the portion of dissipation which is affected by speed scaling, making Dynamic Power Management (DPM) algorithms more effective. However, the adoption of simplistic power models often biased the decision on which technique to adopt, decreasing the effectiveness of the selected implementation. This paper discusses the factors to consider when deciding which technique to implement on a given single-core architecture, highlight the limitations of the current mainstream
On the Energy-Aware Partitioning of Real-Time Tasks on Homogeneous Multi-Processor Systems
No full textIn high-performance computing systems, efficient energy management is a key feature for keeping energy bills low and avoiding thermal dissipation problems, as well as for
controlling the application performance. This paper considers
the problem of partitioning and scheduling a set of real-time
tasks on a realistic hardware platform consisting of a number
of homogeneous processors. Several well-known heuristics are
compared to identify the approach that better reduces the overall
energy consumption of the entire system. Despite the actual state
Another well-known approach is the Dynamic Power Man-
of art, the approach which minimizes the number of active cores
is the most energy efficient
An energy-aware algorithm exploiting limited preemptive scheduling under fixed priorities
No full textThis paper presents a new energy-aware algorithm that integrates Dynamic Voltage and Frequency Scaling (DVFS) and Dynamic Power Management (DPM) techniques to further reduce energy consumption in embedded systems. It consists of an off-line DVFS-stage, for computing the speed that minimizes energy consumption during active intervals while guaranteeing timing constraints, and an online DPM-stage, for prolonging sleep intervals by postponing task execution. Moreover, limited preemptive scheduling is exploited to reduce preemption costs and further extend sleep intervals under fixed-priority systems, with respect to fully preemptive schedulers. The online algorithm has a constant complexity and preemption costs are taken into account in the analysis. A set of simulation experiments are reported to illustrate the behavior of the proposed approach as a function of different parameters and compare its performance with the state-of-art methods available in the literature
Power Management in Real-Time Embedded Systems
No full textWith the improvement of the computer science and electronic tecnologies, nowadays, it’s possibile to realize devices very small, with extraordinary computation capabilities and with a good cost for unit.
Hi-tech products are everywhere around us and in the future we’ll be immersed in a world where everything will be electronic.
In this scenario, it’s born the issue of the energy saving, especially in real-time systems, with an high level of integration in the monitored environment and a not infinite power supply.
It means to try to reduce the waste of energy, with a smart organization of the jobs and resources, allowing the satisfation all requirements (e.g.: time, few resources, shared resources).
In this thesis, a software module will be proposed, between the operating system and user applications, to obtain those targets, with a set of devices such as the CPU, radio modules and servomechanisms.
Servo motors are the muscles of many devices and from their analysis the best updating period can be extracted to reduce the energy according to the applied torque.
About radio modules, the system makes that they fall asleep when they aren’t used and wakes up them just in time to be ready when they are required.
The CPU manager is the core of the discussion and implements three inter-task reclaiming algorithms. Results are compared with a DPM approach, to investigate trade-offs.
Algorithms were studied for hard real-time systems, so they respect always the time constraints of tasks and devices
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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