1,721,136 research outputs found
Can We Trust AI-Powered Real-Time Embedded Systems? (Invited Paper)
No full textThe excellent performance of deep neural networks and machine learning algorithms is pushing the industry to adopt such a technology in several application domains, including safety-critical ones, as self-driving vehicles, autonomous robots, and diagnosis support systems for medical applications. However, most of the AI methodologies available today have not been designed to work in safety-critical environments and several issues need to be solved, at different architecture levels, to make them trustworthy. This paper presents some of the major problems existing today in AI-powered embedded systems, highlighting possible solutions and research directions to support them, increasing their security, safety, and time predictability
Distributed Coordination Protocol for the Connectivity Maintenance in a Network of Mobile Units
No full textThe coordination of a team made by a set of mobile robots involves several challenges since, given a task to be accomplished by the team, the mobility of each robotic unit is often constrained by several factors. Connectivity is one of the most important factors. Cooperating robots must keep connected for many reasons: to plan a working strategy, to coordinate movements and actions, to re-configure the network in case of unexpected events. This paper describes a fully distributed coordination strategy expressly targeted to the maintenance of the connectivity among mobile robots. The proposed approach is based on the periodic broadcast of state information, which is used to drive the mobility strategies of nodes. The team uses a Leader/Follower organization, where Leaders have to move toward predefined locations to perform the given task, while Followers have to coordinate to maintain the global network connectivity, i.e., the multi-hop connection between Leaders. The proposed scheme is analyzed to derive its formal properties, and simulation results are presented to show the protocol behaviour under different working conditions
Time Properties of the Bust Protocol Under the NPA Budget Allocation Scheme
Full text linkToken passing is a channel access technique used in several communication networks. Among them, one of the most effective solution for supporting both real-time traffic (synchronous messages) and non real-time traffic (asynchronous messages), is the so-called timed-token protocol. Recently, a new token passing protocol, called Budget Sharing Token protocol (BuST), was proposed to improve the existing timed-token approaches in terms of synchronous bandwidth guarantee, while guaranteeing a minimum throughput for the asynchronous traffic.
This paper analyzes the ability of BuST to manage real-time and non real-time traffic in comparison with the classic timed-token protocol and its modified version, under the Normalized Proportional Allocation (NPA) scheme. We will show that BuST achieves higher guaranteed real-time bandwidth than the original timed-token protocol, and improves the service for the non real-time traffic respect to its modified version
Feasibility Analysis under Fixed Priority Scheduling with Fixed Preemption Points
No full textLimited preemption models have been proposed as a viable alternative between the two extreme cases of fully preemptive and non-preemptive scheduling. In particular, allowing preemption to occur only at predefined preemption points reduces context switch costs, simplifies the access to shared resources, and allows more predictable estimations of worst-case execution times. Current results related to such a model, however, exhibit two major deficiencies: (i) The exact response time analysis has a high computational complexity; (ii) The maximum lengths of then on-preemptive regions was not completely investigated in all possible scenarios. In this paper, we address the problem of scheduling a set of real-time tasks having fixed priorities and fixed preemption points. In particular, under specific but not restrictive assumptions we simplified the feasibility analysis and proposed an efficient feasibility test. Finally, an algorithm for computing the maximum length of fixed non-preemptive regions for each task is described, and some simulation experiments are presented to validate the proposed approach
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
Semi-Partitioned Scheduling of Dynamic Real-Time Workload: A Practical Approach Based on Analysis-Driven Load Balancing
Full text linkRecent work showed that semi-partitioned scheduling can achieve near-optimal schedulability performance, is simpler to implement compared to global scheduling, and less heavier in terms of runtime overhead, thus resulting in an excellent choice for implementing real-world systems. However, semi-partitioned scheduling typically leverages an off-line design to allocate tasks across the available processors, which requires a-priori knowledge of the workload. Conversely, several simple global schedulers, as global earliest-deadline first (G-EDF), can transparently support dynamic workload without requiring a task-allocation phase. Nonetheless, such schedulers exhibit poor worst-case performance.
This work proposes a semi-partitioned approach to efficiently schedule dynamic real-time workload on a multiprocessor system. A linear-time approximation for the C=D splitting scheme under partitioned EDF scheduling is first presented to reduce the complexity of online scheduling decisions. Then, a load-balancing algorithm is proposed for admitting new real-time workload in the system with limited workload re-allocation. A large-scale experimental study shows that the linear-time approximation has a very limited utilization loss compared to the exact technique and the proposed approach achieves very high schedulability performance, with a consistent improvement on G-EDF and pure partitioned EDF scheduling
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
Energy Saving Exploiting the Limited Preemption Task Model
No full textLimited preemptive scheduling has been shown to dominate both non-preemptive and fully preemptive scheduling under fixed priority systems, as far as schedulability is concerned. This paper suggests the use of DVS and DMP techniques under limited preemptive scheduling to further reduce energy consumption with respect to a fully preemptive or non-preemptive approach
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
- …
