Scheduling Periodic Real-Time Tasks with Heterogeneous Reward Requirements

Abstract—We study the problem of scheduling periodic real-time tasks which have individual minimum reward requirements. We consider situations where tasks generate jobs that can be provided arbitrary service times before their deadlines, and obtain rewards based on the service times received by the jobs of the task. We show that this model is compatible with the imprecise computation models and the increasing reward with increasing service models. In contrast to previous work on these models, which mainly focus on maximizing the total reward in the system, we additionally aim to fulfill different reward requirements of different tasks. This provides better fairness and also allows fine-grained tradeoff between tasks. We first derive a necessary and sufficient condition for a system with reward requirements of tasks to be feasible. We next obtain an off-line feasibility optimal scheduling policy. We then study a sufficient condition for a policy to be feasibility optimal or achieve some approximation bound. This condition serves as a guideline for designing on-line scheduling policy and we obtain a greedy policy based on it. We prove that the on-line policy is feasibility optimal when all tasks have the same periods, and also obtain an approximation bound for the policy under general cases. We test our policies through comparative simulations. I

Exploring the resilience of uncertain nonlinear handling chain systems in container ports with a novel sliding mode control

Uncertain handling chain system (HCS) of container ports brings steady-state error to the original control decisions, and even worse, dramatically degrades the system performance. The steady-state error will cause unsatisfied freight requirement to be much higher than the expected value for a long time, resulting in the decrease of system robustness and resilience. In this work, a novel sliding mode control with power integral reaching law (SMC-P) is presented for nonlinear HCS of container ports under uncertainty. Specifically, the integral of system state variable, the exponential reaching law and the power of the switching function are integrated to the traditional reaching law. And it is proven that the eliminated steady-state error, the accelerated approach speed, and the reduced chattering can be effectively obtained by SMC-P. A nonlinear HCS in container ports with uncertain freight requirement and handling ability is considered. SMC-P is compared with traditional method, genetic algorithm, quasi-sliding mode control and integral sliding mode control. Simulation results show that SMC-P does not only balance both steady-state error reduction and chattering avoidance caused by uncertainty, but also optimize the performance, robustness, and resilience of the uncertain nonlinear HCS. This study also brings economic and sustainability contributions for port authorities.info:eu-repo/semantics/publishedVersio

The Search for Smart Schools: Identifying Texas School Districts’ Best Practices

This report outlines findings from the TXSmartSchools.org (TSS) Capstone Team’s mixed methodology study identifying best practices in high performing and cost-efficient school districts. TSS was particularly interested in finding best practices transferable from high performing school districts to low performing districts. The Capstone Team accomplished this using the TSS concept of “fiscal peers.” After completing a narrative literature review on the best practices in public education, the Capstone Team examined the effect of various school district expenditures on academic performance and cost efficiency through quantitative methods. The Capstone Team’s findings suggest the amount of money invested in practices are not indicative of the quality of the programs. Additional findings demonstrate the administrative cost ratio caps do not improve cost efficiency, and investments in bilingual education are associated with improved academic performance. To better describe the practices employed in school districts, semistructured interviews were conducted with school district officials. The findings from interviews with chief business officers and superintendents capture the importance of culture in district practices and operations. Based on the quantitative and qualitative findings, the Capstone Team makes recommendations that can be implemented at the district and state level. Further research is needed that will allow educators and researchers to better identify the best practices that will improve Texas schools’ and districts’ student academic achievement and fiscal efficiency

Modularity for Large Virtual Reality Applications

International audienceThis paper focuses on the design of high performance VR applications. These applications usually involve various I/O devices and complex simulations. A parallel architecture or grid infrastructure is required to provide the necessary I/O and processing capabilities. Developing such applications faces several difficulties, two important ones being software engineering and performance issues. We argue that application modularity is a key concept to help the developer handle the complexity of these applications. We discuss how various approaches borrowed from other existing works can be combined to significantly improve the modularity of VR applications. This led to the development of the FlowVR middleware that associates a data-flow model with a hierarchical component model. Different case studies are presented to discuss the benefits of the approach proposed

Attention Allocation Aid for Visual Search

This paper outlines the development and testing of a novel, feedback-enabled attention allocation aid (AAAD), which uses real-time physiological data to improve human performance in a realistic sequential visual search task. Indeed, by optimizing over search duration, the aid improves efficiency, while preserving decision accuracy, as the operator identifies and classifies targets within simulated aerial imagery. Specifically, using experimental eye-tracking data and measurements about target detectability across the human visual field, we develop functional models of detection accuracy as a function of search time, number of eye movements, scan path, and image clutter. These models are then used by the AAAD in conjunction with real time eye position data to make probabilistic estimations of attained search accuracy and to recommend that the observer either move on to the next image or continue exploring the present image. An experimental evaluation in a scenario motivated from human supervisory control in surveillance missions confirms the benefits of the AAAD.Comment: To be presented at the ACM CHI conference in Denver, Colorado in May 201

Inter-workgroup barrier synchronisation on graphics processing units

GPUs are parallel devices that are able to run thousands of independent threads concurrently. Traditional GPU programs are data-parallel, requiring little to no communication, i.e. synchronisation, between threads. However, classical concurrency in the context of CPUs often exploits synchronisation idioms that are not supported on GPUs. By studying such idioms on GPUs, with an aim to facilitate them in a portable way, a wider and more generic space of GPU applications can be made possible. While the breadth of this thesis extends to many aspects of GPU systems, the common thread throughout is the global barrier: an execution barrier that synchronises all threads executing a GPU application. The idea of such a barrier might seem straightforward, however this investigation reveals many challenges and insights. In particular, this thesis includes the following studies: Execution models: while a general global barrier can deadlock due to starvation on GPUs, it is shown that the scheduling guarantees of current GPUs can be used to dynamically create an execution environment that allows for a safe and portable global barrier across a subset of the GPU threads. Application optimisations: a set GPU optimisations are examined that are tailored for graph applications, including one optimisation enabled by the global barrier. It is shown that these optimisations can provided substantial performance improvements, e.g. the barrier optimisation achieves over a 10X speedup on AMD and Intel GPUs. The performance portability of these optimisations is investigated, as their utility varies across input, application, and architecture. Multitasking: because many GPUs do not support preemption, long-running GPU compute tasks (e.g. applications that use the global barrier) may block other GPU functions, including graphics. A simple cooperative multitasking scheme is proposed that allows graphics tasks to meet their deadlines with reasonable overheads.Open Acces

Factors shaping the evolution of electronic documentation systems

The main goal is to prepare the space station technical and managerial structure for likely changes in the creation, capture, transfer, and utilization of knowledge. By anticipating advances, the design of Space Station Project (SSP) information systems can be tailored to facilitate a progression of increasingly sophisticated strategies as the space station evolves. Future generations of advanced information systems will use increases in power to deliver environmentally meaningful, contextually targeted, interconnected data (knowledge). The concept of a Knowledge Base Management System is emerging when the problem is focused on how information systems can perform such a conversion of raw data. Such a system would include traditional management functions for large space databases. Added artificial intelligence features might encompass co-existing knowledge representation schemes; effective control structures for deductive, plausible, and inductive reasoning; means for knowledge acquisition, refinement, and validation; explanation facilities; and dynamic human intervention. The major areas covered include: alternative knowledge representation approaches; advanced user interface capabilities; computer-supported cooperative work; the evolution of information system hardware; standardization, compatibility, and connectivity; and organizational impacts of information intensive environments

NASA Tech Briefs, August 1991

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences