Search results for "Scheduling"
showing 10 items of 275 documents
Scheduling in Targeted Transient Surveys and a New Telescope for CHASE
2010
We present a method for scheduling observations in small field-of-view transient targeted surveys. The method is based on maximizing the probability of detection of transient events of a given type and age since occurrence; it requires knowledge of the time since the last observation for every observed field, the expected light curve of the event, and the expected rate of events in the fields where the search is performed. In order to test this scheduling strategy we use a modified version of the genetic scheduler developed for the telescope control system RTS2. In particular, we present example schedules designed for a future 50 cm telescope that will expand the capabilities of the CHASE s…
Understanding Decision Support in Large-Scale Disasters: Challenges in Humanitarian Logistics Distribution
2017
Disasters are characterized by conflicting, uncertain, or lacking data. Nevertheless, humanitarian responders need to make rapid decisions. This is particularly true for the immediate response to a sudden onset disaster. Since most humanitarian decision support systems (DSS) make important assumptions on data availability and quality that are often not fulfilled in practice, decision-makers are largely left to their experience. In this paper, we identify three major challenges for an operational DSS to support distribution planning: (i) deep uncertainty; (ii) reflecting field conditions and constraints; and (iii) rapid humanitarian logistics modeling. We review the relevant theories and pro…
Ranking and comparing key factors causing time-overruns in on-site construction
2022
For years, the construction industry has looked for ways to avoid time-overruns in construction. Despite previous research mapping the factors affecting time performance, site-managers have difficulties in reducing the time-overrun. In order to create a clearer guidance on how to control time-performance, this study investigates the resource related factors because they are within the site-manager’s control. Three Case studies were followed and a survey including 36 participants where conducted. Both investigated and ranked the likelihood of delay due to the seven different resource factors. The ranking of the resource factors was identified as: (1) Construction design, (2) Connecting works…
Online Scheduling of Task Graphs on Heterogeneous Platforms
2020
Modern computing platforms commonly include accelerators. We target the problem of scheduling applications modeled as task graphs on hybrid platforms made of two types of resources, such as CPUs and GPUs. We consider that task graphs are uncovered dynamically, and that the scheduler has information only on the available tasks, i.e., tasks whose predecessors have all been completed. Each task can be processed by either a CPU or a GPU, and the corresponding processing times are known. Our study extends a previous $4\sqrt{m/k}$ 4 m / k -competitive online algorithm by Amaris et al. [1] , where $m$ m is the number of CPUs and $k$ k the number of GPUs ( $m\geq k$ m ≥ k ). We prove that no online…
Use of Supercomputing towards the Generation of a Process Execution Plan in Distributed Real-Time Systems
2010
This work consider the scheduling of periodic tasks or processes with real-time constraints in a distributed environment. Each task must be executed meeting deadlines, precedence relationships and resources constraints. The problem of scheduling tasks on a distributed environment can be viewed as a problem of assigning processes to the processors but keeping the schedulability in local environments. Thus, the problem can be divided in two phases: the first phase is assigning processes to processors and the second is to schedule assigned processes in each processor in the distributed environment. This paper focuses in the first phase. It introduces a heuristic mechanism for assigning process…
A distributed agro-hydrological model for irrigation water demand assessment
2008
Abstract The actual irrigation water demand in a district in Sicily (Italy) was assessed by the spatially distributed agro-hydrological model SIMODIS (SImulation and Management of On-Demand Irrigation Systems) . For each element with homogeneous crop and soil conditions, in which the considered area can be divided, the model numerically solves the one-dimensional water flow equation with vegetation parameters derived from Earth Observation data. In SIMODIS, the irrigation scheduling is set by means of two parameters: the threshold value of soil water pressure head in the root zone, h m , and the fraction of soil water deficit to be re-filled, Δ . This study investigated the possibility of i…
Dynamic scheduling of periodic skippable tasks in an overloaded real-time system
2008
International audience; The need for supporting dynamic real-time environments where changes in workloads may occur requires a scheduling framework that explicitly addresses overload conditions, allows the system to achieve graceful degradation and supports a mechanism capable of determining the load to be shed from the system to handle the overload. In applications ranging from video reception to air-craft control, tasks enter periodically and have response time constraints, but missing a deadline is acceptable, provided most deadlines are met. Such tasks are said to be occasionally skippable and have an assigned skip parameter. We look at the problem of uniprocessor scheduling of skippabl…
Deadline-based QoS Algorithms for High-performance Networks
2007
Quality of service (QoS) is becoming an attractive feature for high-performance networks and parallel machines because it could allow a more efficient use of resources. Deadline-based algorithms can provide powerful QoS provision. However, the cost associated with keeping ordered lists of packets makes them impractical for high-performance networks. In this paper, we explore how to adapt efficiently the earliest deadline first family of algorithms to the high-speed networks environments. The results show excellent performance using just two virtual channels, FIFO queues, and a cost feasible with today's technology.
Software-Based EDF Message Scheduling on CAN Networks
2006
In this paper, a CAN-based communication system has been used to transmit data between different kinds of sensors and the drive control of an electrical vehicle. Software-based earliest deadline first (EDF) scheduling has been applied to order the data, making possible that more relevant measures meet with their delivery time and, discarding, if necessary, less relevant ones are discarded. The messages use their time-to-deadline as their priority level. With this mechanism, alongside with the discard of data that has lost its deadline, is it possible to deal with saturated that would require a bus utilization well above 100%.
Optimal deadline assignment for periodic real-time tasks in dynamic priority systems
2006
Real-time systems are often designed using a set of periodic tasks. Task periods are usually set by the system requirements, but deadlines and computation times can be modified in order to improve system performance. Sensitivity analysis in real-time systems has focused on changes in task computation times using fixed priority analysis. Only a few studies deal with the modification of deadlines in dynamic priority scheduling. The aim of this work is to provide a sensitivity analysis for task deadlines in the context of dynamic-priority, pre-emptive, uniprocessor scheduling. In this paper, we present a deadline minimisation method that achieves the maximum reduction. As undertaken in other s…