An empirical analysis of algorithms for partially Clairvoyant scheduling

Subramani, K.; Desovski, D.

doi:10.1080/17445760601029560

Cited by 5 publications

(22 citation statements)

References 16 publications

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“…The start times of jobs are variable according to the controller, but they use the worst case execution times to decide if a schedule exists. There are schedulable constraint sets which do not have a schedule, if the worst case execution time is assumed, as shown in [17]. In case the number of parameters of the system increases, the efficiency of the controller decreases due to the heavy computing required to schedule jobs.…”

Section: Related Workmentioning

confidence: 99%

“…[12] introduced Partially Clairvoyant scheduling to reduce the inflexibility of static scheduling in hard real-time systems. Partially Clairvoyant scheduling is explained in detail and motivated in [4,17] and [15]. [4] proposes a sequential online dispatcher for dispatching jobs with a schedule.…”

Section: Organizationmentioning

confidence: 99%

“…Standard constraints express the difference relationships between the start times or finish times of two jobs. (ii) E is an axis-parallel rectangle aph [17] represented by:…”

Section: Constraint Modelmentioning

confidence: 99%

“…The algorithm described in [17] is used to generate a Partially Clairvoyant schedule from a test-case generated by GA. The schedule is written into a file which would be read by the online dispatcher.…”

Section: Schedule Generationmentioning

confidence: 99%

“…This form of scheduling was proposed in [4] and further discussed in [17]. A problem that is orthogonal to the scheduling problem is the dispatching problem, i.e., actually assigning jobs to points on the time line.…”

Section: Introductionmentioning

confidence: 98%

See 4 more Smart Citations

Distributed algorithms for partially clairvoyant dispatchers

2007

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Real-time systems are increasingly appearing in complex and dynamic environments such as cruise controllers, life support systems and nuclear reactors. These systems contain components that sense, control and stabilize the environment towards achieving the mission or target. These consociate components synchronize, compute and control themselves locally or have a centralized component to achieve their mission. Distributed computing techniques improve the overall performance and reliability of large real-time systems with spread components.Partially Clairvoyant scheduling was introduced in Saksena, M., PhD thesis (1994) to determine the schedulability of hard real-time jobs with variable execution times. The problem of deciding the Partially Clairvoyant schedulability of a constrained set of jobs was well studied in Gerber, R., et al., IEEE Trans.

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Section: Related Workmentioning

confidence: 99%

Section: Organizationmentioning

confidence: 99%

“…Standard constraints express the difference relationships between the start times or finish times of two jobs. (ii) E is an axis-parallel rectangle aph [17] represented by:…”

Section: Constraint Modelmentioning

confidence: 99%

Section: Schedule Generationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Distributed algorithms for partially clairvoyant dispatchers

2007

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On the Design and Implementation of a Shared Memory Dispatcher for Partially Clairvoyant Schedulers

Subramani

Yellajyosula

2007

Int J Parallel Prog

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With the onset of distributed computing in hard real-time applications, the problem of assigning to, scheduling in, and executing jobs on processors, has received a lot of attention. Usually, real-time systems are embedded in closed loop reactive environments with uncertain behaviors and such systems take varying times to respond to such stimuli. One of the fundamental features of such systems is the presence of complex timing constraints between pairs of jobs. A secondary feature is the non-constant nature of the execution times of jobs. Real-time operating systems such as MARUTI can measure the interval within which the execution time varies (Mosse et al. ) to schedule jobs with varying execution times and non-trivial timing constraints. The schedulability of the job set is determined offline and a set of dispatch functions are produced from the given set of constraints if the job set is schedulable. The dispatch functions bind the start time of a job J to an interval that depends on the start and execution times of jobs sequenced before J . The online dispatcher of the system reads these dispatch functions and computes the interval within which a job can start without violating the constraints imposed on the system. In certain situations, the dispatcher fails to dispatch a job as the time to compute the dispatch functions associated with a job is greater than the interval within which the job needs to be dispatched. This , we propose and implement a partially clairvoyant dispatching algorithm on a shared memory cluster with Concurrent Read Exclusive Write (CREW) architecture and contrast it with the sequential approach. For a preset number of processors, our approach has O(1) dispatch complexity while using a total of O(n 2 ) space, while the sequential approach requires (n) time. The detailed implementation profile obtained clearly demonstrates the superiority of the multiprocessor approach to dispatching. We also address the issue of scalability of the dispatcher for increasing number of processors and show that job sets of different sizes require different number of processors. Finally, we demonstrate the effect of execution time on the dispatchability of schedules.

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Periodic Linear Programming with applications to real-time scheduling

Subramani¹

2005

Math. Struct. Comp. Sci.

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In this paper we introduce a new mathematical modelling technique called Periodic Linear Programming; the periodic properties of Periodic Linear Programs (PLPs) permit the specification of inter-period constraints in embedded systems, in a straightforward and natural manner. We analyse PLPs in which the relationship between program variables is restricted to the class of difference constraints. Our analysis establishes that such PLPs can be reduced to simple linear programs, and hence decided in polynomial time. The class of difference constraints is extremely important from the perspective of embedded systems design, in that it permits the specification of complex timing constraints in real-time specification languages. A PLP can be thought of as a finite-description tool that represents infinite-state systems; although we use this tool purely for the purpose of modelling real-time scheduling problems, PLPs also find applications in other areas, such as concurrency design. In studying this programming paradigm, we develop novel techniques that, to the best of our knowledge, are not part of the literature. We build on the PLP structure to introduce a generalisation called Periodic Quantified Linear Programming; this programming paradigm permits the specification and analysis of uncertainty in the parameters of a PLP. Consequently, a Periodic Quantified Linear Program (PQLP) is the natural modelling tool to capture the requirements of periodic, embedded systems that are characterised by uncertainty in the execution times of processes, periodicity and relative timing constraints. In this paper, we use the PQLP structure to model and solve the periodic version of the zero-clairvoyant scheduling problem. Modelling uncertainty in the problem description is a typical technique used to incorporate a measure of fault-tolerance in the specification.

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An empirical analysis of algorithms for partially Clairvoyant scheduling

Cited by 5 publications

References 16 publications

Distributed algorithms for partially clairvoyant dispatchers

Distributed algorithms for partially clairvoyant dispatchers

On the Design and Implementation of a Shared Memory Dispatcher for Partially Clairvoyant Schedulers

Periodic Linear Programming with applications to real-time scheduling

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