Minimizing waiting time for tasks waiting in the queue for execution is one of the important scheduling criteria which took a wide area in scheduling preemptive tasks. In this paper we present Changeable Time Quantum (CTQ) approach combined with the round-robin algorithm, we try to adjust the time quantum according to the burst times of the tasks in the ready queue. There are two important bene...

A simple fork and join type of job structure has been extensively used for performance evaluation of processor scheduling policies in multiprocessor systems. However, parallel programs often exhibit a more complicated structure. It is not clear how the program structure affects the performance of processor scheduling policies. This paper studies the impact of the program structure on the perfor...

Our work required a model for scheduling real-time tasks that extended the state of the art, supporting a flexible mix of preemptive and non-preemptive scheduling. Mixing these two kinds of scheduling is useful because preemption permits flexible allocation of CPU time while nonpreemptive scheduling has many benefits in software engineering (since race conditions become much more difficult to c...

We consider the problem of preemptively scheduling a set of n jobs on m (identical, uniformly related, or unrelated) parallel machines. The scheduler may reject a subset of the jobs and thereby incur jobdependent penalties for each rejected job, and he must construct a schedule for the remaining jobs so as to optimize the preemptive makespan on the m machines plus the sum of the penalties of th...

In this lecture we’ll study online preemptive scheduling on m machines of arbitrary speeds. We’ll first review the problem and it’s associated literature, then give an optimal deterministic algorithm known as ”RatioStretch”. RatioStretch uses the optimal competitive ratio R > 1 as an input, and achieves R whenever such an R is obtainable. The exact optimal R maybe computed via a linear program,...

Large-scale controlled evacuations require emergency services to select evacuation routes, decide departure times, and mobilize resources to issue orders, all under strict time constraints. Existing algorithms almost always allow for preemptive evacuation schedules, which are less desirable in practice. This paper proposes, for the first time, a constraint-based scheduling model that optimizes ...

In Real-time system, utilization based schedulability test is a common approach to determine whether or not tasks can be admitted without violating deadline requirements. The exact problem has previously been proven intractable even upon single processors; sufficient conditions are presented here for determining whether a given periodic task system will meet all deadlines if scheduled non-preem...

Traditional multiprocessor real-time scheduling partitions a task set and applies uniprocessor scheduling on each processor. By allowing a task to resume on another processor than the task was preempted on, some task sets can be scheduled where the partitioned method fails. We address fixed-priority preemptive scheduling of periodically arriving tasks on m equally powerful processors. We compar...

We consider a scheduling problem, which we call the scheduling and wavelength assignment (SWA) problem, arising in optical networks that are based on the wavelength-divisionmultiplexing (WDM) technology. We prove that the SWA problem is -complete for both the preemptive and the nonpreemptive cases. Furthermore, we propose two efficient approximation algorithms. The first is for the preemptive c...