Question
Suppose youre managing a collection of processors and must schedule a sequence of jobs over time. The jobs have the following characteristics. Each job j
Suppose youre managing a collection of processors and must schedule a sequence of jobs over time. The jobs have the following characteristics. Each job j has an arrival time aj when it is first available for processing, a length Lj which indicates how much processing time it needs, and a deadline dj by which it must be finished. (Well assume 0 < Lj < dj - aj.) Each job can be run on any of the processors, but only on one at a time; it can also be preempted and resumed from where it left off (possibly after a delay) on another processor. Moreover, the collection of processors is not entirely static either: You have an overall pool of k possible processors; but for each processor i, there is an interval of time [ti, ti] during which it is available; it is unavailable at all other times. Given all this data about job requirements and processor availability, youd like to decide whether the jobs can all be completed or not. Give a polynomial-time algorithm that either produces a schedule completing all jobs by their deadlines or reports (correctly) that no such schedule exists. You may assume that all the parameters associated with the problem are integers. Example. Suppose we have two jobs J1 and J2. J1 arrives at time 0, is due at time 4, and has length 3. J2 arrives at time 1, is due at time 3, and has length 2. We also have two processors P1 and P2. P1 is available between times 0 and 4; P2 is available between times 2 and 3. In this case, there is a schedule that gets both jobs done. At time 0, we start job J1 on processor P1. At time 1, we preempt J1 to start J2 on P1. At time 2, we resume J1 on P2. (J2 continues processing on P1.) At time 3, J2 completes by its deadline. P2 ceases to be available, so we move J1 back to P1 to finish its remaining one unit of processing there. At time 4, J1 completes its processing on P1. Notice that there is no solution that does not involve preemption and moving of jobs.
Step by Step Solution
There are 3 Steps involved in it
Step: 1
Get Instant Access to Expert-Tailored Solutions
See step-by-step solutions with expert insights and AI powered tools for academic success
Step: 2
Step: 3
Ace Your Homework with AI
Get the answers you need in no time with our AI-driven, step-by-step assistance
Get Started