Assume that jobs A-D arrive in the ready queue in quick succession and have the CPU cycle requirements listed below. Using the SRT algorithm, the average turnaround time is ____. Arrival time: 0 1 2 3
Job: A B C D
CPU cycle: 6 3 1 4
A) 2.5
B) 6.25
C) 7.75
D) 9.0

Question

Quizplus · Accepted Answer

SRT (Shortest Remaining Time) is a preemptive version of SJF scheduling in which the processor is allocated to the job that has the smallest amount of time remaining to complete.
In this scenario, the first job A has a CPU cycle requirement of 6, which is larger than the other jobs. Therefore, the CPU will be allocated to jobs B, C, and D in the order of their arrival time. 
The SRT algorithm works as follows:
- At time 0, job A arrives in the ready queue with a CPU cycle requirement of 6.
- The CPU is allocated to job B, which has a CPU cycle requirement of 3.
- At time 2, job C arrives in the ready queue with a CPU cycle requirement of 1. Since B has 1 CPU cycle remaining and C has 1 cycle, job C is allocated to the CPU for 1 cycle.
- At time 3, job D arrives in the ready queue with a CPU cycle requirement of 4. Since B has completed its task, D is allocated to the CPU with a CPU cycle requirement of 4.
- Job A is now the only job remaining in the ready queue, and it is allocated the CPU for its remaining 5 cycles.
The turnaround time for each job is calculated as the difference between the completion time and the arrival time. For example, the completion time for job B is 4, and its turnaround time is 4 - 1 = 3. The completion time for job C is 3, and its turnaround time is 3 - 2 = 1. The completion time for job D is 7, and its turnaround time is 7 - 3 = 4. The completion time for job A is 12, and its turnaround time is 12 - 0 = 12. Therefore, the average turnaround time is (3 + 1 + 4 + 12) / 4 = 5. The closest answer choice to this is B (6.25).

Assume That Jobs A-D Arrive in the Ready Queue in Quick