Consider the following simple schedule:
| job number | arrival time | running time | priority |
|---|---|---|---|
| 0 | 0 | 8 | 1 |
| 1 | 1 | 8 | 1 |
| 2 | 3 | 4 | 2 |
The flow of execution of functions calls is as follows:
scheduler_start_up(s = 4)
--> scheduler initialized
scheduler_new_job(job_number = 0, time = 0, running_time = 8, priority = 1)
--> returns true, indicating that job(id=0) should be scheduled at this time.
scheduler_new_job(job_number = 1, time = 1, running_time = 8, priority = 1)
--> returns false, indicating that job(id=1) will not be scheduled at this time.
scheduler_quantum_expired(time = 2)
--> returns 1, indicating that job(id=1) should be run next on the processor.
scheduler_new_job(job_number = 2, time = 3, running_time = 4, priority = 2)
--> returns false, indicating that job(id=2) will not be scheduled at this time.
scheduler_quantum_expired(time = 4)
--> returns 0, indicating that job(id=0) should be run next on the processor.
scheduler_quantum_expired(time = 6)
--> returns 2, indicating that job(id=2) should be run next on the processor.
scheduler_quantum_expired(time = 8)
--> returns 1, indicating that job(id=1) should be run next on the processor.
scheduler_quantum_expired(time = 10)
--> returns 0, indicating that job(id=0) should be run next on the processor.
scheduler_quantum_expired(time = 12)
--> returns 2, indicating that job(id=2) should be run next on the processor.
scheduler_job_finished(job_number = 2, time = 14)
--> returns 1, indicating that job(id=1) should be run next on the processor.
scheduler_quantum_expired(time = 16)
--> returns 0, indicating that job(id=0) should be run next on the processor.
scheduler_job_finished(job_number = 0, time = 18)
--> returns 1, indicating that job(id=1) should be run next on the processor.
scheduler_job_finished(job_number = 1, time = 20)
--> returns -1, indicating that the processor should remain idle.
scheduler average waiting time()
--> returns (28/3) == 9.33
scheduler average turnaround time()
--> returns (48/3) == 16.00
scheduler average response time()
--> returns (4/3) == 1.33
scheduler_clean_up()
--> cleans up and frees all memory used by the scheduler
…it’s important to note that even though the jobs arrive in the order 0 1 2, the order of the jobs in your priority queue will following the rotation: 0 2 1 -> 2 1 0 -> 1 0 2 -> 0 2 1.
When the simulator is executed and the flow of execution is implemented correctly, you will see the following output:
Loaded 3 job(s) using Round Robin (RR) with a quantum of 2 scheduling...
=== [TIME 0] ===
A new job, job 0 (running time=8, priority=1), arrived. Job 0 is now running on processor.
Queue:
At the end of time unit 0...
History: 0
Queue:
=== [TIME 1] ===
A new job, job 1 (running time=8, priority=1), arrived. Job 1 is set to idle (-1).
Queue:
At the end of time unit 1...
History: 00
Queue:
=== [TIME 2] ===
Job 0 had its quantum expire. Processor is now running job 1.
Queue:
At the end of time unit 2...
History: 001
Queue:
=== [TIME 3] ===
A new job, job 2 (running time=4, priority=2), arrived. Job 2 is set to idle (-1).
Queue:
At the end of time unit 3...
History: 0011
Queue:
=== [TIME 4] ===
Job 1 had its quantum expire. Processor is now running job 0.
Queue:
At the end of time unit 4...
History: 00110
Queue:
=== [TIME 5] ===
At the end of time unit 5...
History: 001100
Queue:
=== [TIME 6] ===
Job 0 had its quantum expire. Processor is now running job 2.
Queue:
At the end of time unit 6...
History: 0011002
Queue:
=== [TIME 7] ===
At the end of time unit 7...
History: 00110022
Queue:
=== [TIME 8] ===
Job 2 had its quantum expire. Processor is now running job 1.
Queue:
At the end of time unit 8...
History: 001100221
Queue:
=== [TIME 9] ===
At the end of time unit 9...
History: 0011002211
Queue:
=== [TIME 10] ===
Job 1 had its quantum expire. Processor is now running job 0.
Queue:
At the end of time unit 10...
History: 00110022110
Queue:
=== [TIME 11] ===
At the end of time unit 11...
History: 001100221100
Queue:
=== [TIME 12] ===
Job 0 had its quantum expire. Processor is now running job 2.
Queue:
At the end of time unit 12...
History: 0011002211002
Queue:
=== [TIME 13] ===
At the end of time unit 13...
History: 00110022110022
Queue:
=== [TIME 14] ===
Job 2 finished. Processor is now running job 1.
Queue:
At the end of time unit 14...
History: 001100221100221
Queue:
=== [TIME 15] ===
At the end of time unit 15...
History: 0011002211002211
Queue:
=== [TIME 16] ===
Job 1 had its quantum expire. Processor is now running job 0.
Queue:
At the end of time unit 16...
History: 00110022110022110
Queue:
=== [TIME 17] ===
At the end of time unit 17...
History: 001100221100221100
Queue:
=== [TIME 18] ===
Job 0 finished. Processor is now running job 1.
Queue:
At the end of time unit 18...
History: 0011002211002211001
Queue:
=== [TIME 19] ===
At the end of time unit 19...
History: 00110022110022110011
Queue:
=== [TIME 20] ===
Job 1 finished. Processor is now running job -1.
Queue:
FINAL TIMING DIAGRAM:
History: 00110022110022110011
Average Waiting Time: 9.33
Average Turnaround Time: 16.00
Average Response Time: 1.33