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111 lines
3.4 KiB
Python
111 lines
3.4 KiB
Python
"""
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Non-preemptive Shortest Job First
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Shortest execution time process is chosen for the next execution.
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https://www.guru99.com/shortest-job-first-sjf-scheduling.html
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https://en.wikipedia.org/wiki/Shortest_job_next
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"""
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from __future__ import annotations
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from statistics import mean
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def calculate_waitingtime(
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arrival_time: list[int], burst_time: list[int], no_of_processes: int
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) -> list[int]:
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"""
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Calculate the waiting time of each processes
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Return: The waiting time for each process.
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>>> calculate_waitingtime([0,1,2], [10, 5, 8], 3)
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[0, 9, 13]
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>>> calculate_waitingtime([1,2,2,4], [4, 6, 3, 1], 4)
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[0, 7, 4, 1]
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>>> calculate_waitingtime([0,0,0], [12, 2, 10],3)
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[12, 0, 2]
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"""
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waiting_time = [0] * no_of_processes
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remaining_time = [0] * no_of_processes
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# Initialize remaining_time to waiting_time.
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for i in range(no_of_processes):
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remaining_time[i] = burst_time[i]
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ready_process: list[int] = []
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completed = 0
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total_time = 0
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# When processes are not completed,
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# A process whose arrival time has passed \
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# and has remaining execution time is put into the ready_process.
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# The shortest process in the ready_process, target_process is executed.
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while completed != no_of_processes:
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ready_process = []
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target_process = -1
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for i in range(no_of_processes):
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if (arrival_time[i] <= total_time) and (remaining_time[i] > 0):
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ready_process.append(i)
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if len(ready_process) > 0:
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target_process = ready_process[0]
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for i in ready_process:
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if remaining_time[i] < remaining_time[target_process]:
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target_process = i
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total_time += burst_time[target_process]
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completed += 1
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remaining_time[target_process] = 0
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waiting_time[target_process] = (
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total_time - arrival_time[target_process] - burst_time[target_process]
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)
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else:
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total_time += 1
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return waiting_time
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def calculate_turnaroundtime(
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burst_time: list[int], no_of_processes: int, waiting_time: list[int]
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) -> list[int]:
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"""
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Calculate the turnaround time of each process.
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Return: The turnaround time for each process.
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>>> calculate_turnaroundtime([0,1,2], 3, [0, 10, 15])
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[0, 11, 17]
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>>> calculate_turnaroundtime([1,2,2,4], 4, [1, 8, 5, 4])
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[2, 10, 7, 8]
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>>> calculate_turnaroundtime([0,0,0], 3, [12, 0, 2])
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[12, 0, 2]
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"""
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turn_around_time = [0] * no_of_processes
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for i in range(no_of_processes):
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turn_around_time[i] = burst_time[i] + waiting_time[i]
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return turn_around_time
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if __name__ == "__main__":
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print("[TEST CASE 01]")
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no_of_processes = 4
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burst_time = [2, 5, 3, 7]
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arrival_time = [0, 0, 0, 0]
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waiting_time = calculate_waitingtime(arrival_time, burst_time, no_of_processes)
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turn_around_time = calculate_turnaroundtime(
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burst_time, no_of_processes, waiting_time
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)
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# Printing the Result
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print("PID\tBurst Time\tArrival Time\tWaiting Time\tTurnaround Time")
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for i, process_id in enumerate(list(range(1, 5))):
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print(
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f"{process_id}\t{burst_time[i]}\t\t\t{arrival_time[i]}\t\t\t\t"
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f"{waiting_time[i]}\t\t\t\t{turn_around_time[i]}"
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)
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print(f"\nAverage waiting time = {mean(waiting_time):.5f}")
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print(f"Average turnaround time = {mean(turn_around_time):.5f}")
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