first come first served Algorithm

The First Come First Served (FCFS) algorithm is a simple, intuitive scheduling technique used in various systems, including operating systems, networks, and queues in general. As the name suggests, this algorithm processes requests in the order they arrive, without prioritization or regard for their urgency. In essence, it operates on a "first-in, first-out" (FIFO) basis, ensuring fairness among all requests since no request can jump ahead in the queue. The simplicity and ease of implementation of the FCFS algorithm make it a popular choice for simple systems or as a baseline for comparison against more sophisticated scheduling algorithms. However, the FCFS algorithm has its limitations, particularly in scenarios where some requests have higher priority or require urgent attention. Since the algorithm processes requests sequentially, it can lead to poor performance in terms of average waiting time, response time, or turnaround time, especially if the earliest request takes a long time to complete, causing subsequent requests to wait. This phenomenon, known as the convoy effect, can lead to inefficiencies and increased waiting times for all requests in the system. Despite these drawbacks, the FCFS algorithm remains a fundamental and straightforward scheduling technique that serves as a foundation for understanding more complex scheduling algorithms.
# Implementation of First Come First Served scheduling algorithm
# In this Algorithm we just care about the order that the processes arrived
# without carring about their duration time
# https://en.wikipedia.org/wiki/Scheduling_(computing)#First_come,_first_served
from typing import List


def calculate_waiting_times(duration_times: List[int]) -> List[int]:
    """
    This function calculates the waiting time of some processes that have a
    specified duration time.
        Return: The waiting time for each process.
    >>> calculate_waiting_times([5, 10, 15])
    [0, 5, 15]
    >>> calculate_waiting_times([1, 2, 3, 4, 5])
    [0, 1, 3, 6, 10]
    >>> calculate_waiting_times([10, 3])
    [0, 10]
    """
    waiting_times = [0] * len(duration_times)
    for i in range(1, len(duration_times)):
        waiting_times[i] = duration_times[i - 1] + waiting_times[i - 1]
    return waiting_times


def calculate_turnaround_times(
    duration_times: List[int], waiting_times: List[int]
) -> List[int]:
    """
    This function calculates the turnaround time of some processes.
        Return: The time difference between the completion time and the
                arrival time.
                Practically waiting_time + duration_time
    >>> calculate_turnaround_times([5, 10, 15], [0, 5, 15])
    [5, 15, 30]
    >>> calculate_turnaround_times([1, 2, 3, 4, 5], [0, 1, 3, 6, 10])
    [1, 3, 6, 10, 15]
    >>> calculate_turnaround_times([10, 3], [0, 10])
    [10, 13]
    """
    return [
        duration_time + waiting_times[i]
        for i, duration_time in enumerate(duration_times)
    ]


def calculate_average_turnaround_time(turnaround_times: List[int]) -> float:
    """
    This function calculates the average of the turnaround times
        Return: The average of the turnaround times.
    >>> calculate_average_turnaround_time([0, 5, 16])
    7.0
    >>> calculate_average_turnaround_time([1, 5, 8, 12])
    6.5
    >>> calculate_average_turnaround_time([10, 24])
    17.0
    """
    return sum(turnaround_times) / len(turnaround_times)


def calculate_average_waiting_time(waiting_times: List[int]) -> float:
    """
    This function calculates the average of the waiting times
        Return: The average of the waiting times.
    >>> calculate_average_waiting_time([0, 5, 16])
    7.0
    >>> calculate_average_waiting_time([1, 5, 8, 12])
    6.5
    >>> calculate_average_waiting_time([10, 24])
    17.0
    """
    return sum(waiting_times) / len(waiting_times)


if __name__ == "__main__":
    # process id's
    processes = [1, 2, 3]

    # ensure that we actually have processes
    if len(processes) == 0:
        print("Zero amount of processes")
        exit()

    # duration time of all processes
    duration_times = [19, 8, 9]

    # ensure we can match each id to a duration time
    if len(duration_times) != len(processes):
        print("Unable to match all id's with their duration time")
        exit()

    # get the waiting times and the turnaround times
    waiting_times = calculate_waiting_times(duration_times)
    turnaround_times = calculate_turnaround_times(duration_times, waiting_times)

    # get the average times
    average_waiting_time = calculate_average_waiting_time(waiting_times)
    average_turnaround_time = calculate_average_turnaround_time(turnaround_times)

    # print all the results
    print("Process ID\tDuration Time\tWaiting Time\tTurnaround Time")
    for i, process in enumerate(processes):
        print(
            f"{process}\t\t{duration_times[i]}\t\t{waiting_times[i]}\t\t{turnaround_times[i]}"
        )
    print(f"Average waiting time = {average_waiting_time}")
    print(f"Average turn around time = {average_turnaround_time}")

LANGUAGE:

DARK MODE: