Some scheduling algorithms

fcfs.py

'''
FCFS Algorithm:
- Take process from front of priority queue.
- Let it execute until process terminates (i.e. for duration of process)
- Pop it from the queue and add to list of completed tasks.
- Repeat until zero processes left.
'''

def fcfs(queue, verbose=False):
    completed = []
    tick = 0

    # Run until the queue is empty of processes.
    while queue:
        current_process = queue.pop(0)

        if verbose:
            print(current_process)

        # Run each process until completion.
        while current_process.duration > 0:
            current_process.duration -= 1
            tick += 1

        # Once process is complete, push it to completed list.
        completed.append(current_process)

    print(tick)
    return completed


queue = [Task("A", 10, 3), Task("B", 30, 2), Task("C", 5, 1)]

print(fcfs(queue))

round_robin.py

'''
Round Robin Algorithm:
- Take process from front of priority queue.
- Decrement process duration and quantum.
- Increment tick.
- Check if process is complete (duration = 0)
  - If so, push process to completed list.
- Check if quantum is zero (quantum = 0)
  - If so, push process to back of queue.
'''

def round_robin(queue, verbose=False):
    completed = []
    tick = 0

    # Run until queue is empty of processes.
    while queue:
        current_process = queue.pop(0)
        quantum = 5

        if verbose:
            print(current_process)

        # Each task has `quantum` ticks to run before being moved to the back.
        while quantum > 0:
            quantum -= 1
            current_process.duration -= 1

            tick += 1

            # Check if process has completed.
            if current_process.duration == 0:
                completed.append(current_process)
                break

        # Only push the task back on the queue if its not complete.
        if not current_process.duration == 0:
            queue.append(current_process)

    print(tick)
    return completed


queue = [Task("A", 10, 3), Task("B", 30, 2), Task("C", 5, 1)]

print(round_robin(queue))

task.py

class Task:
    def __init__(self, label, duration, priority):
        self.label = label
        self.duration = duration
        self.priority = priority

    def __str__(self):
        return f"Task {self.label}\nDuration: {self.duration}\nPriority: {self.priority}"

    def __repr__(self):
        return str((self.label, self.duration, self.priority))