Python implementation of the Robin Round (RR) preemptive scheduling algorithm.

rr-scheduling.py

# Python3 program for implementation of RR scheduling

# Function to find the waiting time for all processes
def findWaitingTime(processes, n, bt, wt, quantum):
    rem_bt = [0] * n

    # Copy the burst time into rt[]
    for i in range(n):
        rem_bt[i] = bt[i]
    t = 0  # Current time

    # Keep traversing processes in round robin manner until all of them are not done.
    while(1):
        done = True

        # Traverse all processes one by
        # one repeatedly
        for i in range(n):

            # If burst time of a process is greater
            # than 0 then only need to process further
            if (rem_bt[i] > 0):
                done = False  # There is a pending process

                if (rem_bt[i] > quantum):

                    # Increase the value of t i.e. shows
                    # how much time a process has been processed
                    t += quantum

                    # Decrease the burst_time of current process by quantum
                    rem_bt[i] -= quantum

                # If burst time is smaller than or equal
                # to quantum. Last cycle for this process
                else:

                    # Increase the value of t i.e. shows
                    # how much time a process has been processed
                    t = t + rem_bt[i]

                    # Waiting time is current time minus
                    # time used by this process
                    wt[i] = t - bt[i]

                    # As the process gets fully executed
                    # make its remaining burst time = 0
                    rem_bt[i] = 0

        # If all processes are done
        if (done == True):
            break

# Function to calculate turn around time


def findTurnAroundTime(processes, n, bt, wt, tat):

    # Calculating turnaround time
    for i in range(n):
        tat[i] = bt[i] + wt[i]


# Function to calculate average waiting and turn-around times.
def findavgTime(processes, n, bt, quantum):
    wt = [0] * n
    tat = [0] * n

    # Function to find waiting time of all processes
    findWaitingTime(processes, n, bt,
                    wt, quantum)

    # Function to find turn around time for all processes
    findTurnAroundTime(processes, n, bt,
                       wt, tat)

    # Display processes along with all details
    print("Processes Burst Time	 Waiting",
          "Time Turn-Around Time")
    total_wt = 0
    total_tat = 0
    for i in range(n):

        total_wt = total_wt + wt[i]
        total_tat = total_tat + tat[i]
        print(" ", i + 1, "\t\t", bt[i],
              "\t\t", wt[i], "\t\t", tat[i])

    print("\nAverage waiting time = %.5f " % (total_wt / n))
    print("Average turn around time = %.5f " % (total_tat / n))


# Driver code
if __name__ == "__main__":

    # Process id's
    proc = [1, 2, 3]
    n = 3

    # Burst time of all processes
    burst_time = [10, 5, 8]

    # Time quantum
    quantum = 2
    findavgTime(proc, n, burst_time, quantum)