##### Highest Response Ratio Next (HRRN) Scheduling

Highest Response Ratio Next (HRRN) Scheduling: It is non-preemptive scheduling algorithm. This select the process with highest ration of response and burst time. It minimizes the turn around time.

Response Time = (Latest response time)  - (Arrival Time)

Response Ratio = Response time(or Turn around time) / Burst Time = (WT + BT) / BT

Example: Consider the following table:

 Process no. Arrival Time Burst Time P1 0 6 P2 2 1 P3 4 4 P4 5 3

Find the average waiting time and average turn around time using HRRN algorithm?

Solution: Using HRRN algorithm, response ratio for first term (only one process ready to execute):

Response ratio (RR) = (WT1 + BT1) / (BT1) = (0 + 6)/6 = 1 Response ratio for second term:

RR2 = (4 + 1)/1 = 5

RR3 = (2 + 4)/4 = 1.5

RR4 = (1 + 3)/3 = 1.33

HRRN algorithm selects process with highest RR P2: Response ratio for third term:

RR3 = (3 + 4)/4 = 1.75

RR4 = (2 +3)/3 = 1.67

HRRN algorithm selects process with highest RR P3: At the last, HRRN selects final process to executes: Therefore,

 Waiting Time Turn Around Time Completion Time Process No. Arrival Time Burst Time 6 - 6 = 0 6 - 0 = 6 6 P1 0 6 5 - 1 = 4 7 - 2 = 5 7 P2 2 1 7 - 4 = 3 11 - 4 = 7 11 P3 4 4 9 - 3 = 6 14 - 5 = 9 14 P4 5 3

Average Turn Arround Time = (6 + 5 + 7 + 9) / 4 = 6.75

Average Waiting Time = (0 + 4  + 3 + 6) / 4 = 3.25