# Highest Response Ratio Next (HRRN) CPU Scheduling

Last Updated : 04 Dec, 2023

CPU scheduling is the process of deciding which process will own the CPU to use while another process is suspended. The main function of CPU scheduling is to ensure that whenever the CPU remains idle, the OS has at least selected one of the processes available in the ready-to-use line. Highest Response Ratio Next (HRRN) Scheduling is a part of nonpreemptive CPU scheduling.

## What is the Highest Response Ratio Next (HRRN) Scheduling?

One of the most optimal scheduling algorithms is the Highest Response Ratio Next (HRNN). This algorithm is a non-preemptive algorithm in which, HRRN scheduling is done based on an extra parameter, which is called Response Ratio. Given N processes with their Arrival times and Burst times, the task is to find the average waiting time and an average turnaround time using the HRRN scheduling algorithm.Â

The name itself states that we need to find the response ratio of all available processes and select the one with the highest Response Ratio. A process once selected will run till completion. below is the formula to calculate the Response Ratio.

Response Ratio = (W + S)/S

Here, W is the waiting time of the process so far and S is the Burst time of the process.

## Characteristics of HRRN Scheduling

• Highest Response Ratio Next is a non-preemptive CPU Scheduling algorithm and it is considered as one of the most optimal scheduling algorithms.
• The criteria for HRRN is Response Ratio, and the mode is Non-Preemptive.Â
• HRRN is considered as the modification of the Shortest Job First to reduce the problem of starvation.
• In comparison with SJF, during the HRRN scheduling algorithm, the CPU is allotted to the next process which has the highest response ratio, and not to the process having less burst time.

## Performance of HRRN Scheduling

• Shorter Processes are favored.
• Aging without service increases the ratio, longer jobs can get past shorter jobs.

## Examples of Â Highest Response Ratio Next (HRRN) Scheduling

Example-1: Consider the following table of arrival time and burst time for four processes P1, P2, P3, P4Â and P5. Â

Processes Arrival time Â Burst Time
P1 Â  0ms 3ms
P2 Â  Â  Â  Â  Â  Â  2ms 6ms
P3Â  4ms 4ms
P4 Â  Â Â  6ms 5ms
P5 8ms 2ms

The Highest Response Ratio Next CPU Scheduling Algorithm will work on the basis of steps as mentioned below:

At time= 0,

• Available Processes: P1, Hence P1 starts executing till its completion.
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
0-2ms P1 0ms Â  P1 2ms 3ms 1ms

At time = 2,

• Available Processes: P1, P2
• But P1 keep executing as HRRN is a non-preemptive algorithm and thus it will finish its execution
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
2-3ms P1 0ms P2 P1 1ms 1ms 0ms
P2 2ms 0ms 6ms 6ms

At time = 3,

• Process P1 finish its execution
• Process P2 starts executing as it is only process available.
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
3-4ms P2 2ms Â  P2 1ms 6ms 5ms

At time = 4,

• Process P3 arrives and wait for process P2 to execute
• Process P2 continue its execution
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
4-6ms P2 2ms P3 P2 2ms 5ms 3ms
P3 4ms 0ms 4ms 4ms

At time = 6,

• Process P4 arrives and wait for the process P2 to execute
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
6-8ms P2 2ms P3, P4 P2 2ms 3ms 1ms
P3 4ms 0ms 4ms 4ms
P4 6ms 0ms 5ms 5ms

At time = 8,

• Process P5 arrives and wait for its execution in the ready queue
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
8-9ms P2 2ms P3, P4, P5 P2 1ms 1ms 0ms
P3 4ms 0ms 4ms 4ms
P4 6ms 0ms 5ms 5ms
P5 8ms 0ms 2ms 2ms

At time = 9,

• Process P2 completes its executionÂ
• Now there are 3 processes available, P3, P4 and P5. Since, P3, P4, P5 were available after 4, 6 and 8 units respectively.
• Therefore, waiting time for P3, P4 and P5 are (9 – 4 =)5, (9 – 6 =)3, and (9 – 8 =)1 unit respectively.
• Using the formula given above, Â (Response Ratio = (W + S)/S) calculate the Response Ratios of P3, P4 and P5 respectively as 2.25, 1.6 and 1.5.
• Clearly, P3 has the highest Response Ratio and so it gets scheduled
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
9-13ms P3 4ms P4, P5 P3 4ms 4ms 0ms
P4 6ms 0ms 5ms 5ms
P5 8ms 0ms 2ms 2ms

At time = 13,

• Available Processes: P4 and P5
• Response Ratios of P4 and P5 are 2.4 and 3.5 respectively using the above formula.
• Clearly, P5 has the highest Response Ratio and so it gets scheduled
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
13-15ms P4 6ms P4 P5 0ms 5ms 5ms
P5 8ms 2ms 2ms 0ms

At time = 15,

• After completion of process P5, Process P4 is selected at last and execute till it gets finished
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
15-20ms P4 6ms Â  P4 5ms 5ms 0ms

At time = 20,

• Process P4 will finish its execution.
• The overall execution of the processes will be as shown below:
Time Instance Process Arrival Time Ready Queue Running Queue Execution Time Initial Burst Time Remaining BurstÂ
Time
0-2ms P1 0ms Â  P1 2ms 3ms 1ms
2-3ms P1 0ms P2 P1 1ms 1ms 0ms
P2 2ms 0ms 6ms 6ms
3-4ms P2 2ms Â  P2 1ms 6ms 5ms
4-6ms P2 2ms P3 P2 2ms 5ms 3ms
P3 4ms 0ms 4ms 4ms
6-8ms P2 2ms P3, P4 P2 2ms 3ms 1ms
P3 4ms 0ms 4ms 4ms
P4 6ms 0ms 5ms 5ms
8-9ms P2 2ms P3, P4, P5 P2 1ms 1ms 0ms
P3 4ms 0ms 4ms 4ms
P4 6ms 0ms 5ms 5ms
P5 8ms 0ms 2ms 2ms
9-13ms P3 4ms P4, P5 P3 4ms 4ms 0ms
P4 6ms 0ms 5ms 5ms
P5 8ms 0ms 2ms 2ms
13-15ms P4 6ms P4 P5 0ms 5ms 5ms
P5 8ms 2ms 2ms 0ms
15-20ms P4 6ms Â  P4 5ms 5ms 0ms

Gantt Chart –Â

Since, completion time (C.T) can be directly determined by Gantt chart, andÂ Â

Turn Around Time (TAT)
= (Completion Time) – (Arrival Time)

Also, Waiting Time (WT)
= (Turn Around Time) – (Burst Time)Â

Therefore, final table look like,Â Â

Processes AT BT CT TAT WT
P1 0 3 3 3-0 = 3 3-3 = 0
P2 2 6 9 9-2 = 7 7-6 = 1
P3 4 4 13 13-4 = 9 9-4 = 5
P4 6 5 20 20-6 = 14 14-5 = 9
P5 8 2 15 15-8 = 7 7-2 = 5

Output:Â Â

Total Turn Around Time = 40 ms
So, Average Turn Around Time = 40/5 = 8.00 ms

And, Total Waiting Time = 20 ms
So, Average Waiting Time = 20/5 = 4.00 msÂ

## Implementation of HRRN SchedulingÂ Â

• Input the number of processes, their arrival times and burst times.
• Sort them according to their arrival times.
• At any given time calculate the response ratios and select the appropriate process to be scheduled.
• Calculate the turn around time as completion time – arrival time.
• Calculate the waiting time as turn around time – burst time.
• Turn around time divided by the burst time gives the normalized turn around time.
• Sum up the waiting and turn around times of all processes and divide by the number of processes to get the average waiting and turn around time.

Below is the implementation of above approach:Â

## C++

 `// C++ program for Highest Response Ratio Next (HRRN)` `// Scheduling` `#include ` `using` `namespace` `std;` `// Defining process details` `struct` `process {` `    ``char` `name;` `    ``int` `at, bt, ct, wt, tt;` `    ``int` `completed;` `    ``float` `ntt;` `} p[10];`   `int` `n;`   `// Sorting Processes by Arrival Time` `void` `sortByArrival()` `{` `    ``struct` `process temp;` `    ``int` `i, j;`   `    ``// Selection Sort applied` `    ``for` `(i = 0; i < n - 1; i++) {` `        ``for` `(j = i + 1; j < n; j++) {`   `            ``// Check for lesser arrival time` `            ``if` `(p[i].at > p[j].at) {`   `                ``// Swap earlier process to front` `                ``temp = p[i];` `                ``p[i] = p[j];` `                ``p[j] = temp;` `            ``}` `        ``}` `    ``}` `}`   `int` `main()` `{` `    ``int` `i, j, sum_bt = 0;` `    ``char` `c;` `    ``float` `t, avgwt = 0, avgtt = 0;` `    ``n = 5;`   `    ``// predefined arrival times` `    ``int` `arriv[] = { 0, 2, 4, 6, 8 };`   `    ``// predefined burst times` `    ``int` `burst[] = { 3, 6, 4, 5, 2 };`   `    ``// Initializing the structure variables` `    ``for` `(i = 0, c = ``'A'``; i < n; i++, c++) {` `        ``p[i].name = c;` `        ``p[i].at = arriv[i];` `        ``p[i].bt = burst[i];`   `        ``// Variable for Completion status` `        ``// Pending = 0` `        ``// Completed = 1` `        ``p[i].completed = 0;`   `        ``// Variable for sum of all Burst Times` `        ``sum_bt += p[i].bt;` `    ``}`   `    ``// Sorting the structure by arrival times` `    ``sortByArrival();` `    ``cout << ``"PN\tAT\tBT\tWT\tTAT\tNTT"``;` `    ``for` `(t = p[0].at; t < sum_bt;) {`   `        ``// Set lower limit to response ratio` `        ``float` `hrr = -9999;`   `        ``// Response Ratio Variable` `        ``float` `temp;`   `        ``// Variable to store next process selected` `        ``int` `loc;` `        ``for` `(i = 0; i < n; i++) {`   `            ``// Checking if process has arrived and is` `            ``// Incomplete` `            ``if` `(p[i].at <= t && p[i].completed != 1) {`   `                ``// Calculating Response Ratio` `                ``temp = (p[i].bt + (t - p[i].at)) / p[i].bt;`   `                ``// Checking for Highest Response Ratio` `                ``if` `(hrr < temp) {`   `                    ``// Storing Response Ratio` `                    ``hrr = temp;`   `                    ``// Storing Location` `                    ``loc = i;` `                ``}` `            ``}` `        ``}`   `        ``// Updating time value` `        ``t += p[loc].bt;`   `        ``// Calculation of waiting time` `        ``p[loc].wt = t - p[loc].at - p[loc].bt;`   `        ``// Calculation of Turn Around Time` `        ``p[loc].tt = t - p[loc].at;`   `        ``// Sum Turn Around Time for average` `        ``avgtt += p[loc].tt;`   `        ``// Calculation of Normalized Turn Around Time` `        ``p[loc].ntt = ((``float``)p[loc].tt / p[loc].bt);`   `        ``// Updating Completion Status` `        ``p[loc].completed = 1;`   `        ``// Sum Waiting Time for average` `        ``avgwt += p[loc].wt;` `        ``cout << ``"\n"` `<< p[loc].name << ``"\t"` `<< p[loc].at;` `        ``cout << ``"\t"` `<< p[loc].bt << ``"\t"` `<< p[loc].wt;` `        ``cout << ``"\t"` `<< p[loc].tt << ``"\t"` `<< p[loc].ntt;` `    ``}` `    ``cout << ``"\nAverage waiting time: "` `<< avgwt / n << endl;` `    ``cout << ``"Average Turn Around time:"` `<< avgtt / n;` `}` `// This code is contributed by shivi_Aggarwal`

## C

 `// C program for Highest Response Ratio Next (HRRN) Scheduling` `#include `   `// Defining process details` `struct` `process {` `    ``char` `name;` `    ``int` `at, bt, ct, wt, tt;` `    ``int` `completed;` `    ``float` `ntt;` `} p[10];`   `int` `n;`   `// Sorting Processes by Arrival Time` `void` `sortByArrival()` `{` `    ``struct` `process temp;` `    ``int` `i, j;`   `    ``// Selection Sort applied` `    ``for` `(i = 0; i < n - 1; i++) {` `        ``for` `(j = i + 1; j < n; j++) {`   `            ``// Check for lesser arrival time` `            ``if` `(p[i].at > p[j].at) {`   `                ``// Swap earlier process to front` `                ``temp = p[i];` `                ``p[i] = p[j];` `                ``p[j] = temp;` `            ``}` `        ``}` `    ``}` `}`   `void` `main()` `{` `    ``int` `i, j, t, sum_bt = 0;` `    ``char` `c;` `    ``float` `avgwt = 0, avgtt = 0;` `    ``n = 5;`   `    ``// predefined arrival times` `    ``int` `arriv[] = { 0, 2, 4, 6, 8 };`   `    ``// predefined burst times` `    ``int` `burst[] = { 3, 6, 4, 5, 2 };`   `    ``// Initializing the structure variables` `    ``for` `(i = 0, c = ``'A'``; i < n; i++, c++) {` `        ``p[i].name = c;` `        ``p[i].at = arriv[i];` `        ``p[i].bt = burst[i];`   `        ``// Variable for Completion status` `        ``// Pending = 0` `        ``// Completed = 1` `        ``p[i].completed = 0;`   `        ``// Variable for sum of all Burst Times` `        ``sum_bt += p[i].bt;` `    ``}`   `    ``// Sorting the structure by arrival times` `    ``sortByArrival();` `    ``printf``(``"\nName\tArrival Time\tBurst Time\tWaiting Time"``);` `    ``printf``(``"\tTurnAround Time\t Normalized TT"``);` `    ``for` `(t = p[0].at; t < sum_bt;) {`   `        ``// Set lower limit to response ratio` `        ``float` `hrr = -9999;`   `        ``// Response Ratio Variable` `        ``float` `temp;`   `        ``// Variable to store next process selected` `        ``int` `loc;` `        ``for` `(i = 0; i < n; i++) {`   `            ``// Checking if process has arrived and is Incomplete` `            ``if` `(p[i].at <= t && p[i].completed != 1) {`   `                ``// Calculating Response Ratio` `                ``temp = (p[i].bt + (t - p[i].at)) / p[i].bt;`   `                ``// Checking for Highest Response Ratio` `                ``if` `(hrr < temp) {`   `                    ``// Storing Response Ratio` `                    ``hrr = temp;`   `                    ``// Storing Location` `                    ``loc = i;` `                ``}` `            ``}` `        ``}`   `        ``// Updating time value` `        ``t += p[loc].bt;`   `        ``// Calculation of waiting time` `        ``p[loc].wt = t - p[loc].at - p[loc].bt;`   `        ``// Calculation of Turn Around Time` `        ``p[loc].tt = t - p[loc].at;`   `        ``// Sum Turn Around Time for average` `        ``avgtt += p[loc].tt;`   `        ``// Calculation of Normalized Turn Around Time` `        ``p[loc].ntt = ((``float``)p[loc].tt / p[loc].bt);`   `        ``// Updating Completion Status` `        ``p[loc].completed = 1;`   `        ``// Sum Waiting Time for average` `        ``avgwt += p[loc].wt;` `        ``printf``(``"\n%c\t\t%d\t\t"``, p[loc].name, p[loc].at);` `        ``printf``(``"%d\t\t%d\t\t"``, p[loc].bt, p[loc].wt);` `        ``printf``(``"%d\t\t%f"``, p[loc].tt, p[loc].ntt);` `    ``}` `    ``printf``(``"\nAverage waiting time:%f\n"``, avgwt / n);` `    ``printf``(``"Average Turn Around time:%f\n"``, avgtt / n);` `}`

## Java

 `// Java equivalent ` `import` `java.util.Arrays; ` `  `  `// Defining process details ` `class` `Process { ` `    ``char` `name; ` `    ``int` `at, bt, ct, wt, tt; ` `    ``int` `completed; ` `    ``float` `ntt; ` `} ` `  `  `public` `class` `HRRN { ` `  `  `    ``// Sorting Processes by Arrival Time ` `    ``static` `void` `sortByArrival(Process p[], ``int` `n) ` `    ``{ ` `        ``Process temp; ` `        ``int` `i, j; ` `  `  `        ``// Selection Sort applied ` `        ``for` `(i = ``0``; i < n - ``1``; i++) { ` `            ``for` `(j = i + ``1``; j < n; j++) { ` `  `  `                ``// Check for lesser arrival time ` `                ``if` `(p[i].at > p[j].at) { ` `  `  `                    ``// Swap earlier process to front ` `                    ``temp = p[i]; ` `                    ``p[i] = p[j]; ` `                    ``p[j] = temp; ` `                ``} ` `            ``} ` `        ``} ` `    ``} ` `  `  `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``int` `i, j, sum_bt = ``0``; ` `        ``char` `c; ` `        ``float` `t, avgwt = ``0``, avgtt = ``0``; ` `        ``int` `n = ``5``; ` `  `  `        ``// predefined arrival times ` `        ``int` `arriv[] = { ``0``, ``2``, ``4``, ``6``, ``8` `}; ` `  `  `        ``// predefined burst times ` `        ``int` `burst[] = { ``3``, ``6``, ``4``, ``5``, ``2` `}; ` `  `  `        ``Process[] p = ``new` `Process[n]; ` `  `  `        ``// Initializing the structure variables ` `        ``for` `(i = ``0``, c = ``'A'``; i < n; i++, c++) { ` `            ``p[i] = ``new` `Process(); ` `            ``p[i].name = c; ` `            ``p[i].at = arriv[i]; ` `            ``p[i].bt = burst[i]; ` `  `  `            ``// Variable for Completion status ` `            ``// Pending = 0 ` `            ``// Completed = 1 ` `            ``p[i].completed = ``0``; ` `  `  `            ``// Variable for sum of all Burst Times ` `            ``sum_bt += p[i].bt; ` `        ``} ` `  `  `        ``// Sorting the structure by arrival times ` `        ``sortByArrival(p, n); ` `        ``System.out.println(``"PN\tAT\tBT\tWT\tTAT\tNTT"``); ` `        ``for` `(t = p[``0``].at; t < sum_bt;) { ` `  `  `            ``// Set lower limit to response ratio ` `            ``float` `hrr = -``9999``; ` `  `  `            ``// Response Ratio Variable ` `            ``float` `temp; ` `  `  `            ``// Variable to store next process selected ` `            ``int` `loc = -``1``; ` `            ``for` `(i = ``0``; i < n; i++) { ` `  `  `                ``// Checking if process has arrived and is ` `                ``// Incomplete ` `                ``if` `(p[i].at <= t && p[i].completed != ``1``) { ` `  `  `                    ``// Calculating Response Ratio ` `                    ``temp = (p[i].bt + (t - p[i].at)) / p[i].bt; ` `  `  `                    ``// Checking for Highest Response Ratio ` `                    ``if` `(hrr < temp) { ` `  `  `                        ``// Storing Response Ratio ` `                        ``hrr = temp; ` `  `  `                        ``// Storing Location ` `                        ``loc = i; ` `                    ``} ` `                ``} ` `            ``} ` `  `  `            ``// Updating time value ` `            ``t += p[loc].bt; ` `  `  `            ``// Calculation of waiting time ` `            ``p[loc].wt = (``int``)(t - p[loc].at - p[loc].bt); ` `  `  `            ``// Calculation of Turn Around Time ` `            ``p[loc].tt = (``int``)(t - p[loc].at); ` `  `  `            ``// Sum Turn Around Time for average ` `            ``avgtt += p[loc].tt; ` `  `  `            ``// Calculation of Normalized Turn Around Time ` `            ``p[loc].ntt = ((``float``)p[loc].tt / p[loc].bt); ` `  `  `            ``// Updating Completion Status ` `            ``p[loc].completed = ``1``; ` `  `  `            ``// Sum Waiting Time for average ` `            ``avgwt += p[loc].wt; ` `            ``System.out.println(p[loc].name + ``"\t"` `+ p[loc].at + ``"\t"` `+ p[loc].bt ` `                               ``+ ``"\t"` `+ p[loc].wt + ``"\t"` `+ p[loc].tt ` `                               ``+ ``"\t"` `+ p[loc].ntt); ` `        ``} ` `        ``System.out.println(``"Average waiting time: "` `+ (avgwt / n)); ` `        ``System.out.println(``"Average Turn Around time:"` `+ (avgtt / n)); ` `    ``} ` `}`

## Python3

 `# Python3 program for Highest Response Ratio` `# Next (HRRN) Scheduling`   `# Function to sort process by arrival time` `def` `sortByArrival(at, n):` `    `  `    ``# Selection Sort applied  ` `    ``for` `i ``in` `range``(``0``, n ``-` `1``):` `        ``for` `j ``in` `range``(i ``+` `1``, n):` `            `  `            ``# Check for lesser arrival time  ` `            ``if` `at[i] > at[j]:` `                `  `                ``# Swap earlier process to front` `                ``at[i], at[j] ``=` `at[j], at[i]`   `# Driver code` `if` `__name__ ``=``=` `'__main__'``:` `    `  `    ``sum_bt ``=` `0` `    ``avgwt ``=` `0` `    ``avgTT ``=` `0` `    ``n ``=` `5` `    `  `    ``completed ``=``[``0``] ``*` `n` `    ``waiting_time ``=` `[``0``] ``*` `n` `    ``turnaround_time ``=` `[``0``] ``*` `n` `    ``normalised_TT ``=` `[``0``] ``*` `n` `    `  `    ``# Predefined arrival times  ` `    ``arrival_time ``=` `[ ``0``, ``2``, ``4``, ``6``, ``8` `]` `    `  `    ``# Predefined burst times  ` `    ``burst_time ``=` `[ ``3``, ``6``, ``4``, ``5``, ``2` `]` `    ``process ``=` `[]` `    `  `    ``# Initializing the structure variables  ` `    ``for` `i ``in` `range``(``0``, n):` `        ``process.append(``chr``(``65` `+` `i))` `        ``sum_bt ``+``=` `burst_time[i]` `        `  `    ``# Sorting the structure by arrival times  ` `    ``sortByArrival(arrival_time, n)` `    ``print``(``"Name"``, ``"Arrival time"``, ` `          ``"Burst time"``, ``"Waiting Time"``, ` `          ``"Turnaround "``, ``"Normalized TT"``)` `    ``t ``=` `arrival_time[``0``]` `    `  `    ``while``(t < sum_bt):` `        `  `        ``# Set lower limit to response ratio  ` `        ``hrr ``=` `-``9999` `        ``temp, loc ``=` `0``, ``0` `        `  `        ``for` `i ``in` `range``(``0``, n):` `            `  `            ``# Checking if process has arrived ` `            ``# and is Incomplete  ` `            ``if` `arrival_time[i] <``=` `t ``and` `completed[i] !``=` `1``:` `                `  `                ``# Calculating Response Ratio  ` `                ``temp ``=` `((burst_time[i] ``+` `                        ``(t ``-` `arrival_time[i])) ``/` `                         ``burst_time[i])` `                         `  `                ``# Checking for Highest Response Ratio  ` `                ``if` `hrr < temp:` `                    `  `                    ``# Storing Response Ratio  ` `                    ``hrr ``=` `temp` `                    `  `                    ``# Storing Location ` `                    ``loc ``=` `i` `                    `  `        ``# Updating time value  ` `        ``t ``+``=` `burst_time[loc]` `        `  `        ``# Calculation of waiting time ` `        ``waiting_time[loc] ``=` `(t ``-` `arrival_time[loc] ``-` `                                 ``burst_time[loc])` `        `  `        ``# Calculation of Turn Around Time  ` `        ``turnaround_time[loc] ``=` `t ``-` `arrival_time[loc]` `        `  `        ``# Sum Turn Around Time for average  ` `        ``avgTT ``+``=` `turnaround_time[loc]` `        `  `        ``# Calculation of Normalized Turn Around Time  ` `        ``normalised_TT ``=` `float``(turnaround_time[loc] ``/` `                              ``burst_time[loc])` `        `  `        ``# Updating Completion Status ` `        ``completed[loc] ``=` `1` `        `  `        ``# Sum Waiting Time for average  ` `        ``avgwt ``+``=` `waiting_time[loc]` `        `  `        ``print``(process[loc], ``"\t\t"``, arrival_time[loc],` `              ``"\t\t"``, burst_time[loc], ``"\t\t"``, ` `              ``waiting_time[loc], ``"\t\t"``, ` `              ``turnaround_time[loc], ``"\t\t"``, ` `              ``"{0:.6f}"``.``format``(normalised_TT))`   `    ``print``(``"Average waiting time: {0:.6f}"``.``format``(avgwt ``/` `n))` `    ``print``(``"Average Turn Around time:  {0:.6f}"``.``format``(avgTT ``/` `n))`   `# This code is contributed by etcharla revanth rao`

## C#

 `using` `System;` `using` `System.Collections;` `using` `System.Collections.Generic;` `using` `System.Linq;`   `// C# equivalent ` `  `  `// Defining process details ` `class` `Process { ` `    ``public` `char` `name; ` `    ``public` `int` `at, bt, ct, wt, tt; ` `    ``public` `int` `completed; ` `    ``public` `float` `ntt; ` `} `   `class` `HelloWorld {` `    `  `    ``// Sorting Processes by Arrival Time ` `    ``public` `static` `void` `sortByArrival(Process[] p, ``int` `n) ` `    ``{ ` `        ``Process temp; ` `        ``int` `i, j; ` `  `  `        ``// Selection Sort applied ` `        ``for` `(i = 0; i < n - 1; i++) { ` `            ``for` `(j = i + 1; j < n; j++) { ` `  `  `                ``// Check for lesser arrival time ` `                ``if` `(p[i].at > p[j].at) { ` `  `  `                    ``// Swap earlier process to front ` `                    ``temp = p[i]; ` `                    ``p[i] = p[j]; ` `                    ``p[j] = temp; ` `                ``} ` `            ``} ` `        ``} ` `    ``} ` `    `  `    ``static` `void` `Main() {` `        ``int` `i, j, sum_bt = 0; ` `        ``char` `c; ` `        ``float` `t, avgwt = 0, avgtt = 0; ` `        ``int` `n = 5; ` `  `  `        ``// predefined arrival times ` `        ``int``[] arriv = { 0, 2, 4, 6, 8 }; ` `  `  `        ``// predefined burst times ` `        ``int``[] burst = { 3, 6, 4, 5, 2 }; ` `  `  `        ``Process[] p = ``new` `Process[n]; ` `  `  `        ``// Initializing the structure variables ` `        ``for` `(i = 0, c = ``'A'``; i < n; i++, c++) { ` `            ``p[i] = ``new` `Process(); ` `            ``p[i].name = c; ` `            ``p[i].at = arriv[i]; ` `            ``p[i].bt = burst[i]; ` `  `  `            ``// Variable for Completion status ` `            ``// Pending = 0 ` `            ``// Completed = 1 ` `            ``p[i].completed = 0; ` `  `  `            ``// Variable for sum of all Burst Times ` `            ``sum_bt += p[i].bt; ` `        ``} ` `  `  `        ``// Sorting the structure by arrival times ` `        ``sortByArrival(p, n); ` `        ``Console.WriteLine(``"PN\tAT\tBT\tWT\tTAT\tNTT"``); ` `        ``for` `(t = p[0].at; t < sum_bt;) { ` `  `  `            ``// Set lower limit to response ratio ` `            ``float` `hrr = -9999; ` `  `  `            ``// Response Ratio Variable ` `            ``float` `temp; ` `  `  `            ``// Variable to store next process selected ` `            ``int` `loc = -1; ` `            ``for` `(i = 0; i < n; i++) { ` `  `  `                ``// Checking if process has arrived and is ` `                ``// Incomplete ` `                ``if` `(p[i].at <= t && p[i].completed != 1) { ` `  `  `                    ``// Calculating Response Ratio ` `                    ``temp = (p[i].bt + (t - p[i].at)) / p[i].bt; ` `  `  `                    ``// Checking for Highest Response Ratio ` `                    ``if` `(hrr < temp) { ` `  `  `                        ``// Storing Response Ratio ` `                        ``hrr = temp; ` `  `  `                        ``// Storing Location ` `                        ``loc = i; ` `                    ``} ` `                ``} ` `            ``} ` `  `  `            ``// Updating time value ` `            ``t += p[loc].bt; ` `  `  `            ``// Calculation of waiting time ` `            ``p[loc].wt = (``int``)(t - p[loc].at - p[loc].bt); ` `  `  `            ``// Calculation of Turn Around Time ` `            ``p[loc].tt = (``int``)(t - p[loc].at); ` `  `  `            ``// Sum Turn Around Time for average ` `            ``avgtt += p[loc].tt; ` `  `  `            ``// Calculation of Normalized Turn Around Time ` `            ``p[loc].ntt = ((``float``)p[loc].tt / p[loc].bt); ` `  `  `            ``// Updating Completion Status ` `            ``p[loc].completed = 1; ` `  `  `            ``// Sum Waiting Time for average ` `            ``avgwt += p[loc].wt; ` `            ``Console.WriteLine(p[loc].name + ``"\t"` `+ p[loc].at + ``"\t"` `+ p[loc].bt ` `                               ``+ ``"\t"` `+ p[loc].wt + ``"\t"` `+ p[loc].tt ` `                               ``+ ``"\t"` `+ p[loc].ntt); ` `        ``} ` `        ``Console.WriteLine(``"Average waiting time: "` `+ (avgwt / n)); ` `        ``Console.WriteLine(``"Average Turn Around time:"` `+ (avgtt / n)); ` `    ``}` `}`   `// The code is contributed by Nidhi goel.`

## Javascript

 `// javascript program for Highest Response Ratio Next (HRRN)` `// Scheduling`   `// Defining process details` `class process {` `    `  `    ``constructor(){` `        ``this``.name = ``'#'``;` `        ``this``.at = 0;` `        ``this``.bt = 0;` `        ``this``.ct = 0;` `        ``this``.wt = 0;` `        ``this``.tt = 0;` `        ``this``.completed= 0;` `        ``this``.ntt = 0;` `    ``}`   `} ` `let p = ``new` `Array(10);` `for``(let i = 0; i < 10; i++){` `    ``p[i] = ``new` `process();` `}`   `let n;`   `// Sorting Processes by Arrival Time` `function` `sortByArrival()` `{` `    ``let temp;` `    ``let i, j;`   `    ``// Selection Sort applied` `    ``for` `(i = 0; i < n - 1; i++) {` `        ``for` `(j = i + 1; j < n; j++) {`   `            ``// Check for lesser arrival time` `            ``if` `(p[i].at > p[j].at) {`   `                ``// Swap earlier process to front` `                ``temp = p[i];` `                ``p[i] = p[j];` `                ``p[j] = temp;` `            ``}` `        ``}` `    ``}` `}`     `let i, j, sum_bt = 0;` `let c;` `let t, avgwt = 0, avgtt = 0;` `n = 5;`   `// predefined arrival times` `let arriv = [0, 2, 4, 6, 8];`   `// predefined burst times` `let burst = [3, 6, 4, 5, 2];`   `// Initializing the structure variables` `for` `(i = 0, c = ``'A'``; i < n; i++) {` `    ``p[i].name = c;` `    ``p[i].at = arriv[i];` `    ``p[i].bt = burst[i];`   `    ``// Variable for Completion status` `    ``// Pending = 0` `    ``// Completed = 1` `    ``p[i].completed = 0;`   `    ``// Variable for sum of all Burst Times` `    ``sum_bt += p[i].bt;` `    ``c = String.fromCharCode(c.charCodeAt(0) + 1);` `}`   `// Sorting the structure by arrival times` `sortByArrival();` `console.log(``"PN\tAT\tBT\tWT\tTAT\tNTT"``);`   `for` `(t = p[0].at; t < sum_bt;) {`   `    ``// Set lower limit to response ratio` `    ``let hrr = -9999;`   `    ``// Response Ratio Variable` `    ``let temp;`   `    ``// Variable to store next process selected` `    ``let loc;` `    ``for` `(i = 0; i < n; i++) {`   `        ``// Checking if process has arrived and is` `        ``// Incomplete` `        ``if` `(p[i].at <= t && p[i].completed != 1) {`   `            ``// Calculating Response Ratio` `            ``temp = (p[i].bt + (t - p[i].at)) / p[i].bt;`   `            ``// Checking for Highest Response Ratio` `            ``if` `(hrr < temp) {`   `                ``// Storing Response Ratio` `                ``hrr = temp;`   `                ``// Storing Location` `                ``loc = i;` `            ``}` `        ``}` `    ``}`   `    ``// Updating time value` `    ``t += p[loc].bt;`   `    ``// Calculation of waiting time` `    ``p[loc].wt = t - p[loc].at - p[loc].bt;`   `    ``// Calculation of Turn Around Time` `    ``p[loc].tt = t - p[loc].at;`   `    ``// Sum Turn Around Time for average` `    ``avgtt += p[loc].tt;`   `    ``// Calculation of Normalized Turn Around Time` `    ``p[loc].ntt = (p[loc].tt / p[loc].bt);`   `    ``// Updating Completion Status` `    ``p[loc].completed = 1;`   `    ``// Sum Waiting Time for average` `    ``avgwt += p[loc].wt;` `    ``console.log(p[loc].name + ``"\t"` `+ p[loc].at + ``"\t"` `+ p[loc].bt + ``"\t"` `+ p[loc].wt + ``"\t"` `+ p[loc].tt + ``"\t"` `+ p[loc].ntt);` `}` `console.log(``"\nAverage waiting time: "` `+ avgwt / n);` `console.log(``"Average Turn Around time:"` `+ avgtt / n);`   `// This code is contributed by Nidhi goel. `

Output

```PN    AT    BT    WT    TAT    NTT
A    0    3    0    3    1
B    2    6    1    7    1.16667
C    4    4    5    9    2.25
E    8    2    5    7    3.5
D    6    5    9    14    2.8
Average waiting time: 4
Average Turn Around time:8

```

• HRRN Scheduling algorithm generally gives better performance than the shortest job first Scheduling.
• There is a reduction in waiting time for longer jobs and also it encourages shorter jobs.
• Using HRRN algorithm, the throughput increases.

• The on ground implementation of HRRN scheduling is not possible as it is not possible know the burst time of every job in advance.
• In this scheduling, there may occur overload on the CPU.

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

### Q.1: Is HRRN preemptive or non preemptive?

The HRRN algorithm is non-preemptive in nature, and it bases scheduling decisions on an additional parameter known as response ratio. Every job that is open is assigned a response ratio, the job with the highest response ratio takes precedence over the others.

### Q.2: What are the problems with HRRN?

The following is the HRNN scheduling algorithm’s drawback:

• The inability to predict the peak period of each operation makes the practical application of HRRN scheduling unfeasible.