Priority CPU Scheduling with different arrival time Set 2 (original) (raw)

Last Updated : 28 Dec, 2024

**Prerequisite -Program for Priority Scheduling - Set 1
Priority scheduling is a non-preemptive algorithm and one of the most common scheduling algorithms in batch systems. Each process is assigned first arrival time (less arrival time process first) if two processes have same arrival time, then compare to priorities (highest process first). Also, if two processes have same priority then compare to process number (less process number first). This process is repeated while all process get executed.

**Implementation -

1. First input the processes with their arrival time, burst time and priority.
2. First process will schedule, which have the lowest arrival time, if two or more processes will have lowest arrival time, then whoever has higher priority will schedule first.
3. Now further processes will be schedule according to the arrival time and priority of the process. (Here we are assuming that lower the priority number having higher priority). If two process priority are same then sort according to process number.
   Note: In the question, They will clearly mention, which number will have higher priority and which number will have lower priority.
4. Once all the processes have been arrived, we can schedule them based on their priority.

**Gantt Chart -

**Examples -

**Input :
process no-> 1 2 3 4 5
arrival time-> 0 1 3 2 4
burst time-> 3 6 1 2 4
priority-> 3 4 9 7 8
**Output :
Process_no arrival_time Burst_time Complete_time Turn_Around_Time Waiting_Time
1 0 3 3 3 0
2 1 6 9 8 2
3 3 1 16 13 12
4 2 2 11 9 7
5 4 4 15 11 7
Average Waiting Time is : 5.6
Average Turn Around time is : 8.8

C++ `

// C++ implementation for Priority Scheduling with //Different Arrival Time priority scheduling /*1. sort the processes according to arrival time 2. if arrival time is same the acc to priority 3. apply fcfs */

#include <bits/stdc++.h>

using namespace std;

#define totalprocess 5

// Making a struct to hold the given input

struct process { int at,bt,pr,pno; };

process proc[50];

/* Writing comparator function to sort according to priority if arrival time is same */

bool comp(process a,process b) { if(a.at == b.at) { return a.pr<b.pr; } else { return a.at<b.at; } }

// Using FCFS Algorithm to find Waiting time void get_wt_time(int wt[]) { // declaring service array that stores cumulative burst time int service[50];

// Initialising initial elements of the arrays service[0] = proc[0].at; wt[0]=0;

for(int i=1;i<totalprocess;i++) { service[i]=proc[i-1].bt+service[i-1];

wt[i]=service[i]-proc[i].at;

// If waiting time is negative, change it into zero

if(wt[i]<0)
{
wt[i]=0;
}

}

}

void get_tat_time(int tat[],int wt[]) { // Filling turnaroundtime array

for(int i=0;i<totalprocess;i++) { tat[i]=proc[i].bt+wt[i]; }

}

void findgc() { //Declare waiting time and turnaround time array int wt[50],tat[50];

double wavg=0,tavg=0;

// Function call to find waiting time array get_wt_time(wt); //Function call to find turnaround time get_tat_time(tat,wt);

int stime[50],ctime[50];

stime[0] = proc[0].at; ctime[0]=stime[0]+tat[0];

// calculating starting and ending time for(int i=1;i<totalprocess;i++) { stime[i]=ctime[i-1]; ctime[i]=stime[i]+tat[i]-wt[i]; }

cout<<"Process_no\tStart_time\tComplete_time\tTurn_Around_Time\tWaiting_Time"<<endl;

// display the process details

for(int i=0;i<totalprocess;i++) { wavg += wt[i]; tavg += tat[i];

    cout<<proc[i].pno<<"\t\t"<<
        stime[i]<<"\t\t"<<ctime[i]<<"\t\t"<<
        tat[i]<<"\t\t\t"<<wt[i]<<endl;
}

    // display the average waiting time
    //and average turn around time

cout<<"Average waiting time is : ";
cout<<wavg/(float)totalprocess<<endl;
cout<<"average turnaround time : ";
cout<<tavg/(float)totalprocess<<endl;

}

int main() { int arrivaltime[] = { 1, 2, 3, 4, 5 }; int bursttime[] = { 3, 5, 1, 7, 4 }; int priority[] = { 3, 4, 1, 7, 8 };

for(int i=0;i<totalprocess;i++) { proc[i].at=arrivaltime[i]; proc[i].bt=bursttime[i]; proc[i].pr=priority[i]; proc[i].pno=i+1; }

//Using inbuilt sort function

sort(proc,proc+totalprocess,comp);

//Calling function findgc for finding Gantt Chart

findgc(); 

return 0;

}

// This code is contributed by Anukul Chand.

Java

import java.util.*;

class Process { int at, bt, pr, pno;

Process(int pno, int at, int bt, int pr) {
    this.pno = pno;
    this.pr = pr;
    this.at = at;
    this.bt = bt;
}

}

public class PriorityScheduling { static final int totalprocess = 5; static Process proc[] = new Process[totalprocess];

static boolean comp(Process a, Process b) {
    if (a.at == b.at) {
        return a.pr < b.pr;
    } else {
        return a.at < b.at;
    }
}

static void get_wt_time(int wt[]) {
    int service[] = new int[totalprocess];
    service[0] = proc[0].at;
    wt[0] = 0;

    for (int i = 1; i < totalprocess; i++) {
        service[i] = proc[i - 1].bt + service[i - 1];
        wt[i] = service[i] - proc[i].at;
        if (wt[i] < 0) {
            wt[i] = 0;
        }
    }
}

static void get_tat_time(int tat[], int wt[]) {
    for (int i = 0; i < totalprocess; i++) {
        tat[i] = proc[i].bt + wt[i];
    }
}

static void findgc() {
    int wt[] = new int[totalprocess];
    int tat[] = new int[totalprocess];
    double wavg = 0, tavg = 0;

    get_wt_time(wt);
    get_tat_time(tat, wt);

    int stime[] = new int[totalprocess];
    int ctime[] = new int[totalprocess];

    stime[0] = proc[0].at;
    ctime[0] = stime[0] + tat[0];

    for (int i = 1; i < totalprocess; i++) {
        stime[i] = ctime[i - 1];
        ctime[i] = stime[i] + tat[i] - wt[i];
    }

    System.out.println("Process_no\tStart_time\tComplete_time\tTurn_Around_Time\tWaiting_Time");

    for (int i = 0; i < totalprocess; i++) {
        wavg += wt[i];
        tavg += tat[i];

        System.out.println(proc[i].pno + "\t\t" + stime[i] + "\t\t" + ctime[i] + "\t\t" + tat[i] + "\t\t\t" + wt[i]);
    }

    System.out.println("Average waiting time is : " + wavg / totalprocess);
    System.out.println("Average turnaround time : " + tavg / totalprocess);
}

public static void main(String[] args) {
    int arrivaltime[] = {1, 2, 3, 4, 5};
    int bursttime[] = {3, 5, 1, 7, 4};
    int priority[] = {3, 4, 1, 7, 8};

    for (int i = 0; i < totalprocess; i++) {
        proc[i] = new Process(i + 1, arrivaltime[i], bursttime[i], priority[i]);
    }

    Arrays.sort(proc, (a, b) -> {
        if (a.at == b.at) {
            return a.pr - b.pr;
        } else {
            return a.at - b.at;
        }
    });

    findgc();
}

}

Python

Python3 implementation for Priority Scheduling with

Different Arrival Time priority scheduling

"""1. sort the processes according to arrival time 2. if arrival time is same the acc to priority 3. apply fcfs """

totalprocess = 5 proc = [] for i in range(5): l = [] for j in range(4): l.append(0) proc.append(l)

Using FCFS Algorithm to find Waiting time

def get_wt_time( wt):

# declaring service array that stores
# cumulative burst time 
service = [0] * 5

# Initialising initial elements 
# of the arrays 
service[0] = 0
wt[0] = 0

for i in range(1, totalprocess): 
    service[i] = proc[i - 1][1] + service[i - 1] 
    wt[i] = service[i] - proc[i][0] + 1

    # If waiting time is negative,
    # change it o zero 
    if(wt[i] < 0) :     
        wt[i] = 0
    

def get_tat_time(tat, wt):

# Filling turnaroundtime array 
for i in range(totalprocess):
    tat[i] = proc[i][1] + wt[i] 

def findgc():

# Declare waiting time and
# turnaround time array 
wt = [0] * 5
tat = [0] * 5

wavg = 0
tavg = 0

# Function call to find waiting time array 
get_wt_time(wt) 

# Function call to find turnaround time 
get_tat_time(tat, wt) 

stime = [0] * 5
ctime = [0] * 5
stime[0] = 1
ctime[0] = stime[0] + tat[0]

# calculating starting and ending time 
for i in range(1, totalprocess): 
    stime[i] = ctime[i - 1] 
    ctime[i] = stime[i] + tat[i] - wt[i] 

print("Process_no\tStart_time\tComplete_time",
           "\tTurn_Around_Time\tWaiting_Time")

# display the process details 
for i in range(totalprocess):
    wavg += wt[i] 
    tavg += tat[i] 
    
    print(proc[i][3], "\t\t", stime[i], 
                     "\t\t", end = " ")
    print(ctime[i], "\t\t", tat[i], "\t\t\t", wt[i]) 


# display the average waiting time 
# and average turn around time 
print("Average waiting time is : ", end = " ")
print(wavg / totalprocess)
print("average turnaround time : " , end = " ")
print(tavg / totalprocess)

Driver code

if name =="main": arrivaltime = [1, 2, 3, 4, 5] bursttime = [3, 5, 1, 7, 4] priority = [3, 4, 1, 7, 8]

for i in range(totalprocess): 

    proc[i][0] = arrivaltime[i] 
    proc[i][1] = bursttime[i] 
    proc[i][2] = priority[i] 
    proc[i][3] = i + 1

# Using inbuilt sort function 
proc = sorted (proc, key = lambda x:x[2])
proc = sorted (proc)

# Calling function findgc for
# finding Gantt Chart 
findgc() 

This code is contributed by

Shubham Singh(SHUBHAMSINGH10)

C#

// C# implementation for Priority Scheduling with // Different Arrival Time priority scheduling // 1. sort the processes according to arrival time // 2. if arrival time is same the acc to priority // 3. apply fcfs using System;

class Program { static int totalprocess = 5; static int[][] proc = new int[totalprocess][]; static int[] arrivaltime = new int[] {1, 2, 3, 4, 5}; static int[] bursttime = new int[] {3, 5, 1, 7, 4}; static int[] priority = new int[] {3, 4, 1, 7, 8};

// Driver code
static void Main(string[] args)
{
    for (int i = 0; i < totalprocess; i++)
    {
        proc[i] = new int[4];
        proc[i][0] = arrivaltime[i];
        proc[i][1] = bursttime[i];
        proc[i][2] = priority[i];
        proc[i][3] = i + 1;
    }

    Array.Sort(proc, (x, y) => x[2].CompareTo(y[2]));
    Array.Sort(proc, (x, y) => x[0].CompareTo(y[0]));
    Findgc();
}

// Using FCFS Algorithm to find Waiting time 
static void GetWtTime(int[] wt)
{
    
    // declaring service array that stores
    // cumulative burst time 
    int[] service = new int[totalprocess];
    
    // Initialising initial elements 
    // of the arrays
    service[0] = 0;
    wt[0] = 0;

    for (int i = 1; i < totalprocess; i++)
    {
        service[i] = proc[i - 1][1] + service[i - 1];
        wt[i] = service[i] - proc[i][0] + 1;

        // If waiting time is negative,
        // change it o zero 
        if (wt[i] < 0)
        {
            wt[i] = 0;
        }
    }
}

// Filling turnaroundtime array
static void GetTatTime(int[] tat, int[] wt)
{
    for (int i = 0; i < totalprocess; i++)
    {
        tat[i] = proc[i][1] + wt[i];
    }
}

static void Findgc()
{
    
    // Declare waiting time and
    // turnaround time array 
    int[] wt = new int[totalprocess];
    int[] tat = new int[totalprocess];
    int wavg = 0;
    int tavg = 0;
    
     // Function call to find waiting time array 
    GetWtTime(wt);
    
    // Function call to find turnaround time
    GetTatTime(tat, wt);
    int[] stime = new int[totalprocess];
    int[] ctime = new int[totalprocess];
    stime[0] = 1;
    ctime[0] = stime[0] + tat[0];

    Console.WriteLine("Process_no\tStart_time\tComplete_time\tTurn_Around_Time\tWaiting_Time");

    // calculating starting and ending time
    for (int i = 0; i < totalprocess; i++)
    {
        wavg += wt[i];
        tavg += tat[i];
        Console.WriteLine(proc[i][3] + "\t\t" + stime[i] + "\t\t" + ctime[i] + "\t\t" + tat[i] + "\t\t\t" + wt[i]);
        
        
        // display the process details
        if (i != totalprocess - 1)
        {
            stime[i + 1] = ctime[i];
            ctime[i + 1] = stime[i + 1] + tat[i + 1] - wt[i + 1];
        }
    }

    // display the average waiting time 
    // and average turn around time
    Console.WriteLine("Average waiting time is: " + (double)wavg / totalprocess);
    Console.WriteLine("Average turnaround time is: " + (double)tavg / totalprocess);
}

}

// This code is contributed by shiv1o43g

JavaScript

var totalprocess = 5; var proc = []; for (var i = 0; i < 5; i++) { var l = []; for (var j = 0; j < 4; j++) { l.push(0); } proc.push(l); }

function get_wt_time(wt) { var service = new Array(5).fill(0); service[0] = 0; wt[0] = 0; for (var i = 1; i < totalprocess; i++) { service[i] = proc[i - 1][1] + service[i - 1]; wt[i] = service[i] - proc[i][0] + 1; if (wt[i] < 0) { wt[i] = 0; } } }

function get_tat_time(tat, wt) { for (var i = 0; i < totalprocess; i++) { tat[i] = proc[i][1] + wt[i]; } }

function findgc() { var wt = new Array(5).fill(0); var tat = new Array(5).fill(0); var wavg = 0; var tavg = 0; get_wt_time(wt); get_tat_time(tat, wt); var stime = new Array(5).fill(0); var ctime = new Array(5).fill(0); stime[0] = 1; ctime[0] = stime[0] + tat[0]; for (var i = 1; i < totalprocess; i++) { stime[i] = ctime[i - 1]; ctime[i] = stime[i] + tat[i] - wt[i]; } console.log("Process_no\tStart_time\tComplete_time\tTurn_Around_Time\tWaiting_Time" ); for (var i = 0; i < totalprocess; i++) { wavg += wt[i]; tavg += tat[i]; console.log( proc[i][3] + "\t\t" + stime[i] + "\t\t" + ctime[i] + "\t\t" + tat[i] + "\t\t\t" + wt[i] ); } console.log("Average waiting time is : " + wavg / totalprocess); console.log("average turnaround time : " + tavg / totalprocess); }

var arrivaltime = [1, 2, 3, 4, 5]; var bursttime = [3, 5, 1, 7, 4]; var priority = [3, 4, 1, 7, 8]; for (var i = 0; i < totalprocess; i++) { proc[i][0] = arrivaltime[i]; proc[i][1] = bursttime[i]; proc[i][2] = priority[i]; proc[i][3] = i + 1; }

proc.sort(function (a, b) { if (a[2] == b[2]) { return a[0] - b[0]; } else { return a[2] - b[2]; } }); findgc();

// This code is contributed by shiv1o43g

`

**Output:

Process_no Start_time Complete_time Turn_Around_Time Waiting_Time
1 1 4 3 0
2 5 10 8 3
3 4 5 2 1
4 10 17 13 6
5 17 21 16 12
Average Waiting Time is : 4.4
Average Turn Around time is : 8.4

**Time Complexity: O(N * logN), where N is the total number of processes.
**Auxiliary Space: O(N)