Preemptive Priority Scheduling Algorithms

Priority Scheduling

• A preemptive priority algorithm will preemptive the CPU if the priority of the newly arrival process is higher than the priority of the currently running process.

SAMPLE INPUT:

Process	Burst Time	Arrival Time	Priority
P1	3	0	3
P2	2	1	2
P3	1	2	4
P4	1	3	2
P5	2	4	1
P6	4	5	5

GANTT CHART:

0	1	2	3	4	5	6	7	8	9	10	11	12
P1	P2	P2	P4	P5	P5	P1	P1	P3	P6	P6	P6	P6

Waiting Time (Waiting time – Arrival Time):

Turning Time ((Waiting time – Arrival Time)+Burst Time):

           

            Waiting                Arrival Time             Waiting Time              Turning Time

                 5                              0                        (5-0)=5                       (5-0)+3=8

                 1                              1                        (1-1)=0                       (1-1)+2=2

                 8                              2                        (8-2)=6                       (8-2)+1=7

                 3                              3                        (3-3)=0                       (3-3)+1=1

                 4                              4                        (4-4)=0                       (4-4)+2=2

                 9                              5                        (9-5)=4                       (9-5)+4=8                                                               Total Waiting Time 15            Total Turning Time 28

Average Waiting Time = Total Waiting Time / 6

       = 15 / 6

       = 2.5

Average Turning Time = Total Turning Time / 6

       = 28 / 6

       = 4.6667

Design:
Codes:

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Preemptive Priority Scheduling Algorithm in JAVA

/*~~~~~~~~~~Frame PreemptivePriority.java~~~~~~~~~~~*/

import javax.swing.*;

import java.lang.*;

public class PreemptivePriority extends javax.swing.JFrame {

/** Creates new form PreemptivePriority */

public PreemptivePriority() {

initComponents();

}

PriorityMethod m = new PriorityMethod();

int[] B = new int[10];

int[] A = new int[10];

int[] P = new int[10];

/*~~~~~~~~~~~Button Calculate~~~~~~~~~~~~*/

private void btnCalculateMouseClicked(java.awt.event.MouseEvent evt) {

// TODO add your handling code here:

B[1]=Integer.parseInt(txtB1.getText());

B[2]=Integer.parseInt(txtB2.getText());

B[3]=Integer.parseInt(txtB3.getText());

B[4]=Integer.parseInt(txtB4.getText());

B[5]=Integer.parseInt(txtB5.getText());

B[6]=Integer.parseInt(txtB6.getText());

A[1]=Integer.parseInt(txtA1.getText());

A[2]=Integer.parseInt(txtA2.getText());

A[3]=Integer.parseInt(txtA3.getText());

A[4]=Integer.parseInt(txtA4.getText());

A[5]=Integer.parseInt(txtA5.getText());

A[6]=Integer.parseInt(txtA6.getText());

P[1]=Integer.parseInt(txtP1.getText());

P[2]=Integer.parseInt(txtP2.getText());

P[3]=Integer.parseInt(txtP3.getText());

P[4]=Integer.parseInt(txtP4.getText());

P[5]=Integer.parseInt(txtP5.getText());

P[6]=Integer.parseInt(txtP6.getText());

String str = String.valueOf(m.AverageWaitingTime(B,A,P));

Double f = new Double(str);

double d = f.doubleValue();

d=d*100.0;

long dI = (long)d;

double e = ((double)dI)/100.0;

String str2 = String.valueOf(m.AverageTurningTime(B,A,P));

Double f2 = new Double(str2);

double d2 = f2.doubleValue();

d2=d2*100.0;

long dI2 = (long)d2;

double e2 = ((double)dI2)/100.0;

txtAwt.setText(String.valueOf(e));

txtAtt.setText(String.valueOf(e2));

}

/*~~~~~~~~~~~End Button Calculate~~~~~~~~~~~~*/

/*~~~~~~~~~~~Button New~~~~~~~~~~~~*/

private void btnSaveMouseClicked1(java.awt.event.MouseEvent evt) {

// TODO add your handling code here:

txtB1.setText("");

txtB2.setText("");

txtB3.setText("");

txtB4.setText("");

txtB5.setText("");

txtB6.setText("");

txtA1.setText("");

txtA2.setText("");

txtA3.setText("");

txtA4.setText("");

txtA5.setText("");

txtA6.setText("");

txtP1.setText("");

txtP2.setText("");

txtP3.setText("");

txtP4.setText("");

txtP5.setText("");

txtP6.setText("");

txtB1.setEnabled(true);

txtB2.setEnabled(true);

txtB3.setEnabled(true);

txtB4.setEnabled(true);

txtB5.setEnabled(true);

txtB6.setEnabled(true);

txtA1.setEnabled(true);

txtA2.setEnabled(true);

txtA3.setEnabled(true);

txtA4.setEnabled(true);

txtA5.setEnabled(true);

txtA6.setEnabled(true);

txtP1.setEnabled(true);

txtP2.setEnabled(true);

txtP3.setEnabled(true);

txtP4.setEnabled(true);

txtP5.setEnabled(true);

txtP6.setEnabled(true);

btnNew.setEnabled(false);

btnSave.setEnabled(true);

txtB1.requestFocus();

txtAwt.setText("");

txtAtt.setText("");

table1.removeAll();

btnCalculate.setEnabled(false);

}

/*~~~~~~~~~~~End Button New~~~~~~~~~~~~*/

/*~~~~~~~~~~~Button Save~~~~~~~~~~~~*/

private void btnSaveMouseClicked(java.awt.event.MouseEvent evt) {

if(txtB1.getText()=="" || txtB2.getText()=="" || txtB3.getText()=="" || txtB4.getText()=="" || txtB5.getText()=="" || txtB6.getText()=="" || txtA1.getText()=="" || txtA2.getText()=="" || txtA3.getText()=="" || txtA4.getText()=="" || txtA5.getText()=="" || txtA6.getText()=="" || txtP1.getText()=="" || txtP2.getText()=="" || txtP3.getText()=="" || txtP4.getText()=="" || txtP5.getText()=="" || txtP6.getText()=="")

JOptionPane.showMessageDialog(null,"Filled-up first all fields to continue...");

else{

table1.setValueAt(lbl1.getText(),0,0);

table1.setValueAt(txtB1.getText(),0,1);

table1.setValueAt(txtA1.getText(),0,2);

table1.setValueAt(txtP1.getText(),0,3);

table1.setValueAt(lbl2.getText(),1,0);

table1.setValueAt(txtB2.getText(),1,1);

table1.setValueAt(txtA2.getText(),1,2);

table1.setValueAt(txtP2.getText(),1,3);

table1.setValueAt(lbl3.getText(),2,0);

table1.setValueAt(txtB3.getText(),2,1);

table1.setValueAt(txtA3.getText(),2,2);

table1.setValueAt(txtP3.getText(),2,3);

table1.setValueAt(lbl4.getText(),3,0);

table1.setValueAt(txtB4.getText(),3,1);

table1.setValueAt(txtA4.getText(),3,2);

table1.setValueAt(txtP4.getText(),3,3);

table1.setValueAt(lbl5.getText(),4,0);

table1.setValueAt(txtB5.getText(),4,1);

table1.setValueAt(txtA5.getText(),4,2);

table1.setValueAt(txtP5.getText(),4,3);

table1.setValueAt(lbl6.getText(),5,0);

table1.setValueAt(txtB6.getText(),5,1);

table1.setValueAt(txtA6.getText(),5,2);

table1.setValueAt(txtP6.getText(),5,3);

txtB1.setEnabled(false);

txtB2.setEnabled(false);

txtB3.setEnabled(false);

txtB4.setEnabled(false);

txtB5.setEnabled(false);

txtB6.setEnabled(false);

txtA1.setEnabled(false);

txtA2.setEnabled(false);

txtA3.setEnabled(false);

txtA4.setEnabled(false);

txtA5.setEnabled(false);

txtA6.setEnabled(false);

txtP1.setEnabled(false);

txtP2.setEnabled(false);

txtP3.setEnabled(false);

txtP4.setEnabled(false);

txtP5.setEnabled(false);

txtP6.setEnabled(false);

btnNew.setEnabled(true);

btnSave.setEnabled(false);

btnCalculate.setEnabled(true);

}

}

/*~~~~~~~~~~~End Button Save~~~~~~~~~~~~*/

/**

* @param args the command line arguments

*/

public static void main(String args[]) {

java.awt.EventQueue.invokeLater(new Runnable() {

public void run() {

new PreemptivePriority().setVisible(true);

}

});

}

/*~~~~~~~~~~~~~~Method PriorityMethod.java~~~~~~~~~~~~~~~~~~~*/

import javax.swing.*;

public class PriorityMethod {

public double AverageWaitingTime(int[] burst, int[] arrival, int[] priority){

int i, j = 0, Tt=0, Time=0, min, max1=0;

char[] S = new char[10];

char[] start = new char[10];

int[] Wt = new int[10];

int[] B = new int[10];

int[] A = new int[10];

int[] P = new int[10];

double Twt=0.0, Awt;

for(i=1;i<=6;i++)

{

B[i]=burst[i];

A[i]=arrival[i];

P[i]=priority[i];

Wt[i]=0;

S[i]='T';

start[i]='F';

Tt=Tt+B[i];

if(A[i]>Time)

Time=A[i];

if(P[i]>max1)

max1=P[i];

}

int w=0,flag=0,t=0;

i=1;

while(t

{

if(A[i]<=t && B[i]!=0)

{

if(flag==0)

{

Wt[i]=Wt[i]+w;

}

B[i]=B[i]-1;

if(B[i]==0)

S[i]='F';

start[i]='T';

t++;

w=w+1;

if(S[i]!='F')

{

j=1;flag=1;

while(j<=6 && flag!=0)

{

if(S[j]!='F' && P[i]>P[j] && A[j]<=t && i!=j)

{

flag=0;

Wt[i]=Wt[i]-w;

i=j;

}

else

{

flag=1;

}

j++;

}

}

else

{

i++;

j=1;

while(A[j]<=t &&j<=6)

{

if(P[i]>P[j] && S[j]!='F')

{

flag=0;

i=j;

}

j++;

}

}

}

else{

if(flag==0)

i++;

t++;

}

}

while(w

{

min=max1+1;

i=1;

while(i<=6)

{

if(min>P[i] && S[i]=='T')

{

min=P[i];

j=i;

}

i++;

}

i=j;

if(w==Time && start[i]=='T')

{

w=w+B[i];

S[i]='F';

}

else

{

Wt[i]=Wt[i]+w;

w=w+B[i];

S[i]='F';

}

}

for(i=1;i<=6;i++)

Twt=Twt+(Wt[i]-A[i]);

Awt=Twt/6;

JOptionPane.showMessageDialog(null,"Waiting Time Info for every Process\n\tP1 = "+

(Wt[1]-A[1])+"\n\tP2 = "+(Wt[2]-A[2])+"\n\tP3 = "+(Wt[3]-A[3])+"\n\tP4 = "+

(Wt[4]-A[4])+"\n\tP5 = "+(Wt[5]-A[5])+"\n\tP6 = "+(Wt[6]-A[6]));

return Awt;

}

public double AverageTurningTime(int[] burst, int[] arrival, int[] priority){

int i, j = 0, Tt=0, Time=0, min, max1=0;

char[] S = new char[10];

char[] start = new char[10];

int[] Wt = new int[10];

int[] B = new int[10];

int[] A = new int[10];

int[] P = new int[10];

int[] Wtm = new int[10];

double Ttt=0.0, Att;

for(i=1;i<=6;i++)

{

B[i]=burst[i];

Wtm[i]=B[i];

A[i]=arrival[i];

P[i]=priority[i];

Wt[i]=0;

S[i]='T';

start[i]='F';

Tt=Tt+B[i];

if(A[i]>Time)

Time=A[i];

if(P[i]>max1)

max1=P[i];

}

int w=0,flag=0,t=0;

i=1;

while(t

{

if(A[i]<=t && B[i]!=0)

{

if(flag==0)

{

Wt[i]=Wt[i]+w;

}

B[i]=B[i]-1;

if(B[i]==0)

S[i]='F';

start[i]='T';

t++;

w=w+1;

if(S[i]!='F')

{

j=1;flag=1;

while(j<=6 && flag!=0)

{

if(S[j]!='F' && P[i]>P[j] && A[j]<=t && i!=j)

{

flag=0;

Wt[i]=Wt[i]-w;

i=j;

}

else

{

flag=1;

}

j++;

}

}

else

{

i++;

j=1;

while(A[j]<=t &&j<=6)

{

if(P[i]>P[j] && S[j]!='F')

{

flag=0;

i=j;

}

j++;

}

}

}

else{

if(flag==0)

i++;

t++;

}

}

while(w

{

min=max1+1;

i=1;

while(i<=6)

{

if(min>P[i] && S[i]=='T')

{

min=P[i];

j=i;

}

i++;

}

i=j;

if(w==Time && start[i]=='T')

{

w=w+B[i];

S[i]='F';

}

else

{

Wt[i]=Wt[i]+w;

w=w+B[i];

S[i]='F';

}

}

for(i=1;i<=6;i++)

Ttt=Ttt+((Wt[i]-A[i])+Wtm[i]);

Att=Ttt/6;

JOptionPane.showMessageDialog(null,"Turning Time Info for every Process\n\tP1 = "+

((Wt[1]-A[1])+Wtm[1])+"\n\tP2 = "+((Wt[2]-A[2])+Wtm[2])+"\n\tP3 = "+

((Wt[3]-A[3])+Wtm[3])+"\n\tP4 = "+((Wt[4]-A[4])+Wtm[4])+"\n\tP5 = "+

((Wt[5]-A[5])+Wtm[5])+"\n\tP6 = "+((Wt[6]-A[6])+Wtm[6]));

return Att;

}

}

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