I have been trying to write a program for deadlock detection algorithm in java language but when I input data that should produce deadlock, the program always outputs that "No deadlock occurs". I am a beginner and would appreciate it if anyone can tell me what's wrong with my code.
here is my code:
package org.me.deadlockdetection;
import java.applet.Applet;
import java.awt.*;
import java.util.Scanner;
public class DeadlockDetection{
private int processes, resources, max[][], allocate[][],need[][], available[];
public static void main(String[] args) {
System.out.println("******* Deadlock detection algorithm *******");
new DeadlockDetection().input();
new DeadlockDetection().show();
new DeadlockDetection().cal();
}
public void input(){
Scanner sc=new Scanner(System.in);
System.out.print("Enter no. of processes: ");
processes=sc.nextInt(); //no. of process
System.out.print("Enter no. of resources: ");
resources=sc.nextInt(); //no. of resources
need=new int[processes][resources]; //initializing arrays
max=new int[processes][resources];
allocate=new int[processes][resources];
available=new int[resources];
System.out.println("Enter allocation matrix -->");
for(int i=0;i<processes;i++)
for(int j=0;j<resources;j++)
allocate[i][j]=sc.nextInt(); //allocation matrix
System.out.println("Enter max matrix -->");
for(int i=0;i<processes;i++)
for(int j=0;j<resources;j++)
max[i][j]=sc.nextInt(); //max matrix
System.out.println("Enter available matrix -->");
for(int j=0;j<resources;j++)
available[j]=sc.nextInt(); //available matrix
sc.close();
}
public void show(){
//int i,j;
System.out.println("Processes Allocation Max Available");
for(int i=0;i<processes;i++){
System.out.println("P"+(i+1));
System.out.println(" ");
for(int j=0;j<resources;j++){
System.out.println(" "+allocate[i][j]);
}
System.out.println(" ");
for(int j=0;j<resources;j++){
System.out.println(" "+max[i][j]);
}
System.out.println(" ");
if(i==0){
for(int j=0;j<resources;j++){
System.out.println(" "+available[j]);
}
}
}
}
public void cal(){
int finish[],temp,flag=1, k,c1=0;
int dead[];
int safe[];
int i,j;
finish=new int[100];
dead=new int[100];
safe=new int[100];
for(i=0;i<processes;i++)
{
finish[i]=0;
}
//find need matrix
for(i=0;i<processes;i++)
{
for(j=0;j<resources;j++)
{
need[i][j]=max[i][j]-allocate[i][j];
}
}
while(flag==1)
{
flag=0;
for(i=0;i<processes;i++)
{
int c=0;
for(j=0;j<resources;j++)
{
if((finish[i]==0)&&(need[i][j]<=available[j]))
{
c++;
if(c==resources)
{
for(k=0;k<resources;k++)
{
available[k]+=allocate[i][j];
finish[i]=1;
flag=1;
}
if(finish[i]==1)
{
i=processes;
}
}
}
}
}
}
j=0;
flag=0;
for(i=0;i<processes;i++)
{
if(finish[i]==0)
{
dead[j]=i;
j++;
flag=1;
}
}
if(flag==1)
{
System.out.println("\n\nSystem is in Deadlock and the Deadlock process are\n");
for(i=0;i<processes;i++)
{
System.out.println("P"+dead[i]);
}
}
else
{
System.out.println("No deadlock occure");
}
}
}
The Run:
******* Deadlock detection algorithm *******
Enter no. of processes: 3
Enter no. of resources: 3
Enter allocation matrix -->
3 3 3
2 0 3
1 2 4
Enter max matrix -->
3 6 8
4 3 3
3 4 4
Enter available matrix -->
1 2 0
Processes Allocation Max Available
No deadlock occure
The result should be:
System is in Deadlock and the Deadlock process are
p0
p1
p2
In main, you create 3 separate instances:
new DeadlockDetection().input();
new DeadlockDetection().show();
new DeadlockDetection().cal();
This means that when you call show() and cal(), processes is always 0 because creating a new instance throws away the stuff you did in input(). You should have this instead:
DeadlockDetection dd = new DeadlockDetection();
dd.input();
dd.show();
dd.cal();