[girish3110]

Hello there!! Am havin a lil problem with a program that should carry out iterative methods,namely Jacobi and Seidel methods. The problem is that I don't know (or I can't) how to stop the iteration. The code is given below and if anyone could make any adjustments,plz...

#include <iostream.h>
#include <conio.h>
#include <iomanip.h>
#define err 1e-4
void main()
{
	int a[3],b[3],c[3],d[3],i,n,choice=0;

	//Displays the 'format' of the linear equations.
	for (i=1;i<=3;i++)
		cout<<"a"<<i<<"x + b"<<i<<"y + c"<<i<<"z = d"<<i<<endl;
	cout<<endl;
	
	//Asks user to input the values of a,b,c,d and the accuracy of the calculation.
	for (i=0;i<3;i++)
	{
		cout<<"Enter value of a"<<i+1<<" :";
		cin>>a[i];
		cout<<"Enter value of b"<<i+1<<" :";
		cin>>b[i];
		cout<<"Enter value of c"<<i+1<<" :";
		cin>>c[i];
		cout<<"Enter value of d"<<i+1<<" :";
		cin>>d[i];
		cout<<endl;
	}
	cout<<"Enter the accuracy(number of decimal places): ";
	cin>>n;
	//clrscr();

	//Displays the linear equations.
	for (i=0;i<3;i++)
		cout<<a[i]<<"x + "<<b[i]<<"y + "<<c[i]<<"z = "<<d[i]<<endl;
	cout<<endl;

	//Asks user to choose iterative method.
	do
	{
		cout<<"Choose iterative method..."<<endl<<endl;
		cout<<"1. Gauss Jacobi"<<endl;
		cout<<"2. Gauss Seidel"<<endl<<endl;
		cout<<"Enter choice: ";
		cin>>choice;
		if ((choice==1) || (choice==2)) //Exit the WHILE..DO loop if either 1 or 2 is input.
			break;
	}while((choice!=1)||(choice!=2));

	if (choice==1) //If 1 is input, perform Gauss-Jacobi method;
	{
		int k=1;
		float x,y,z,x1,y1,z1,x2,y2,z2;
		y=0;
		z=0;
		x=0;
		x1=(d[0]-(b[0]*y)-(c[0]*z))/a[0];
		y1=(d[1]-(a[1]*x)-(c[1]*z))/b[1];
		z1=(d[2]-(a[2]*x)-(b[2]*y))/c[2];
		cout<<"x:"<<setprecision(n)<<x1<<"\t";
		cout<<"y:"<<setprecision(n)<<y1<<"\t";
		cout<<"z:"<<setprecision(n)<<z1<<endl<<endl;
		do
		{
			x2=x;
			y2=y;
			z2=z;
			x=(d[0]-(b[0]*y1)-(c[0]*z1))/a[0];
			y=(d[1]-(a[1]*x1)-(c[1]*z1))/b[1];
			z=(d[2]-(a[2]*x1)-(b[2]*y1))/c[2];
			k++;
			x1=x;
			y1=y;
			z1=z;
			cout<<"x:"<<setprecision(n)<<x1<<"\t";
			cout<<"y:"<<setprecision(n)<<y1<<"\t";
			cout<<"z:"<<setprecision(n)<<z1<<endl<<endl;
		}while(???);

		cout<<"Using Gauss-Jacobi Method..."<<endl;
		cout<<"Number of iterations performed: "<<k<<endl;
		cout<<"Value of x is "<<x1<<endl;
		cout<<"Value of y is "<<y1<<endl;
		cout<<"Value of z is "<<z1<<endl;
	}

	else //If 2 is input, perform Gauss-Seidel method.
		cout<<"Seidel";
}

The Do...WHILE loop is the problem. Try using the following values for the program:
a1=8 , b1=-3 , c1=2 , d1=20
a2 =4 , b2=11 , c2=-1 , d2=33
a3=6 , b3=3 , c3=12 , d3=35

The answers should be x= 3.0168 , y= 1.9859 and z=0.9118

[pradeep]

What algorithm is this?

[girish3110]

It's used to solve a system of linear equations by using iteration and the method is that of Jacobi.

[girish3110]

Can anyone help me?? I just need to know whever the values of x2-x1 are converging...