/**Jacobi iterations for 3-banded matrix****************************************************************/
public double[] jacobi3(double[] rhs) {
double[] sol = new double[lines];
double[] previous = new double[lines];
int i,ii;
int iterations=0;
boolean ready=false;

while (!ready){
for (ii=0;ii<=n;ii++){previous[ii]=sol[ii];}
sol[0]=(rhs[0]-m[l][0]*previous[n]-m[r][0]*previous[1])/m[c][0];
for(i=1;i<=n-1;i++){
sol[i]=(rhs[i]-m[l][i]*previous[i-1]-m[r][i]*previous[i+1])/m[c][i];}
sol[n]=(rhs[n]-m[l][n]*previous[n-1]-m[r][n]*previous[0])/m[c][n];

ready=test(sol,previous); // Testing for convergence
iterations++;}
System.out.println("jacobi iterations= "+iterations);
return sol;
}// jacobi3

/**Forward Gauss Seidel-Successive Over Relaxation for 3-banded matrix****************************************************************/
public double[] fgs3(double[] rhs, double w ) {
double[] hsol = new double[lines];
double[] previous = new double[lines];
int i,ii;
int iterations=0;
boolean ready=false;

while (!ready){
for (ii=0;ii<=n;ii++){previous[ii]=hsol[ii];}

//Forward Gauss Seidel, periodicity included
hsol[0]=(w*(rhs[0]-m[r][0]*previous[1]-m[l][0]*hsol[n])+(1-w)*m[c][0]*previous[0])/m[c][0];
for(i=1;i<=n-1;i++){
hsol[i]=(w*(rhs[i]-m[r][i]*previous[i+1]-m[l][i]*hsol[i-1])+(1-w)*m[c][i]*previous[i])/m[c][i];}
hsol[n]=(w*(rhs[n]-m[r][n]*previous[0]-m[l][n]*hsol[n-1])+(1-w)*m[c][n]*previous[n])/m[c][n];

ready=test(hsol,previous); // Testing for convergence
iterations++;}

System.out.println("fgs iterations= "+iterations);
return hsol;
}// fgs3

/**Backward Gauss seidel, over relaxated, for 3-banded matrix****************************************************************/
public double[] bgs3(double[] rhs, double w ) {
double[] sol = new double[lines];
double[] hsol = new double[lines];
int j,ii;
int iterations=0;
boolean ready=false;

while (!ready){
for (ii=0;ii<=n;ii++){hsol[ii]=sol[ii];}

// Backward Gauss Seidel, periodicity included
sol[n]=(w*(rhs[n]-m[l][n]*hsol[n-1]-m[r][n]*sol[0])+(1-w)*m[c][n]*hsol[n])/m[c][n];;
for(j=n-1;j>=1;j--){
sol[j]=(w*(rhs[j]-m[l][j]*hsol[j-1]-m[r][j]*sol[j+1])+(1-w)*m[c][j]*hsol[j])/m[c][j];}
sol[0]=(w*(rhs[0]-m[l][0]*hsol[n]-m[r][0]*sol[1])+(1-w)*m[c][0]*hsol[0])/m[c][0];

ready=test(sol,hsol); // Testing for convergence
iterations++;}

System.out.println("bgs iterations= "+iterations);
return sol;
}// bgs3

/**Symmetric Successive Over Relaxation for 3-banded matrix****************************************************************/
public double[] ssor3(double[] rhs, double w ) {
double[] sol = new double[lines];
double[] hsol = new double[lines];
double[] previous = new double[lines];
int j,i,ii;
int iterations=0;
boolean ready=false;
 

while (!ready){
for (ii=0;ii<=n;ii++){previous[ii]=sol[ii];}

// Forward Gauss Seidel, one half-step
hsol[0]=(w*(rhs[0]-m[r][0]*previous[1]-m[l][0]*hsol[n])+(1-w)*m[c][0]*previous[0])/m[c][0];
for(i=1;i<=n-1;i++){
hsol[i]=(w*(rhs[i]-m[r][i]*previous[i+1]-m[l][i]*hsol[i-1])+(1-w)*m[c][i]*previous[i])/m[c][i];}
hsol[n]=(w*(rhs[n]-m[r][n]*previous[0]-m[l][n]*hsol[n-1])+(1-w)*m[c][n]*previous[n])/m[c][n];

// Backward Gauss Seidel, next half-step
sol[n]=(w*(rhs[n]-m[l][n]*hsol[n-1]-m[r][n]*sol[0])+(1-w)*m[c][n]*hsol[n])/m[c][n];;
for(j=n-1;j>=1;j--){
sol[j]=(w*(rhs[j]-m[l][j]*hsol[j-1]-m[r][j]*sol[j+1])+(1-w)*m[c][j]*hsol[j])/m[c][j];}
sol[0]=(w*(rhs[0]-m[l][0]*hsol[n]-m[r][0]*sol[1])+(1-w)*m[c][0]*hsol[0])/m[c][0];

ready=test(sol,previous); // Testing for convergence
iterations++;}

System.out.println(" ssor iterations="+iterations);
return sol;
}// ssor3
 

public boolean test(double[] sol, double[] previous) {
int p=1;
double diff;
double lim=Math.pow(10.,-6);
boolean rdy=false;

testloop: for (int k=0 ; k<=n ; k++){
//System.out.println("k="+k);
diff=Math.abs(sol[k]-previous[k]);
//System.out.println("diff="+diff);
if (diff >= lim ) {p=1;}
else {p=0;}
switch (p) {
case 1: rdy=false;break testloop;
case 0: rdy=true;continue;}
}
return rdy;
}// test