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hits.java
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hits.java
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import java.util.*;
import java.io.*;
import java.lang.*;
import static java.lang.Math.*;
public class hits {
int iter;
int initval;
String filename;
int n; // number of vertices in the graph
int m; // number of edges in the graph
int[][] L; // adjacency matrix
double[] h0;
double[] a0;
final double errorrate = 0.00001;
hits() {} //default constructor
hits(int iter, int initval, String filename) // 3 argument constructor to initialize class variables with provided command line arguments
{
this.iter = iter;
this.initval = initval;
this.filename = filename;
try {
Scanner scanner = new Scanner(new File(filename));
n = scanner.nextInt();
m = scanner.nextInt();
L = new int[n][n]; //Adjacency matrix representation of graph
for(int i = 0; i < n; i++)
for(int j = 0; j < n; j++)
L[i][j] = 0;
while(scanner.hasNextInt())
{
L[scanner.nextInt()][scanner.nextInt()] = 1;
//System.out.println(scanner.nextInt());
}
h0 = new double[n];
a0 = new double[n];
switch(initval) {
case 0:
for(int i = 0; i < n; i++) {
h0[i] = 0;
a0[i] = 0;
}
break;
case 1:
for(int i = 0; i < n; i++) {
h0[i] = 1;
a0[i] = 1;
}
break;
case -1:
for(int i =0; i < n; i++) {
h0[i] = 1.0/n;
a0[i] = 1.0/n;
}
break;
case -2:
for(int i =0; i < n; i++) {
h0[i] = 1.0/Math.sqrt(n);
a0[i] = 1.0/Math.sqrt(n);
}
break;
}
}
catch(FileNotFoundException fnfe)
{
}
}
public static void main(String[] args)
{
if(args.length != 3) {
System.out.println("Usage: hits iterations initialvalue filename");
return;
}
int iterations = Integer.parseInt(args[0]);
int initialvalue = Integer.parseInt(args[1]);
String filename = args[2];
if( !(initialvalue >= -2 && initialvalue <= 1) ) {
System.out.println("Enter -2, -1, 0 or 1 for initialvalue");
return;
}
hits ht = new hits(iterations, initialvalue, filename);
ht.hitsAlgo();
}
boolean isConverged(double[] p, double[] q)
{
for(int i = 0 ; i < n; i++) {
if ( abs(p[i] - q[i]) > errorrate )
return false;
}
return true;
}
public void hitsAlgo()
{
double[] h = new double[n];
double[] a = new double[n];
double a_scale_factor = 0.0;
double a_sum_square = 0.0;
double h_scale_factor = 0.0;
double h_sum_square = 0.0;
double[] aprev = new double[n]; //last iterations values of a, used for convergence
double[] hprev = new double[n]; //last iterations values of h, used for convergence
//If the graph has N greater than 10, then the values for iterations, initialvalue revert to 0 and -1 respectively
if(n > 10) {
iter = 0;
for(int i =0; i < n; i++) {
h[i] = 1.0/n;
a[i] = 1.0/n;
hprev[i] = h[i];
aprev[i] = a[i];
}
int i = 0;
do {
for(int r = 0; r < n; r++) {
aprev[r] = a[r];
hprev[r] = h[r];
}
//A step starts
for(int p = 0; p < n; p++) {
a[p] = 0.0;
}
for(int j = 0; j < n; j++) {
for(int k = 0; k < n; k++) {
if(L[k][j] == 1) {
a[j] += h[k];
}
}
}//A step ends
//H step starts
for(int p = 0; p < n; p++) {
h[p] = 0.0;
}
for(int j = 0; j < n; j++) {
for(int k = 0; k < n; k++) {
if(L[j][k] == 1) {
h[j] += a[k];
}
}
}//H step ends
//Scaling A starts
a_scale_factor = 0.0;
a_sum_square = 0.0;
for(int l = 0; l < n; l++) {
a_sum_square += a[l]*a[l];
}
a_scale_factor = Math.sqrt(a_sum_square);
for(int l = 0; l < n; l++) {
a[l] = a[l]/a_scale_factor;
}//Scaling A ends
//Scaling H starts
h_scale_factor = 0.0;
h_sum_square = 0.0;
for(int l = 0; l < n; l++) {
h_sum_square += h[l]*h[l];
}
h_scale_factor = Math.sqrt(h_sum_square);
for(int l = 0; l < n; l++) {
h[l] = h[l]/h_scale_factor;
}// Scaling H ends
i++; // incr the interation counter
} while( false == isConverged(a, aprev) || false == isConverged(h, hprev));
System.out.println("Iter: " + i);
for(int l = 0; l < n; l++) {
System.out.printf(" A/H[%d]=%.6f/%.6f\n",l,Math.round(a[l]*1000000.0)/1000000.0,Math.round(h[l]*1000000.0)/1000000.0);
}
return;
}
//Initialization
for(int i = 0; i < n; i++)
{
h[i] = h0[i];
a[i] = a0[i];
hprev[i] = h[i];
aprev[i] = a[i];
}
//Base Case
System.out.print("Base: 0 :");
for(int i = 0; i < n; i++) {
System.out.printf(" A/H[%d]=%.6f/%.6f",i,Math.round(a0[i]*1000000.0)/1000000.0,Math.round(h0[i]*1000000.0)/1000000.0);
//System.out.println("a0[" + i + "]= " + a0[i]);
}
if (iter != 0) {
for(int i = 0; i < iter; i++) { //iteration starts
//A step starts
for(int p = 0; p < n; p++) {
a[p] = 0.0;
}
for(int j = 0; j < n; j++) {
for(int k = 0; k < n; k++) {
if(L[k][j] == 1) {
a[j] += h[k];
}
}
}//A step ends
//H step starts
for(int p = 0; p < n; p++) {
h[p] = 0.0;
}
for(int j = 0; j < n; j++) {
for(int k = 0; k < n; k++) {
if(L[j][k] == 1) {
h[j] += a[k];
}
}
}//H step ends
//Scaling A starts
a_scale_factor = 0.0;
a_sum_square = 0.0;
for(int l = 0; l < n; l++) {
a_sum_square += a[l]*a[l];
}
a_scale_factor = Math.sqrt(a_sum_square);
for(int l = 0; l < n; l++) {
a[l] = a[l]/a_scale_factor;
}//Scaling A ends
//Scaling H starts
h_scale_factor = 0.0;
h_sum_square = 0.0;
for(int l = 0; l < n; l++) {
h_sum_square += h[l]*h[l];
}
h_scale_factor = Math.sqrt(h_sum_square);
for(int l = 0; l < n; l++) {
h[l] = h[l]/h_scale_factor;
}// Scaling H ends
System.out.println();
System.out.print("Iter: " + (i+1) + " :");
for(int l = 0; l < n; l++) {
System.out.printf(" A/H[%d]=%.6f/%.6f",l,Math.round(a[l]*1000000.0)/1000000.0,Math.round(h[l]*1000000.0)/1000000.0);
}
}//iteration ends
} // if iter != 0 ends
else
{
int i = 0;
do {
for(int r = 0; r < n; r++) {
aprev[r] = a[r];
hprev[r] = h[r];
}
//A step starts
for(int p = 0; p < n; p++) {
a[p] = 0.0;
}
for(int j = 0; j < n; j++) {
for(int k = 0; k < n; k++) {
if(L[k][j] == 1) {
a[j] += h[k];
}
}
}//A step ends
//H step starts
for(int p = 0; p < n; p++) {
h[p] = 0.0;
}
for(int j = 0; j < n; j++) {
for(int k = 0; k < n; k++) {
if(L[j][k] == 1) {
h[j] += a[k];
}
}
}//H step ends
//Scaling A starts
a_scale_factor = 0.0;
a_sum_square = 0.0;
for(int l = 0; l < n; l++) {
a_sum_square += a[l]*a[l];
}
a_scale_factor = Math.sqrt(a_sum_square);
for(int l = 0; l < n; l++) {
a[l] = a[l]/a_scale_factor;
}//Scaling A ends
//Scaling H starts
h_scale_factor = 0.0;
h_sum_square = 0.0;
for(int l = 0; l < n; l++) {
h_sum_square += h[l]*h[l];
}
h_scale_factor = Math.sqrt(h_sum_square);
for(int l = 0; l < n; l++) {
h[l] = h[l]/h_scale_factor;
}// Scaling H ends
i++; // incr the interation counter
System.out.println();
System.out.print("Iter: " + i + " :");
for(int l = 0; l < n; l++) {
System.out.printf(" A/H[%d]=%.6f/%.6f",l,Math.round(a[l]*1000000.0)/1000000.0,Math.round(h[l]*1000000.0)/1000000.0);
}
} while( false == isConverged(a, aprev) || false == isConverged(h, hprev));
}
System.out.println();
}
}