PageRank的一个简单实现

 

public class PageRank {
	private BinaryData adjacencyMatrix = null;
	private double threshold = 0.000000001;
	private double alpha = 0.3;
	private double beta = 0.6;
	private double gamma = 0.1;
	
	private UnitaryData preference = new ArrayUnitaryData(new double[]{1, 1, 1});
	// initialize to a random value
	private UnitaryData rank = new ArrayUnitaryData(new double[]{0, 0, 0});
	private UnitaryData oldRank = new ArrayUnitaryData(new double[]{1, 1, 1});
	private int length = 0;
	
	private UnitaryData alphaPart = new ArrayUnitaryData(new double[]{1, 1, 1});
	private UnitaryData betaPart = new ArrayUnitaryData(new double[]{1, 1, 1});
	private UnitaryData gammaPart = new ArrayUnitaryData(new double[]{1, 1, 1});
	
	public PageRank(BinaryData data){
		((ArrayBinaryData)data).Stochastic();
		
		adjacencyMatrix = data;
		
		length = rank.getDimension();
	}
	
	public void Iteration(){
		adjacencyMatrix.print();
		
		// alphaPart
		for (int i = 0; i < length; i++) {
			alphaPart.setValue(i, alpha * rank.getValue(i));
		}
		
		// betaPart
		for (int i = 0; i < length; i++) {
			double temp = 0;
			for (int j = 0; j < length; j++) {
				temp += adjacencyMatrix.getValue(i, j) * rank.getValue(j);
			}
			temp *= beta;
			betaPart.setValue(i, temp);
		}
		
		// gammaPart
		for (int i = 0; i < length; i++) {
			gammaPart.setValue(i, gamma * preference.getValue(i));
		}
		
		// sum
		for (int i = 0; i < length; i++) {
			rank.setValue(i, alphaPart.getValue(i) + betaPart.getValue(i) + gammaPart.getValue(i));
		}
		
		for (int j = 0; j < length; j++) {
			System.out.print(rank.getValue(j));
			System.out.print('\n');
		}
		
		for (int j = 0; j < length; j++) {
			System.out.print(oldRank.getValue(j));
			System.out.print('\n');
		}
		
		System.out.print('\n');
	}
	
	public void Run(){
		for (int i = 0; i < 100; i++) {
			Iteration();
			if (CheckFinish()) {
				break;
			}
			oldRank = rank.clone();
		}
	}
	
	public boolean CheckFinish(){
		int passed = 0;
		for (int i = 0; i < length; i++) {
			double diff = Math.abs(rank.getValue(i) - oldRank.getValue(i));
			if (diff < threshold) {
				passed += 1; 
			}
		}
		
		if (passed == length) {
			return true;
		}else {
			return false;
		}
	}
	
	public static void main(String[] args) {
		double a[][] = {
				{0, 3, 5},
				{3, 0, 1},
				{5, 1, 0}
		};
		
		BinaryData g = new ArrayBinaryData(a);
		PageRank PR = new PageRank(g);
		
		PR.Run();
	}
}