QuickpropUpdateRule.java

package func.nn.backprop;

/**
 * An update rule for the Quickprop algorithm
 * @author Andrew Guillory gtg008g@mail.gatech.edu
 * @version 1.0
 */
public class QuickpropUpdateRule extends WeightUpdateRule {
    
    /**
     * The learning rate
     */
    private double learningRate;

    /**
     * Make a new quickprop update rule
     * @param learningRate the learning rate
     */
    public QuickpropUpdateRule(double learningRate) {
        this.learningRate = learningRate;
    }
    
    /**
     * Make a new quickprop update rule
     */
    public QuickpropUpdateRule() {
    	this(.2);
    }

    /**
     * @see nn.backprop.BackPropagationUpdateRule#update(nn.backprop.BackPropagationLink)
     */
    public void update(BackPropagationLink link) {
        if (link.getLastError() == 0) {
            // the first run
            link.changeWeight(-learningRate * link.getError());
        } else {
            // jump to parabola min
            link.changeWeight(link.getError() 
                / (link.getLastError() - link.getError())
                    * link.getLastChange()
                - learningRate * link.getError());
        }
    }

}