[机器学习]BP神经网络 java实现

阳光穿透心脏的1/2处 2022-05-30 02:25 329阅读 0赞

代码转载处

https://www.cnblogs.com/hesi/p/7218602.html

对他文章的代码进行了修改优化

代码如下

package classfour;
    
    public abstract class Student {
    	// 输入层
    	protected double[] input;
    	// 输入层权重
    	protected double[][] inputWeight;
    	// 隐藏层
    	protected double[] hide;
    	// 隐藏层权重
    	protected double[][] hideWeight;
    	// 输出
    	protected double[] out;
    	// 实际值
    	protected double[] target;
    	// 学习率
    	protected double rate;
    
    	/**
    	 * 初始化
    	 * 
    	 * @param inputNode
    	 *            输入层的个数
    	 * @param hideNode
    	 *            隐藏层的个数
    	 * @param outNode
    	 *            输出层的个数
    	 * @param rate
    	 *            学习率
    	 */
    	public Student(int inputNode, int hideNode, int outNode, double rate) {
    		input = new double[inputNode + 1];
    		hide = new double[hideNode + 1];
    		out = new double[outNode];
    		inputWeight = new double[hideNode][inputNode + 1];
    		hideWeight = new double[outNode][hideNode + 1];
    		init(inputWeight);
    		init(hideWeight);
    		this.rate = rate;
    	}
    
    	/**
    	 * 
    	 * @param 初始化权重
    	 */
    	public void init(double[][] weight) {
    		for (int i = 0; i < weight.length; i++) {
    			for (int j = 0; j < weight[i].length; j++) {
    				weight[i][j] = Math.random()>0.5?Math.random():-Math.random();
    			}
    		}
    	}
    
    	public abstract void study(double[] data, double[] result);
    
    	public double[] predict(double[] data) {
    		this.setInput(data);
    		double[] output = new double[out.length + 1];
    		forward(input, inputWeight, hide);
    		forward(hide, hideWeight, output);
    		for (int i = 0; i < out.length; i++) {
    			out[i] = output[i + 1];
    		}
    		return out;
    	}
    
    	protected void setInput(double[] input) {
    		this.input[0] = 1.0;
    		for (int i = 0; i < input.length; i++) {
    			this.input[i + 1] = input[i];
    		}
    	}
    
    	/**
    	 * 激励函数,这里为逻辑回归
    	 * 
    	 * @param z
    	 * @return
    	 */
    	protected double Sigmoid(double z) {
    		return 1d / (1d + Math.pow(Math.E, -z));
    	}
    
    	/**
    	 * 代价函数 计算误差
    	 * 
    	 * @param data
    	 * @param result
    	 * @return
    	 */
    	public double costFunction(double[][] data, double[][] result) {
    		double sum = 0d;
    		for (int i = 0; i < result.length; i++) {
    			sum += getSum(data[i], result[i]);
    		}
    		return -sum / result.length;
    	}
    
    	private double getSum(double[] data, double[] result) {
    		double[] predict = predict(data);
    		double sum = 0d;
    		for (int i = 0; i < predict.length; i++) {
    			sum += Math.log(predict[i]) * result[i] + (1 - result[i]) * Math.log(1 - predict[i]);
    		}
    		return sum;
    	}
    
    	public void forward(double[] x, double[][] weight, double[] out) {
    		out[0] = 1d;
    		for (int i = 0; i < weight.length; i++) {
    			double sum = 0d;
    			for (int j = 0; j < x.length; j++) {
    				sum += x[j] * weight[i][j];
    			}
    			out[i + 1] = Sigmoid(sum);
    		}
    	}
    }

package classfour;
    
    public class WangJunLe extends Student {
    
    	public WangJunLe(int inputNode, int hideNode, int outNode, double rate) {
    		super(inputNode, hideNode, outNode, rate);
    	}
    
    	@Override
    	public void study(double[] data, double[] result) {
    		super.setInput(data);
    		super.target = result;
    		double[] output = new double[out.length + 1];
    		// 前向传播
    		forward(input, inputWeight, hide);
    		forward(hide, hideWeight, output);
    		// 后向传播
    		backpropagation(output);
    	}
    
    	/**
    	 * 
    	 * @param x为输入层
    	 * @param weight为权重
    	 * @param out为下一层
    	 */
    	public void forward(double[] x, double[][] weight, double[] out) {
    		out[0] = 1d;
    		for (int i = 0; i < weight.length; i++) {
    			double sum = 0d;
    			for (int j = 0; j < x.length; j++) {
    				sum += x[j] * weight[i][j];
    			}
    			out[i + 1] = Sigmoid(sum);
    		}
    	}
    
    	/**
    	 * 后向传播
    	 * 
    	 * @param out
    	 *            为我们预测的输出结果
    	 */
    	private void backpropagation(double[] out) {
    		double[] error = getError(out);
    		double[] hideError = getHideError(error);
    		updateWeight(hideError, inputWeight, input);
    		updateWeight(error, hideWeight, hide);
    	}
    
    	private void updateWeight(double[] error, double[][] weight, double[] x) {
    		for (int i = 0; i < weight.length; i++) {
    			for (int j = 0; j < weight[i].length; j++) {
    				weight[i][j] += rate * error[i] * x[j];
    			}
    		}
    	}
    
    	/**
    	 * 误差为实际值减预测值
    	 * @param out 为我们预测的输出结果
    	 * @return 返回误差
    	 */
    	private double[] getError(double[] out) {
    		double[] error = new double[out.length - 1];
    		for (int i = 0; i < target.length; i++) {
    			error[i] = target[i] - out[i + 1];
    		}
    		return error;
    	}
    	/**
    	 * 获取隐藏层的错误
    	 * 就是权重*上层误差之和
    	 * @param error
    	 * @return
    	 */
    	private double[] getHideError(double[] error) {
    		double[] hideError = new double[hide.length - 1];
    		for (int i = 0; i < hideError.length; i++) {
    			double sum = 0;
    			for (int j = 0; j < hideWeight.length; j++) {
    				sum += hideWeight[j][i + 1] * error[j];
    			}
    			hideError[i] = sum * hide[i + 1] * (1d - hide[i + 1]);
    		}
    		return hideError;
    	}
    
    	@Override
    	/**
    	 * 获取数据集 前向传播得到结果进行返回
    	 */
    	public double[] predict(double[] data) {
    		super.setInput(data);
    		double[] output = new double[out.length + 1];
    		forward(input, inputWeight, hide);
    		forward(hide, hideWeight, output);
    		for (int i = 0; i < out.length; i++) {
    			out[i] = output[i + 1];
    		}
    		return out;
    	}
    
    }

package classfour;
    
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Random;
    
    import classfour.Student;
    import classfour.WangJunLe;
    
    public class Exam {
    
    	/**
    	 * @param args
    	 * @throws IOException
    	 */
    	public static void main(String[] args) throws IOException {
    		Student bp = new WangJunLe(32, 4, 4, 0.05);
    		List<Integer> list = new ArrayList<Integer>();
    		for (int i = 1; i <= 9; i++) {
    			list.add(i);
    			list.add(-i);
    		}
    		for (int i = 0; i != 100000; i++) {
    			for (int value : list) {
    				double[] real = new double[4];
    				if (value >= 0)
    					if ((value & 1) == 1)
    						real[0] = 1;
    					else
    						real[1] = 1;
    				else if ((value & 1) == 1)
    					real[2] = 1;
    				else
    					real[3] = 1;
    
    				double[] binary = new double[32];
    				int index = 31;
    				do {
    					binary[index--] = (value & 1);
    					value >>>= 1;
    				} while (value != 0);
    				bp.study(binary, real);
    			}
    		}
    
    		System.out.println("请输入一个任意数字，将自动判断它是正数还是复数，奇数还是偶数。");
    
    		while (true) {
    			byte[] input = new byte[10];
    			System.in.read(input);
    			Integer value = Integer.parseInt(new String(input).trim());
    			int rawVal = value;
    			double[] binary = new double[32];
    			int index = 31;
    			do {
    				binary[index--] = (value & 1);
    				value >>>= 1;
    			} while (value != 0);
    
    			double[] result = bp.predict(binary);
    			int idx = -1;
    			for (int i = 0; i != result.length; i++) {
    				if (result[i] > 0.5) {
    					idx = i;
    					break;
    				}
    			}
    			for (double d : result) {
    				System.out.println(d);
    			}
    			switch (idx) {
    			case 0:
    				System.out.format("%d是一个正奇数\n", rawVal);
    				break;
    			case 1:
    				System.out.format("%d是一个正偶数\n", rawVal);
    				break;
    			case 2:
    				System.out.format("%d是一个负奇数\n", rawVal);
    				break;
    			case 3:
    				System.out.format("%d是一个负偶数\n", rawVal);
    				break;
    			}
    		}
    	}
    }