经过训练的神经网络对所有评估行输出相同的结果

Question

训练我的网络时似乎没有问题，因为它收敛并低于 0.01 误差。但是，当我加载经过训练的网络并引入评估集时，它会为所有评估集行输出相同的结果（实际预测，而不是训练阶段）。我使用具有 9 个输入的弹性传播、1 个具有 7 个隐藏神经元和 1 个输出神经元的隐藏层来训练我的网络。更新：我的数据使用最小-最大规范化。我正在尝试预测电力负荷数据。

这是示例数据，前 9 行是输入，第 10 行是理想值：

0.5386671932975533, 1100000.0, 0.0, 1.0, 40.0, 1.0, 30.0, 9.0, 2014.0 , 0.5260616667545941
0.5260616667545941, 1100000.0, 0.0, 1.0, 40.0, 2.0, 30.0, 9.0, 2014.0, 0.5196499668339777
0.5196499668339777, 1100000.0, 0.0, 1.0, 40.0, 3.0, 30.0, 9.0, 2014.0, 0.5083828048375548
0.5083828048375548, 1100000.0, 0.0, 1.0, 40.0, 4.0, 30.0, 9.0, 2014.0, 0.49985462144799725
0.49985462144799725, 1100000.0, 0.0, 1.0, 40.0, 5.0, 30.0, 9.0, 2014.0, 0.49085956670499675
0.49085956670499675, 1100000.0, 0.0, 1.0, 40.0, 6.0, 30.0, 9.0, 2014.0, 0.485008112408512

完整代码如下：

public class ANN
{   
//training
//public final static String SQL = "SELECT load_input, day_of_week, weekend_day, type_of_day, week_num, time, day_date, month, year, ideal_value FROM sample WHERE (year,month,day_date,time) between (2012,4,1,1) and (2014,9,29, 96) ORDER BY ID";
//testing
public final static String SQL = "SELECT load_input, day_of_week, weekend_day, type_of_day, week_num, time, day_date, month, year, ideal_value FROM sample WHERE (year,month,day_date,time) between (2014,9,30,1) and (2014,9,30, 92) ORDER BY ID";
//validation
//public final static String SQL = "SELECT load_input, day_of_week, weekend_day, type_of_day, week_num, time, day_date, month, year, ideal_value FROM sample WHERE (year,month,day_date,time) between (2014,9,30,93) and (2014,9,30, 96) ORDER BY ID";
public final static int INPUT_SIZE = 9;
public final static int IDEAL_SIZE = 1;
public final static String SQL_DRIVER = "org.postgresql.Driver";
public final static String SQL_URL = "jdbc:postgresql://localhost/ANN";
public final static String SQL_UID = "postgres";
public final static String SQL_PWD = "";

public static void main(String args[])
{   
    Mynetwork();
    //train network. will add customizable params later.
    //train(trainingData());
    //evaluate network
    evaluate(trainingData());
    Encog.getInstance().shutdown();
}
public static void evaluate(MLDataSet testSet)
{
    BasicNetwork network = (BasicNetwork)EncogDirectoryPersistence.loadObject(new File("directory"));

    // test the neural network
    System.out.println("Neural Network Results:");
    for(MLDataPair pair: testSet ) {
        final MLData output = network.compute(pair.getInput());
        System.out.println(pair.getInput().getData(0) + "," + pair.getInput().getData(1) + "," + pair.getInput().getData(2) + "," + pair.getInput().getData(3) + "," + pair.getInput().getData(4) + "," + pair.getInput().getData(5) + "," + pair.getInput().getData(6) + "," + pair.getInput().getData(7) + "," + pair.getInput().getData(8) + "," + "Predicted=" + output.getData(0) + ", Actual=" + pair.getIdeal().getData(0));
    }
}
public static BasicNetwork Mynetwork()
{
    //basic neural network template. Inputs should'nt have activation functions
    //because it affects data coming from the previous layer and there is no previous layer before the input.
    BasicNetwork network = new BasicNetwork();
    //input layer with 2 neurons.
    //The 'true' parameter means that it should have a bias neuron. Bias neuron affects the next layer.
    network.addLayer(new BasicLayer(null , true, 9));
    //hidden layer with 3 neurons
    network.addLayer(new BasicLayer(new ActivationSigmoid(), true, 5));
    //output layer with 1 neuron
    network.addLayer(new BasicLayer(new ActivationSigmoid(), false, 1));
    network.getStructure().finalizeStructure() ;
    network.reset();

    return network;
}
public static void train(MLDataSet trainingSet)
{
    //Backpropagation(network, dataset, learning rate, momentum)
    //final Backpropagation train = new Backpropagation(Mynetwork(), trainingSet, 0.1, 0.9);
    final ResilientPropagation train = new ResilientPropagation(Mynetwork(), trainingSet);
    //final QuickPropagation train = new QuickPropagation(Mynetwork(), trainingSet, 0.9);

    int epoch = 1;

    do {
        train.iteration();
        System.out.println("Epoch #" + epoch + " Error:" + train.getError());
        epoch++;
    } while((train.getError() > 0.01)); 
    System.out.println("Saving network");
    System.out.println("Saving Done");
    EncogDirectoryPersistence.saveObject(new File("directory"), Mynetwork());
}
public static MLDataSet trainingData()
{
    MLDataSet trainingSet = new SQLNeuralDataSet(
            ANN.SQL,
            ANN.INPUT_SIZE,
            ANN.IDEAL_SIZE,
            ANN.SQL_DRIVER,
            ANN.SQL_URL,
            ANN.SQL_UID,
            ANN.SQL_PWD);

    return trainingSet;
}

}

这是我的结果：

Predicted=0.4451817588640455, Actual=0.5260616667545941
Predicted=0.4451817588640455, Actual=0.5196499668339777
Predicted=0.4451817588640455, Actual=0.5083828048375548
Predicted=0.4451817588640455, Actual=0.49985462144799725
Predicted=0.4451817588640455, Actual=0.49085956670499675
Predicted=0.4451817588640455, Actual=0.485008112408512
Predicted=0.4451817588640455, Actual=0.47800504210686795
Predicted=0.4451817588640455, Actual=0.4693212349328293
(...and so on with the same "predicted")

我期待的结果（出于演示目的，我用一些随机的东西更改了 "predicted"，表明网络实际上正在预测）：

Predicted=0.4451817588640455, Actual=0.5260616667545941
Predicted=0.5123312331212122, Actual=0.5196499668339777
Predicted=0.435234234234254365, Actual=0.5083828048375548
Predicted=0.673424556563455, Actual=0.49985462144799725
Predicted=0.2344673345345544235, Actual=0.49085956670499675
Predicted=0.123346457544324, Actual=0.485008112408512
Predicted=0.5673452342342342, Actual=0.47800504210686795
Predicted=0.678435234423423423, Actual=0.4693212349328293

Answer 1

当您使用神经网络得到奇怪的结果时，首先要考虑的原因是归一化。您的数据必须归一化，否则，是的，训练将导致 NN 偏斜，这将始终产生相同的结果，这是一个常见的症状。

在将数据输入神经网络之前，请始终规范化您的数据。这很重要，因为如果您考虑 sigmoid 激活函数，它对于较大的值（正值和负值）基本上是平坦的，从而导致您的神经网络具有恒定的行为。尝试正常化 input = (input-median(input)) / std(input)

经过训练的神经网络对所有评估行输出相同的结果

Trained neural network outputs the same results for all evaluation rows

java

neural-network

encog