StoppingCriteria.cpp

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#include <shark/Data/Csv.h>
#include <shark/Models/LinearModel.h>//single dense layer
#include <shark/Models/ConcatenatedModel.h>//for stacking layers to a feed forward neural network
#include <shark/Algorithms/GradientDescent/Rprop.h> //Optimization algorithm
#include <shark/ObjectiveFunctions/Loss/CrossEntropy.h> //Loss used for training
#include <shark/ObjectiveFunctions/Loss/ZeroOneLoss.h> //The real loss for testing.
#include <shark/Algorithms/Trainers/OptimizationTrainer.h> // Trainer wrapping iterative optimization
#include <shark/Algorithms/StoppingCriteria/MaxIterations.h> //A simple stopping criterion that stops after a fixed number of iterations
#include <shark/Algorithms/StoppingCriteria/TrainingError.h> //Stops when the algorithm seems to converge
#include <shark/Algorithms/StoppingCriteria/GeneralizationQuotient.h> //Uses the validation error to track the progress
#include <shark/Algorithms/StoppingCriteria/ValidatedStoppingCriterion.h> //Adds the validation error to the value of the point

#include <iostream>

using namespace shark;
using namespace std;

//this program demonstrates the effect of different stopping criteria on the performance of a neural network.
template<class T>
double experiment(
    AbstractModel<RealVector, RealVector>& network, 
    AbstractStoppingCriterion<T> & stoppingCriterion,
    ClassificationDataset const& trainingset, 
    ClassificationDataset const& testset
){
    initRandomUniform(network,-0.1,0.1);

    //The Cross Entropy maximises the activation of the cth output neuron 
    // compared to all other outputs for a sample with class c.
    CrossEntropy loss;

    //we use IRpropPlus for network optimization
    IRpropPlus optimizer;
    
    //create an optimization trainer and train the model
    OptimizationTrainer<AbstractModel<RealVector, RealVector>,unsigned int > trainer(&loss, &optimizer, &stoppingCriterion);
    trainer.train(network, trainingset);
    
    //evaluate the performance on the test set using the classification loss we choose 0.5 as threshold since Logistic neurons have values between 0 and 1.
    
    ZeroOneLoss<unsigned int, RealVector> loss01(0.5);
    Data<RealVector> predictions = network(testset.inputs()); 
    return loss01(testset.labels(),predictions);
}
int main(){
    //load the diabetes dataset shuffle its entries and split it in training, validation and test set.
    ClassificationDataset data;
    importCSV(data, "data/diabetes.csv",LAST_COLUMN, ',');
    data.shuffle();
    ClassificationDataset test = splitAtElement(data,static_cast<std::size_t>(0.75*data.numberOfElements()));
    ClassificationDataset validation = splitAtElement(data,static_cast<std::size_t>(0.66*data.numberOfElements()));
    
    LinearModel<RealVector,LogisticNeuron> layer1(inputDimension(data),10); 
    LinearModel<RealVector> layer2(10,numberOfClasses(data));
    ConcatenatedModel<RealVector> network = layer1 >> layer2;
    
    //simple stopping criterion which allows for n iterations (here n = 10,100,500)
    MaxIterations<> maxIterations(10);
    double resultMaxIterations1 = experiment(network, maxIterations,data,test);
    maxIterations.setMaxIterations(100);
    double resultMaxIterations2 = experiment(network, maxIterations,data,test);
    maxIterations.setMaxIterations(500);
    double resultMaxIterations3 = experiment(network, maxIterations,data,test);
    
    TrainingError<> trainingError(10,1.e-5);
    double resultTrainingError = experiment(network, trainingError,data,test);
    
    //for the validated stopping criteria we need to define an error function using the validation set
    CrossEntropy loss;
    ErrorFunction validationFunction(validation,&network,&loss);
    GeneralizationQuotient<> generalizationQuotient(10,0.1);
    ValidatedStoppingCriterion validatedLoss(&validationFunction,&generalizationQuotient);
    double resultGeneralizationQuotient = experiment(network, validatedLoss,data,test);
    
    //print the results
    cout << "RESULTS: " << endl;
    cout << "======== \n" << endl;
    cout << "10 iterations   : " << resultMaxIterations1 << endl;
    cout << "100 iterations : " << resultMaxIterations2 << endl;
    cout << "500 iterations : " << resultMaxIterations3 << endl;
    cout << "training Error : " << resultTrainingError << endl;
    cout << "generalization Quotient : " << resultGeneralizationQuotient << endl;
}