public void Learn(
SampleList samples, CalculationArguments arguments)
// samples = yjks
{
arguments.reporter?.WriteStart($"Learning the network using a subset of {samples.Count} random samples...");
Stopwatch timer = new Stopwatch();
timer.Start();
int nSamples = samples.Count; // number of sample rows
int nCoefficients = CoefficientCount();
// Current biasses and weights of the neurons in this network:
Single1D coefficients = new Single1D(nCoefficients);
// The derivatives of the cost with respect to the biasses and weights:
Single1D derivatives = new Single1D(nCoefficients);
Single1D velocities = new Single1D(nCoefficients);
velocities.Clear();
MeasurementList measurements = new MeasurementList(nSamples, Last.Count);
GetCoefficients(coefficients, 0);
Minimization minimization = new Minimization()
{
MaxIter = arguments.settings.MaxIter,
Eps = arguments.settings.Epsilon,
Tol = arguments.settings.Tolerance,
};
float finalCost = minimization.MomentumBasedGradientDescent(coefficients, derivatives, velocities,
(iter) =>
{
SetCoefficients(coefficients, 0);
arguments.reporter?.ReportCoefficients(coefficients);
float cost = GetCostAndDerivatives(samples, derivatives, measurements, arguments);
arguments.reporter?.ReportCostAndDerivatives(cost, derivatives, measurements);
return(cost);
}, arguments.settings.LearningRate, arguments.settings.MomentumCoefficient);
arguments.reporter?.WriteEnd($"The network has learned in {timer.Elapsed.TotalSeconds} s, and the final cost value is {finalCost:F4}.");
}
// ----------------------------------------------------------------------------------------
#region Network
public float GetCostAndDerivatives(
SampleList samples, Single1D derivatives, MeasurementList measurements,
CalculationArguments arguments)
{
CostFunctionEnum costFunction = arguments.settings.CostFunction;
float lambda = arguments.settings.Lambda;
int nSamples = samples.Count;
int nCoeffs = derivatives.Count;
float cost = 0f;
Layer last = Last;
for (int i = 0; i < nCoeffs; i++)
{
derivatives[i] = 0f;
}
for (int iSample = 0; iSample < nSamples; iSample++)
{
arguments.ThrowIfCancellationRequested();
Sample sample = samples[iSample];
Single1D measurement = measurements[iSample];
Input.SetActivations(sample.Inputs, 0);
FeedForward(true);
last.GetActivations(measurement, 0);
cost += CostFunction(measurement, sample.Requirements, costFunction);
int weightCount = CountWeight();
cost += 0.5f * lambda * SumWeightSqr() / weightCount; // regularization
last.CalculateDeltas(sample.Requirements, costFunction);
FeedBackward(true);
AddDerivatives(derivatives, 0, lambda / weightCount);
arguments.reporter?.ReportProgress(iSample, nSamples);
}
arguments.reporter?.ReportProgress(0, nSamples);
cost /= nSamples;
for (int i = 0; i < nCoeffs; i++)
{
derivatives[i] /= nSamples;
}
return(cost);
}
