protected override void EstimateBiasSecondDerivative(RectangularStep downstream)
{
for (int i = 0; i < downstream.Length; i++)
{
// Calculating the sum of: second derivatives of error with respect to the bias weight.
// Note that the bias is implemented as an always-on Neuron with a (the same) weight to the outputs neurons.
BiasStepSize += downstream.ErrorDerivative[i] * 1.0 * 1.0;
}
}