AdvancedOCR.FeedForwardWeights.PropogateSecondDerivatives C# (CSharp) Method

        protected void PropogateSecondDerivatives(Step downstream, Step upstream, int upstreamNeuron, int inputNeuron)
        {
            int weightIndex = inputNeuron * OutputNeurons;

            double upstreamState = upstream.Output[upstreamNeuron];
            double upstreamErrorSecondDerivative = 0.0;

            for (int output = 0; output < OutputNeurons; output++)
            {
                double downstreamErrorSecondDerivative = downstream.ErrorDerivative[output]; // (d^2)E/(dAj)^2, where Aj is the sum of inputs to this downstream unit.

                // Here we calculate (d^2)Ej/(dWij)^2 by multiplying the 2nd derivative of E with respect to the sum of inputs, Aj
                // by the state of Oi, the upstream unit, squared. Refer to Equation 25 in document.
                // The summing happening here is described by equation 23.
                double weight2ndDerivative = downstreamErrorSecondDerivative * upstreamState * upstreamState;

                WeightStepSize[weightIndex] = weight2ndDerivative;

                double weight = Weight[weightIndex];

                // This is implementing the last sigma of Equation 27.
                // This propogates error second derivatives back to previous layer, but will need to be multiplied by the second derivative
                // of the activation function at the previous layer.
                upstreamErrorSecondDerivative += weight * weight * downstreamErrorSecondDerivative;

                weightIndex += 1;

            }

            upstream.ErrorDerivative[upstreamNeuron] += upstreamErrorSecondDerivative;
        }