AdvancedOCR.ConvolutionWeights.PropogateError C# (CSharp) Method

        protected void PropogateError(RectangularStep upstream, RectangularStep downstream, int weightX, int weightY, int mapNumber)
        {
            int weightIndex = mapNumber * Width * Height + weightY * Width + weightX;
            double weight = Weight[weightIndex];

            int downstreamIndex = 0;
            double weightError = 0.0;
            int upstreamIndex = (weightY * upstream.Width) + weightX;
            double weightStepSize = WeightStepSize[weightIndex];

            // This loop here is equivalent to the sigma in equation 19 in Gradient-Based Learning Applied to Document Recognition.
            for (int y = 0; y < downstream.Height; y++)
            {
                for (int x = 0; x < downstream.Width; x++)
                {
                    double upstreamState = upstream.Output[upstreamIndex];
                    double downstreamErrorDerivative = downstream.ErrorDerivative[downstreamIndex];

                    // Calculate inputs error gradient by taking the sum, for all outputs of
                    // dEk/dAj multiplied by dAj/dOj (w/sum =dEj/dOj);
                    double inputError = downstreamErrorDerivative * weight;
                    upstream.ErrorDerivative[upstreamIndex] += inputError;

                    // Calculate the Weight's first derivative with respect to the error
                    double weightErrorGradient = downstreamErrorDerivative * upstreamState;
                    weightError += weightErrorGradient;

                    downstreamIndex += 1;
                    upstreamIndex += 1;
                }
                upstreamIndex += Width - 1; // Equal to: upstream.Width - downstream.Width;
            }
            double deltaWeight = weightError * weightStepSize;
            Weight[weightIndex] -= deltaWeight;
        }