//BackpropagationNode.cpp
//
//
//This file defines functions for the BackpropagationNode class.
//

#ifndef BNODE_C
#define BNODE_C

#include "BackpropagationNode.h"

//------default constructor--------

BackpropagationNode::BackpropagationNode () {}

//general error calculation function - useful for all hidden nodes
double BackpropagationNode::calculateError () {
  double scratch = 0;
  for (int counter = 0; counter < numberOutputConnections; ++counter) {
    scratch += (outputWeight[counter].readNodePointer())->readError() * outputWeight[counter].readWeight();
  }
  error = scratch * output * (1 - output);
  return error;
}

//error calculation for output nodes
inline double BackpropagationNode::calculateOutputNodeError (double actualValue) {
  error = (actualValue - output) * output * (1 - output);
  return error;
}

//adjust the weights on this node to minimize the error in output
//usesful for all except the first hidden layer nodes
void BackpropagationNode::adjustWeight (double eta = 0.5, double alpha = 0.5) {
  for (int counter = 0; counter < numberInputConnections; ++counter) {
	 double scratch = inputWeight[counter].readWeightChange();
	 inputWeight[counter].writeWeightChange (eta * error * (inputWeight[counter].readNodePointer())->readActivation() + alpha * scratch);
	 inputWeight[counter].writeWeight (inputWeight[counter].readWeight() + inputWeight[counter].readWeightChange());
    //now adjust the weight on the corresponding output connections of the node
    //feeding into this one
    (inputWeight[counter].readNodePointer())->writeOutputConnectionWeight(*this, inputWeight[counter].readWeight());
  }
}

//adust the weights on this first hidden layer node to minimize the error in output
// must be different than for other layers because we are using input data values
// instead of the outputs from lower layer nodes
void BackpropagationNode::adjustFirstHiddenLayerNodeWeight (double *inputVector, double eta = 0.7, double alpha = 0.5) {
  for (int counter = 0; counter < numberInputConnections; ++counter) {
    double scratch = inputWeight[counter].readWeightChange();
    inputWeight[counter].writeWeightChange (eta * error * *(inputVector+counter) + alpha*scratch);
    inputWeight[counter].writeWeight (inputWeight[counter].readWeight() + inputWeight[counter].readWeightChange());
  }
}

#endif