//
// Created by fluffymoo on 11.6.18.
//


#include "NeuronLogistic.h"

NeuronLogistic::NeuronLogistic(double a, double b) {

    this->n_activation_function_parameters = 2;
    this->activation_function_parameters = new double[2];

    this->activation_function_parameters[0] = a;
    this->activation_function_parameters[1] = b;

    this->edges_in = new std::vector<Connection*>(0);
    this->edges_out = new std::vector<Connection*>(0);
}

void NeuronLogistic::activate( ) {
    double a = this->activation_function_parameters[0];
    double b = this->activation_function_parameters[1];
    double x = this->potential;

    double ex = std::pow(E, a - x);
    this->state = std::pow(1.0 + ex, -b);

}

double NeuronLogistic::activation_function_get_partial_derivative(int param_idx ) {

    double a = this->activation_function_parameters[0];
    double b = this->activation_function_parameters[1];
    double x = this->potential;

    if(param_idx == 0){
        double ex = std::pow(E, a - x);

        double exa= -std::pow(ex + 1.0, -b);

        return exa * std::log(ex + 1.0);
    }
    else if(param_idx == 1){
        /**
         * TODO
         * Could be write as activation_function_get_derivative() * -1
         */
        double ex = std::pow(E, a - x);
        double ex2 = std::pow(ex + 1.0, -b - 1.0);

        return -b * ex * ex2;
    }

    return 0.0;

}

double NeuronLogistic::activation_function_get_derivative( ) {

    double a = this->activation_function_parameters[0];
    double b = this->activation_function_parameters[1];
    double x = this->potential;

    double ex = std::pow(E, a - x);
    double ex2 = std::pow(ex + 1.0, -b - 1.0);

    return b * ex * ex2;

}