// Util.cpp
// David R. Morrison

#include "util.hpp"

// Activation functions.
// f squashes to the range [0,1]
// g squashes to the range [-2, 2]
// h squashes to the range [-1, 1]
double f(double x)
{
    return 1 / (1 + exp(-x));
}

double g(double x)
{
    return 4 / (1 + exp(-x)) - 2;
}

double h(double x)
{
    return 2 / (1 + exp(-x)) - 1;
}

double fPrime(double x)
{
    return (1 - f(x)) * f(x);
}

double gPrime(double x)
{
    return 1 - h(x) * h(x);
}

double hPrime(double x)
{
    return 0.5 * (1 - h(x) * h(x));
}

// Initialize the random number generator
void initRand()
{
    srand48(time(NULL));
}

// Create a vector of random weights between -.1 and .1
vector<double> getRandomWeights(int size)
{
    vector<double> weights(size);
    for (int i = 0; i < size; ++i)
        weights[i] = drand48() > 0.5 ? drand48() / 10 : -drand48() / 10;

    return weights;
}