Activations.cpp

#include "Activations.h"

namespace nncpp {

	mathFunction* Activations::TANH = new Tanh();
	mathFunction* Activations::SIGMOID = new sigmoid();
	mathFunction* Activations::RELU = new relu();
	mathFunction* Activations::LINEAR = new linear();


	double Tanh::f(double x)
	{
		if (x == std::numeric_limits<double>::max())
			return 1;

		if (x == std::numeric_limits<double>::min())
			return -1;

		double e2x = exp(2.0 * x);
		return (e2x - 1.0) / (e2x + 1.0);
	}
	double Tanh::dfdx(double x)
	{
		double f = Tanh::f(x);
		return 1 - f * f;
	}

	double relu::f(double x)
	{
		if (x < 0)
			return 0;
		return x;
	}

	double relu::dfdx(double x)
	{
		if (x > 0)
			return 1;
		return 0;
	}

	double linear::f(double x)
	{
		return x;
	}

	double linear::dfdx(double x)
	{
		return 1;
	}

	double sigmoid::f(double x)
	{
		return 1.0 / (1.0 + exp(-x));
	}

	double sigmoid::dfdx(double x)
	{
		double f = sigmoid::f(x);
		return f * (1 - f);
	}
}