void Forward(const arma::Mat<eT>& input, arma::Mat<eT>& output)
{
arma::mat maxInput = arma::repmat(arma::max(input), input.n_rows, 1);
output = (maxInput - input);
// Approximation of the hyperbolic tangent. The acuracy however is
// about 0.00001 lower as using tanh. Credits go to Leon Bottou.
output.transform( [](double x)
{
//! Fast approximation of exp(-x) for x positive.
static constexpr double A0 = 1.0;
static constexpr double A1 = 0.125;
static constexpr double A2 = 0.0078125;
static constexpr double A3 = 0.00032552083;
static constexpr double A4 = 1.0172526e-5;
if (x < 13.0)
{
double y = A0 + x * (A1 + x * (A2 + x * (A3 + x * A4)));
y *= y;
y *= y;
y *= y;
y = 1 / y;
return y;
}
return 0.0;
} );
output = input - (maxInput + std::log(arma::accu(output)));
}
void Fn(const arma::Mat<eT>& x, arma::Mat<eT>& y)
{
y = x;
y.transform( [&](eT val) { return std::min(
std::max( val, minValue ), maxValue ); } );
}