Sigmoid.hpp

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#pragma once
 
#include "Activation.hpp"
 
namespace NNFS
{
    class Sigmoid : public Activation
    {
    public:
        Sigmoid() : Activation(ActivationType::SIGMOID) {}
 
        void forward(Eigen::MatrixXd &out, const Eigen::MatrixXd &x) override
        {
            _forward_input = x;
 
            out = 1 / (1 + (-x).array().exp());
 
            _forward_output = out;
        }
 
        void backward(Eigen::MatrixXd &out, const Eigen::MatrixXd &dx) override
        {
            out = _forward_output.array() * (1 - _forward_output.array()) * dx.array();
        }
 
    private:
        Eigen::MatrixXd _forward_output; // Output data for forward pass
    };
} // namespace NNFS