activation_functions.hpp

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/*
 * 
 * Copyright 2025 Nathanne Isip
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 * Redistribution and use in source and binary forms,
 * with or without modification, are permitted provided
 * that the following conditions are met:
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 *    above copyright notice, this list of conditions
 *    and the following disclaimer.
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 *    and the following disclaimer in the documentation
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#ifndef CHISEI_ACTIVATION_FUNCTION_HPP
#define CHISEI_ACTIVATION_FUNCTION_HPP
 
#include <cmath>
 
namespace chisei {
 
    class ActivationFunctions final {
    public:
 
        static constexpr inline double sigmoid_activation(double x) noexcept {
            return 1.0 / (1.0 + std::exp(-x));
        }
 
        static constexpr inline double sigmoid_derivative(double x) noexcept {
            return x * (1.0 - x);
        }
 
        static constexpr inline double relu_activation(double x) noexcept {
            return x > 0.0 ? x : 0.0;
        }
 
        static constexpr inline double relu_derivative(double x) noexcept {
            return x > 0.0 ? 1.0 : 0.0;
        }
 
        static constexpr inline double tanh_activation(double x) noexcept {
            return std::tanh(x);
        }
 
        static constexpr inline double tanh_derivative(double x) noexcept {
            return 1.0 - x * x;
        }
    };
}
 
#endif