diwa_activations.h

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/*
 * This file is part of the Diwa library.
 * Copyright (c) 2024 Nathanne Isip
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
#ifndef DIWA_ACTIVATIONS_H
#define DIWA_ACTIVATIONS_H
 
#include <diwa_conv.h>
#include <math.h>
 
#define DIWA_ACTFUNC_LOWER_BOUND -30.0f 
#define DIWA_ACTFUNC_UPPER_BOUND 30.0f  
typedef double (*diwa_activation)(double);
 
class DiwaActivationFunc final {
private:
    static inline double region = 2.0f; 
    static inline double center = 0.0f; 
public:
    static inline void initializeRadialBasis(double center, double width) {
        DiwaActivationFunc::center = center;
        DiwaActivationFunc::region = 2 * pow(width, 2);
    }
 
    static inline double radialBasis(double x) {
        return exp(
            -pow(x - DiwaActivationFunc::center, 2)
                / DiwaActivationFunc::region
        );
    }
 
    static inline double sigmoid(double x) {
        if(x < DIWA_ACTFUNC_LOWER_BOUND)
            return 0;
        if(x > DIWA_ACTFUNC_UPPER_BOUND)
            return 1;
 
        return 1.0 / (1.0 + exp(-x));
    }
 
    static inline double gaussian(double x) {
        if(x < DIWA_ACTFUNC_LOWER_BOUND)
            return 0;
        if(x > DIWA_ACTFUNC_UPPER_BOUND)
            return 1;
 
        return 1.0 / exp(x * x);
    }
};
 
#endif