/********************************************************
 *  ██████╗  ██████╗████████╗██╗
 * ██╔════╝ ██╔════╝╚══██╔══╝██║
 * ██║  ███╗██║        ██║   ██║
 * ██║   ██║██║        ██║   ██║
 * ╚██████╔╝╚██████╗   ██║   ███████╗
 *  ╚═════╝  ╚═════╝   ╚═╝   ╚══════╝
 * Geophysical Computational Tools & Library (GCTL)
 *
 * Copyright (c) 2022  Yi Zhang (yizhang-geo@zju.edu.cn)
 *
 * GCTL is distributed under a dual licensing scheme. You can redistribute 
 * it and/or modify it under the terms of the GNU Lesser General Public 
 * License as published by the Free Software Foundation, either version 2 
 * of the License, or (at your option) any later version. You should have 
 * received a copy of the GNU Lesser General Public License along with this 
 * program. If not, see <http://www.gnu.org/licenses/>.
 * 
 * If the terms and conditions of the LGPL v.2. would prevent you from using 
 * the GCTL, please consider the option to obtain a commercial license for a 
 * fee. These licenses are offered by the GCTL's original author. As a rule, 
 * licenses are provided "as-is", unlimited in time for a one time fee. Please 
 * send corresponding requests to: yizhang-geo@zju.edu.cn. Please do not forget 
 * to include some description of your company and the realm of its activities. 
 * Also add information on how to contact you by electronic and paper mail.
 ******************************************************/

#include "activation_relu.h"

gctl::relu::relu() {}

gctl::relu::~relu() {}

void gctl::relu::activate(const matrix<double> &z, matrix<double> &a)
{
    // a = activation(z) = max(z, 0)
    // Z = [z1, ..., zn], A = [a1, ..., an], n observations
    a.resize(z.row_size(), z.col_size());

    int i, j;
#pragma omp parallel for private (i, j) schedule(guided) 
    for (i = 0; i < a.row_size(); i++)
    {
        for (j = 0; j < a.col_size(); j++)
        {
            a[i][j] = std::max(z[i][j], 0.0);   
        }
    }
    return;
}

void gctl::relu::apply_jacobian(const matrix<double> &z, 
    const matrix<double> &a, const matrix<double> &f, matrix<double> &g)
{
    // Apply the Jacobian matrix J to a vector f
    // J = d_a / d_z = diag(sign(a)) = diag(a > 0)
    // g = J * f = (a > 0) .* f
    // Z = [z1, ..., zn], G = [g1, ..., gn], F = [f1, ..., fn]
    // Note: When entering this function, Z and G may point to the same matrix
    g.resize(a.row_size(), a.col_size());

    int i, j;
#pragma omp parallel for private (i, j) schedule(guided) 
    for (i = 0; i < g.row_size(); i++)
    {
        for (j = 0; j < g.col_size(); j++)
        {
            if (a[i][j] > 0.0) g[i][j] = f[i][j];
            else g[i][j] = 0.0;
            //g[i][j] = std::max(a[i][j], 0.0)*f[i][j];   
        }
    }
    return;
}

std::string gctl::relu::activation_name() const
{
    return "ReLU";
}

gctl::activation_type_e gctl::relu::activation_type() const
{
    return ReLU;
}