/********************************************************
 *  ██████╗  ██████╗████████╗██╗
 * ██╔════╝ ██╔════╝╚══██╔══╝██║
 * ██║  ███╗██║        ██║   ██║
 * ██║   ██║██║        ██║   ██║
 * ╚██████╔╝╚██████╗   ██║   ███████╗
 *  ╚═════╝  ╚═════╝   ╚═╝   ╚══════╝
 * 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 "dwa.h"

gctl::dwa::dwa()
{
    fx_c_ = 0;
    l_ready_ = false;
}
    
gctl::dwa::~dwa(){}

void gctl::dwa::InitDWA(size_t num, size_t grad_num)
{
    fx_n_ = num;
    K_ = 1.0*num;
    T_ = 1.0;

    wgts_.resize(num, 1.0);
    L_p1_.resize(num, 1.0);
    L_p2_.resize(num, 1.0);
    grad_.resize(grad_num, 0.0);

    rcd_wgts_.push_back(wgts_);
    return;
}

void gctl::dwa::AddSingleLoss(double fx, const array<double> &g)
{
    multi_fx_ += wgts_[fx_c_]*fx;

    L_p2_[fx_c_] = L_p1_[fx_c_];
    L_p1_[fx_c_] = fx;

    for (size_t i = 0; i < g.size(); i++)
    {
        grad_[i] += wgts_[fx_c_]*g[i];
    }

    fx_c_++;
    return;
}

void gctl::dwa::UpdateWeights()
{
    double sum = 0.0;
    for (size_t i = 0; i < fx_n_; i++)
    {
        if (l_ready_) wgts_[i] = exp(L_p1_[i]/(L_p2_[i]*T_));
        else wgts_[i] = 1.0;

        sum += wgts_[i];
    }

    for (size_t i = 0; i < fx_n_; i++)
    {
        wgts_[i] *= K_/sum;
    }

    l_ready_ = true;
    rcd_wgts_.push_back(wgts_);
    return;
}

double gctl::dwa::DWALoss(array<double> &g)
{
    if (fx_c_ != fx_n_)
    {
        throw std::runtime_error("Not enough loss functions evaluated. From gctl::dwa::UpdateWeights()");
    }

    double fx = multi_fx_;
    g = grad_;

    fx_c_ = 0;
    multi_fx_ = 0.0;
    grad_.assign_all(0.0);
    return fx;
}

void gctl::dwa::set_control_temperature(double t)
{
    T_ = t;
    return;
}

void gctl::dwa::set_normal_sum(double k)
{
    K_ = k;
    return;
}

void gctl::dwa::get_records(array<double> &logs)
{
    logs.resize(fx_n_*rcd_wgts_.size());
    for (size_t i = 0; i < rcd_wgts_.size(); i++)
    {
        for (size_t j = 0; j < fx_n_; j++)
        {
            logs[i*fx_n_ + j] = rcd_wgts_[i][j];
        }
    }
    return;
}