blur_sine.h

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/*
 * Copyright 2021 MusicScience37 (Kenta Kabashima)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once
 
#include <cmath>
 
#include <Eigen/Core>
 
#include "num_collect/base/index_type.h"
 
namespace num_prob_collect::regularization {
 
class blur_sine {
public:
    using coeff_type = Eigen::MatrixXd;
 
    using data_type = Eigen::VectorXd;
 
    blur_sine(num_collect::index_type data_size,
        num_collect::index_type solution_size) {
        coeff_.resize(data_size, solution_size);
        for (num_collect::index_type j = 0; j < solution_size; ++j) {
            for (num_collect::index_type i = 0; i < data_size; ++i) {
                static constexpr double factor = 100.0;
                const double sol_rate =
                    static_cast<double>(j) / static_cast<double>(solution_size);
                const double data_rate =
                    static_cast<double>(i) / static_cast<double>(data_size);
                const double diff = sol_rate - data_rate;
                coeff_(i, j) = std::exp(-factor * diff * diff);
            }
        }
 
        solution_.resize(solution_size);
        for (num_collect::index_type i = 0; i < solution_size; ++i) {
            static constexpr double factor = 10.0;
            const double sol_rate =
                static_cast<double>(i) / static_cast<double>(solution_size);
            solution_(i) = std::sin(factor * sol_rate);
        }
 
        data_ = coeff_ * solution_;
    }
 
    [[nodiscard]] auto coeff() const -> const Eigen::MatrixXd& {
        return coeff_;
    }
 
    [[nodiscard]] auto solution() const -> const Eigen::VectorXd& {
        return solution_;
    }
 
    [[nodiscard]] auto data() const -> const Eigen::VectorXd& { return data_; }
 
private:
    Eigen::MatrixXd coeff_;
 
    Eigen::VectorXd solution_;
 
    Eigen::VectorXd data_;
};
 
}  // namespace num_prob_collect::regularization