CubicGrid.hpp

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// This file is part of GQCG-GQCP.
//
// Copyright (C) 2017-2020  the GQCG developers
//
// GQCG-GQCP is free software: 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 3 of the License, or
// (at your option) any later version.
//
// GQCG-GQCP is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with GQCG-GQCP.  If not, see <http://www.gnu.org/licenses/>.
 
#pragma once
 
 
#include "Mathematical/Functions/Function.hpp"
#include "Mathematical/Grid/Field.hpp"
#include "Mathematical/Representation/Matrix.hpp"
#include "Molecule/Molecule.hpp"
 
#include <array>
#include <functional>
#include <numeric>
#include <type_traits>
 
 
namespace GQCP {
 
 
class CubicGrid {
private:
    Vector<double, 3> m_origin;              // the origin of the grid
    std::array<size_t, 3> numbers_of_steps;  // the number of steps in the x, y, z-directions
    std::array<double, 3> step_sizes;        // the step sizes in the x, y, z-directions
 
 
public:
    // CONSTRUCTORS
 
    CubicGrid(const Vector<double, 3>& origin, const std::array<size_t, 3>& numbers_of_steps, const std::array<double, 3>& step_sizes);
 
 
    // NAMED CONSTRUCTORS
 
    static CubicGrid Centered(const Vector<double, 3>& point, const size_t number_of_steps, const double step_size);
 
    static CubicGrid ReadCubeFile(const std::string& filename);
 
    static CubicGrid ReadRegularGridFile(const std::string& filename);
 
 
    // PUBLIC METHODS
 
    template <typename OutputType>
    Field<OutputType> evaluate(const Function<OutputType, Vector<double, 3>>& function) const {
 
        std::vector<OutputType> values;
        values.reserve(this->numberOfPoints());
 
        this->forEach([&values, &function](const Vector<double, 3>& r) {
            values.push_back(function(r));
        });
 
        return Field<OutputType>(values);
    }
 
 
    template <typename T>
    T integrate(const Field<T>& field) const {
 
        // Using field.value(0) as the initial value makes sure that the initialization is already correct: e.g. when a Vector is initialized, it doesn't automatically have the required size due to the default constructor
        auto result = std::accumulate(field.values().begin(), field.values().end(), field.value(0));
        result -= field.value(0);  // subtract the initial value of result
 
        // For cubic grids, the weight of each point is the voxel volume, so we'll have to multiply the final result by this.
        return result * this->voxelVolume();
    }
 
 
    void forEach(const std::function<void(const size_t, const size_t, const size_t)>& callback) const;
 
    void forEach(const std::function<void(const Vector<double, 3>&)>& callback) const;
 
    size_t numberOfPoints() const;
 
    const Vector<double, 3>& origin() const { return this->m_origin; }
 
    Vector<double, 3> position(const size_t i, const size_t j, const size_t k) const;
 
    std::vector<Vector<double, 3>> points() const;
 
    size_t numbersOfSteps(const size_t axis) const { return this->numbers_of_steps[axis]; }
 
    const std::array<size_t, 3>& numbersOfSteps() const { return this->numbers_of_steps; }
 
    double stepSize(const size_t axis) const { return this->step_sizes[axis]; }
 
    const std::array<double, 3>& stepSizes() const { return this->step_sizes; }
 
    double totalVolume() const { return this->voxelVolume() * this->numberOfPoints(); }
 
    void writeToCubeFile(const Field<double>& scalar_field, const std::string& filename, const Molecule& molecule) const;
 
    double voxelVolume() const;
};
 
 
}  // namespace GQCP