NewtonOrbitalOptimizer.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 "Basis/Transformations/ROrbitalRotationGenerators.hpp"
#include "Basis/Transformations/RTransformation.hpp"
#include "Mathematical/Optimization/Minimization/BaseHessianModifier.hpp"
#include "Mathematical/Representation/SquareMatrix.hpp"
#include "Mathematical/Representation/SquareRankFourTensor.hpp"
#include "QCMethod/OrbitalOptimization/BaseOrbitalOptimizer.hpp"
 
#include <utility>
 
 
namespace GQCP {
 
 
class NewtonOrbitalOptimizer: public BaseOrbitalOptimizer {
protected:
    std::shared_ptr<BaseHessianModifier> hessian_modifier;  // the modifier functor that should be used when an indefinite Hessian is encountered
 
    VectorX<double> gradient;
    SquareMatrix<double> hessian;
 
 
public:
    // CONSTRUCTORS
 
    /*
     *  @param hessian_modifier                 the modifier functor that should be used when an indefinite Hessian is encountered
     *  @param convergence_threshold            the threshold used to check for convergence
     *  @param maximum_number_of_iterations     the maximum number of iterations that may be used to achieve convergence
     */
    NewtonOrbitalOptimizer(std::shared_ptr<BaseHessianModifier> hessian_modifier, const double convergence_threshold = 1.0e-08, const size_t maximum_number_of_iterations = 128);
 
 
    // DESTRUCTOR
 
    virtual ~NewtonOrbitalOptimizer() = default;
 
 
    // PUBLIC PURE VIRTUAL METHODS
 
    virtual SquareMatrix<double> calculateGradientMatrix(const RSQHamiltonian<double>& sq_hamiltonian) const = 0;
 
    virtual SquareRankFourTensor<double> calculateHessianTensor(const RSQHamiltonian<double>& sq_hamiltonian) const = 0;
 
    virtual ROrbitalRotationGenerators<double> calculateNewFullOrbitalGenerators(const RSQHamiltonian<double>& sq_hamiltonian) const = 0;
 
    virtual void prepareOrbitalDerivativesCalculation(const RSQHamiltonian<double>& sq_hamiltonian) = 0;
 
 
    // PUBLIC OVERRIDDEN METHODS
 
    RTransformation<double> calculateNewRotationMatrix(const RSQHamiltonian<double>& sq_hamiltonian) const override;
 
    bool checkForConvergence(const RSQHamiltonian<double>& sq_hamiltonian) const override;
 
    virtual void prepareConvergenceChecking(const RSQHamiltonian<double>& sq_hamiltonian) override;
 
 
    // PUBLIC METHODS
 
    VectorX<double> calculateGradientVector(const RSQHamiltonian<double>& sq_hamiltonian) const;
 
    SquareMatrix<double> calculateHessianMatrix(const RSQHamiltonian<double>& sq_hamiltonian) const;
 
    ROrbitalRotationGenerators<double> calculateNewFreeOrbitalGenerators(const RSQHamiltonian<double>& sq_hamiltonian) const;
 
    VectorX<double> directionFromIndefiniteHessian() const;
 
    bool newtonStepIsWellDefined() const;
};
 
 
}  // namespace GQCP