DenseDiagonalization.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/Algorithm/Step.hpp"
#include "Mathematical/Optimization/Eigenproblem/EigenproblemEnvironment.hpp"
 
#include <Eigen/Dense>
 
 
namespace GQCP {
 
 
template <typename _Scalar>
class DenseDiagonalization:
    public Step<EigenproblemEnvironment<_Scalar>> {
public:
    // The scalar type of the matrix elements: real or complex.
    using Scalar = _Scalar;
 
 
public:
    /*
     *  PUBLIC OVERRIDDEN METHODS
     */
 
    std::string description() const override {
        return "Read the matrix from the environment, diagonalize it and write the number of requested eigenpairs to it.";
    }
 
 
    void execute(EigenproblemEnvironment<Scalar>& environment) override {
 
        // Solve the eigenvalue problem using Eigen's routines.
        const auto& A = environment.A;
        Eigen::SelfAdjointEigenSolver<Eigen::Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic>> eigensolver {A};
 
        // Write the eigenvalues and eigenvectors to the environment.
        environment.eigenvalues = eigensolver.eigenvalues();
        environment.eigenvectors = eigensolver.eigenvectors();
    }
};
 
 
}  // namespace GQCP