ResidualVectorCalculation.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"
 
 
namespace GQCP {
 
 
class ResidualVectorCalculation:
    public Step<EigenproblemEnvironment<double>> {
 
private:
    size_t number_of_requested_eigenpairs;
 
 
public:
    /*
     *  CONSTRUCTORS
     */
 
    ResidualVectorCalculation(const size_t number_of_requested_eigenpairs = 1) :
        number_of_requested_eigenpairs {number_of_requested_eigenpairs} {}
 
 
    /*
     *  PUBLIC OVERRIDDEN METHODS
     */
 
    std::string description() const override {
        return "Calculate the residual vectors from the new guesses for the eigenvectors.";
    }
 
 
    void execute(EigenproblemEnvironment<double>& environment) override {
 
        const auto dim = environment.dimension;
 
        const auto& VA = environment.VA;          // VA = A * V (implicitly calculated through the matrix-vector product)
        const auto& Z = environment.Z;            // the (requested number of) eigenvectors of the subspace matrix S
        const auto& Lambda = environment.Lambda;  // the (requested number of) eigenvalues of the subspace matrix S
        const auto& X = environment.X;            // contains the new guesses for the eigenvectors (as a linear combination of the current subspace V)
 
        // Calculate the residual vectors: r_i = VA * z_i - Lambda * x_i
        environment.R = MatrixX<double>::Zero(dim, this->number_of_requested_eigenpairs);
        for (size_t column_index = 0; column_index < this->number_of_requested_eigenpairs; column_index++) {
            environment.R.col(column_index) = VA * Z.col(column_index) - Lambda(column_index) * X.col(column_index);
        }
    }
};
 
 
}  // namespace GQCP