DavidsonSolver.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/IterativeAlgorithm.hpp"
#include "Mathematical/Algorithm/StepCollection.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/CorrectionVectorCalculation.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/GuessVectorUpdate.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/MatrixVectorProductCalculation.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/ResidualVectorCalculation.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/ResidualVectorConvergence.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/SubspaceMatrixCalculation.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/SubspaceMatrixDiagonalization.hpp"
#include "Mathematical/Optimization/Eigenproblem/Davidson/SubspaceUpdate.hpp"
#include "Mathematical/Optimization/Eigenproblem/EigenproblemEnvironment.hpp"
 
 
namespace GQCP {
namespace EigenproblemSolver {
 
 
IterativeAlgorithm<EigenproblemEnvironment<double>> Davidson(const size_t number_of_requested_eigenpairs = 1, const size_t maximum_subspace_dimension = 15, const double convergence_threshold = 1.0e-08, double correction_threshold = 1.0e-12, const size_t maximum_number_of_iterations = 128, const double inclusion_threshold = 1.0e-03) {
 
    // Create the iteration cycle that effectively 'defines' our Davidson solver
    StepCollection<EigenproblemEnvironment<double>> davidson_cycle {};
 
    davidson_cycle
        .add(MatrixVectorProductCalculation())
        .add(SubspaceMatrixCalculation())
        .add(SubspaceMatrixDiagonalization(number_of_requested_eigenpairs))
        .add(GuessVectorUpdate())
        .add(ResidualVectorCalculation(number_of_requested_eigenpairs))
        .add(CorrectionVectorCalculation(number_of_requested_eigenpairs, correction_threshold))  // this solves the residual equations
        .add(SubspaceUpdate(maximum_subspace_dimension, inclusion_threshold));
 
    // Create a convergence criterion on the norm of the residual vectors
    const ResidualVectorConvergence<EigenproblemEnvironment<double>> convergence_criterion {convergence_threshold};
 
    return IterativeAlgorithm<EigenproblemEnvironment<double>>(davidson_cycle, convergence_criterion, maximum_number_of_iterations);
}
 
 
}  // namespace EigenproblemSolver
}  // namespace GQCP