RayleighDampingForm.hpp

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#pragma once
 
#include "Form.hpp"
 
#include <polyfem/solver/forms/ElasticForm.hpp>
#include <polyfem/time_integrator/ImplicitTimeIntegrator.hpp>
#include <polyfem/utils/Types.hpp>
 
namespace polyfem::solver
{
    class RayleighDampingForm : public Form
    {
    public:
        RayleighDampingForm(
            const Form &form_to_damp,
            const time_integrator::ImplicitTimeIntegrator &time_integrator,
            const bool use_stiffness_as_ratio,
            const double stiffness,
            const int n_lagging_iters);
 
        static std::shared_ptr<RayleighDampingForm> create(
            const json &params,
            const std::unordered_map<std::string, std::shared_ptr<Form>> &forms,
            const time_integrator::ImplicitTimeIntegrator &time_integrator);
 
        std::string name() const override { return "rayleigh-damping"; }
 
    protected:
        double value_unweighted(const Eigen::VectorXd &x) const override;
 
        void first_derivative_unweighted(const Eigen::VectorXd &x, Eigen::VectorXd &gradv) const override;
 
        void second_derivative_unweighted(const Eigen::VectorXd &x, StiffnessMatrix &hessian) const override;
 
    public:
        void init_lagging(const Eigen::VectorXd &x) override;
 
        void update_lagging(const Eigen::VectorXd &x, const int iter_num) override;
 
        int max_lagging_iterations() const override { return n_lagging_iters_; }
 
        bool uses_lagging() const override { return true; }
 
        double stiffness() const;
 
    private:
        const Form &form_to_damp_;                                       
        const time_integrator::ImplicitTimeIntegrator &time_integrator_; 
        const bool use_stiffness_as_ratio_;                              
        const double stiffness_;                                         
        const int n_lagging_iters_;                                      
 
        StiffnessMatrix lagged_stiffness_matrix_; 
    };
} // namespace polyfem::solver