InertiaForm.hpp

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#pragma once
 
#include "Form.hpp"
 
#include <polyfem/utils/Types.hpp>
#include <polyfem/time_integrator/ImplicitTimeIntegrator.hpp>
 
#include <Eigen/Core>
 
#include <functional>
 
namespace polyfem::solver
{
    class InertiaForm : public Form
    {
        friend class InertiaForceDerivative;
 
    public:
        InertiaForm(const StiffnessMatrix &mass,
                    const time_integrator::ImplicitTimeIntegrator &time_integrator);
 
        std::string name() const override { return "inertia"; }
 
        using XTildeUpdater = std::function<void(const double, const Eigen::VectorXd &, Eigen::VectorXd &)>;
        // Optional hook for fields whose time-dependent essential boundary values require a
        // lifted time-integrator prediction before applying the mass term.
        void set_x_tilde_updater(XTildeUpdater updater);
 
        void update_quantities(const double t, const Eigen::VectorXd &x) override;
 
    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;
 
    private:
        Eigen::VectorXd x_tilde() const;
 
        // TODO mass might be time dependent
        const StiffnessMatrix &mass_;                                    
        const time_integrator::ImplicitTimeIntegrator &time_integrator_; 
        XTildeUpdater x_tilde_updater_;
        Eigen::VectorXd x_tilde_;
    };
} // namespace polyfem::solver