InertiaForm.cpp

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#include "InertiaForm.hpp"
 
#include <polyfem/time_integrator/ImplicitTimeIntegrator.hpp>
#include <polyfem/utils/Types.hpp>
 
#include <cassert>
 
namespace polyfem::solver
{
    InertiaForm::InertiaForm(const StiffnessMatrix &mass,
                             const time_integrator::ImplicitTimeIntegrator &time_integrator)
        : mass_(mass), time_integrator_(time_integrator)
    {
        assert(mass.size() != 0);
    }
 
    double InertiaForm::value_unweighted(const Eigen::VectorXd &x) const
    {
        const Eigen::VectorXd tmp = x - time_integrator_.x_tilde();
        // FIXME: DBC on x tilde
        const double prod = tmp.transpose() * mass_ * tmp;
        const double energy = 0.5 * prod;
        return energy;
    }
 
    void InertiaForm::first_derivative_unweighted(const Eigen::VectorXd &x, Eigen::VectorXd &gradv) const
    {
        gradv = mass_ * (x - time_integrator_.x_tilde());
    }
 
    void InertiaForm::second_derivative_unweighted(const Eigen::VectorXd &x, StiffnessMatrix &hessian) const
    {
        hessian = mass_;
    }
} // namespace polyfem::solver