NLProblem.hpp

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#pragma once
 
#include <polyfem/solver/FullNLProblem.hpp>
#include <polyfem/assembler/PeriodicBoundary.hpp>
#include <polyfem/solver/forms/lagrangian/AugmentedLagrangianForm.hpp>
 
#include <polyfem/utils/Logger.hpp>
 
namespace polysolve::linear
{
    class Solver;
}
 
namespace polyfem::solver
{
    class NLProblem : public FullNLProblem
    {
    public:
        using typename FullNLProblem::Scalar;
        using typename FullNLProblem::THessian;
        using typename FullNLProblem::TVector;
 
    protected:
        NLProblem(
            const int full_size,
            const std::vector<std::shared_ptr<Form>> &forms,
            const std::vector<std::shared_ptr<AugmentedLagrangianForm>> &penalty_forms,
            const std::shared_ptr<polysolve::linear::Solver> &solver);
 
    public:
        NLProblem(const int full_size,
                  const std::shared_ptr<utils::PeriodicBoundary> &periodic_bc,
                  const double t,
                  const std::vector<std::shared_ptr<Form>> &forms,
                  const std::vector<std::shared_ptr<AugmentedLagrangianForm>> &penalty_forms,
                  const std::shared_ptr<polysolve::linear::Solver> &solver,
                  const double char_length,
                  const double char_force,
                  StiffnessMatrix lumped_mass,
                  const int dimension);
        virtual ~NLProblem() = default;
 
        virtual double value(const TVector &x) override;
        virtual void gradient(const TVector &x, TVector &gradv) override;
        virtual void hessian(const TVector &x, THessian &hessian) override;
 
        virtual bool is_step_valid(const TVector &x0, const TVector &x1) override;
        virtual bool is_step_collision_free(const TVector &x0, const TVector &x1) override;
        virtual double max_step_size(const TVector &x0, const TVector &x1) override;
        void line_search_begin(const TVector &x0, const TVector &x1) override;
        virtual void post_step(const polysolve::nonlinear::PostStepData &data) override;
 
        void solution_changed(const TVector &new_x) override;
 
        void init_lagging(const TVector &x) override;
        void update_lagging(const TVector &x, const int iter_num) override;
 
        // --------------------------------------------------------------------
 
        virtual void update_quantities(const double t, const TVector &x);
 
        int full_size() const { return full_size_; }
        int reduced_size() const { return reduced_size_; }
 
        void use_full_size() { current_size_ = CurrentSize::FULL_SIZE; }
        void use_reduced_size() { current_size_ = CurrentSize::REDUCED_SIZE; }
 
        TVector full_to_reduced(const TVector &full) const;
        virtual TVector full_to_reduced_grad(const TVector &full) const;
        virtual TVector full_to_reduced_diag(const TVector &full_diag) const;
        TVector reduced_to_full(const TVector &reduced) const;
 
        void full_hessian_to_reduced_hessian(StiffnessMatrix &hessian) const;
 
        double normalize_forms() override;
 
        virtual double grad_norm_rescaling(const polysolve::nonlinear::NormType norm_type) const override;
        virtual double step_norm_rescaling(const polysolve::nonlinear::NormType norm_type) const override;
        virtual double energy_norm_rescaling(const polysolve::nonlinear::NormType norm_type) const override;
        virtual double grad_norm(const TVector &grad, const polysolve::nonlinear::NormType norm_type) const override;
        virtual double step_norm(const TVector &x, const polysolve::nonlinear::NormType norm_type) const override;
 
    protected:
        const int full_size_; 
        int reduced_size_;    
 
        enum class CurrentSize
        {
            FULL_SIZE,
            REDUCED_SIZE
        };
        CurrentSize current_size_; 
        int current_size() const
        {
            return current_size_ == CurrentSize::FULL_SIZE ? full_size() : reduced_size();
        }
 
        Eigen::DiagonalMatrix<double, Eigen::Dynamic> current_lumped_mass() const
        {
            return full_to_reduced_diag(lumped_mass_.diagonal()).asDiagonal();
        }
 
        double t_;
        double F0;
        double L;
        int dim;
        Eigen::DiagonalMatrix<double, Eigen::Dynamic> lumped_mass_;
 
    protected:
        std::vector<std::shared_ptr<AugmentedLagrangianForm>> penalty_forms_;
        // The decomposion comes from sec 1.3 of https://www.cs.cornell.edu/courses/cs6241/2021sp/meetings/nb-2021-03-11.pdf
        StiffnessMatrix Q1_;                                         
        StiffnessMatrix Q2_;                                         
        StiffnessMatrix Q2t_;                                        
        StiffnessMatrix R1_;                                         
        Eigen::PermutationMatrix<Eigen::Dynamic, Eigen::Dynamic> P_; 
        TVector Q1R1iTb_;                                            
        std::shared_ptr<polysolve::linear::Solver> solver_;
 
        std::shared_ptr<FullNLProblem> penalty_problem_;
        int num_penalty_constraints_;
 
        void setup_constraints();
        void update_constraint_values();
    };
} // namespace polyfem::solver