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#ifndef __Elasticity_Kugelstadt2021_h__
#define __Elasticity_Kugelstadt2021_h__

#include "SPlisHSPlasH/Common.h"
#include "SPlisHSPlasH/FluidModel.h"
#include "ElasticityBase.h"
#include "SPlisHSPlasH/Utilities/MatrixFreeSolver.h"
#if USE_AVX
#include "SPlisHSPlasH/Utilities/AVX_math.h"
#include "SPlisHSPlasH/Utilities/CholeskyAVXSolver.h"
#endif


namespace SPH
{
    class Elasticity_Kugelstadt2021 : public ElasticityBase
    {
    protected:

        struct Factorization
        {
            Real m_dt;
            Real m_mu;
            Eigen::SparseMatrix<Real, Eigen::RowMajor> m_DT_K;
            Eigen::SparseMatrix<Real, Eigen::RowMajor> m_D;
            Eigen::SparseMatrix<Real, Eigen::ColMajor> m_matHTH;

#ifdef USE_AVX
            CholeskyAVXSolver *m_cholesky;
            Factorization() { m_cholesky = nullptr; }
            ~Factorization() { delete m_cholesky; }
#else
            Eigen::SparseMatrix<Real, Eigen::ColMajor> m_matL;
            Eigen::SparseMatrix<Real, Eigen::ColMajor> m_matLT;
            Eigen::VectorXi m_permInd;
            Eigen::VectorXi m_permInvInd;
#endif
        };

        struct ElasticObject
        {
            std::string m_md5;
            std::vector<unsigned int> m_particleIndices;
            unsigned int m_nFixed;

            std::shared_ptr<Factorization> m_factorization;
#ifdef USE_AVX
            VectorXr m_rhs;
            VectorXr m_sol;
            std::vector<Scalarf8, AlignmentAllocator<Scalarf8, 32>> m_RHS;
            std::vector<Scalarf8, AlignmentAllocator<Scalarf8, 32>> m_f_avx;
            std::vector<Scalarf8, AlignmentAllocator<Scalarf8, 32>> m_sol_avx;
            std::vector<Quaternion8f, AlignmentAllocator<Quaternion8f, 32>> m_quats_avx;
#else
            std::vector<Vector3r, Eigen::aligned_allocator<Vector3r>> m_f;
            std::vector<Vector3r, Eigen::aligned_allocator<Vector3r>> m_sol;
            std::vector<Vector3r, Eigen::aligned_allocator<Vector3r>> m_RHS;
            std::vector<Vector3r, Eigen::aligned_allocator<Vector3r>> m_RHS_perm;
            std::vector<Quaternionr, Eigen::aligned_allocator<Quaternionr>> m_quats;
#endif

            ElasticObject() { m_factorization = nullptr; }
            ~ElasticObject() { m_factorization = nullptr; }
        };

        // initial particle indices, used to access their original positions
        std::vector<unsigned int> m_current_to_initial_index;
        std::vector<unsigned int> m_initial_to_current_index;
        // initial particle neighborhood
        std::vector<std::vector<unsigned int>> m_initialNeighbors;
        // volumes in rest configuration
        std::vector<Real> m_restVolumes;
        std::vector<Matrix3r> m_rotations;
        std::vector<Real> m_stress;
        std::vector<Matrix3r> m_L;
        std::vector<Matrix3r> m_F;
        std::vector<Vector3r> m_vDiff;
        std::vector<Matrix3r> m_RL;
        unsigned int m_iterationsV;
        unsigned int m_maxIterV;
        Real m_maxErrorV;
        Real m_alpha;
        int m_maxNeighbors;
        unsigned int m_totalNeighbors;
        std::vector<ElasticObject*> m_objects;
        Real m_lambda;
        Real m_mu;


#ifdef USE_AVX
        std::vector<Vector3f8, Eigen::aligned_allocator<Vector3f8>> m_precomp_RL_gradW8;
        std::vector<Vector3f8, Eigen::aligned_allocator<Vector3f8>> m_precomp_L_gradW8;
        std::vector<Vector3f8, Eigen::aligned_allocator<Vector3f8>> m_precomp_RLj_gradW8;
        std::vector<unsigned int> m_precomputed_indices8;

        inline static void computeF(const unsigned int i, const Real* x, Elasticity_Kugelstadt2021* e);
#else
        std::vector<Vector3r, Eigen::aligned_allocator<Vector3r>> m_precomp_RL_gradW;
        std::vector<Vector3r, Eigen::aligned_allocator<Vector3r>> m_precomp_L_gradW;
        std::vector<Vector3r, Eigen::aligned_allocator<Vector3r>> m_precomp_RLj_gradW;
        std::vector<unsigned int> m_precomputed_indices;

        typedef Eigen::SimplicialLLT<Eigen::SparseMatrix<double>, Eigen::Lower, Eigen::AMDOrdering<int>> SolverLLT;
#endif

        typedef Eigen::ConjugateGradient<MatrixReplacement, Eigen::Lower | Eigen::Upper, Eigen::IdentityPreconditioner> Solver;

        Solver m_solver;
        void computeRHS(VectorXr& rhs);

        std::string computeMD5(const unsigned int objIndex);
        void initValues();
        void initSystem();
        void initFactorization(std::shared_ptr<Factorization> factorization, std::vector<unsigned int> &particleIndices, const unsigned int nFixed, const Real dt, const Real mu);
        void findObjects();
        void computeMatrixL();
        void precomputeValues();

        void stepElasticitySolver();
        void stepVolumeSolver();

        virtual void initParameters();
        virtual void deferredInit();

        // multiplication of symmetric matrix, represented by a 6D vector, and a
        // 3D vector
        FORCE_INLINE void symMatTimesVec(const Vector6r & M, const Vector3r & v, Vector3r &res)
        {
            res[0] = M[0] * v[0] + M[3] * v[1] + M[4] * v[2];
            res[1] = M[3] * v[0] + M[1] * v[1] + M[5] * v[2];
            res[2] = M[4] * v[0] + M[5] * v[1] + M[2] * v[2];
        }

        void rotationMatricesToAVXQuaternions();

    public:
        static int ITERATIONS_V;
        static int MAX_ITERATIONS_V;
        static int MAX_ERROR_V;
        static int ALPHA;
        static int MAX_NEIGHBORS;

        Elasticity_Kugelstadt2021(FluidModel *model);
        virtual ~Elasticity_Kugelstadt2021(void);

        static NonPressureForceBase* creator(FluidModel* model) { return new Elasticity_Kugelstadt2021(model); }

        virtual void step();
        virtual void reset();
        virtual void performNeighborhoodSearchSort();

        virtual void saveState(BinaryFileWriter &binWriter);
        virtual void loadState(BinaryFileReader &binReader);

        static void matrixVecProd(const Real* vec, Real* result, void* userData);

        void computeRotations();
    };
}

#endif