FDMICCGSolver2.hpp

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// This code is based on Jet framework.
// Copyright (c) 2018 Doyub Kim
// CubbyFlow is voxel-based fluid simulation engine for computer games.
// Copyright (c) 2020 CubbyFlow Team
// Core Part: Chris Ohk, Junwoo Hwang, Jihong Sin, Seungwoo Yoo
// AI Part: Dongheon Cho, Minseo Kim
// We are making my contributions/submissions to this project solely in our
// personal capacity and are not conveying any rights to any intellectual
// property of any third parties.

#ifndef CUBBYFLOW_FDM_ICCG_SOLVER2_HPP
#define CUBBYFLOW_FDM_ICCG_SOLVER2_HPP

#include <Core/Array/ArrayView.hpp>
#include <Core/Solver/FDM/FDMLinearSystemSolver2.hpp>

namespace CubbyFlow
{
class FDMICCGSolver2 final : public FDMLinearSystemSolver2
{
 public:
    FDMICCGSolver2(unsigned int maxNumberOfIterations, double tolerance);

    bool Solve(FDMLinearSystem2* system) override;

    bool SolveCompressed(FDMCompressedLinearSystem2* system) override;

    [[nodiscard]] unsigned int GetMaxNumberOfIterations() const;

    [[nodiscard]] unsigned int GetLastNumberOfIterations() const;

    [[nodiscard]] double GetTolerance() const;

    [[nodiscard]] double GetLastResidual() const;

 private:
    struct Preconditioner final
    {
        void Build(const FDMMatrix2& matrix);

        void Solve(const FDMVector2& b, FDMVector2* x);

        ConstArrayView2<FDMMatrixRow2> A;
        FDMVector2 d;
        FDMVector2 y;
    };

    struct PreconditionerCompressed final
    {
        void Build(const MatrixCSRD& matrix);

        void Solve(const VectorND& b, VectorND* x);

        const MatrixCSRD* A = nullptr;
        VectorND d;
        VectorND y;
    };

    void ClearUncompressedVectors();
    void ClearCompressedVectors();

    // Uncompressed vectors and preconditioner
    FDMVector2 m_r;
    FDMVector2 m_d;
    FDMVector2 m_q;
    FDMVector2 m_s;
    Preconditioner m_precond;

    // Compressed vectors and preconditioner
    VectorND m_rComp;
    VectorND m_dComp;
    VectorND m_qComp;
    VectorND m_sComp;
    PreconditionerCompressed m_precondComp;

    unsigned int m_maxNumberOfIterations;
    unsigned int m_lastNumberOfIterations;
    double m_tolerance;
    double m_lastResidualNorm;
};

using FDMICCGSolver2Ptr = std::shared_ptr<FDMICCGSolver2>;
}  // namespace CubbyFlow

#endif