MG.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_MULTI_GRID_HPP
#define CUBBYFLOW_MULTI_GRID_HPP

#include <functional>

namespace CubbyFlow
{
template <typename BlasType>
struct MGMatrix
{
    std::vector<typename BlasType::MatrixType> levels;
    const typename BlasType::MatrixType& operator[](size_t i) const;
    typename BlasType::MatrixType& operator[](size_t i);
    [[nodiscard]] const typename BlasType::MatrixType& Finest() const;
    [[nodiscard]] typename BlasType::MatrixType& Finest();
};

template <typename BlasType>
struct MGVector
{
    std::vector<typename BlasType::VectorType> levels;
    const typename BlasType::VectorType& operator[](size_t i) const;
    typename BlasType::VectorType& operator[](size_t i);
    [[nodiscard]] const typename BlasType::VectorType& Finest() const;
    [[nodiscard]] typename BlasType::VectorType& Finest();
};

template <typename BlasType>
using MGRelaxFunc = std::function<void(
    const typename BlasType::MatrixType& A,
    const typename BlasType::VectorType& b, unsigned int numberOfIterations,
    double maxTolerance, typename BlasType::VectorType* x,
    typename BlasType::VectorType* buffer)>;

template <typename BlasType>
using MGRestrictFunc =
    std::function<void(const typename BlasType::VectorType& finer,
                       typename BlasType::VectorType* coarser)>;

template <typename BlasType>
using MGCorrectFunc =
    std::function<void(const typename BlasType::VectorType& coarser,
                       typename BlasType::VectorType* finer)>;

template <typename BlasType>
struct MGParameters
{
    size_t maxNumberOfLevels = 1;

    unsigned int numberOfRestrictionIter = 5;

    unsigned int numberOfCorrectionIter = 5;

    unsigned int numberOfCoarsestIter = 20;

    unsigned int numberOfFinalIter = 20;

    MGRelaxFunc<BlasType> relaxFunc;

    MGRestrictFunc<BlasType> restrictFunc;

    MGCorrectFunc<BlasType> correctFunc;

    double maxTolerance = 1e-9;
};

struct MGResult
{
    double lastResidualNorm;
};

template <typename BlasType>
MGResult MGVCycle(const MGMatrix<BlasType>& A, MGParameters<BlasType> params,
                  MGVector<BlasType>* x, MGVector<BlasType>* b,
                  MGVector<BlasType>* buffer);
}  // namespace CubbyFlow

#include <Core/Utils/MG-Impl.hpp>

#endif