opm-simulators/opm/simulators/linalg/MILU.hpp

/*
  Copyright 2015, 2022 Dr. Blatt - HPC-Simulation-Software & Services
  Copyright 2015 Statoil AS

  This file is part of the Open Porous Media project (OPM).

  OPM is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  OPM is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with OPM.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef OPM_MILU_HEADER_INCLUDED
#define OPM_MILU_HEADER_INCLUDED

#include <cmath>
#include <cstddef>
#include <functional>
#include <string>
#include <vector>



namespace Opm
{

enum class MILU_VARIANT{
    /// \brief Do not perform modified ILU
    ILU = 0,
    /// \brief \f$U_{ii} = U_{ii} +\f$  sum(dropped entries)
    MILU_1 = 1,
    /// \brief \f$U_{ii} = U_{ii} + sign(U_{ii}) * \f$ sum(dropped entries)
    MILU_2 = 2,
    /// \brief \f$U_{ii} = U_{ii} sign(U_{ii}) * \f$ sum(|dropped entries|)
    MILU_3 = 3,
    /// \brief \f$U_{ii} = U_{ii} + (U_{ii}>0?1:0) * \f$ sum(dropped entries)
    MILU_4 = 4
};

MILU_VARIANT convertString2Milu(const std::string& milu);


namespace detail
{

template <typename T>
T identityFunctor(const T&);

template <typename T>
T oneFunctor(const T&);

template <typename T>
T signFunctor(const T&);

template <typename T>
T isPositiveFunctor(const T&);

template <typename T>
T absFunctor(const T&);


struct Reorderer
{
    virtual std::size_t operator[](std::size_t i) const = 0;
    virtual ~Reorderer() {}
};

struct NoReorderer : public Reorderer
{
    virtual std::size_t operator[](std::size_t i) const
    {
        return i;
    }
};

struct RealReorderer : public Reorderer
{
    RealReorderer(const std::vector<std::size_t>& ordering)
        : ordering_(&ordering)
    {}
    virtual std::size_t operator[](std::size_t i) const
    {
        return (*ordering_)[i];
    }
    const std::vector<std::size_t>* ordering_;
};


template<class M>
using FieldFunct = std::function<typename M::field_type(const typename M::field_type&)>;

template <typename M>
void milu0_decomposition(M& A, FieldFunct<M> absFunctor = signFunctor<typename M::field_type>,
                         FieldFunct<M> signFunctor = oneFunctor<typename M::field_type>,
                         std::vector<typename M::block_type>* diagonal = nullptr);

template<class M>
void  milu0_decomposition(M& A, std::vector<typename M::block_type>* diagonal)
{
    milu0_decomposition(A, identityFunctor<typename M::field_type>, oneFunctor<typename M::field_type>, diagonal);
}


template<class M>
void milun_decomposition(const M& A, int n, MILU_VARIANT milu, M& ILU,
                         Reorderer& ordering, Reorderer& inverseOrdering);

} // end namespace details

} // end namespace Opm

#endif