partialreassembler.hh

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// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
// vi: set et ts=4 sw=4 sts=4:
//
// SPDX-FileCopyrightText: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
// SPDX-License-Identifier: GPL-3.0-or-later
//
#ifndef DUMUX_PARTIAL_REASSEMBLER_HH
#define DUMUX_PARTIAL_REASSEMBLER_HH
 
#include <algorithm>
#include <vector>
 
#include <dune/grid/common/gridenums.hh>
#include <dune/istl/multitypeblockvector.hh>
 
#include <dumux/io/format.hh>
#include <dumux/common/typetraits/isvalid.hh>
#include <dumux/discretization/method.hh>
#include <dumux/parallel/vectorcommdatahandle.hh>
#include <dumux/common/gridcapabilities.hh>
 
#include "entitycolor.hh"
 
namespace Dumux {
 
class DefaultPartialReassembler
{
public:
    template<typename... Args>
    DefaultPartialReassembler(Args&&... args)
    { DUNE_THROW(Dune::InvalidStateException, "DefaultPartialReassembler should be never constructed!"); }
 
    template<typename... Args>
    void report(Args&&... args) {}
 
    template<typename... Args>
    void resetJacobian(Args&&... args) const {}
 
    template<typename... Args>
    void computeColors(Args&&... args) {}
 
    template<typename... Args>
    void resetColors(Args&&... args) {}
 
    EntityColor dofColor(size_t idx) const
    { return EntityColor::red; }
 
    EntityColor elementColor(size_t idx) const
    { return EntityColor::red; }
 
    EntityColor vertexColor(size_t idx) const
    { return EntityColor::red; }
};

template<class Assembler, class DiscretizationMethod>
class PartialReassemblerEngine
{
public:
    PartialReassemblerEngine(const Assembler&)
    { DUNE_THROW(Dune::NotImplemented, "PartialReassembler for this discretization method!"); }
 
    EntityColor elementColor(size_t idx) const
    { return EntityColor::red; }
 
    EntityColor dofColor(size_t idx) const
    { return EntityColor::red; }
 
    template<typename... Args>
    std::size_t computeColors(Args&&... args) { return 0; }
 
    template<typename... Args>
    void resetJacobian(Args&&... args) const {}
 
    template<typename... Args>
    void resetColors(Args&&... args) {}
};

template<class Assembler>
class PartialReassemblerEngine<Assembler, DiscretizationMethods::Box>
{
    using Scalar = typename Assembler::Scalar;
    using GridGeometry = typename Assembler::GridGeometry;
    using JacobianMatrix = typename Assembler::JacobianMatrix;
    using VertexMapper = typename GridGeometry::VertexMapper;
    static constexpr int dim = GridGeometry::GridView::dimension;
 
public:
    PartialReassemblerEngine(const Assembler& assembler)
    : elementColor_(assembler.gridGeometry().elementMapper().size(), EntityColor::red)
    , vertexColor_(assembler.gridGeometry().vertexMapper().size(), EntityColor::red)
    {}
 
    // returns number of green elements
    std::size_t computeColors(const Assembler& assembler,
                              const std::vector<Scalar>& distanceFromLastLinearization,
                              Scalar threshold)
    {
        const auto& gridGeometry = assembler.gridGeometry();
        const auto& gridView = gridGeometry.gridView();
        const auto& elementMapper = gridGeometry.elementMapper();
        const auto& vertexMapper = gridGeometry.vertexMapper();
 
        // set all vertices to green
        vertexColor_.assign(vertexColor_.size(), EntityColor::green);
 
        // mark the red vertices
        for (unsigned int i = 0; i < vertexColor_.size(); ++i)
        {
            using std::max;
            if (distanceFromLastLinearization[i] > threshold)
                // mark vertex as red if discrepancy is larger than
                // the relative tolerance
                vertexColor_[i] = EntityColor::red;
        }
 
        // Mark all red elements
        for (const auto& element : elements(gridView))
        {
            // find out whether the current element features a red vertex
            bool isRed = false;
 
            int numVertices = element.subEntities(dim);
 
            for (int i = 0; i < numVertices; ++i) {
                int globalI = vertexMapper.subIndex(element, i, dim);
 
                if (vertexColor_[globalI] == EntityColor::red) {
                    isRed = true;
                    break;
                }
            }
 
            int eIdx = elementMapper.index(element);
            // if a vertex is red, the element color is also red, otherwise green
            if (isRed)
                elementColor_[eIdx] = EntityColor::red;
            else
                elementColor_[eIdx] = EntityColor::green;
        }
 
        // mark orange vertices
        for (const auto& element : elements(gridView))
        {
            int eIdx = elementMapper.index(element);
 
            // only red elements tint vertices yellow
            if (elementColor_[eIdx] == EntityColor::red)
            {
                int numVertices = element.subEntities(dim);
 
                for (int i = 0; i < numVertices; ++i) {
                    int globalI = vertexMapper.subIndex(element, i, dim);
 
                    // red vertices don't become orange
                    if (vertexColor_[globalI] != EntityColor::red)
                        vertexColor_[globalI] = EntityColor::orange;
                }
            }
        }
 
        // at this point we communicate the yellow vertices to the
        // neighboring processes because a neighbor process may not see
        // the red vertex for yellow border vertices
        VectorCommDataHandleMin<VertexMapper, std::vector<EntityColor>, dim>
            minHandle(vertexMapper, vertexColor_);
        if constexpr (Dune::Capabilities::canCommunicate<typename GridGeometry::GridView::Traits::Grid, dim>::v)
            gridView.communicate(minHandle,
                                 Dune::InteriorBorder_InteriorBorder_Interface,
                                 Dune::ForwardCommunication);
        else
            DUNE_THROW(Dune::InvalidStateException, "Cannot call computeColors on multiple processes for a grid that cannot communicate codim-" << dim << "-entities.");
 
        // mark yellow elements
        for (const auto& element : elements(gridView))
        {
            int eIdx = elementMapper.index(element);
 
            // only treat non-red elements
            if (elementColor_[eIdx] != EntityColor::red)
            {
                // check whether the element features a orange vertex
                bool isOrange = false;
                int numVertices = element.subEntities(dim);
 
                for (int i = 0; i < numVertices; ++i) {
                    int globalI = vertexMapper.subIndex(element, i, dim);
 
                    if (vertexColor_[globalI] == EntityColor::orange) {
                        isOrange = true;
                        break;
                    }
                }
 
                if (isOrange)
                    elementColor_[eIdx] = EntityColor::yellow;
            }
        }
 
        // change orange vertices to yellow ones if it has at least
        // one green element as a neighbor
        for (const auto& element : elements(gridView))
        {
            int eIdx = elementMapper.index(element);
 
            // only green elements are considered
            if (elementColor_[eIdx] == EntityColor::green)
            {
                int numVertices = element.subEntities(dim);
 
                for (int i = 0; i < numVertices; ++i) {
                    int globalI = vertexMapper.subIndex(element, i, dim);
 
                    // if a vertex is orange, recolor it to yellow
                    if (vertexColor_[globalI] == EntityColor::orange)
                        vertexColor_[globalI] = EntityColor::yellow;
                }
            }
        }
 
        // demote the border orange vertices
        VectorCommDataHandleMax<VertexMapper, std::vector<EntityColor>, dim>
            maxHandle(vertexMapper, vertexColor_);
        if constexpr (Dune::Capabilities::canCommunicate<typename GridGeometry::GridView::Traits::Grid, dim>::v)
            gridView.communicate(maxHandle,
                                 Dune::InteriorBorder_InteriorBorder_Interface,
                                 Dune::ForwardCommunication);
        else
            DUNE_THROW(Dune::InvalidStateException, "Cannot call computeColors on multiple processes for a grid that cannot communicate codim-" << dim << "-entities.");
 
        // promote the remaining orange vertices to red
        for (unsigned int i=0; i < vertexColor_.size(); ++i) {
            // if a vertex is green or yellow don't do anything
            if (vertexColor_[i] == EntityColor::green || vertexColor_[i] == EntityColor::yellow)
                continue;
 
            // set the vertex to red
            vertexColor_[i] = EntityColor::red;
        }
 
        // count green elements
        return std::count_if(elementColor_.begin(), elementColor_.end(),
                             [](EntityColor c){ return c == EntityColor::green; });
    }
 
    void resetJacobian(Assembler& assembler) const
    {
        auto& jacobian = assembler.jacobian();
 
        // loop over all dofs
        for (unsigned int rowIdx = 0; rowIdx < jacobian.N(); ++rowIdx)
        {
            // reset all entries corresponding to a non-green vertex
            if (vertexColor_[rowIdx] != EntityColor::green)
            {
                // set all matrix entries in the row to 0
                auto colIt = jacobian[rowIdx].begin();
                const auto& colEndIt = jacobian[rowIdx].end();
                for (; colIt != colEndIt; ++colIt) {
                    *colIt = 0.0;
                }
            }
        }
    }
 
    void resetColors()
    {
        elementColor_.assign(elementColor_.size(), EntityColor::red);
        vertexColor_.assign(vertexColor_.size(), EntityColor::red);
    }
 
    EntityColor elementColor(size_t idx) const
    { return elementColor_[idx]; }
 
    EntityColor vertexColor(size_t idx) const
    { return vertexColor_[idx]; }
 
    EntityColor dofColor(size_t idx) const
    { return vertexColor_[idx]; }
 
private:
    std::vector<EntityColor> elementColor_;
    std::vector<EntityColor> vertexColor_;
};

template<class Assembler>
class PartialReassemblerEngine<Assembler, DiscretizationMethods::CCTpfa>
{
    using Scalar = typename Assembler::Scalar;
    using GridGeometry = typename Assembler::GridGeometry;
    using JacobianMatrix = typename Assembler::JacobianMatrix;
 
public:
    PartialReassemblerEngine(const Assembler& assembler)
    : elementColor_(assembler.gridGeometry().elementMapper().size(), EntityColor::red)
    {}
 
    // returns number of green elements
    std::size_t computeColors(const Assembler& assembler,
                              const std::vector<Scalar>& distanceFromLastLinearization,
                              Scalar threshold)
    {
        const auto& gridGeometry = assembler.gridGeometry();
        const auto& gridView = gridGeometry.gridView();
        const auto& elementMapper = gridGeometry.elementMapper();
 
        // mark the red elements
        for (const auto& element : elements(gridView))
        {
            int eIdx = elementMapper.index(element);
 
            if (distanceFromLastLinearization[eIdx] > threshold)
            {
                // mark element as red if discrepancy is larger than
                // the relative tolerance
                elementColor_[eIdx] = EntityColor::red;
            }
            else
            {
                elementColor_[eIdx] = EntityColor::green;
            }
        }
 
        // mark the neighbors also red
        // (tested on the distance instead of the color, so the marking does not propagate further)
        const auto& connectivityMap = gridGeometry.connectivityMap();
        for (unsigned eIdx = 0; eIdx < elementColor_.size(); ++eIdx)
        {
            if (distanceFromLastLinearization[eIdx] > threshold)
            {
                for (const auto& connectedDof : connectivityMap[eIdx])
                    elementColor_[connectedDof.globalJ] = EntityColor::red;
            }
        }
 
        // count green elements
        return std::count_if(elementColor_.begin(), elementColor_.end(),
                             [](EntityColor c){return c == EntityColor::green;});
 
    }
 
    void resetJacobian(Assembler& assembler) const
    {
        auto& jacobian = assembler.jacobian();
        const auto& connectivityMap = assembler.gridGeometry().connectivityMap();
 
        // loop over all dofs
        for (unsigned int colIdx = 0; colIdx < jacobian.M(); ++colIdx)
        {
            // reset all entries corresponding to a non-green element
            if (elementColor_[colIdx] != EntityColor::green)
            {
                // set all matrix entries in the column to 0
                jacobian[colIdx][colIdx] = 0;
                for (const auto& dataJ : connectivityMap[colIdx])
                    jacobian[dataJ.globalJ][colIdx] = 0;
            }
        }
    }
 
    void resetColors()
    {
        elementColor_.assign(elementColor_.size(), EntityColor::red);
    }
 
    EntityColor elementColor(size_t idx) const
    { return elementColor_[idx]; }
 
    EntityColor dofColor(size_t idx) const
    { return elementColor_[idx]; }
 
private:
    std::vector<EntityColor> elementColor_;
};

template<class Assembler>
class PartialReassemblerEngine<Assembler, DiscretizationMethods::CCMpfa>
: public PartialReassemblerEngine<Assembler, DiscretizationMethods::CCTpfa>
{
    using ParentType = PartialReassemblerEngine<Assembler, DiscretizationMethods::CCTpfa>;
public:
    using ParentType::ParentType;
};

struct hasVertexColor
{
    template<class Engine>
    auto operator()(Engine&& e) -> decltype(e.vertexColor(0)) {}
};

template<class Assembler>
class PartialReassembler
{
    using Scalar = typename Assembler::Scalar;
    using GridGeometry = typename Assembler::GridGeometry;
    using JacobianMatrix = typename Assembler::JacobianMatrix;
    using VertexMapper = typename GridGeometry::VertexMapper;
 
    using DiscretizationMethod = typename GridGeometry::DiscretizationMethod;
    using Engine = PartialReassemblerEngine<Assembler, DiscretizationMethod>;
 
public:

    PartialReassembler(const Assembler& assembler)
    : engine_(assembler)
    , greenElems_(0)
    {
        const auto& gridGeometry = assembler.gridGeometry();
        totalElems_ = gridGeometry.elementMapper().size();
        totalElems_ = gridGeometry.gridView().comm().sum(totalElems_);
    }

    void computeColors(const Assembler& assembler,
                       const std::vector<Scalar>& distanceFromLastLinearization,
                       Scalar threshold)
    {
        greenElems_ = engine_.computeColors(assembler, distanceFromLastLinearization, threshold);
    }
 
    void resetColors()
    {
        engine_.resetColors();
    }
 
    void resetJacobian(Assembler& assembler) const
    {
        engine_.resetJacobian(assembler);
    }

    template <class Communication>
    void report(const Communication& comm, std::ostream& outStream)
    {
        if (comm.size() > 1)
            greenElems_ = comm.sum(greenElems_);
 
        const auto reassembledElems = totalElems_ - greenElems_;
        const auto width = Fmt::formatted_size("{}", totalElems_);
        outStream << Fmt::format(", reassembled {:{}} ({:3}%) elements",
                                 reassembledElems, width, 100*reassembledElems/totalElems_);
    }
 
    EntityColor elementColor(size_t idx) const
    { return engine_.elementColor(idx); }
 
    EntityColor dofColor(size_t idx) const
    { return engine_.dofColor(idx); }
 
    template<bool enable = decltype(isValid(hasVertexColor()).template check<Engine>())::value,
             typename std::enable_if_t<enable, int> = 0>
    EntityColor vertexColor(size_t idx) const
    { return engine_.vertexColor(idx); }
 
private:
    Engine engine_;
    size_t totalElems_;
    size_t greenElems_;
};
 
} // namespace Dumux
 
#endif