fvbaselinearizer.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:
/*
  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 2 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/>.
 
  Consult the COPYING file in the top-level source directory of this
  module for the precise wording of the license and the list of
  copyright holders.
*/
#ifndef EWOMS_FV_BASE_LINEARIZER_HH
#define EWOMS_FV_BASE_LINEARIZER_HH
 
#include <dune/common/fmatrix.hh>
#include <dune/common/fvector.hh>
#include <dune/common/version.hh>
 
#include <dune/grid/common/gridenums.hh>
 
#include <opm/common/Exceptions.hpp>
#include <opm/common/TimingMacros.hpp>
 
#include <opm/grid/utility/SparseTable.hpp>
 
#include <opm/material/common/MathToolbox.hpp>
 
#include <opm/models/parallel/gridcommhandles.hh>
#include <opm/models/parallel/threadmanager.hpp>
#include <opm/models/parallel/threadedentityiterator.hh>
 
#include <opm/models/discretization/common/baseauxiliarymodule.hh>
#include <opm/models/discretization/common/fvbaseproperties.hh>
#include <opm/models/discretization/common/linearizationtype.hh>
 
#include <cstddef>
#include <exception>   // current_exception, rethrow_exception
#include <iostream>
#include <map>
#include <memory>
#include <mutex>
#include <set>
#include <vector>
 
namespace Opm {
 
// forward declarations
template<class TypeTag>
class EcfvDiscretization;
 
template<class TypeTag>
class FvBaseLinearizer
{
    using Model = GetPropType<TypeTag, Properties::Model>;
    using Discretization = GetPropType<TypeTag, Properties::Discretization>;
    using Problem = GetPropType<TypeTag, Properties::Problem>;
    using Simulator = GetPropType<TypeTag, Properties::Simulator>;
    using GridView = GetPropType<TypeTag, Properties::GridView>;
    using Scalar = GetPropType<TypeTag, Properties::Scalar>;
    using Evaluation = GetPropType<TypeTag, Properties::Evaluation>;
    using DofMapper = GetPropType<TypeTag, Properties::DofMapper>;
    using ElementMapper = GetPropType<TypeTag, Properties::ElementMapper>;
    using ElementContext = GetPropType<TypeTag, Properties::ElementContext>;
 
    using SolutionVector = GetPropType<TypeTag, Properties::SolutionVector>;
    using GlobalEqVector = GetPropType<TypeTag, Properties::GlobalEqVector>;
    using SparseMatrixAdapter = GetPropType<TypeTag, Properties::SparseMatrixAdapter>;
    using EqVector = GetPropType<TypeTag, Properties::EqVector>;
    using Constraints = GetPropType<TypeTag, Properties::Constraints>;
    using Stencil = GetPropType<TypeTag, Properties::Stencil>;
    using ThreadManager = GetPropType<TypeTag, Properties::ThreadManager>;
 
    using GridCommHandleFactory = GetPropType<TypeTag, Properties::GridCommHandleFactory>;
 
    using Toolbox = MathToolbox<Evaluation>;
 
    using Element = typename GridView::template Codim<0>::Entity;
    using ElementIterator = typename GridView::template Codim<0>::Iterator;
 
    using Vector = GlobalEqVector;
 
    using IstlMatrix = typename SparseMatrixAdapter::IstlMatrix;
 
    enum { numEq = getPropValue<TypeTag, Properties::NumEq>() };
    enum { historySize = getPropValue<TypeTag, Properties::TimeDiscHistorySize>() };
 
    using MatrixBlock = typename SparseMatrixAdapter::MatrixBlock;
    using VectorBlock = Dune::FieldVector<Scalar, numEq>;
 
    static constexpr bool linearizeNonLocalElements = getPropValue<TypeTag, Properties::LinearizeNonLocalElements>();
 
 
public:
    FvBaseLinearizer() = default;
 
    // copying the linearizer is not a good idea
    FvBaseLinearizer(const FvBaseLinearizer&) = delete;
 
    static void registerParameters()
    {}
 
    void init(Simulator& simulator)
    {
        simulatorPtr_ = &simulator;
        eraseMatrix();
        elementCtx_.clear();
        fullDomain_ = std::make_unique<FullDomain>(simulator.gridView());
    }
 
    void eraseMatrix()
    {
        jacobian_.reset();
    }
 
    void linearize()
    {
        linearizeDomain();
        linearizeAuxiliaryEquations();
    }
 
    void linearizeDomain()
    {
        linearizeDomain(*fullDomain_);
    }
 
    template <class SubDomainType>
    void linearizeDomain(const SubDomainType& domain)
    {
        OPM_TIMEBLOCK(linearizeDomain);
        // we defer the initialization of the Jacobian matrix until here because the
        // auxiliary modules usually assume the problem, model and grid to be fully
        // initialized...
        if (!jacobian_) {
            initFirstIteration_();
        }
 
        // Called here because it is no longer called from linearize_().
        if (static_cast<std::size_t>(domain.view.size(0)) == model_().numTotalDof()) {
            // We are on the full domain.
            resetSystem_();
        }
        else {
            resetSystem_(domain);
        }
 
        int succeeded;
        try {
            linearize_(domain);
            succeeded = 1;
        }
        catch (const std::exception& e)
        {
            std::cout << "rank " << simulator_().gridView().comm().rank()
                      << " caught an exception while linearizing:" << e.what()
                      << "\n"  << std::flush;
            succeeded = 0;
        }
        catch (...)
        {
            std::cout << "rank " << simulator_().gridView().comm().rank()
                      << " caught an exception while linearizing"
                      << "\n"  << std::flush;
            succeeded = 0;
        }
        succeeded = simulator_().gridView().comm().min(succeeded);
 
        if (!succeeded) {
            throw NumericalProblem("A process did not succeed in linearizing the system");
        }
    }
 
    void finalize()
    { jacobian_->finalize(); }
 
    void linearizeAuxiliaryEquations()
    {
        OPM_TIMEBLOCK(linearizeAuxiliaryEquations);
        // flush possible local caches into matrix structure
        jacobian_->commit();
 
        auto& model = model_();
        const auto& comm = simulator_().gridView().comm();
        for (unsigned auxModIdx = 0; auxModIdx < model.numAuxiliaryModules(); ++auxModIdx) {
            bool succeeded = true;
            try {
                model.auxiliaryModule(auxModIdx)->linearize(*jacobian_, residual_);
            }
            catch (const std::exception& e) {
                succeeded = false;
 
                std::cout << "rank " << simulator_().gridView().comm().rank()
                          << " caught an exception while linearizing:" << e.what()
                          << "\n"  << std::flush;
            }
 
            succeeded = comm.min(succeeded);
 
            if (!succeeded) {
                throw NumericalProblem("linearization of an auxiliary equation failed");
            }
        }
    }
 
    const SparseMatrixAdapter& jacobian() const
    { return *jacobian_; }
 
    SparseMatrixAdapter& jacobian()
    { return *jacobian_; }
 
    const GlobalEqVector& residual() const
    { return residual_; }
 
    GlobalEqVector& residual()
    { return residual_; }
 
    void setLinearizationType(LinearizationType linearizationType)
    { linearizationType_ = linearizationType; }
 
    const LinearizationType& getLinearizationType() const
    { return linearizationType_; }
 
    void updateDiscretizationParameters()
    {
        // This linearizer stores no such parameters.
    }
 
    void updateBoundaryConditionData()
    {
        // This linearizer stores no such data.
    }
 
    void updateFlowsInfo()
    {
        // This linearizer stores no such data.
    }
 
    const std::map<unsigned, Constraints>& constraintsMap() const
    { return constraintsMap_; }
 
    const auto& getFlowsInfo() const
    { return flowsInfo_; }
 
    const auto& getFloresInfo() const
    { return floresInfo_; }
 
    template <class SubDomainType>
    void resetSystem_(const SubDomainType& domain)
    {
        if (!jacobian_) {
            initFirstIteration_();
        }
 
        // loop over selected elements
        using GridViewType = decltype(domain.view);
        ThreadedEntityIterator<GridViewType, /*codim=*/0> threadedElemIt(domain.view);
#ifdef _OPENMP
#pragma omp parallel
#endif
        {
            const unsigned threadId = ThreadManager::threadId();
            auto elemIt = threadedElemIt.beginParallel();
            MatrixBlock zeroBlock;
            zeroBlock = 0.0;
            for (; !threadedElemIt.isFinished(elemIt); elemIt = threadedElemIt.increment()) {
                const Element& elem = *elemIt;
                ElementContext& elemCtx = *elementCtx_[threadId];
                elemCtx.updatePrimaryStencil(elem);
                // Set to zero the relevant residual and jacobian parts.
                for (unsigned primaryDofIdx = 0;
                     primaryDofIdx < elemCtx.numPrimaryDof(/*timeIdx=*/0);
                     ++primaryDofIdx)
                {
                    const unsigned globI = elemCtx.globalSpaceIndex(primaryDofIdx, /*timeIdx=*/0);
                    residual_[globI] = 0.0;
                    jacobian_->clearRow(globI, 0.0);
                }
            }
        }
    }
 
private:
    Simulator& simulator_()
    { return *simulatorPtr_; }
 
    const Simulator& simulator_() const
    { return *simulatorPtr_; }
 
    Problem& problem_()
    { return simulator_().problem(); }
 
    const Problem& problem_() const
    { return simulator_().problem(); }
 
    Model& model_()
    { return simulator_().model(); }
 
    const Model& model_() const
    { return simulator_().model(); }
 
    const GridView& gridView_() const
    { return problem_().gridView(); }
 
    const ElementMapper& elementMapper_() const
    { return model_().elementMapper(); }
 
    const DofMapper& dofMapper_() const
    { return model_().dofMapper(); }
 
    void initFirstIteration_()
    {
        // initialize the BCRS matrix for the Jacobian of the residual function
        createMatrix_();
 
        // initialize the Jacobian matrix and the vector for the residual function
        residual_.resize(model_().numTotalDof());
        resetSystem_();
 
        // create the per-thread context objects
        elementCtx_.clear();
        elementCtx_.reserve(ThreadManager::maxThreads());
        for (unsigned threadId = 0; threadId != ThreadManager::maxThreads(); ++ threadId) {
            elementCtx_.push_back(std::make_unique<ElementContext>(simulator_()));
        }
    }
 
    // Construct the BCRS matrix for the Jacobian of the residual function
    void createMatrix_()
    {
        const auto& model = model_();
        Stencil stencil(gridView_(), model_().dofMapper());
 
        // for the main model, find out the global indices of the neighboring degrees of
        // freedom of each primary degree of freedom
        sparsityPattern_.clear();
        sparsityPattern_.resize(model.numTotalDof());
 
        for (const auto& elem : elements(gridView_())) {
            stencil.update(elem);
 
            for (unsigned primaryDofIdx = 0; primaryDofIdx < stencil.numPrimaryDof(); ++primaryDofIdx) {
                const unsigned myIdx = stencil.globalSpaceIndex(primaryDofIdx);
 
                for (unsigned dofIdx = 0; dofIdx < stencil.numDof(); ++dofIdx) {
                    const unsigned neighborIdx = stencil.globalSpaceIndex(dofIdx);
                    sparsityPattern_[myIdx].insert(neighborIdx);
                }
            }
        }
 
        // add the additional neighbors and degrees of freedom caused by the auxiliary
        // equations
        const std::size_t numAuxMod = model.numAuxiliaryModules();
        for (unsigned auxModIdx = 0; auxModIdx < numAuxMod; ++auxModIdx) {
            model.auxiliaryModule(auxModIdx)->addNeighbors(sparsityPattern_);
        }
 
        // allocate raw matrix
        jacobian_ = std::make_unique<SparseMatrixAdapter>(simulator_());
 
        // create matrix structure based on sparsity pattern
        jacobian_->reserve(sparsityPattern_);
    }
 
    // reset the global linear system of equations.
    void resetSystem_()
    {
        residual_ = 0.0;
        // zero all matrix entries
        jacobian_->clear();
    }
 
    // query the problem for all constraint degrees of freedom. note that this method is
    // quite involved and is thus relatively slow.
    void updateConstraintsMap_()
    {
        if (!enableConstraints_()) {
            // constraints are not explictly enabled, so we don't need to consider them!
            return;
        }
 
        constraintsMap_.clear();
 
        // loop over all elements...
        ThreadedEntityIterator<GridView, /*codim=*/0> threadedElemIt(gridView_());
#ifdef _OPENMP
#pragma omp parallel
#endif
        {
            const unsigned threadId = ThreadManager::threadId();
            ElementIterator elemIt = threadedElemIt.beginParallel();
            for (; !threadedElemIt.isFinished(elemIt); elemIt = threadedElemIt.increment()) {
                // create an element context (the solution-based quantities are not
                // available here!)
                const Element& elem = *elemIt;
                ElementContext& elemCtx = *elementCtx_[threadId];
                elemCtx.updateStencil(elem);
 
                // check if the problem wants to constrain any degree of the current
                // element's freedom. if yes, add the constraint to the map.
                for (unsigned primaryDofIdx = 0;
                     primaryDofIdx < elemCtx.numPrimaryDof(/*timeIdx=*/0);
                     ++primaryDofIdx)
                {
                    Constraints constraints;
                    elemCtx.problem().constraints(constraints,
                                                  elemCtx,
                                                  primaryDofIdx,
                                                  /*timeIdx=*/0);
                    if (constraints.isActive()) {
                        const unsigned globI = elemCtx.globalSpaceIndex(primaryDofIdx, /*timeIdx=*/0);
                        constraintsMap_[globI] = constraints;
                        continue;
                    }
                }
            }
        }
    }
 
    // linearize the whole or part of the system
    template <class SubDomainType>
    void linearize_(const SubDomainType& domain)
    {
        OPM_TIMEBLOCK(linearize_);
 
        // We do not call resetSystem_() here, since that will set
        // the full system to zero, not just our part.
        // Instead, that must be called before starting the linearization.
 
        // before the first iteration of each time step, we need to update the
        // constraints. (i.e., we assume that constraints can be time dependent, but they
        // can't depend on the solution.)
        if (model_().newtonMethod().numIterations() == 0) {
            updateConstraintsMap_();
        }
 
        applyConstraintsToSolution_();
 
        // to avoid a race condition if two threads handle an exception at the same time,
        // we use an explicit lock to control access to the exception storage object
        // amongst thread-local handlers
        std::mutex exceptionLock;
 
        // storage to any exception that needs to be bridged out of the
        // parallel block below. initialized to null to indicate no exception
        std::exception_ptr exceptionPtr = nullptr;
 
        // relinearize the elements...
        using GridViewType = decltype(domain.view);
        ThreadedEntityIterator<GridViewType, /*codim=*/0> threadedElemIt(domain.view);
#ifdef _OPENMP
#pragma omp parallel
#endif
        {
            auto elemIt = threadedElemIt.beginParallel();
            auto nextElemIt = elemIt;
            try {
                for (; !threadedElemIt.isFinished(elemIt); elemIt = nextElemIt) {
                    // give the model and the problem a chance to prefetch the data required
                    // to linearize the next element, but only if we need to consider it
                    nextElemIt = threadedElemIt.increment();
                    if (!threadedElemIt.isFinished(nextElemIt)) {
                        const auto& nextElem = *nextElemIt;
                        if (linearizeNonLocalElements ||
                            nextElem.partitionType() == Dune::InteriorEntity)
                        {
                            model_().prefetch(nextElem);
                            problem_().prefetch(nextElem);
                        }
                    }
 
                    const auto& elem = *elemIt;
                    if (!linearizeNonLocalElements && elem.partitionType() != Dune::InteriorEntity) {
                        continue;
                    }
 
                    linearizeElement_(elem);
                }
            }
            // If an exception occurs in the parallel block, it won't escape the
            // block; terminate() is called instead of a handler outside!  hence, we
            // tuck any exceptions that occur away in the pointer. If an exception
            // occurs in more than one thread at the same time, we must pick one of
            // them to be rethrown as we cannot have two active exceptions at the
            // same time. This solution essentially picks one at random. This will
            // only be a problem if two different kinds of exceptions are thrown, for
            // instance if one thread experiences a (recoverable) numerical issue
            // while another is out of memory.
            catch(...) {
                std::lock_guard<std::mutex> take(exceptionLock);
                exceptionPtr = std::current_exception();
                threadedElemIt.setFinished();
            }
        }  // parallel block
 
        // after reduction from the parallel block, exceptionPtr will point to
        // a valid exception if one occurred in one of the threads; rethrow
        // it here to let the outer handler take care of it properly
        if (exceptionPtr) {
            std::rethrow_exception(exceptionPtr);
        }
 
        applyConstraintsToLinearization_();
    }
 
    // linearize an element in the interior of the process' grid partition
    template <class ElementType>
    void linearizeElement_(const ElementType& elem)
    {
        const unsigned threadId = ThreadManager::threadId();
 
        ElementContext& elementCtx = *elementCtx_[threadId];
        auto& localLinearizer = model_().localLinearizer(threadId);
 
        // the actual work of linearization is done by the local linearizer class
        localLinearizer.linearize(elementCtx, elem);
 
        // update the right hand side and the Jacobian matrix
        if (getPropValue<TypeTag, Properties::UseLinearizationLock>()) {
            globalMatrixMutex_.lock();
        }
 
        const std::size_t numPrimaryDof = elementCtx.numPrimaryDof(/*timeIdx=*/0);
        for (unsigned primaryDofIdx = 0; primaryDofIdx < numPrimaryDof; ++primaryDofIdx) {
            const unsigned globI = elementCtx.globalSpaceIndex(/*spaceIdx=*/primaryDofIdx, /*timeIdx=*/0);
 
            // update the right hand side
            residual_[globI] += localLinearizer.residual(primaryDofIdx);
 
            // update the global Jacobian matrix
            for (unsigned dofIdx = 0; dofIdx < elementCtx.numDof(/*timeIdx=*/0); ++dofIdx) {
                const unsigned globJ = elementCtx.globalSpaceIndex(/*spaceIdx=*/dofIdx, /*timeIdx=*/0);
 
                jacobian_->addToBlock(globJ, globI, localLinearizer.jacobian(dofIdx, primaryDofIdx));
            }
        }
 
        if (getPropValue<TypeTag, Properties::UseLinearizationLock>()) {
            globalMatrixMutex_.unlock();
        }
    }
 
    // apply the constraints to the solution. (i.e., the solution of constraint degrees
    // of freedom is set to the value of the constraint.)
    void applyConstraintsToSolution_()
    {
        if (!enableConstraints_()) {
            return;
        }
 
        // TODO: assuming a history size of 2 only works for Euler time discretizations!
        auto& sol = model_().solution(/*timeIdx=*/0);
        auto& oldSol = model_().solution(/*timeIdx=*/1);
 
        for (const auto& constraint : constraintsMap_) {
            sol[constraint.first] = constraint.second;
            oldSol[constraint.first] = constraint.second;
        }
    }
 
    // apply the constraints to the linearization. (i.e., for constrain degrees of
    // freedom the Jacobian matrix maps to identity and the residual is zero)
    void applyConstraintsToLinearization_()
    {
        if (!enableConstraints_()) {
            return;
        }
 
        for (const auto& constraint : constraintsMap_) {
            // reset the column of the Jacobian matrix
            // put an identity matrix on the main diagonal of the Jacobian
            jacobian_->clearRow(constraint.first, Scalar(1.0));
 
            // make the right-hand side of constraint DOFs zero
            residual_[constraint.first] = 0.0;
        }
    }
 
    static bool enableConstraints_()
    { return getPropValue<TypeTag, Properties::EnableConstraints>(); }
 
    Simulator* simulatorPtr_{};
    std::vector<std::unique_ptr<ElementContext>> elementCtx_;
 
    // The constraint equations (only non-empty if the
    // EnableConstraints property is true)
    std::map<unsigned, Constraints> constraintsMap_;
 
    struct FlowInfo
    {
        int faceId;
        VectorBlock flow;
        unsigned int nncId;
    };
    SparseTable<FlowInfo> flowsInfo_;
    SparseTable<FlowInfo> floresInfo_;
 
    // the jacobian matrix
    std::unique_ptr<SparseMatrixAdapter> jacobian_;
 
    // the right-hand side
    GlobalEqVector residual_;
 
    LinearizationType linearizationType_;
 
    std::mutex globalMatrixMutex_;
 
    std::vector<std::set<unsigned int>> sparsityPattern_;
 
    struct FullDomain
    {
        explicit FullDomain(const GridView& v) : view (v) {}
        GridView view;
        std::vector<bool> interior; // Should remain empty.
    };
    // Simple domain object used for full-domain linearization, it allows
    // us to have the same interface for sub-domain and full-domain work.
    // Pointer since it must defer construction, due to GridView member.
    std::unique_ptr<FullDomain> fullDomain_;
};
 
} // namespace Opm
 
#endif