linear/pdesolver.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-FileCopyrightInfo: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
// SPDX-License-Identifier: GPL-3.0-or-later
//
#ifndef DUMUX_LINEAR_PDE_SOLVER_HH
#define DUMUX_LINEAR_PDE_SOLVER_HH
 
#include <cmath>
#include <memory>
#include <iostream>
#include <type_traits>
 
#include <dune/common/timer.hh>
#include <dune/common/exceptions.hh>
#include <dune/common/parallel/mpicommunication.hh>
#include <dune/common/parallel/mpihelper.hh>
#include <dune/common/std/type_traits.hh>
#include <dune/istl/bvector.hh>
#include <dune/istl/multitypeblockvector.hh>
 
#include <dumux/common/parameters.hh>
#include <dumux/common/exceptions.hh>
#include <dumux/common/typetraits/vector.hh>
#include <dumux/common/timeloop.hh>
#include <dumux/common/pdesolver.hh>
#include <dumux/common/variablesbackend.hh>
 
#include <dumux/linear/matrixconverter.hh>
 
namespace Dumux::Detail::LinearPDESolver {
 
template <class Solver, class Matrix>
using SetMatrixDetector = decltype(std::declval<Solver>().setMatrix(std::declval<std::shared_ptr<Matrix>>()));
 
template<class Solver, class Matrix>
static constexpr bool linearSolverHasSetMatrix()
{ return Dune::Std::is_detected<SetMatrixDetector, Solver, Matrix>::value; }
 
} // end namespace Dumux::Detail::LinearPDESolver
 
namespace Dumux {
 
template <class Assembler, class LinearSolver,
          class Comm = Dune::Communication<Dune::MPIHelper::MPICommunicator>>
class LinearPDESolver : public PDESolver<Assembler, LinearSolver>
{
    using ParentType = PDESolver<Assembler, LinearSolver>;
    using Scalar = typename Assembler::Scalar;
    using JacobianMatrix = typename Assembler::JacobianMatrix;
    using SolutionVector = typename Assembler::SolutionVector;
    using ResidualVector = typename Assembler::ResidualType;
    using TimeLoop = TimeLoopBase<Scalar>;
    using Backend = VariablesBackend<typename ParentType::Variables>;
    using LinearAlgebraNativeBackend = VariablesBackend<ResidualVector>;
    static constexpr bool assemblerExportsVariables = Detail::PDESolver::assemblerExportsVariables<Assembler>;
 
public:
    using typename ParentType::Variables;
    using Communication = Comm;
 
    LinearPDESolver(std::shared_ptr<Assembler> assembler,
                    std::shared_ptr<LinearSolver> linearSolver,
                    const Communication& comm = Dune::MPIHelper::getCommunication(),
                    const std::string& paramGroup = "")
    : ParentType(assembler, linearSolver)
    , paramGroup_(paramGroup)
    , reuseMatrix_(false)
    , comm_(comm)
    {
        initParams_(paramGroup);
 
        // set the linear system (matrix & residual) in the assembler
        this->assembler().setLinearSystem();
    }
 
    LinearPDESolver(std::shared_ptr<Assembler> assembler,
                    std::shared_ptr<LinearSolver> linearSolver,
                    const std::string& paramGroup)
    : LinearPDESolver(assembler, linearSolver, Dune::MPIHelper::getCommunication(), paramGroup)
    {}
 
    bool apply(Variables& vars) override
    {
        Dune::Timer assembleTimer(false);
        Dune::Timer solveTimer(false);
        Dune::Timer updateTimer(false);
 
        if (verbosity_ >= 1 && enableDynamicOutput_)
            std::cout << "Assemble: r(x^k) = dS/dt + div F - q;   M = grad r"
                      << std::flush;
 
        // assemble
 
        // linearize the problem at the current solution
        assembleTimer.start();
        if (reuseMatrix_)
            this->assembler().assembleResidual(vars);
        else
            this->assembler().assembleJacobianAndResidual(vars);
        assembleTimer.stop();
 
        // linear solve
 
        // Clear the current line using an ansi escape
        // sequence.  for an explanation see
        // http://en.wikipedia.org/wiki/ANSI_escape_code
        const char clearRemainingLine[] = { 0x1b, '[', 'K', 0 };
 
        if (verbosity_ >= 1 && enableDynamicOutput_)
            std::cout << "\rSolve: M deltax^k = r"
                      << clearRemainingLine << std::flush;
 
        // solve the resulting linear equation system
        solveTimer.start();
 
        // set the delta vector to zero
        ResidualVector deltaU = LinearAlgebraNativeBackend::zeros(Backend::size(Backend::dofs(vars)));
 
        // solve by calling the appropriate implementation depending on whether the linear solver
        // is capable of handling MultiType matrices or not
        bool converged = solveLinearSystem_(deltaU);
        solveTimer.stop();
 
        if (!converged)
            return false;
 
        // update
        if (verbosity_ >= 1 && enableDynamicOutput_)
            std::cout << "\rUpdate: x^(k+1) = x^k - deltax^k"
                      << clearRemainingLine << std::flush;
 
        // update the current solution and secondary variables
        updateTimer.start();
        auto uCurrent = Backend::dofs(vars);
        Backend::axpy(-1.0, deltaU, uCurrent);
        Backend::update(vars, uCurrent);
        if constexpr (!assemblerExportsVariables)
            this->assembler().updateGridVariables(Backend::dofs(vars));
        updateTimer.stop();
 
        if (verbosity_ >= 1)
        {
            const auto elapsedTot = assembleTimer.elapsed() + solveTimer.elapsed() + updateTimer.elapsed();
            if (enableDynamicOutput_)
                std::cout << '\r';
            std::cout << "Assemble/solve/update time: "
                      <<  assembleTimer.elapsed() << "(" << 100*assembleTimer.elapsed()/elapsedTot << "%)/"
                      <<  solveTimer.elapsed() << "(" << 100*solveTimer.elapsed()/elapsedTot << "%)/"
                      <<  updateTimer.elapsed() << "(" << 100*updateTimer.elapsed()/elapsedTot << "%)"
                      << "\n";
        }
 
        return true;
    }
 
    void solve(Variables& vars) override
    {
        bool converged = apply(vars);
        if (!converged)
            DUNE_THROW(NumericalProblem, "Linear solver didn't converge.\n");
    }
 
    void report(std::ostream& sout = std::cout) const
    {}
 
    Scalar suggestTimeStepSize(Scalar oldTimeStep) const
    {
        return oldTimeStep;
    }
 
    void setVerbosity(int val)
    { verbosity_ = val; }
 
    int verbosity() const
    { return verbosity_ ; }
 
    const std::string& paramGroup() const
    { return paramGroup_; }
 
    void reuseMatrix(bool reuse = true)
    {
        reuseMatrix_ = reuse;
 
        if constexpr (Detail::LinearPDESolver::linearSolverHasSetMatrix<LinearSolver, JacobianMatrix>())
            if (reuseMatrix_)
                this->linearSolver().setMatrix(this->assembler().jacobian());
    }
 
private:
 
    virtual bool solveLinearSystem_(ResidualVector& deltaU)
    {
        if constexpr (Detail::LinearPDESolver::linearSolverHasSetMatrix<LinearSolver, JacobianMatrix>())
        {
            if (reuseMatrix_)
                return this->linearSolver().solve(deltaU, this->assembler().residual());
        }
        else
        {
            if (reuseMatrix_ && comm_.size() > 1)
                DUNE_THROW(Dune::NotImplemented,
                    "Reuse matrix for parallel runs with a solver that doesn't support the setMatrix interface"
                );
        }
 
        assert(this->checkSizesOfSubMatrices(this->assembler().jacobian()) && "Matrix blocks have wrong sizes!");
 
        return this->linearSolver().solve(
            this->assembler().jacobian(),
            deltaU,
            this->assembler().residual()
        );
    }
 
    void initParams_(const std::string& group = "")
    {
        verbosity_ = comm_.rank() == 0 ? getParamFromGroup<int>(group, "LinearPDESolver.Verbosity", 2) : 0;
        enableDynamicOutput_ = getParamFromGroup<bool>(group, "LinearPDESolver.EnableDynamicOutput", true);
    }
 
    int verbosity_;
 
    bool enableDynamicOutput_;
 
    std::string paramGroup_;
 
    bool reuseMatrix_;
 
    Communication comm_;
};
 
} // end namespace Dumux
 
#endif