multistagetimestepper.hh 5.96 KB
 Dennis Gläser committed Mar 24, 2021 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 // -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- // vi: set et ts=4 sw=4 sts=4: /***************************************************************************** * See the file COPYING for full copying permissions. * * * * This program 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. * * * * This program 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 this program. If not, see . * *****************************************************************************/ /*! * \file  Melanie Lipp committed May 04, 2021 21  * \ingroup TimeStepping  Dennis Gläser committed Mar 24, 2021 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125  * \brief A time stepper performing a single time step of a transient simulation */ #ifndef DUMUX_TIMESTEPPING_MULTISTAGE_TIMESTEPPER_HH #define DUMUX_TIMESTEPPING_MULTISTAGE_TIMESTEPPER_HH #include #include #include namespace Dumux::Experimental { //! forward declaration template class MultiStageMethod; //! Data object for the parameters of a given stage template class MultiStageParams { struct Params { Scalar alpha, betaDt, timeAtStage, dtFraction; bool skipTemporal, skipSpatial; }; public: //! Extract params for stage i from method m MultiStageParams(const MultiStageMethod& m, std::size_t i, const Scalar t, const Scalar dt) : size_(i+1) { params_.resize(size_); for (std::size_t k = 0; k < size_; ++k) { auto& p = params_[k]; p.alpha = m.temporalWeight(i, k); p.betaDt = m.spatialWeight(i, k)*dt; p.timeAtStage = t + m.timeStepWeight(k)*dt; p.dtFraction = m.timeStepWeight(k); using std::abs; p.skipTemporal = (abs(p.alpha) < 1e-6); p.skipSpatial = (abs(p.betaDt) < 1e-6); } } std::size_t size () const { return size_; } //! weights of the temporal operator residual (\f$\alpha_{ik} \f$) Scalar temporalWeight (std::size_t k) const { return params_[k].alpha; } //! weights of the spatial operator residual (\f$\beta_{ik} \f$) Scalar spatialWeight (std::size_t k) const { return params_[k].betaDt; } //! the time at which we have to evaluate the operators Scalar timeAtStage (std::size_t k) const { return params_[k].timeAtStage; } //! the fraction of a time step corresponding to the k-th stage Scalar timeStepFraction (std::size_t k) const { return params_[k].dtFraction; } //! If \f$\alpha_{ik} = 0\f$ Scalar skipTemporal (std::size_t k) const { return params_[k].skipTemporal; } //! If \f$\beta_{ik} = 0\f$ Scalar skipSpatial (std::size_t k) const { return params_[k].skipSpatial; } private: std::size_t size_; std::vector params_; }; /*! * \brief Time stepping with a multi-stage method * \note We limit ourselves to "diagonally" implicit multi-stage methods where solving * a stage can only depend on the values of the same stage and stages before * but not future stages (which would require solving larger linear systems) */ template class MultiStageTimeStepper { using Variables = typename PDESolver::Variables; using Scalar = typename Variables::Scalar; using StageParams = MultiStageParams; public: /*! * \brief The constructor * \param pdeSolver Solver class for solving a PDE in each stage * \param msMethod The multi-stage method which is to be used for time integration * \todo TODO: Add time step control if the pde solver doesn't converge */ MultiStageTimeStepper(std::shared_ptr pdeSolver, std::shared_ptr> msMethod) : pdeSolver_(pdeSolver) , msMethod_(msMethod) {} /*! * \brief Advance one time step of the given time loop  Melanie Lipp committed Apr 07, 2021 126  * \param vars The variables object at the current time level.  Dennis Gläser committed Mar 24, 2021 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166  * \param t The current time level * \param dt The time step size to be used * \note We expect the time level in vars to correspond to the given time t * \todo: TODO: Add time step control if the pde solver doesn't converge */ void step(Variables& vars, const Scalar t, const Scalar dt) { // make sure there are no traces of previous stages pdeSolver_->assembler().clearStages(); for (auto stageIdx = 1UL; stageIdx <= msMethod_->numStages(); ++stageIdx) { // extract parameters for this stage from the time stepping method auto stageParams = std::make_shared(*msMethod_, stageIdx, t, dt); // prepare the assembler for this stage pdeSolver_->assembler().prepareStage(vars, stageParams); // assemble & solve pdeSolver_->solve(vars); } // clear traces of previously registered stages pdeSolver_->assembler().clearStages(); } /*! * \brief Set/change the time step method */ void setMethod(std::shared_ptr> msMethod) { msMethod_ = msMethod; } private: std::shared_ptr pdeSolver_; std::shared_ptr> msMethod_; }; } // end namespace Dumux::Experimental #endif