simple_integrator_impl.hpp

Go to the documentation of this file.

/*
 * SPDX-FileCopyrightText: Copyright (c) 2025:  Goethe University Frankfurt
 * SPDX-License-Identifier: LicenseRef-UG4-LGPL-3.0
 *
 * Author: Arne Naegel
 * 
 * This file is part of UG4.
 * 
 * UG4 is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 3 (as published by the
 * Free Software Foundation) with the following additional attribution
 * requirements (according to LGPL/GPL v3 §7):
 * 
 * (1) The following notice must be displayed in the Appropriate Legal Notices
 * of covered and combined works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (2) The following notice must be displayed at a prominent place in the
 * terminal output of covered works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (3) The following bibliography is recommended for citation and must be
 * preserved in all covered files:
 * "Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G. A massively
 *   parallel geometric multigrid solver on hierarchically distributed grids.
 *   Computing and visualization in science 16, 4 (2013), 151-164"
 * "Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G. UG4 -- a novel
 *   flexible software system for simulating pde based models on high performance
 *   computers. Computing and visualization in science 16, 4 (2013), 165-179"
 * 
 * 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 Lesser General Public License for more details.
 */
 
#ifndef __H__LIMEX__SIMPLE_INTEGRATOR_IMPL_HPP__
#define __H__LIMEX__SIMPLE_INTEGRATOR_IMPL_HPP__
 
namespace ug {
 
template<typename TDomain, typename TAlgebra>
bool SimpleTimeIntegrator<TDomain, TAlgebra>::apply_single_stage
(
  SmartPtr<grid_function_type> u1,
  number t1,
  ConstSmartPtr<grid_function_type> u0,
  number t0
)
{
  LIMEX_PROFILE_FUNC()
 
  // short-cuts
  GridLevel const &gl = u0->grid_level();
  time_disc_type &tdisc = *tdisc_dep_type::m_spTimeDisc;
  typename base_type::solver_type &solver = *base_type::m_spSolver;
 
  // create solution vector & right hand side
  SmartPtr<grid_function_type> uold;
 
  // init solution time series
  SmartPtr<vector_time_series_type> m_spSolTimeSeries;        
  m_spSolTimeSeries=make_sp(new vector_time_series_type());
  m_spSolTimeSeries->clear();
  m_spSolTimeSeries->push(u0->clone(), t0);
 
  // init solver (and matrix operator)
  SmartPtr<typename base_type::assembled_operator_type> spAssOp;
  spAssOp = make_sp(new typename base_type::assembled_operator_type(tdisc_dep_type::m_spTimeDisc, gl));
  solver.init(spAssOp);
 
  // integrate
  double t = t0;
  number currdt = base_type::m_dt;
  int step = 1;
 
  double final_dt = base_type::m_dt;
 
  if(!base_type::m_bNoLogOut)
    UG_LOG("+++ Integrating: [\t"<< t0 <<"\t, \t"<< t1 <<"\t] with\t" << currdt <<"\n");
 
  while(!hasTerminated(t, t0, t1)) {
    if(!base_type::m_bNoLogOut)
      UG_LOG("+++ Timestep +++" << step << "\n");
      
    if (this->debug_writer_valid())
    {
      char debug_name_ext[16]; snprintf(debug_name_ext, 16, "%04d", step);
      this->enter_debug_writer_section(std::string("SimpleTimeIntegrator_step") + debug_name_ext);
    }
 
    // determine step size
    UG_COND_THROW(currdt < base_type::get_dt_min(), "Time step size below minimum. ABORTING!")
      number dt = std::min(currdt, t1-t);
    final_dt = dt;
 
    // prepare step
    tdisc.prepare_step(m_spSolTimeSeries, dt);
    if (solver.prepare(*u1) == false)
    {
      if(!base_type::m_bNoLogOut)
        UG_LOG("Initialization failed! RETRY");
 
      currdt *= base_type::get_reduction_factor();
      continue;
    }
    //UG_LOG("m_spSolTimeSeries.size="<< m_spSolTimeSeries->size());
 
    // execute step
    if (solver.apply(*u1))
    {
      //
      // ACCEPT step
      //
 
      // post prcess (e.g. physics)
      if(!base_type::m_bNoLogOut)
      {
        // m_spSolTimeSeries->oldest() actually holds a pointer to a grid function
        // but as the time series does not know this, we have to cast ourselves
        // SmartPtr<grid_function_type> tmpOld = m_spSolTimeSeries->oldest().template cast_static<grid_function_type>();
        this->notify_finalize_step(u1, step, t+dt, dt);
      }
 
      // update time
      t += dt;
 
      // push updated solution into time series (and continue)
      //SmartPtr<typename base_type::vector_type> utmp = m_spSolTimeSeries->oldest();
      //VecAssign(*utmp, static_cast<typename base_type::vector_type> (*u1) );
      uold = m_spSolTimeSeries->push_discard_oldest(u1->clone(), t).template cast_static<grid_function_type>();
      }
    else
    {
      //
      // REJECT step
      //
      UG_LOG("Solution failed! RETRY");
      currdt *= base_type::get_reduction_factor();
      continue;
    }
 
    // consistency check
    if (step == 1 && m_spDerivative.valid())
    {
      UG_LOG("Computing consistency error: "<< std::endl);
      UG_ASSERT(static_cast<typename base_type::vector_type*> (&*u1) != &(*u0),
          "Huhh: Different vectors required!");
      *m_spDerivative = *u0;
      m_initial_consistency_error = m_spBanachSpace->distance(*m_spDerivative, *u1);
    }
 
    if (this->debug_writer_valid())
    {
      this->leave_debug_writer_section();
      char debug_name_ext[16]; snprintf(debug_name_ext, 16, "%04d", step);
      this->write_debug(*u1, std::string("TimeSolution_step") + debug_name_ext);
    }
 
    step++;
    // tdisc.finish_step_elem(m_spSolTimeSeries, dt);
  }
 
  if(base_type::m_bNoLogOut)
  {
    this->notify_finalize_step(u1, /*uold,*/ step, t, final_dt);
  }
 
 
  if (m_spDerivative.valid())
  {
 
    //
    // approximate derivative (by forward difference)
    //
    UG_ASSERT(static_cast<typename base_type::vector_type*> (&*u1) != &(*uold),
          "Huhh: Different vectors required!");
 
    VecScaleAdd(static_cast<typename TAlgebra::vector_type&>(*m_spDerivative),
        1.0/final_dt, static_cast<typename TAlgebra::vector_type&>(*u1),
        -1.0/final_dt, static_cast<typename TAlgebra::vector_type&>(*uold));
 
  }
 
  m_spSolTimeSeries->clear();
 
  return true;
 
};
bool SimpleTimeIntegrator<TDomain, TAlgebra>::apply_single_stage {…}
 
template<typename TDomain, typename TAlgebra>
bool SimpleTimeIntegrator<TDomain, TAlgebra>::apply_multi_stage
(
  SmartPtr<grid_function_type> u1,
  number t1,
  ConstSmartPtr<grid_function_type> u0,
  number t0
)
{
 
  LIMEX_PROFILE_FUNC()
 
  // short-cuts
  GridLevel const &gl = u0->grid_level();
  time_disc_type &tdisc = *tdisc_dep_type::m_spTimeDisc;
  typename base_type::solver_type &solver = *base_type::m_spSolver;
 
  //using TimeIntegratorSubject<TDomain,TAlgebra>::notify_step_postprocess;
 
  // create solution vector & right hand side
  SmartPtr<grid_function_type> uold = u0->clone();
 
  // init solution time series
  SmartPtr<vector_time_series_type> m_spSolTimeSeries;
  m_spSolTimeSeries=make_sp(new vector_time_series_type());
  m_spSolTimeSeries->clear();
  m_spSolTimeSeries->push(u0->clone(), t0);
 
  // init solver (and matrix operator)
  SmartPtr<typename base_type::assembled_operator_type> spAssOp=make_sp(new typename base_type::assembled_operator_type(tdisc_dep_type::m_spTimeDisc, gl));
  solver.init(spAssOp);
 
  // integrate
  double t = t0;
  number currdt = base_type::m_dt;
  int step = 1;
 
  double final_dt = base_type::m_dt;
 
  if(!base_type::m_bNoLogOut)
    UG_LOG("+++ Integrating: ["<< t0 <<", "<< t1 <<"] with " << currdt <<"\n");
 
  while(!hasTerminated(t, t0, t1))
  {
    if(!base_type::m_bNoLogOut)
      UG_LOG("++++++ TIMESTEP " << step++ << " BEGIN (current time: " << t << ") ++++++\n");
 
    // determine step size
    UG_COND_THROW(currdt < base_type::get_dt_min(), "Time step size below minimum. ABORTING!")
    number dt = std::min(currdt, t1-t);
 
    final_dt = dt;
 
    double told = t;
 
    const int num_stages = tdisc.num_stages();
    int s=1;
    do // 'for-each-stage' loop
    { 
 
      // for (int s=1; s<=num_stages; ++s)
      if(!base_type::m_bNoLogOut)
        UG_LOG("+++ STAGE "<< s << " BEGIN +++\n");
 
      // set stage
      tdisc.set_stage(s);
 
      // prepare step
      tdisc.prepare_step(m_spSolTimeSeries, dt);
      if (solver.prepare(*u1) == false) break;
 
      // execute step
      if (!solver.apply(*u1)) break;
 
      // stage was successful:
      // a. update (intermediate) time
      t = tdisc.future_time();
 
      // b. push updated solution into time series (and continue)
      SmartPtr<typename base_type::vector_type> oldest= m_spSolTimeSeries->oldest();
      VecAssign(*oldest, static_cast<typename base_type::vector_type> (*u1));
      m_spSolTimeSeries->push_discard_oldest(oldest, t);
 
      // c. output
      if(!base_type::m_bNoLogOut)
        UG_LOG("+++ STAGE "<< s << " END +++\n");
 
    } while ((++s) <=num_stages);
 
 
    if (s<=num_stages)
    {
      // REJECT time step
      if(!base_type::m_bNoLogOut)
        UG_LOG("Solution failed! RETRY");
 
      currdt *= this->get_reduction_factor();
      t = told;
      continue;
    }
    else
    {
      if(!base_type::m_bNoLogOut)
      {
        this->notify_finalize_step(u1, /*uold, */step, t, dt);
      }
 
      // ACCEPT time step
      if (!hasTerminated(t, t0, t1))
        *uold = *u1;   // save solution (but not in last step)
      // tdisc.finish_step_elem(m_spSolTimeSeries, dt);
 
      if(!base_type::m_bNoLogOut)
        UG_LOG("++++++ TIMESTEP " << step++ << " END   (current time: " << t << ") ++++++\n");
    }
  }
 
  if(base_type::m_bNoLogOut)
  {
    this->notify_finalize_step(u1, /*uold,*/ step, t, final_dt);
  }
  return true;
};
bool SimpleTimeIntegrator<TDomain, TAlgebra>::apply_multi_stage {…}
 
} // ug
 
#endif // __H__LIMEX__SIMPLE_INTEGRATOR_IMPL_HPP__