TRUSTSchema_RK.tpp

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#ifndef TRUSTSchema_RK_TPP_included
#define TRUSTSchema_RK_TPP_included
 
template <Ordre_RK _ORDRE_ > template<Ordre_RK _O_>
std::enable_if_t<_O_ == Ordre_RK::DEUX_WILLIAMSON || _O_ == Ordre_RK::TROIS_WILLIAMSON || _O_ == Ordre_RK::QUATRE_WILLIAMSON, int>
TRUSTSchema_RK<_ORDRE_>::faire_un_pas_de_temps_eqn_base_generique(Equation_base& eqn)
{
  static constexpr int NB_PTS = (_ORDRE_ == Ordre_RK::DEUX_WILLIAMSON) ? 2 : 3;
 
  // Warning on the first 100 time steps if facsec equals 1 to prompt the user to reconsider
  if (nb_pas_dt() >= 0 && nb_pas_dt() <= NW && facsec_ == 1) print_warning(NW);
 
  DoubleTab& xi = eqn.inconnue().valeurs(), &xip1 = eqn.inconnue().futur();
  DoubleTrav present(xi), qi(xi);
  present = xi;
  qi = xi;
 
  for (int i = 0; i < NB_PTS; i++)
    {
      // compute: q_i = a_{i-1} * q_{i-1} + dt * f(x_{i-1})
      qi *= get_a<_ORDRE_,NB_PTS>()[i];
      qi.ajoute(dt_, eqn.derivee_en_temps_inco(xip1));
 
      // compute: x_i = x_{i-1} + b_i * q_i
      xi.ajoute(get_b<_ORDRE_,NB_PTS>()[i], qi);
    }
 
  xip1 = xi;
  xi -= present;
  xi /= dt_;
  update_critere_statio(xi, eqn);
 
  // Update boundary condition on futur:
  eqn.domaine_Cl_dis().imposer_cond_lim(eqn.inconnue(), temps_courant() + pas_de_temps());
  xip1.echange_espace_virtuel();
 
  // xi = x0;
  xi = present;
 
  return 1;
}
 
template <Ordre_RK _ORDRE_ > template<Ordre_RK _O_>
std::enable_if_t<_O_ == Ordre_RK::DEUX_CLASSIQUE || _O_ == Ordre_RK::TROIS_CLASSIQUE || _O_ == Ordre_RK::QUATRE_CLASSIQUE || _O_ == Ordre_RK::QUATRE_CLASSIQUE_3_8, int>
TRUSTSchema_RK<_ORDRE_>::faire_un_pas_de_temps_eqn_base_generique(Equation_base& eqn)
{
  // Warning on the first 100 time steps if facsec equals 1 to prompt the user to reconsider
  if (nb_pas_dt() >= 0 && nb_pas_dt() <= NW && facsec_ == 1) print_warning(NW);
 
  static constexpr bool IS_DEUX = (_O_ == Ordre_RK::DEUX_CLASSIQUE) , IS_TROIS = (_O_ == Ordre_RK::TROIS_CLASSIQUE), IS_QUATRE = (_O_ == Ordre_RK::QUATRE_CLASSIQUE);
  static constexpr int NB_PTS = IS_DEUX ? 2 : ( IS_TROIS ? 3 : 4);
  static constexpr int NB_BUTCHER = IS_DEUX ? 0 : ( IS_TROIS ? 1 : ( IS_QUATRE ? 2 : 3 ));
 
  DoubleTab& present = eqn.inconnue().valeurs(), &futur = eqn.inconnue().futur();
  if (ki_.size()!=NB_PTS)
    {
      ki_.resize(NB_PTS);
      // just for initializing the array structure ...
      for (int i = 0; i < NB_PTS; i++) ki_[i] = present;
    }
 
  DoubleTrav sauv(present);
  sauv = present; // sauv = y0
 
  // Step 1
  eqn.derivee_en_temps_inco(ki_[0]); // ki[0] = f(y0)
  ki_[0] *= dt_; // ki[0] = h * f(y0)
 
  for (int step = 1; step < NB_PTS; step++ ) // ATTENTION : ne touche pas !
    {
      present = sauv; // back to y0
      for (int i = 0; i < step; i++) present.ajoute(get_butcher_coeff<_ORDRE_,NB_PTS-1>().at(step-1).at(i), ki_[i]); // Et ouiiiiiiii :-)
 
      eqn.derivee_en_temps_inco(ki_[step]);
      ki_[step] *= dt_;
    }
 
  futur = sauv; // futur = y1 = y0
  for (int i = 0; i < NB_PTS; i++) futur.ajoute(BUTCHER_TAB.at(NB_BUTCHER).at(i), ki_[i]);
 
  update_critere_statio(futur, eqn);
 
  // Update boundary condition on futur:
  eqn.domaine_Cl_dis().imposer_cond_lim(eqn.inconnue(), temps_courant() + pas_de_temps());
  futur.echange_espace_virtuel();
 
  present = sauv; // back to y0
 
  return 1;
}
 
#endif /* TRUSTSchema_RK_TPP_included */