Leap_frog.cpp

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#include <Domaine_Cl_dis_base.h>
#include <Equation_base.h>
#include <Leap_frog.h>
 
Implemente_instanciable(Leap_frog,"Leap_frog",Schema_Temps_base);
// XD leap_frog schema_temps_base leap_frog INHERITS_BRACE This is the leap-frog scheme.
 
Sortie& Leap_frog::printOn(Sortie& s) const
{
  return  Schema_Temps_base::printOn(s);
}
 
Entree& Leap_frog::readOn(Entree& s)
{
  return Schema_Temps_base::readOn(s) ;
}
 
////////////////////////////////
//                            //
// Schema characteristics     //
//                            //
////////////////////////////////
 
 
/*! @brief Returns the number of temporal values to keep.
 *
 * Here: n-2, n-1, n, and n+1, so 4.
 *
 */
int Leap_frog::nb_valeurs_temporelles() const
{
  return 4;
}
 
/*! @brief Returns the number of future temporal values.
 *
 * Here: n+1, so 1.
 *
 */
int Leap_frog::nb_valeurs_futures() const
{
  return 1 ;
}
 
/*! @brief Returns the time at the i-th future value.
 *
 * Here: t(n+1)
 *
 */
double Leap_frog::temps_futur(int i) const
{
  assert(i==1);
  return temps_courant()+pas_de_temps();
}
 
/*! @brief Returns the time that fields must return when valeurs() is called.
 *
 *     Here: t(n+1)
 *
 */
double Leap_frog::temps_defaut() const
{
  return temps_courant()+pas_de_temps();
}
 
/////////////////////////////////////////
//                                     //
// End of schema characteristics       //
//                                     //
/////////////////////////////////////////
 
 
/*! @brief Performs a Leap_frog time step on the equation passed as parameter.
 *
 * @param (Equation_base& eq) the equation to advance by one time step
 * @return (int) always returns 1
 */
int Leap_frog::faire_un_pas_de_temps_eqn_base(Equation_base& eq)
{
  // EXAMPLE FOR AN EXPLICIT SCHEME USING U(n) and U(n+1)
  // Un+1=Un+dt*F
  //  Un
  DoubleTab& present = eq.inconnue().valeurs();
 
  // Un+1
  DoubleTab& futur = eq.inconnue().futur();
 
  // Un+1=F
  eq.derivee_en_temps_inco(futur);
  futur.echange_espace_virtuel();
 
  // WRITE HERE THE COMPUTATION OF U(n+1) AS A FUNCTION OF U(n) AND OF derivee
  // futur*=dt; Un+1=dt*F
  // futur+=present; Un+1=Un+dt*F
  // IF IT WERE A SCHEME INVOLVING U(n-1)
  //    if ((nb_pas_dt_>4) && ((nb_pas_dt_ % 10) != 0)) {
  // if (nb_pas_dt_>4) {
  if ((nb_pas_dt_>4) && ((nb_pas_dt_ % 10) != 0))
    {
      DoubleTab& passe = eq.inconnue().passe();
      double gamma=0.2;
      DoubleTab& passe2 = eq.inconnue().passe(2);
      DoubleTab& correcteur=passe;
      correcteur*=(1.-2.*gamma);
      correcteur.ajoute(gamma, present, VECT_REAL_ITEMS);
      correcteur.ajoute(gamma, passe2, VECT_REAL_ITEMS);
      futur*=(2*dt_);
      futur+=correcteur;
    }
  else
    {
      futur*=dt_;
      futur+=present;
    }
 
  eq.domaine_Cl_dis().imposer_cond_lim(eq.inconnue(),temps_courant()+pas_de_temps());
  DoubleTab tmp(futur);
  tmp -= present;
  tmp /= dt_;
  update_critere_statio(tmp, eq);
  futur.echange_espace_virtuel();
 
  return 1;
}