/***************************************************************************
                 module classe sshb.h  -  description
***************************************************************************/
// Mohamed Berrada
// locean-ipsl.upmc, Paris, April 24, 2009
//===========================================================================
//                          methode forward
forward (YREAL x1,YREAL x2,YREAL x3,YREAL x4)
{ /*	1	from	sshb			1  i 	j         t-1
	2	from	sshn			1  i 	j         t-1
	3	from	sshn			1  i 	j         t
	4	from	sshn_c			1  i 	j   */

  /* YS1  */
  /*     A 
	 R */
  if(Yt==TU){
#ifdef YE_sshn_c
    if( ndiag_rst==0)
      YS1=x4;
    else{
      if( neuler == 0)
	YS1=x4;
      else 
	YS1=sshb_neuler1(Yi,Yj);
    }
#else
    if( neuler == 0)//   ! Euler 1st time step : swap only
      YS1=x4;//sshn_neuler0(Yi,Yj);
    else
      YS1=sshb_neuler1(Yi,Yj); // valeur chargee depuis restart (neuler=1)
    //    YS1=0.;
#endif
  }
  else{
#ifdef YE_sshn_c
      if( Yt == TU+1 && ndiag_rst == 0)//   ! Euler 1st time step : swap only
#else
    if(Yt==TU+1 && neuler == 0)//      ! Euler (forward) time stepping, no time filter
      //! swap of arrays
#endif
      YS1=x2;
    
    else{//                                          ! Leap-frog time stepping and time filter
      //! time filter and array swap
      YS1= atfp * ( x1 + x3) + atfp1 * x2;
    }
}
  //
}

//===========================================================================
//                         methode  backward

backward (YREAL x1,YREAL x2,YREAL x3,YREAL x4)
{
  YJ1I1=0.;     YJ1I2=0.;    YJ1I3=0.;    YJ1I4=0.;
  
  if(Yt==TU){
 #ifdef YE_sshn_c
    YJ1I4=1.;
#else
    if( neuler == 0)//   ! Euler 1st time step : swap only
      YJ1I4=1.;
    else
      YJ1I4=0.;
#endif
 }
  else{
#ifdef YE_sshn_c
    if( Yt == TU+1){//   ! Euler 1st time step : swap only
      YJ1I1=0.;     YJ1I2=1.;    YJ1I3=0.;    YJ1I4=0.;
    }
#else
    if(Yt==TU+1 && neuler == 0){//      ! Euler (forward) time stepping, no time filter
      YJ1I1=0.;     YJ1I2=1.;    YJ1I3=0.;    YJ1I4=0.;
    }
    //! swap of arrays
#endif
    else{//                                          ! Leap-frog time stepping and time filter
      //! time filter and array swap
      YS1= atfp * ( x1 + x3) + atfp1 * x2;
      YJ1I1=atfp;
      YJ1I2=atfp1;
      YJ1I3=atfp;
    }
  }
  //
  
}

//===========================================================================
//**************************  FIN DU MODULE sshb   **************************