/***************************************************************************
                 module classe zwisd_va_dynzdf_imp.h  -  description
***************************************************************************/
// Mohamed Berrada
// locean-ipsl.upmc, Paris, April 17, 2009
//===========================================================================
//                          methode forward
forward (YREAL x1, YREAL x2)
{ /*	1	from	zdf_avt_avmu_avmv	3  i 	j    k	  t
	2	from	zdf_avt_avmu_avmv	3  i 	j    k+1  t*/   
  /* YS1*/
  /*     */
  /* YS2*/
  /*     */
  /* YS3*/
  /*     
	 */

  if(Yt==TU){
    YS1=0.;
    YS2=0.;
    YS3=0.;
  }
  else{
    double zzws;
    double  zcoef = -r2dt/fse3v(Yi,Yj,Yk);
    if(Yi==0 || Yi==NX-1 || Yj==0 || Yj==NY-1 || Yk== NZ-1){
      YS1=0.;
      YS2=0.;
      YS3=0.;
    }
    else{
      
      YS1 = zcoef* x1/ fse3vw(Yi,Yj,Yk  );
      zzws = zcoef* x2/fse3vw(Yi,Yj,Yk+1);
      YS2 = zzws* vmask(Yi,Yj,Yk+1);
      YS3 = 1. - YS1 - zzws;
      //      ! Surface boudary conditions
      if(Yk==0){
	YS1 = 0.e0;
	YS3 = 1. - YS2;
      }
    }
  }
  //
}

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

backward (YREAL x1, YREAL x2)
{
  
  YJ1I1=0.;     YJ1I2=0.; 
  YJ2I1=0.;     YJ2I2=0.; 
  YJ3I1=0.;     YJ3I2=0.; 
  if(Yt!=TU){  
    double  zcoef = -r2dt/fse3v(Yi,Yj,Yk);
    if(Yi==0 || Yi==NX-1 || Yj==0 || Yj==NY-1 || Yk== NZ-1){
      YJ1I1=0.;     YJ1I2=0.; 
      YJ2I1=0.;     YJ2I2=0.; 
      YJ3I1=0.;     YJ3I2=0.; 
    }
    else{
      
      YJ1I1 = zcoef/ fse3vw(Yi,Yj,Yk  );
      double dzzws_x2 = zcoef/fse3vw(Yi,Yj,Yk+1);
      YJ2I2 = dzzws_x2* vmask(Yi,Yj,Yk+1);
      YJ3I1 = -YJ1I1;
      YJ3I2 = -dzzws_x2;
      //      ! Surface boudary conditions
      if(Yk==0){
	YJ1I1 = 0.;
	YJ3I1= 0.;
	YJ3I2 =- YJ2I2;
      }
    }
  }
  //
}

  //===========================================================================
//*************************  FIN DU MODULE zwisd_va_dynzdf_imp   *************************