/***************************************************************************
                 module classe zwisd_ua_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	2  i 	j    k	  t
	2	from	zdf_avt_avmu_avmv	2  i 	j    k+1  t*/   
  /* YS1 */
  /*     A 4.671131788614972e-17
	 R 1.088374593705250e-16*/
  /* YS2 */
  /*     A 2.089031091690222e-17
	 R 4.907327859125863e-17*/
  /*     */
  /* YS3*/
  /*      A 0
	  R 0*/

  if(Yt==TU)
    YS1=0.;
  else{
    double zzws;
    double  zcoef = -r2dt/fse3u(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/ fse3uw(Yi,Yj,Yk  );
      zzws = zcoef * x2/fse3uw(Yi,Yj,Yk+1);
      YS2 = zzws* umask(Yi,Yj,Yk+1);
      YS3 = 1. - YS1 - zzws;
      //      ! Surface boudary conditions
      if(Yk==0){
	YS1 = 0.;
	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/fse3u(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 / fse3uw(Yi,Yj,Yk  );
      double dzzws_x2 = zcoef/fse3uw(Yi,Yj,Yk+1);
      YJ2I2 = dzzws_x2* umask(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_ua_dynzdf_imp  ********************