/***************************************************************************
                 module classe spguv_dynspg_flt.h  -  description
***************************************************************************/
// Mohamed Berrada
// locean-ipsl.upmc, Paris, April 20, 2009
//===========================================================================
//                          methode forward
forward (YREAL x1,YREAL x2,YREAL x3)
{/*	1	from	gcx2			1  i+1 	j         t
	2	from	gcx2			1  i 	j         t
	3	from	gcx2			1  i 	j+1       t*/

  /* YS1  */
  /*     A 
	 R */
  if(Yt==TU){
    YS1=0.;
    YS2=0.;
  }
  else{
    double znugdt =  rnu * grav * r2dt;
    if(Yi==0 || Yi==NX-1 || Yj==0 || Yj==NY-1 ){
      YS1=0.;
    }
    else{
      //          ! trend of Transport divergence gradient
      //    double   ztdgu = znugdt * (gcx(Yi+1,Yj  ) - gcx(Yi,Yj) ) / e1u(Yi,Yj);
      //    double   ztdgv = znugdt * (gcx(Yi  ,Yj+1) - gcx(Yi,Yj) ) / e2v(Yi,Yj);
      double   ztdgu = znugdt * (x1 - x2 ) / e1u(Yi,Yj);
      double   ztdgv = znugdt * (x3 - x2 ) / e2v(Yi,Yj);
      //        ! multiplied by z2dt
      YS1 = r2dt * ztdgu;
      YS2 = r2dt * ztdgv;
    }
  }
  //
  /*   if(Yt==6 && Yi==28 && Yj==3)  xtest("spg YS_spg",YS1,Yi,Yj,Yk,Yt);
 if(Yt==6 && Yi==28 && Yj==3)  xtest("spg x1",x1,Yi,Yj,Yk,Yt);
 if(Yt==6 && Yi==28 && Yj==3)  xtest("spg x2",x2,Yi,Yj,Yk,Yt);
 if(Yt==6 && Yi==28 && Yj==3)  xtest("spg x3",x3,Yi,Yj,Yk,Yt);*/
  
}

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

backward (YREAL x1,YREAL x2,YREAL x3)
{//(12 7 0; 4)
  double znugdt,dztdgu_x1,dztdgu_x2,dztdgv_x2,dztdgv_x3;
  YJ1I1=0.;     YJ1I2=0.;     YJ1I3=0.;
  YJ2I1=0.;     YJ2I2=0.;     YJ2I3=0.;
  if(Yt!=TU){  
     znugdt =  rnu * grav * r2dt;
    if(Yi==0 || Yi==NX-1 || Yj==0 || Yj==NY-1 ){
      YJ1I1=0.;     YJ1I2=0.;     YJ1I3=0.;
      YJ2I1=0.;     YJ2I2=0.;     YJ2I3=0.;
    }
    else{
      //          ! trend of Transport divergence gradient
      dztdgu_x1 =  znugdt / e1u(Yi,Yj);
      dztdgu_x2 = -znugdt / e1u(Yi,Yj);
      dztdgv_x2 = -znugdt / e2v(Yi,Yj);
      dztdgv_x3 =  znugdt / e2v(Yi,Yj);
      //        ! multiplied by z2dt
      YJ1I1=r2dt * dztdgu_x1;
      YJ1I2=r2dt * dztdgu_x2;
      YJ1I3=0.;
      YJ2I1=0.;
      YJ2I2=r2dt * dztdgv_x2; 
      YJ2I3=r2dt * dztdgv_x3;
    }
  }
  //
  /*  if(Yi==11 && Yj== 11 &&Yt==3)
    {
      if(Ycurward==BACKWARD) 
	printf("BACKWARD:\n");
      if(Ycurward==LINWARD) 
	printf("LINWARD:\n");
      printf("x1:%24.16e x2:%24.16e x3:%24.16e \n",x1,x2,x3);
      // printf("znugdt:%24.16e  \n",znugdt);
      printf("dztdgu_x1:%24.16e  \n",dztdgu_x1);
      printf("dztdgu_x2:%24.16e  \n",dztdgu_x2);
      printf("dztdgv_x2:%24.16e  \n",dztdgv_x2);
      printf("dztdgv_x3:%24.16e  \n",dztdgv_x3);
    }*/ 
}

  //===========================================================================
//*************************  FIN DU MODULE spguv_dynspg_flt   *************************