/***************************************************************************
                 module classe solsor_gc1_x_r.h  -  description
***************************************************************************/
// Julien Brajard
// locean-ipsl.upmc, Paris, April 25, 2011
//===========================================================================
//                          methode forward
forward (YREAL x1, YREAL x2, YREAL x3, YREAL x4, YREAL x5, YREAL x6, YREAL x7, YREAL x8)
{
/*  	1	from	gcx_dynspg_flt		1  i 	j    	  t
     	2	from	gcb_dynspg_flt		1  i 	j    	  t
	3	from	solsor_gc2_x_r		1  i 	j-1  k-1  t
	4	from	solsor_gc2_x_r		1  i-1 	j    k-1  t
	5	from	solsor_gc2_x_r		1  i+1 	j    k-1  t
	6	from	solsor_gc2_x_r		1  i 	j+1  k-1  t
	7	from	solsor_gc2_x_r		1  i 	j    k-1  t
	8       from    solsor_flag             2  NX   NY   k-1  t
} 
output 1 : gcx
oupput 2 : gcr (pour l'arrêt des itérations

*/
 if(Yt==TU)
   {
     YS1=0;
     YS2=0;
   }
 else {
   int t;
   if(Yt==TU+1 && neuler==0)
     t=0;
   else
     t=1;
   
   if (x8==1)
     {
       YS1=x7;
       YS2=0;
     }
   else
     {
       if (Yk==0) {
	 if ( ( (Yi==0) | (Yj==0) ) | ( (Yi==NX-1) | (Yj==NY-1) ) {
	     YS1=0;
	     YS2=0;
	   }
	   else {
	     YS1=x1;
	     YS2=0;
	   } 
	   } //Yk=0;
	 else {
	   YREAL gcx,gcr,ztmp,zres;
	   int ishift=Yj%2;
	   if ((Yi+1)%2==ishift) { //! Guess black update
	     ztmp = x2 
	       - gcp(ji,jj,0,t) * x3   
	       - gcp(ji,jj,1,t) * x4   
	       - gcp(ji,jj,2,t) * x5   
	       - gcp(ji,jj,3,t) * x6;
	     //     ! Estimate of the residual
	     zres = ztmp - x7;
	     YS2 = zres * gcdmat(ji,jj,t) * zres;
	     //               ! Guess update
	     YS1 = sor * ztmp + (1.-sor) * x7;
	   }
	   else
	     {
	       YS2=0;
	       YS1=x7;
	     }
	   
	 }
	 
	 
       } // Yk>0
     } //if x8==0
 } //Yt>TU
}

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

backward () {
}