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FUNCTION FORWARD_UP_ADV,B_IC=B_IC,del_t,del_x,del_y,times
ss=SIZE(B_IC.A0, /DIMENSIONS)

ss=SIZE(B_IC.A0, /DIMENSIONS)
C_u = FLTARR(ss[0],ss[1])
C_v = FLTARR(ss[0],ss[1])
A_FC=FLTARR(times, ss[0], ss[1])

for i = 0, ss[0]-1 do begin
   for j = 0, ss[1]-1 do begin
      C_u[i,j] = B_IC.UU[i,j]*(del_t/del_x)
      C_v[i,j] = B_IC.VV[i,j]*(del_t/del_y)
   endfor
endfor


A_FC(0,*,*)=  B_IC.A0(*,*)
  FOR t=0, times-2 DO BEGIN
      FOR i=2, ss[0]-2 DO BEGIN
          FOR j=2, ss[1]-2 DO BEGIN
               A_FC(t+1,i,j)= A_FC(t,i,j)+ (((C_u[i,j])*(A_FC(t,i+1,j)-A_FC(t,i-1,j))) - ((C_v[i,j])*(A_FC(t,i,j+1)-A_FC(t,i,j-1))))        
          ENDFOR
      ENDFOR
  ENDFOR
 PRINT,'forward up done' 
RETURN, A_FC








;C_u = FLTARR(ss[0],ss[1])
;C_v = FLTARR(ss[0],ss[1])
;A_FU=FLTARR(times, ss[0], ss[1]);;
;
;for i = 0, ss[0]-1 do begin
;   for j = 0, ss[1]-1 do begin
;      C_u[i,j] = B_IC.UU[i,j]*(del_t/del_x)
;      C_v[i,j] = B_IC.VV[i,j]*(del_t/del_y)
;   endfor
;endfor;
;;
;
;A_FU(0,*,*)=  B_IC.A0(*,*)
;  FOR t=0, times-2, del_t*4 DO BEGIN
;      FOR ii=2, ss[0]-3 DO BEGIN
;          FOR jj=2, ss[1]-3 DO BEGIN   
;               A_FU(t+1,ii,jj)= A_FU(t,ii,jj)-((C_u(ii-1,jj)* A_FU(t,ii,jj) - A_FU(t,ii-1,jj)) - (C_v[ii,jj]*( A_FU(t,ii,jj) -  A_FU(t,ii,jj-1))))  
;               ; A_FC(t+1,i,j)=   A_FC(t,i,j)+ ((0.5*(C_u[i,j])*(A_FC(t,i+1,j)-A_FC(t,i-1,j))) - (0.5*(C_v[i,j])*(A_FC(t,i,j+1)-A_FC(t,i,j-1))))        
;              ;IF (UU(ii,jj) LT 0) THEN  A_FU(t+1,ii,jj)= (C_u(ii-1,jj)*(A0(ii+1,jj) - A0(ii,jj))) +   (C_v[ii,jj-1]*(A0(ii,jj+1) - A0(ii,jj)))
;              ;IF (UU(ii,jj) GT 0) THEN  A_FU(t+1,ii,jj)= (C_u(ii-1,jj)*(A0(ii+1,jj) - A0(ii-1,jj))) + (C_v[ii,jj-1]*(A0(ii,jj+1) - A0(ii,jj-1)))             
;          ENDFOR
;      ENDFOR
      ; PRINT,'STOP'
;  ENDFOR
  
 ;PRINT,'Forward up done'
;RETURN, A_FC

END
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