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FUNCTION SEC_ORD_LEAP_FROG_3D, ADV=ADV,del_x,del_y,del_z,del_t,times


ss=SIZE(ADV.uu,/ DIMENSIONS)
;A_LF2=FLTARR(times, ss[0], ss[1], ss[2])

C_u = FLTARR(ss[0],ss[1], ss[2])
C_v = FLTARR(ss[0],ss[1], ss[2])
C_w = FLTARR(ss[0],ss[1], ss[2])

for i = 0, ss[0]-1 do begin
   for j = 0, ss[1]-1 do begin
        for k = 0, ss[2]-1 do begin
              C_u[i,j,k] = ADV.uu[i,j,k]*(del_t/del_x)
              C_v[i,j,k] = ADV.vv[i,j,k]*(del_t/del_y)
              C_w[i,j,k] = ADV.ww[i,j,k]*(del_t/del_z)
        endfor
   endfor
endfor


;A_LF2(0,*,*)=  B.A0(*,*)


adv_ut = FLTARR(times,ss[0],ss[1], ss[2])
adv_vt = FLTARR(times,ss[0],ss[1], ss[2])
adv_wt = FLTARR(times,ss[0],ss[1], ss[2])
adv_tt = FLTARR(times,ss[0],ss[1], ss[2])

adv_ut(0,*,*,*)=REFORM(ADV.uu(*,*,*))
adv_vt(0,*,*,*)=REFORM(ADV.vv(*,*,*))
adv_wt(0,*,*,*)=REFORM(ADV.ww(*,*,*))
adv_tt(0,*,*,*)=REFORM(ADV.tt(*,*,*))


  FOR t=0, times-2 DO BEGIN
    FOR i=1, ss[0]-2 DO BEGIN
          FOR j=1, ss[1]-2 DO BEGIN    
              FOR k=1, ss[2]-2 DO BEGIN
                  IF (t EQ 0) THEN BEGIN
                      adv_ut(t+1,i,j,k)= adv_ut(t,i,j,k)+ (((C_u[i,j,k])*(adv_ut(t,i+1,j,k)-adv_ut(t,i-1,j,k))) - ((C_v[i,j,k])*(adv_ut(t,i,j+1,k)-adv_ut(t,i,j-1,k))) - ((C_w[i,j,k])*(adv_ut(t,i,j,k+1)-adv_ut(t,i,j,k-1)))) 
                      adv_vt(t+1,i,j,k)= adv_vt(t,i,j,k)+ (((C_v[i,j,k])*(adv_vt(t,i+1,j,k)-adv_vt(t,i-1,j,k))) - ((C_v[i,j,k])*(adv_vt(t,i,j+1,k)-adv_vt(t,i,j-1,k))) - ((C_w[i,j,k])*(adv_vt(t,i,j,k+1)-adv_vt(t,i,j,k-1)))) 
                      adv_wt(t+1,i,j,k)= adv_vt(t,i,j,k)+ (((C_w[i,j,k])*(adv_wt(t,i+1,j,k)-adv_wt(t,i-1,j,k))) - ((C_v[i,j,k])*(adv_wt(t,i,j+1,k)-adv_wt(t,i,j-1,k))) - ((C_w[i,j,k])*(adv_wt(t,i,j,k+1)-adv_wt(t,i,j,k-1)))) 
                      adv_tt(t+1,i,j,k)= adv_tt(t,i,j,k)+ (((C_u[i,j,k])*(adv_tt(t,i+1,j,k)-adv_tt(t,i-1,j,k))) - ((C_v[i,j,k])*(adv_tt(t,i,j+1,k)-adv_tt(t,i,j-1,k))) - ((C_w[i,j,k])*(adv_tt(t,i,j,k+1)-adv_tt(t,i,j,k-1)))) 
                  ENDIF       
                         adv_ut(t+1,i,j,k)= adv_ut(t,i,j,k)- (((C_u(i,j,k)*adv_ut(t,i+1,j,k)-adv_ut(t,i-1,j,k))) - ((C_v(i,j,k))*(adv_ut(t,i,j+1,k)-adv_ut(t,i,j-1,k))) -((C_w(i,j,k)*adv_ut(t,i,j,k+1)-adv_ut(t,i,j,k-1))))  
                         adv_vt(t+1,i,j,k)= adv_vt(t,i,j,k)- (((C_v(i,j,k)*adv_ut(t,i+1,j,k)-adv_vt(t,i-1,j,k))) - ((C_v(i,j,k))*(adv_vt(t,i,j+1,k)-adv_vt(t,i,j-1,k))) -((C_w(i,j,k)*adv_vt(t,i,j,k+1)-adv_vt(t,i,j,k-1))))  
                         adv_wt(t+1,i,j,k)= adv_wt(t,i,j,k)- (((C_w(i,j,k)*adv_ut(t,i+1,j,k)-adv_wt(t,i-1,j,k))) - ((C_v(i,j,k))*(adv_wt(t,i,j+1,k)-adv_wt(t,i,j-1,k))) -((C_w(i,j,k)*adv_wt(t,i,j,k+1)-adv_wt(t,i,j,k-1))))  
                         adv_tt(t+1,i,j,k)= adv_tt(t,i,j,k)- (((C_u(i,j,k)*adv_ut(t,i+1,j,k)-adv_tt(t,i-1,j,k))) - ((C_v(i,j,k))*(adv_tt(t,i,j+1,k)-adv_tt(t,i,j-1,k))) -((C_w(i,j,k)*adv_tt(t,i,j,k+1)-adv_tt(t,i,j,k-1))))                        
             ENDFOR
         ENDFOR
    ENDFOR
 ENDFOR
      
         
  advt={ut:adv_ut, vt:adv_vt, wt:adv_wt, tt:adv_tt}
PRINT,'>>>>>>>>>>  Sec order leap frog done'

RETURN, advt

END
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