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!Environment Canada - Atmospheric Science and Technology License/Disclaimer, 
!                     version 3; Last Modified: May 7, 2008.
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***s/p adw_trilin_ad - ADJ of adw_trilin_tl
*
#include "model_macros_f.h"
*

      subroutine adw_trilin_ad ( F_out,  F_in, F_dt,  6
     %                           F_capx, F_capy, F_capz,
     %                                   F_inm,      F_nm,
     %                           F_capxm,F_capym,F_capzm,F_num,i0,in,j0,jn,kn)
*
      implicit none
*
      integer F_num, F_nm(F_num), i0, in, j0, jn, kn
*
      real F_dt, F_in(*), F_inm(*)
*
      real F_out (F_num),F_capx (F_num),F_capy (F_num),F_capz (F_num)
      real               F_capxm(F_num),F_capym(F_num),F_capzm(F_num)
*
*author
*     monique tanguay
*
*revision
* v2_31 - Tanguay M.        - initial MPI version
* v3_00 - Tanguay M.        - restore vectorization in adjoint of semi-Lag.
* v3_03 - Tanguay M.        - Adjoint Lam configuration 
* v3_11 - Tanguay M.        - Remove restoration of vectorization in adjoint of semi-Lag
* v3_11 - Lee V.            - OpenMP for ADW_TRILIN_AD
*
*language
*     fortran 77
*
*object
*     see id section
*
*ADJ of
*arguments
*______________________________________________________________________
*              |                                                 |     |
* NAME         | DESCRIPTION                                     | I/O |
*--------------|-------------------------------------------------|-----|
*              |                                                 |     |
* F_out        | F_dt * result of interpolation                  |  o  |
* F_in         | field to interpolate                            |  i  |
*              |                                                 |     |
* F_dt         | multiplicative constant (1.0 or timestep lenght)|  i  |
*              |                                                 |     |
* F_n          | positions in the 3D volume of interpolation     |  i  |
*              | boxes                                           |     |
*              |                                                 |     |
* F_capx       | \                                               |  i  |
* F_capy       |   precomputed displacements                     |  i  |
* F_capz       | / along the x,y,z directions                    |  i  |
*              |                                                 |     |
* F_num        | number of points to interpolate                 |  i  |
*______________|_________________________________________________|_____|
*
*implicits
#include "glb_ld.cdk"
#include "adw.cdk"
************************************************************************
      integer n,nn, nijag, o1, o2, i,j,k,nij,kilon,kk,ki0,kin
*
      real psum(Adw_nit*Adw_njt*l_nk,4)
      real*8 prf1_8, prf2_8, prf3_8, prf4_8, prf1_y_8, prf2_y_8
      real*8 prf1m_8,prf2m_8,prf3m_8,prf4m_8,prf1m_y_8,prf2m_y_8
*
      real*8 ZERO_8
      parameter (ZERO_8 = 0.0)
*
      nij   = l_ni*l_nj
      nijag = Adw_nit * Adw_njt
*
*     Initialize local adjoint variables
*     ----------------------------------
      prf1_8 = ZERO_8
      prf2_8 = ZERO_8
      prf3_8 = ZERO_8
      prf4_8 = ZERO_8
      prf1_y_8 = ZERO_8
      prf2_y_8 = ZERO_8
*
      kilon = (kn+4)/4

!$omp parallel private(n,nn,o1,o2,i,j,k,kk,ki0,kin,
!$omp& prf1_8,prf2_8,prf3_8,prf4_8,prf1_y_8,prf2_y_8,
!$omp& prf1m_8,prf2m_8,prf3m_8,prf4m_8,
!$omp& prf1m_y_8,prf2m_y_8)  shared(psum)

!$omp do
      do 200 kk=1,4
         do n=1,Adw_nit*Adw_njt*l_nk
            psum(n,kk) = 0.0
         enddo
         ki0 = 1 + kilon*(kk-1)
         kin = min(ki0+kilon-1,kn)
      do 100 k=ki0,kin
      do  90 j=j0,jn
      do  80 i=i0,in
*
      n  = nij*(k-1) + ((j-1)*l_ni) + i 
*
      o1 = F_nm(n)
      o2 = F_nm(n) + Adw_nit
*
*     TRAJECTORY
*     ----------
************************************************************************
*     x interpolation
************************************************************************
      prf1m_8 = (1.0 - F_capxm(n)) * F_inm(o1) + F_capxm(n) * F_inm(o1+1)
      prf2m_8 = (1.0 - F_capxm(n)) * F_inm(o2) + F_capxm(n) * F_inm(o2+1)
*
      o1 = o1 + nijag
      o2 = o2 + nijag
*
      prf3m_8 = (1.0 - F_capxm(n)) * F_inm(o1) + F_capxm(n) * F_inm(o1+1)
      prf4m_8 = (1.0 - F_capxm(n)) * F_inm(o2) + F_capxm(n) * F_inm(o2+1)
************************************************************************
*     y interpolation
************************************************************************
      prf1m_y_8= (1.0 - F_capym(n)) * prf1m_8 + F_capym(n)  * prf2m_8
      prf2m_y_8= (1.0 - F_capym(n)) * prf3m_8 + F_capym(n)  * prf4m_8
*
************************************************************************
*     ADJ of
*     z interpolation
************************************************************************
      prf2_y_8  =      F_capzm(n)  * F_out(n) * F_dt
      prf1_y_8  = (1.0-F_capzm(n)) * F_out(n) * F_dt
      F_capz(n) = F_capz(n) + (prf2m_y_8 - prf1m_y_8) * F_out(n) * F_dt
      F_out (n) = ZERO_8
*
************************************************************************
*     ADJ of
*     y interpolation
************************************************************************
      prf4_8    =      F_capym(n)     * prf2_y_8 
      prf3_8    = (1.0-F_capym(n))    * prf2_y_8 
*
      prf2_8    =      F_capym(n)     * prf1_y_8 
      prf1_8    = (1.0-F_capym(n))    * prf1_y_8 
*
      F_capy(n) = F_capy(n) + (prf4m_8 - prf3m_8) * prf2_y_8
     %                      + (prf2m_8 - prf1m_8) * prf1_y_8 
*
************************************************************************
*     x interpolation
************************************************************************
      psum(o2+1,kk) = psum(o2+1,kk)  +      F_capxm(n)  * prf4_8
      psum(o2  ,kk) = psum(o2  ,kk)  + (1.0-F_capxm(n)) * prf4_8
*
      psum(o1+1,kk) = psum(o1+1,kk)  +      F_capxm(n)  * prf3_8
      psum(o1  ,kk) = psum(o1  ,kk)  + (1.0-F_capxm(n)) * prf3_8
*
      F_capx(n)  = F_capx(n) + (F_inm(o2+1) - F_inm(o2)) * prf4_8
     %                       + (F_inm(o1+1) - F_inm(o1)) * prf3_8
*
      o1 = F_nm(n)
      o2 = F_nm(n) + Adw_nit
*
      psum(o2+1,kk) = psum(o2+1,kk)  +      F_capxm(n)  * prf2_8
      psum(o2  ,kk) = psum(o2  ,kk)  + (1.0-F_capxm(n)) * prf2_8
*
      psum(o1+1,kk) = psum(o1+1,kk)  +      F_capxm(n)  * prf1_8
      psum(o1  ,kk) = psum(o1  ,kk)  + (1.0-F_capxm(n)) * prf1_8
*
      F_capx(n)  = F_capx(n) + (F_inm(o2+1) - F_inm(o2)) * prf2_8
     %                       + (F_inm(o1+1) - F_inm(o1)) * prf1_8
*
   80 continue
   90 continue
  100 continue
  200 continue
!$omp enddo

!$omp do
      do nn=1,Adw_nit*Adw_njt*l_nk
      do k=1,4
         F_in(nn)= F_in(nn)+psum(nn,k)
      enddo
      enddo
!$omp enddo

!$omp end parallel
*
      return
      end