MODULE compute_caldyn_fast_mod
  USE grid_param, ONLY : llm
  IMPLICIT NONE
  PRIVATE

  PUBLIC :: compute_caldyn_fast

CONTAINS

  SUBROUTINE compute_caldyn_fast(tau,u,rhodz,theta,pk,geopot,du)
    USE icosa
    USE trace
    USE caldyn_vars_mod
    USE omp_para, ONLY : ll_begin, ll_end
    REAL(rstd),INTENT(IN)    :: tau                ! "solve" u-tau*du/dt = rhs
    REAL(rstd),INTENT(INOUT) :: u(iim*3*jjm,llm)   ! OUT if tau>0
    REAL(rstd),INTENT(IN)    :: rhodz(iim*jjm,llm)
    REAL(rstd),INTENT(IN)    :: theta(iim*jjm,llm,nqdyn)
    REAL(rstd),INTENT(INOUT) :: pk(iim*jjm,llm)
    REAL(rstd),INTENT(INOUT) :: geopot(iim*jjm,llm+1)
    REAL(rstd),INTENT(INOUT)   :: du(iim*3*jjm,llm)
    REAL(rstd) :: berni(iim*jjm,llm)  ! Bernoulli function
    REAL(rstd) :: berniv(iim*jjm,llm)  ! moist Bernoulli function

    INTEGER :: i,j,ij,l
    !REAL(rstd) :: cp_ik, qv, temp, chi, nu, due, due_right, due_lup, due_ldown
    REAL(rstd) :: cp_ik, qv, temp, chi, due, due_right, due_lup, due_ldown

    CALL trace_start("compute_caldyn_fast")

    IF(dysl_caldyn_fast) THEN
#include "../kernels_hex/caldyn_fast.k90"
    ELSE

    ! Compute Bernoulli term
    IF(boussinesq) THEN
       DO l=ll_begin,ll_end
          !DIR$ SIMD
          DO ij=ij_begin,ij_end         
             berni(ij,l) = pk(ij,l)
             ! from now on pk contains the vertically-averaged geopotential
             pk(ij,l) = .5*(geopot(ij,l)+geopot(ij,l+1))
          END DO
       END DO
    ELSE ! compressible

       DO l=ll_begin,ll_end
          SELECT CASE(caldyn_thermo)
          CASE(thermo_theta) ! vdp = theta.dpi => B = Phi
             !DIR$ SIMD
             DO ij=ij_begin,ij_end         
                berni(ij,l) = .5*(geopot(ij,l)+geopot(ij,l+1))
             END DO
          CASE(thermo_entropy) ! vdp = dG + sdT => B = Phi + G, G=h-Ts=T*(cpp-s) 
             !DIR$ SIMD
             DO ij=ij_begin,ij_end         
                berni(ij,l) = .5*(geopot(ij,l)+geopot(ij,l+1)) &
                     + pk(ij,l)*(cpp-theta(ij,l,1)) ! pk=temperature, theta=entropy
             END DO
          CASE(thermo_moist) 
             !DIR$ SIMD
             DO ij=ij_begin,ij_end         
                ! du/dt = grad(Bd)+rv.grad(Bv)+s.grad(T)
                ! Bd = Phi + gibbs_d
                ! Bv = Phi + gibbs_v
                ! pk=temperature, theta=entropy
                qv = theta(ij,l,2)
                temp = pk(ij,l)
                chi = log(temp/Treff)
                nu = (chi*(cpp+qv*cppv)-theta(ij,l,1))/(Rd+qv*Rv) ! log(p/preff)
                berni(ij,l) = .5*(geopot(ij,l)+geopot(ij,l+1)) &
                     + temp*(cpp*(1.-chi)+Rd*nu)
                berniv(ij,l) = .5*(geopot(ij,l)+geopot(ij,l+1)) &
                     + temp*(cppv*(1.-chi)+Rv*nu)
            END DO
          END SELECT
       END DO

    END IF ! Boussinesq/compressible

!!! u:=u+tau*du, du = -grad(B)-theta.grad(pi)
    DO l=ll_begin,ll_end
       IF(caldyn_thermo == thermo_moist) THEN
          !DIR$ SIMD
          DO ij=ij_begin,ij_end         
             due_right =  berni(ij+t_right,l)-berni(ij,l)       &
                  + 0.5*(theta(ij,l,1)+theta(ij+t_right,l,1))   &
                       *(pk(ij+t_right,l)-pk(ij,l))             &
                  + 0.5*(theta(ij,l,2)+theta(ij+t_right,l,2))   &
                       *(berniv(ij+t_right,l)-berniv(ij,l))
             
             due_lup = berni(ij+t_lup,l)-berni(ij,l)            &
                  + 0.5*(theta(ij,l,1)+theta(ij+t_lup,l,1))     &
                       *(pk(ij+t_lup,l)-pk(ij,l))               &
                  + 0.5*(theta(ij,l,2)+theta(ij+t_lup,l,2))     &
                       *(berniv(ij+t_lup,l)-berniv(ij,l))
             
             due_ldown = berni(ij+t_ldown,l)-berni(ij,l)        &
                  + 0.5*(theta(ij,l,1)+theta(ij+t_ldown,l,1))   &
                       *(pk(ij+t_ldown,l)-pk(ij,l))             &
                  + 0.5*(theta(ij,l,2)+theta(ij+t_ldown,l,2))   &
                       *(berniv(ij+t_ldown,l)-berniv(ij,l))
             
             du(ij+u_right,l) = du(ij+u_right,l) - ne_right*due_right
             du(ij+u_lup,l)   = du(ij+u_lup,l)   - ne_lup*due_lup
             du(ij+u_ldown,l) = du(ij+u_ldown,l) - ne_ldown*due_ldown
             u(ij+u_right,l) = u(ij+u_right,l) + tau*du(ij+u_right,l)
             u(ij+u_lup,l)   = u(ij+u_lup,l)   + tau*du(ij+u_lup,l)
             u(ij+u_ldown,l) = u(ij+u_ldown,l) + tau*du(ij+u_ldown,l)
          END DO
       ELSE
          !DIR$ SIMD
          DO ij=ij_begin,ij_end         
             due_right =  0.5*(theta(ij,l,1)+theta(ij+t_right,l,1))  &
                  *(pk(ij+t_right,l)-pk(ij,l))        &
                  +  berni(ij+t_right,l)-berni(ij,l)
             due_lup = 0.5*(theta(ij,l,1)+theta(ij+t_lup,l,1))    &
                  *(pk(ij+t_lup,l)-pk(ij,l))          &
                  +  berni(ij+t_lup,l)-berni(ij,l)
             due_ldown = 0.5*(theta(ij,l,1)+theta(ij+t_ldown,l,1)) &
                  *(pk(ij+t_ldown,l)-pk(ij,l))      &
                  +   berni(ij+t_ldown,l)-berni(ij,l)
             du(ij+u_right,l) = du(ij+u_right,l) - ne_right*due_right
             du(ij+u_lup,l)   = du(ij+u_lup,l)   - ne_lup*due_lup
             du(ij+u_ldown,l) = du(ij+u_ldown,l) - ne_ldown*due_ldown
             u(ij+u_right,l) = u(ij+u_right,l) + tau*du(ij+u_right,l)
             u(ij+u_lup,l)   = u(ij+u_lup,l)   + tau*du(ij+u_lup,l)
             u(ij+u_ldown,l) = u(ij+u_ldown,l) + tau*du(ij+u_ldown,l)
          END DO
       END IF
    END DO

    END IF ! dysl
    CALL trace_end("compute_caldyn_fast")

  END SUBROUTINE compute_caldyn_fast

END MODULE compute_caldyn_fast_mod