Program f01ej_a1w_fe

!     F01EJ_A1W_F Example Program Text

!     Mark 30.3 Release. NAG Copyright 2024.

!     .. Use Statements ..
      Use iso_c_binding, Only: c_ptr
      Use nagad_library, Only: f01ej_a1w_f, nagad_a1w_get_derivative,          &
                               nagad_a1w_inc_derivative,                       &
                               nagad_a1w_ir_interpret_adjoint_sparse,          &
                               nagad_a1w_ir_register_variable,                 &
                               nagad_a1w_ir_remove, nagad_a1w_ir_zero_adjoints &
                               , nagad_a1w_w_rtype, x10aa_a1w_f, x10ab_a1w_f,  &
                               x10za_a1w_f, Assignment (=)
      Use nag_library, Only: nag_wp, x04caf
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
      Type (c_ptr)                     :: ad_handle
      Type (nagad_a1w_w_rtype)         :: imnorm
      Integer                          :: i, ifail, j, lda, n
!     .. Local Arrays ..
      Type (nagad_a1w_w_rtype), Allocatable :: a(:,:), a_in(:,:)
      Real (Kind=nag_wp), Allocatable  :: a_r(:,:)
!     .. Executable Statements ..
      Write (nout,*) 'F01EJ_A1W_F Example Program Results'
      Write (nout,*)
      Flush (nout)

!     Skip heading in data file
      Read (nin,*)
      Read (nin,*) n

      lda = n
      Allocate (a(lda,n),a_in(lda,n),a_r(lda,n))

!     Read A from data file
      Read (nin,*)(a_r(i,1:n),i=1,n)
      a_in = a_r

!     Create AD tape
      Call x10za_a1w_f

!     Create AD configuration data object
      ifail = 0
      Call x10aa_a1w_f(ad_handle,ifail)

!     Register variables to differentiate w.r.t.
      Call nagad_a1w_ir_register_variable(a_in)

      a = a_in

!     ifail: behaviour on error exit
!             =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
      ifail = 0

!     Find log( A )
      Call f01ej_a1w_f(ad_handle,n,a,lda,imnorm,ifail)

!     Print solution
      a_r = a
      ifail = 0
      Call x04caf('G','N',n,n,a_r,lda,'log(A)',ifail)

      Write (nout,*)
      Write (nout,*) ' Derivatives calculated: First order adjoints'
      Write (nout,*) ' Computational mode    : algorithmic'

      Write (nout,*)
      Write (nout,*) ' Derivatives of diagonal of log(A) w.r.t. diagonal of A'
      Write (nout,*)
!     Setup evaluation of derivatives via adjoints
      Do i = 1, n
        Call nagad_a1w_ir_zero_adjoints
        Call nagad_a1w_inc_derivative(a(i,i),1.0_nag_wp)
        ifail = 0
        Call nagad_a1w_ir_interpret_adjoint_sparse(ifail)

!       Get derivatives
        Do j = 1, n
          a_r(i,j) = nagad_a1w_get_derivative(a_in(j,j))
        End Do
      End Do
      Call x04caf('General',' ',n,n,a_r,n,'       d(logA(i,i))/da(j,j)',ifail)

!     Remove computational data object and tape
      Call x10ab_a1w_f(ad_handle,ifail)
      Call nagad_a1w_ir_remove

    End Program f01ej_a1w_fe