NAG Library Manual, Mark 28.4
```    Program f01ej_a1w_fe

!     F01EJ_A1W_F Example Program Text

!     Mark 28.4 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use iso_c_binding, Only: c_ptr
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 ..
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

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

!     Read A from data file
a_in = a_r

Call x10za_a1w_f

!     Create AD configuration data object
ifail = 0

!     Register variables to differentiate w.r.t.

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 )

!     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
ifail = 0

!       Get derivatives
Do j = 1, n