Module x10ba_a1w_fe_mod
! .. Use Statements ..
Use iso_c_binding, Only: c_funloc, c_int, c_ptr
Use nagad_library, Only: nagad_a1w_get_derivative, &
nagad_a1w_inc_derivative, &
nagad_a1w_ir_register_variable, &
nagad_a1w_w_rtype, x10ba_a1w_f, x10bb_a1w_f, &
x10bj_a1w_f, x10cj_a1w_f, Assignment (=)
Use nag_library, Only: nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Accessibility Statements ..
Private
Public :: comp_eval, procarg
Contains
Subroutine procarg(ad_handle,x,y)
! .. Scalar Arguments ..
Type (c_ptr) :: ad_handle
Type (nagad_a1w_w_rtype), Intent (In) :: x
Type (nagad_a1w_w_rtype), Intent (Out) :: y
! .. Local Scalars ..
Type (c_ptr) :: cb_handle
Integer :: ifail
! .. Intrinsic Procedures ..
Intrinsic :: log
! .. Executable Statements ..
! Create callback data object
ifail = 0
Call x10ba_a1w_f(cb_handle,ifail)
! Write x to callback data object
ifail = 0
Call x10bj_a1w_f(cb_handle,x,ifail)
! Evaluate primal y value
y = 0.0_nag_wp
y%value = log(1.0_nag_wp+x%value)
! Register y
Call nagad_a1w_ir_register_variable(y)
! Write y to callback data object
ifail = 0
Call x10bj_a1w_f(cb_handle,y,ifail)
! Push comp_eval onto global tape
ifail = 0
Call x10bb_a1w_f(cb_handle,c_funloc(comp_eval),ifail)
End Subroutine procarg
Subroutine comp_eval(callmode,cb_handle) Bind (C)
! .. Scalar Arguments ..
Type (c_ptr), Value :: cb_handle
Integer (Kind=c_int), Value :: callmode
! .. Local Scalars ..
Type (nagad_a1w_w_rtype) :: x, y
Real (Kind=nag_wp) :: xa, ya
Integer :: ifail
! .. Executable Statements ..
If (callmode/=1) Then
! Read x and y from callback data object
ifail = 0
Call x10cj_a1w_f(cb_handle,x,ifail)
Call x10cj_a1w_f(cb_handle,y,ifail)
! Get algorithmic derivative of z w.r.t. y
ya = nagad_a1w_get_derivative(y)
! Evaluate derivative w.r.t. x = dz/dy * dy/dx
xa = ya*1.0_nag_wp/(1.0_nag_wp+x%value)
! Increment derivative w.r.t x
Call nagad_a1w_inc_derivative(x,xa)
End If
End Subroutine comp_eval
End Module x10ba_a1w_fe_mod
Program x10ba_a1w_fe
! X10BA_A1W_F Example Program Text
! Mark 30.1 Release. NAG Copyright 2024.
! .. Use Statements ..
Use iso_c_binding, Only: c_ptr
Use nagad_library, Only: log, nagad_a1w_get_derivative, &
nagad_a1w_ir_create => x10za_a1w_f, &
nagad_a1w_ir_interpret_adjoint_sparse, &
nagad_a1w_ir_register_variable, &
nagad_a1w_ir_remove, nagad_a1w_set_derivative, &
nagad_a1w_w_rtype, nagad_algorithmic, &
nagad_dstate, x10aa_a1w_f, x10ab_a1w_f, &
x10ac_a1w_f, x10bc_a1w_f, Assignment (=), &
Operator (+)
Use nag_library, Only: nag_wp
Use x10ba_a1w_fe_mod, Only: procarg
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nout = 6
! .. Local Scalars ..
Type (c_ptr), Volatile :: ad_handle
Type (nagad_a1w_w_rtype) :: x, x1, y, y1
Real (Kind=nag_wp) :: dydx, dydx_exp
Integer :: cb_mode, ifail, mode
! .. Executable Statements ..
Write (nout,*) 'X10BA_A1W_F Example Program Results'
! Create AD tape
Call nagad_a1w_ir_create
x = 0.1_nag_wp
x1 = x
Write (nout,*)
Write (nout,*) 'Testing Callback insertion'
! Create AD configuration data object
ifail = 0
Call x10aa_a1w_f(ad_handle,ifail)
! Set computational mode to nagad_algorithmic
mode = nagad_algorithmic
ifail = 0
Call x10ac_a1w_f(ad_handle,mode,ifail)
! Evaluate derivative first by operator extensions
Write (nout,*)
Write (nout,*) ' 1. Direct algorithmic differentiation'
Call nagad_a1w_ir_register_variable(x)
! Set callback computational mode
cb_mode = nagad_dstate
ifail = 0
Call x10bc_a1w_f(ad_handle,cb_mode,ifail)
y = log(1.0_nag_wp+x)
! Get derivatives
Call nagad_a1w_set_derivative(y,1.0_nag_wp)
Call nagad_a1w_ir_interpret_adjoint_sparse(ifail)
dydx = nagad_a1w_get_derivative(x)
dydx_exp = 1.0_nag_wp/(1.0_nag_wp+x%value)
Write (nout,99999) 'Input value of x : ', x%value
Write (nout,99999) 'Output value of ln(1+x) : ', y%value
Write (nout,99999) 'AD evaluated derivative : ', dydx
Write (nout,99999) 'Directly computed derivative : ', dydx_exp
! Now evaluate adjoint of supplied routine procarg manually
! using the companion callback comp_eval
Write (nout,*)
Write (nout,*) ' 1. Differentiation via callback'
Call procarg(ad_handle,x1,y1)
Call nagad_a1w_set_derivative(y1,1.0_nag_wp)
Call nagad_a1w_ir_interpret_adjoint_sparse(ifail)
dydx = nagad_a1w_get_derivative(x1)
Write (nout,99999) 'Input value of x1 : ', x1%value
Write (nout,99999) 'Output value of ln(1+x) : ', y1%value
Write (nout,99999) 'Callback evaluated derivative: ', dydx
99999 Format (1X,A,1P,E11.3)
! Remove computational data object and tape
Call x10ab_a1w_f(ad_handle,ifail)
Call nagad_a1w_ir_remove
End Program x10ba_a1w_fe