Program e01bg_t1w_fe
! E01BG_T1W_F Example Program Text
! Mark 30.1 Release. NAG Copyright 2024.
! .. Use Statements ..
Use iso_c_binding, Only: c_ptr
Use nagad_library, Only: e01be_t1w_f, e01bg_t1w_f, &
nagad_t1w_set_derivative, nagad_t1w_w_rtype, &
x10aa_t1w_f, x10ab_t1w_f, Assignment (=), &
Operator (*), Operator (+)
Use nag_library, Only: nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Type (c_ptr) :: ad_handle
Real (Kind=nag_wp) :: fr, xr
Integer :: i, ifail, m, n, r
! .. Local Arrays ..
Type (nagad_t1w_w_rtype), Allocatable :: d(:), f(:), pd(:), pf(:), &
px(:), x(:)
Real (Kind=nag_wp), Allocatable :: df(:), dx(:)
! .. Executable Statements ..
Write (nout,*) 'E01BG_T1W_F Example Program Results'
! Skip heading in data file
Read (nin,*)
Read (nin,*) n
m = 1
Allocate (d(n),f(n),x(n),dx(n),df(n),px(m),pf(m),pd(m))
! Initialize x and f arrays using data
Do r = 1, n
Read (nin,*) xr, fr
x(r) = xr
f(r) = fr
End Do
! Create AD configuration data object
ifail = 0
Call x10aa_t1w_f(ad_handle,ifail)
px(1) = 0.5_nag_wp*(x(n/2)+x(n/2+1))
Do i = 1, 2*n
If (i<=n) Then
Call nagad_t1w_set_derivative(x(i),1.0_nag_wp)
Else
Call nagad_t1w_set_derivative(f(i-n),1.0_nag_wp)
End If
! Call the AD routine
ifail = 0
Call e01be_t1w_f(ad_handle,n,x,f,d,ifail)
! Evaluate interpolant and derivatives at a mid-point
Call e01bg_t1w_f(ad_handle,n,x,f,d,m,px,pf,pd,ifail)
If (i<=n) Then
dx(i) = pf(1)%tangent
x(i)%tangent = 0.0_nag_wp
Else
df(i-n) = pf(1)%tangent
f(i-n)%tangent = 0.0_nag_wp
End If
End Do
Write (nout,*)
Write (nout,*) ' Derivatives calculated: First order tangents'
Write (nout,*) ' Computational mode : algorithmic'
! Get derivative of interpolated value w.r.t data points and values
Write (nout,*)
Write (nout,99999) 'Interpolated value at x = ', px(1)%value, ' is: ', &
pf(1)%value
99999 Format (1X,A,F7.3,A,E12.5)
Write (nout,*)
Write (nout,*) ' Derivatives of interpolated value w.r.t. x and f:'
Write (nout,*)
Write (nout,*) ' i d/dx d/df'
Do i = 1, n
Write (nout,99998) i, dx(i), df(i)
End Do
99998 Format (1X,I5,1X,E12.5,1X,E12.5)
! Remove computational data object
ifail = 0
Call x10ab_t1w_f(ad_handle,ifail)
End Program e01bg_t1w_fe