! C05AWF Example Program Text
! Mark 30.1 Release. NAG Copyright 2024.
Module c05awfe_mod
! C05AWF Example Program Module:
! Parameters and User-defined Routines
! .. Use Statements ..
Use nag_library, Only: nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Accessibility Statements ..
Private
Public :: f
! .. Parameters ..
Integer, Parameter, Public :: nout = 6
Contains
Function f(x,iuser,ruser)
! .. Function Return Value ..
Real (Kind=nag_wp) :: f
! .. Scalar Arguments ..
Real (Kind=nag_wp), Intent (In) :: x
! .. Array Arguments ..
Real (Kind=nag_wp), Intent (Inout) :: ruser(*)
Integer, Intent (Inout) :: iuser(*)
! .. Intrinsic Procedures ..
Intrinsic :: exp
! .. Executable Statements ..
f = exp(-x) - x
Return
End Function f
End Module c05awfe_mod
Program c05awfe
! C05AWF Example Main Program
! .. Use Statements ..
Use c05awfe_mod, Only: f, nout
Use nag_library, Only: c05awf, nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Local Scalars ..
Real (Kind=nag_wp) :: eps, eta, x
Integer :: ifail, k, nfmax
! .. Local Arrays ..
Real (Kind=nag_wp) :: ruser(1)
Integer :: iuser(1)
! .. Executable Statements ..
Write (nout,*) 'C05AWF Example Program Results'
Write (nout,*)
! Repeat with tolerance eps set to varying powers of 10:
loop: Do k = 3, 4
eps = 10.0E0_nag_wp**(-k)
x = 1.0E0_nag_wp
eta = 0.0E0_nag_wp
nfmax = 200
ifail = -1
Call c05awf(x,eps,eta,f,nfmax,iuser,ruser,ifail)
Select Case (ifail)
Case (0)
Write (nout,99999) 'With eps = ', eps, ' root = ', x
Case (:-1)
Exit loop
Case (3,4)
Write (nout,99999) 'With eps = ', eps, ' final value = ', x
End Select
End Do loop
99999 Format (1X,A,E10.2,A,F14.5)
End Program c05awfe