!   E04HCF Example Program Text
!   Mark 27.3 Release. NAG Copyright 2021.
    Module e04hcfe_mod

!     E04HCF 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                           :: funct
!     .. Parameters ..
      Integer, Parameter, Public       :: liw = 1, n = 4, nout = 6
      Integer, Parameter, Public       :: lw = 3*n
    Contains
      Subroutine funct(iflag,n,xc,fc,gc,iw,liw,w,lw)
!       Routine to evaluate objective function and its 1st derivatives.

!       .. Scalar Arguments ..
        Real (Kind=nag_wp), Intent (Out) :: fc
        Integer, Intent (Inout)        :: iflag
        Integer, Intent (In)           :: liw, lw, n
!       .. Array Arguments ..
        Real (Kind=nag_wp), Intent (Out) :: gc(n)
        Real (Kind=nag_wp), Intent (Inout) :: w(lw)
        Real (Kind=nag_wp), Intent (In) :: xc(n)
        Integer, Intent (Inout)        :: iw(liw)
!       .. Executable Statements ..
        fc = (xc(1)+10.0_nag_wp*xc(2))**2 + 5.0_nag_wp*(xc(3)-xc(4))**2 +      &
          (xc(2)-2.0_nag_wp*xc(3))**4 + 10.0_nag_wp*(xc(1)-xc(4))**4
        gc(1) = 2.0_nag_wp*(xc(1)+10.0_nag_wp*xc(2)) +                         &
          40.0_nag_wp*(xc(1)-xc(4))**3
        gc(2) = 20.0_nag_wp*(xc(1)+10.0_nag_wp*xc(2)) +                        &
          4.0_nag_wp*(xc(2)-2.0_nag_wp*xc(3))**3
        gc(3) = 10.0_nag_wp*(xc(3)-xc(4)) - 8.0_nag_wp*(xc(2)-2.0_nag_wp*xc(3) &
          )**3
        gc(4) = 10.0_nag_wp*(xc(4)-xc(3)) - 40.0_nag_wp*(xc(1)-xc(4))**3

        Return

      End Subroutine funct
    End Module e04hcfe_mod
    Program e04hcfe

!     E04HCF Example Main Program

!     .. Use Statements ..
      Use e04hcfe_mod, Only: funct, liw, lw, n, nout
      Use nag_library, Only: e04hcf, nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Local Scalars ..
      Real (Kind=nag_wp)               :: f
      Integer                          :: ifail
!     .. Local Arrays ..
      Real (Kind=nag_wp)               :: g(n), w(lw), x(n)
      Integer                          :: iw(liw)
!     .. Executable Statements ..
      Write (nout,*) 'E04HCF Example Program Results'

!     Set up an arbitrary point at which to check the 1st derivatives

      x(1:n) = (/1.46_nag_wp,-0.82_nag_wp,0.57_nag_wp,1.21_nag_wp/)

      Write (nout,*)
      Write (nout,*) 'The test point is'
      Write (nout,99999) x(1:n)

      ifail = -1
      Call e04hcf(n,funct,x,f,g,iw,liw,w,lw,ifail)

      If (ifail>=0) Then
        Write (nout,*)

        If (ifail==0) Then
          Write (nout,*) '1st derivatives are consistent with function values'
        Else
          Write (nout,*) 'Probable error in calculation of 1st derivatives'
        End If

        Write (nout,*)
        Write (nout,99998) 'At the test point, FUNCT gives the function value' &
          , f
        Write (nout,*) 'and the 1st derivatives'
        Write (nout,99997) g(1:n)
      End If

99999 Format (1X,4F10.4)
99998 Format (1X,A,1P,E12.4)
99997 Format (1X,1P,4E12.3)
    End Program e04hcfe