!   E05KBF Example Program Text
!   Mark 28.3 Release. NAG Copyright 2022.

    Module e05kbfe_mod

!     E05KBF Example Program Module:
!            Parameters and User-defined Routines

!     .. Use Statements ..
      Use iso_c_binding, Only: c_ptr
      Use nag_library, Only: nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Accessibility Statements ..
      Private
      Public                           :: objfun
!     .. Parameters ..
      Integer, Parameter, Public       :: nout = 6
    Contains
      Subroutine objfun(nvar,x,f,inform,iuser,ruser,cpuser)

!       Routine to evaluate E05KBF objective function.

!       .. Scalar Arguments ..
        Type (c_ptr), Intent (In)      :: cpuser
        Real (Kind=nag_wp), Intent (Out) :: f
        Integer, Intent (Inout)        :: inform
        Integer, Intent (In)           :: nvar
!       .. Array Arguments ..
        Real (Kind=nag_wp), Intent (Inout) :: ruser(*)
        Real (Kind=nag_wp), Intent (In) :: x(nvar)
        Integer, Intent (Inout)        :: iuser(*)
!       .. Local Scalars ..
        Real (Kind=nag_wp)             :: x1, x2
!       .. Intrinsic Procedures ..
        Intrinsic                      :: exp
!       .. Executable Statements ..

!       This is a two-dimensional objective function.
!       As an example of using the inform mechanism,
!       terminate if any other problem size is supplied.

        If (nvar/=2) Then
          inform = -1
        Else
          inform = 0

          If (inform>=0) Then

!           If INFORM>=0 then we're prepared to evaluate OBJFUN
!           at the current X

            x1 = x(1)
            x2 = x(2)

            f = 3.0E0_nag_wp*(1.0E0_nag_wp-x1)**2*exp(-(x1**2)-(x2+            &
              1.0E0_nag_wp)**2) - 1.0E1_nag_wp*(x1/5.0E0_nag_wp-x1**3-x2**5)*  &
              exp(-x1**2-x2**2) - 1.0E0_nag_wp/3.0E0_nag_wp*exp(-(x1+          &
              1.0E0_nag_wp)**2-x2**2)
          End If

        End If

        Return
      End Subroutine objfun
    End Module e05kbfe_mod
    Program e05kbfe

!     E05KBF Example Main Program

!     .. Use Statements ..
      Use e05kbfe_mod, Only: nout, objfun
      Use iso_c_binding, Only: c_null_ptr, c_ptr
      Use nag_library, Only: e04kfu, e04raf, e04rgf, e04rhf, e04rzf, e04zmf,   &
                             e05kbf, nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nvar = 2
!     .. Local Scalars ..
      Type (c_ptr)                     :: cpuser, handle
      Integer                          :: i, ifail
!     .. Local Arrays ..
      Real (Kind=nag_wp)               :: bl(nvar), bu(nvar), rinfo(100),      &
                                          ruser(1), stats(100), x(nvar)
      Integer                          :: iidx(nvar), iuser(1)
!     .. Executable Statements ..

      cpuser = c_null_ptr

      Write (nout,*) 'E05KBF Example Program Results'

!     Initialize handle
      ifail = 0
      Call e04raf(handle,nvar,ifail)

!     Define Simple box bounds
      bl(1:nvar) = (/-3.0_nag_wp,-3.0_nag_wp/)
      bu(1:nvar) = (/3.0_nag_wp,3.0_nag_wp/)
      ifail = 0
      Call e04rhf(handle,nvar,bl,bu,ifail)

!     Add nonlinear objective information
      iidx(1:nvar) = (/(i,i=1,nvar)/)
      ifail = 0
      Call e04rgf(handle,nvar,iidx,ifail)

!     Add options

      ifail = 0
      Call e04zmf(handle,'Print Level = 1',ifail)

!     Solve the problem.
      ifail = 0
      Call e05kbf(handle,objfun,e04kfu,nvar,x,rinfo,stats,iuser,ruser,cpuser,  &
        ifail)

!     Clean up
      ifail = 0
      Call e04rzf(handle,ifail)

    End Program e05kbfe