!   E02GBF Example Program Text
!   Mark 28.6 Release. NAG Copyright 2022.
    Module e02gbfe_mod

!     E02GBF 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                           :: monit
!     .. Parameters ..
      Integer, Parameter, Public       :: n = 4, nin = 5, nout = 6
    Contains
      Subroutine monit(n,x,niter,k,el1n)

!       .. Scalar Arguments ..
        Real (Kind=nag_wp), Intent (In) :: el1n
        Integer, Intent (In)           :: k, n, niter
!       .. Array Arguments ..
        Real (Kind=nag_wp), Intent (In) :: x(n)
!       .. Executable Statements ..
        Write (nout,*)
        Write (nout,99999) 'Results at iteration ', niter
        Write (nout,*) 'X-values'
        Write (nout,99998) x
        Write (nout,99997) 'Norm of residuals =', el1n

        Return

99999   Format (1X,A,I5)
99998   Format (1X,4F15.4)
99997   Format (1X,A,E12.5)
      End Subroutine monit
    End Module e02gbfe_mod
    Program e02gbfe

!     E02GBF Example Main Program

!     .. Use Statements ..
      Use e02gbfe_mod, Only: monit, n, nin, nout
      Use nag_library, Only: e02gbf, nag_wp
!     .. Implicit None Statement ..
      Implicit None
!     .. Local Scalars ..
      Real (Kind=nag_wp)               :: el1n, t
      Integer                          :: i, ifail, iprint, iw, k, l, lde, m,  &
                                          mpl, mxs
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: e(:,:), f(:), w(:), x(:)
      Integer, Allocatable             :: indx(:)
!     .. Executable Statements ..
      Write (nout,*) 'E02GBF Example Program Results'

!     Skip heading in data file
      Read (nin,*)

      Read (nin,*) m
      lde = n
      l = m
      mpl = m + l
      iw = 3*mpl + 5*n + n**2 + (n+1)*(n+2)/2
      Allocate (e(lde,mpl),f(mpl),x(n),indx(mpl),w(iw))

      Do i = 1, m
        Read (nin,*) t, f(i)
        e(1:4,i) = (/1.0_nag_wp,t,t*t,t*t*t/)
        e(1:4,m+i) = (/0.0_nag_wp,1.0_nag_wp,2.0_nag_wp*t,3.0_nag_wp*t*t/)
        f(m+i) = 0.0_nag_wp
      End Do

      x(1:n) = 0.0_nag_wp
      mxs = 50

!     * Set IPRINT=1 to obtain output from MONIT at each iteration *
      iprint = 0

      ifail = -1
      Call e02gbf(m,n,m+l,e,lde,f,x,mxs,monit,iprint,k,el1n,indx,w,iw,ifail)

    End Program e02gbfe