Program f08nsfe

!     F08NSF Example Program Text

!     Mark 28.3 Release. NAG Copyright 2022.

!     .. Use Statements ..
      Use nag_library, Only: nag_wp, x04dbf, zgehrd
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Complex (Kind=nag_wp), Parameter :: zero = (0.0E0_nag_wp,0.0E0_nag_wp)
      Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
      Integer                          :: i, ifail, info, lda, lwork, n
!     .. Local Arrays ..
      Complex (Kind=nag_wp), Allocatable :: a(:,:), tau(:), work(:)
      Character (1)                    :: clabs(1), rlabs(1)
!     .. Executable Statements ..
      Write (nout,*) 'F08NSF Example Program Results'
!     Skip heading in data file
      Read (nin,*)
      Read (nin,*) n
      lda = n
      lwork = 64*n
      Allocate (a(lda,n),tau(n-1),work(lwork))

!     Read A from data file

      Read (nin,*)(a(i,1:n),i=1,n)

!     Reduce A to upper Hessenberg form

!     The NAG name equivalent of zgehrd is f08nsf
      Call zgehrd(n,1,n,a,lda,tau,work,lwork,info)

!     Set the elements below the first subdiagonal to zero

      Do i = 1, n - 2
        a(i+2:n,i) = zero
      End Do

!     Print upper Hessenberg form

      Write (nout,*)
      Flush (nout)

!     ifail: behaviour on error exit
!             =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
      ifail = 0
      Call x04dbf('General',' ',n,n,a,lda,'Bracketed','F7.4',                  &
        'Upper Hessenberg form','Integer',rlabs,'Integer',clabs,80,0,ifail)

    End Program f08nsfe