```    Program f08psfe

!     F08PSF Example Program Text

!     Mark 26.1 Release. NAG Copyright 2017.

!     .. Use Statements ..
Use nag_library, Only: nag_wp, x02ajf, x04dbf, zgemm, zhseqr,            &
zlange => f06uaf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Complex (Kind=nag_wp)            :: alpha, beta
Real (Kind=nag_wp)               :: norm
Integer                          :: i, ifail, info, ldc, ldd, ldh, ldz,  &
lwork, n
!     .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: c(:,:), d(:,:), h(:,:), w(:),      &
work(:), z(:,:)
Real (Kind=nag_wp)               :: rwork(1)
Character (1)                    :: clabs(1), rlabs(1)
!     .. Intrinsic Procedures ..
Intrinsic                        :: cmplx
!     .. Executable Statements ..
Write (nout,*) 'F08PSF Example Program Results'
Write (nout,*)
Flush (nout)
!     Skip heading in data file
ldc = n
ldd = n
ldh = n
ldz = n
lwork = n
Allocate (c(ldc,n),d(ldd,n),h(ldh,n),w(n),work(lwork),z(ldz,n))

!     Read H from data file

!     Store H in D
d(1:ldd,1:n) = h(1:ldh,1:n)

!     Print matrix H
!     ifail: behaviour on error exit
!            =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04dbf('General',' ',n,n,h,ldh,'Bracketed','F7.4','Matrix H',       &
'Integer',rlabs,'Integer',clabs,80,0,ifail)

!     Calculate the eigenvalues and Schur factorization of H

!     The NAG name equivalent of zhseqr is f08psf
Call zhseqr('Schur form','Initialize Z',n,1,n,h,ldh,w,z,ldz,work,lwork,  &
info)

Write (nout,*)
If (info>0) Then
Write (nout,*) 'Failure to converge.'
Else

!       Compute A - Z*T*Z^H from Schur factorization of A, and store in matrix
!       D
!       The NAG name equivalent of zgemm is f06zaf
alpha = cmplx(1,kind=nag_wp)
beta = cmplx(0,kind=nag_wp)
Call zgemm('N','N',n,n,n,alpha,z,ldz,h,ldh,beta,c,ldc)
alpha = cmplx(-1,kind=nag_wp)
beta = cmplx(1,kind=nag_wp)
Call zgemm('N','C',n,n,n,alpha,c,ldc,z,ldz,beta,d,ldd)

!       Find norm of matrix D and print warning if it is too large
!       f06uaf is the NAG name equivalent of the LAPACK auxiliary zlange
norm = zlange('O',ldd,n,d,ldd,rwork)

If (norm>x02ajf()**0.5_nag_wp) Then
Write (nout,*) 'Norm of A-(Z*T*Z^H) is much greater than 0.'
Write (nout,*) 'Schur factorization has failed.'
Else
!         Print eigenvalues
Write (nout,*) 'Eigenvalues'
Write (nout,99999)(w(i),i=1,n)
End If

End If

99999 Format ((3X,4(' (',F7.4,',',F7.4,')',:)))
End Program f08psfe
```