Program f08nnfe

!     F08NNF Example Program Text

!     Mark 30.2 Release. NAG Copyright 2024.

!     .. Use Statements ..
      Use nag_library, Only: nag_wp, x04daf, zgeev
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nb = 64, nin = 5, nout = 6
!     .. Local Scalars ..
      Integer                          :: i, ifail, info, lda, ldvr, lwork, n
!     .. Local Arrays ..
      Complex (Kind=nag_wp), Allocatable :: a(:,:), vr(:,:), w(:), work(:)
      Complex (Kind=nag_wp)            :: dummy(1,1)
      Real (Kind=nag_wp), Allocatable  :: rwork(:)
!     .. Intrinsic Procedures ..
      Intrinsic                        :: max, nint, real
!     .. Executable Statements ..
      Write (nout,*) 'F08NNF Example Program Results'
      Write (nout,*)
!     Skip heading in data file
      Read (nin,*)
      Read (nin,*) n
      lda = n
      ldvr = n
      Allocate (a(lda,n),vr(ldvr,n),w(n),rwork(2*n))

!     Use routine workspace query to get optimal workspace.
      lwork = -1
!     The NAG name equivalent of zgeev is f08nnf
      Call zgeev('No left vectors','Vectors (right)',n,a,lda,w,dummy,1,vr,     &
        ldvr,dummy,lwork,rwork,info)

!     Make sure that there is enough workspace for block size nb.
      lwork = max((nb+1)*n,nint(real(dummy(1,1))))
      Allocate (work(lwork))

!     Read the matrix A from data file

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

!     Compute the eigenvalues and right eigenvectors of A

!     The NAG name equivalent of zgeev is f08nnf
      Call zgeev('No left vectors','Vectors (right)',n,a,lda,w,dummy,1,vr,     &
        ldvr,work,lwork,rwork,info)

      If (info==0) Then

!       Print solution

        Write (nout,*) 'Eigenvalues'
        Write (nout,99999) w(1:n)

        Write (nout,*)
        Flush (nout)

!       ifail: behaviour on error exit
!              =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
        ifail = 0
        Call x04daf('General',' ',n,n,vr,ldvr,'Eigenvectors',ifail)

      Else
        Write (nout,*)
        Write (nout,99998) 'Failure in ZGEEV.  INFO = ', info
      End If

99999 Format ((3X,4(' (',F7.4,',',F7.4,')',:)))
99998 Format (1X,A,I4)
    End Program f08nnfe