Program f08qffe
! F08QFF Example Program Text
! Mark 29.2 Release. NAG Copyright 2023.
! .. Use Statements ..
Use nag_library, Only: dtrexc, nag_wp, x04caf
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ifail, ifst, ilst, info, ldq, &
ldt, n
! .. Local Arrays ..
Real (Kind=nag_wp), Allocatable :: q(:,:), t(:,:), work(:)
! .. Executable Statements ..
Write (nout,*) 'F08QFF Example Program Results'
Write (nout,*)
Flush (nout)
! Skip heading in data file
Read (nin,*)
Read (nin,*) n
ldq = 1
ldt = n
Allocate (q(ldq,1),t(ldt,n),work(n))
! Read T from data file
Read (nin,*)(t(i,1:n),i=1,n)
! Read the row indices
Read (nin,*) ifst, ilst
! Reorder the Schur factor T
! The NAG name equivalent of dtrexc is f08qff
Call dtrexc('No update',n,t,ldt,q,ldq,ifst,ilst,work,info)
If (info>0) Then
Write (nout,99999) info, ilst
Write (nout,*)
Flush (nout)
End If
! Print reordered Schur factor
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04caf('General',' ',n,n,t,ldt,'Reordered Schur form',ifail)
99999 Format (' Reordering could not be completed. INFO = ',I3,' ILST = ',I5)
End Program f08qffe