Program f08mefe
! F08MEF Example Program Text
! Mark 30.0 Release. NAG Copyright 2024.
! .. Use Statements ..
Use nag_library, Only: dbdsqr, f06qhf, nag_wp, x04caf
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Real (Kind=nag_wp), Parameter :: one = 1.0_nag_wp
Real (Kind=nag_wp), Parameter :: zero = 0.0_nag_wp
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: ifail, info, ldc, ldu, ldvt, n
Character (1) :: uplo
! .. Local Arrays ..
Real (Kind=nag_wp), Allocatable :: c(:,:), d(:), e(:), u(:,:), vt(:,:), &
work(:)
! .. Executable Statements ..
Write (nout,*) 'F08MEF Example Program Results'
! Skip heading in data file
Read (nin,*)
Read (nin,*) n
ldc = 1
ldu = n
ldvt = n
Allocate (c(ldc,1),d(n),e(n-1),u(ldu,n),vt(ldvt,n),work(4*n))
! Read B from data file
Read (nin,*) d(1:n)
Read (nin,*) e(1:n-1)
Read (nin,*) uplo
! Initialize U and VT to be the unit matrix
Call f06qhf('General',n,n,zero,one,u,ldu)
Call f06qhf('General',n,n,zero,one,vt,ldvt)
! Calculate the SVD of B
! The NAG name equivalent of dbdsqr is f08mef
Call dbdsqr(uplo,n,n,n,0,d,e,vt,ldvt,u,ldu,c,ldc,work,info)
Write (nout,*)
If (info>0) Then
Write (nout,*) 'Failure to converge.'
Else
! Print singular values, left & right singular vectors
Write (nout,*) 'Singular values'
Write (nout,99999) d(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 x04caf('General',' ',n,n,vt,ldvt,'Right singular vectors, by row' &
,ifail)
Write (nout,*)
Flush (nout)
ifail = 0
Call x04caf('General',' ',n,n,u,ldu,'Left singular vectors, by column' &
,ifail)
End If
99999 Format (3X,(8F8.4))
End Program f08mefe