Program f08ktfe
! F08KTF Example Program Text
! Mark 28.4 Release. NAG Copyright 2022.
! .. Use Statements ..
Use nag_library, Only: f06tff, nag_wp, x04dbf, zbdsqr, zgebrd, zungbr
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ic, ifail, info, lda, ldc, ldu, &
ldvt, lwork, m, n
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: a(:,:), c(:,:), taup(:), tauq(:), &
u(:,:), vt(:,:), work(:)
Real (Kind=nag_wp), Allocatable :: d(:), e(:), rwork(:)
Character (1) :: clabs(1), rlabs(1)
! .. Executable Statements ..
Write (nout,*) 'F08KTF Example Program Results'
! Skip heading in data file
Read (nin,*)
Do ic = 1, 2
Read (nin,*) m, n
lda = m
ldc = n
ldu = m
ldvt = n
lwork = 64*(m+n)
Allocate (a(lda,n),c(ldc,n),taup(n),tauq(n),u(ldu,n),vt(ldvt,n), &
work(lwork),d(n),e(n-1),rwork(4*n-4))
! Read A from data file
Read (nin,*)(a(i,1:n),i=1,m)
! Reduce A to bidiagonal form
! The NAG name equivalent of zgebrd is f08ksf
Call zgebrd(m,n,a,lda,d,e,tauq,taup,work,lwork,info)
If (m>=n) Then
! Copy A to VT and U
Call f06tff('Upper',n,n,a,lda,vt,ldvt)
Call f06tff('Lower',m,n,a,lda,u,ldu)
! Form P**H explicitly, storing the result in VT
! The NAG name equivalent of zungbr is f08ktf
Call zungbr('P',n,n,m,vt,ldvt,taup,work,lwork,info)
! Form Q explicitly, storing the result in U
Call zungbr('Q',m,n,n,u,ldu,tauq,work,lwork,info)
! Compute the SVD of A
! The NAG name equivalent of zbdsqr is f08msf
Call zbdsqr('Upper',n,n,m,0,d,e,vt,ldvt,u,ldu,c,ldc,rwork,info)
! Print singular values, left & right singular vectors
Write (nout,*)
Write (nout,*) 'Example 1: 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 x04dbf('General',' ',n,n,vt,ldvt,'Bracketed','F7.4', &
'Example 1: right singular vectors, by row','Integer',rlabs, &
'Integer',clabs,80,0,ifail)
Write (nout,*)
Flush (nout)
Call x04dbf('General',' ',m,n,u,ldu,'Bracketed','F7.4', &
'Example 1: left singular vectors, by column','Integer',rlabs, &
'Integer',clabs,80,0,ifail)
Else
! Copy A to VT and U
Call f06tff('Upper',m,n,a,lda,vt,ldvt)
Call f06tff('Lower',m,m,a,lda,u,ldu)
! Form P**H explicitly, storing the result in VT
! The NAG name equivalent of zungbr is f08ktf
Call zungbr('P',m,n,m,vt,ldvt,taup,work,lwork,info)
! Form Q explicitly, storing the result in U
Call zungbr('Q',m,m,n,u,ldu,tauq,work,lwork,info)
! Compute the SVD of A
! The NAG name equivalent of zbdsqr is f08msf
Call zbdsqr('Lower',m,n,m,0,d,e,vt,ldvt,u,ldu,c,ldc,rwork,info)
! Print singular values, left & right singular vectors
Write (nout,*)
Write (nout,*) 'Example 2: singular values'
Write (nout,99999) d(1:m)
Write (nout,*)
Flush (nout)
ifail = 0
Call x04dbf('General',' ',m,n,vt,ldvt,'Bracketed','F7.4', &
'Example 2: right singular vectors, by row','Integer',rlabs, &
'Integer',clabs,80,0,ifail)
Write (nout,*)
Flush (nout)
Call x04dbf('General',' ',m,m,u,ldu,'Bracketed','F7.4', &
'Example 2: left singular vectors, by column','Integer',rlabs, &
'Integer',clabs,80,0,ifail)
End If
Deallocate (a,c,taup,tauq,u,vt,work,d,e,rwork)
End Do
99999 Format (8X,4(F7.4,11X,:))
End Program f08ktfe