Program f08atfe
! F08ATF Example Program Text
! Mark 29.1 Release. NAG Copyright 2023.
! .. Use Statements ..
Use nag_library, Only: nag_wp, x04dbf, zgeqrf, zungqr
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ifail, info, lda, lwork, m, n
Character (30) :: title
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: a(:,:), tau(:), work(:)
Character (1) :: clabs(1), rlabs(1)
! .. Executable Statements ..
Write (nout,*) 'F08ATF Example Program Results'
! Skip heading in data file
Read (nin,*)
Read (nin,*) m, n
lda = m
lwork = 64*n
Allocate (a(lda,n),tau(n),work(lwork))
! Read A from data file
Read (nin,*)(a(i,1:n),i=1,m)
! Compute the QR factorization of A
! The NAG name equivalent of zgeqrf is f08asf
Call zgeqrf(m,n,a,lda,tau,work,lwork,info)
! Form the leading N columns of Q explicitly
! The NAG name equivalent of zungqr is f08atf
Call zungqr(m,n,n,a,lda,tau,work,lwork,info)
! Print the leading N columns of Q only
Write (nout,*)
Write (title,99999) n
Flush (nout)
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04dbf('General',' ',m,n,a,lda,'Bracketed','F7.4',title,'Integer', &
rlabs,'Integer',clabs,80,0,ifail)
99999 Format ('The leading ',I2,' columns of Q')
End Program f08atfe