NAG Library Manual, Mark 30.1
Interfaces:  FL   CL   CPP   AD 

NAG AD Library Introduction
Example description
    Program f08ae_p0w_fe

!     F08AE_P0W_F Example Program Text

!     Mark 30.1 Release. NAG Copyright 2024.

!     .. Use Statements ..
      Use iso_c_binding, Only: c_ptr
      Use nagad_library, Only: f08ae_p0w_f
      Use nag_library, Only: nag_wp, x04caf
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nb = 64, nin = 5, nout = 6
!     .. Local Scalars ..
      Type (c_ptr)                     :: ad_handle
      Integer                          :: i, ifail, lda, lwork, m, n
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: a(:,:), tau(:), work(:)
!     .. Executable Statements ..

      Write (nout,*) 'F08AE_P0W_F Example Program Results'
      Write (nout,*)
      Flush (nout)
!     Skip heading in data file
      Read (nin,*)
      Read (nin,*) m, n
      lda = m
      lwork = nb*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 dgeqrf is f08ae_p0w_f
      Call f08ae_p0w_f(ad_handle,m,n,a,lda,tau,work,lwork,ifail)

!     Print R
!     ifail: behaviour on error exit
!            =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
      ifail = 0
      Call x04caf('Upper','Non',n,n,a,lda,'R from QR factorization of A',      &
        ifail)

    End Program f08ae_p0w_fe