NAG Library Manual, Mark 28.4
```    Program f07kdfe

!     F07KDF Example Program Text

!     Mark 28.4 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use nag_library, Only: dpstrf, nag_wp, x04caf, x04ebf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Real (Kind=nag_wp), Parameter    :: zero = 0.0E0_nag_wp
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Real (Kind=nag_wp)               :: tol
Integer                          :: i, ifail, info, j, lda, n, rank
Character (1)                    :: uplo
!     .. Local Arrays ..
Real (Kind=nag_wp), Allocatable  :: a(:,:), work(:)
Integer, Allocatable             :: piv(:)
Character (1)                    :: clabs(1), rlabs(1)
!     .. Executable Statements ..
Write (nout,*) 'F07KDF Example Program Results'
!     Skip heading in data file
lda = n
Allocate (a(lda,n),piv(n),work(2*n))

!     Read A from data file
If (uplo=='U') Then
Else If (uplo=='L') Then
End If
tol = -1.0_nag_wp

!     Factorize A
!     The NAG name equivalent of dpstrf is f07kdf
Call dpstrf(uplo,n,a,lda,piv,rank,tol,work,info)

!     Zero out columns rank+1 to n
If (uplo=='U') Then
Do j = rank + 1, n
a(rank+1:j,j) = zero
End Do
Else If (uplo=='L') Then
Do j = rank + 1, n
a(j:n,j) = zero
End Do
End If

!     Print rank
Write (nout,*)
Write (nout,'(1X,A15,I3)') 'Computed rank: ', rank

!     Print factor
Write (nout,*)
Flush (nout)
ifail = 0
Call x04caf(uplo,'Nonunit',n,n,a,lda,'Factor',ifail)

!     Print pivot indices
Write (nout,*)
Write (nout,*) 'PIV'
Flush (nout)

ifail = 0
Call x04ebf('General','Non-unit',1,n,piv,1,'I11',' ','No',rlabs,'No',    &
clabs,80,1,ifail)

End Program f07kdfe
```