Program f07kdfe

!     F07KDF Example Program Text

!     Mark 30.0 Release. NAG Copyright 2024.

!     .. 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
      Read (nin,*)
      Read (nin,*) n, uplo
      lda = n
      Allocate (a(lda,n),piv(n),work(2*n))

!     Read A from data file
      If (uplo=='U') Then
        Read (nin,*)(a(i,i:n),i=1,n)
      Else If (uplo=='L') Then
        Read (nin,*)(a(i,1:i),i=1,n)
      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