NAG Library Manual, Mark 27.2
```    Program f11dbfe

!     F11DBF Example Program Text

!     Mark 27.2 Release. NAG Copyright 2021.

!     .. Use Statements ..
Use nag_library, Only: f11daf, f11dbf, nag_wp
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Real (Kind=nag_wp)               :: dtol
Integer                          :: i, ifail, la, lfill, liwork, n, nnz, &
nnzc, npivm
Character (1)                    :: check, milu, pstrat, trans
!     .. Local Arrays ..
Real (Kind=nag_wp), Allocatable  :: a(:), x(:), y(:)
Integer, Allocatable             :: icol(:), idiag(:), ipivp(:),         &
ipivq(:), irow(:), istr(:), iwork(:)
!     .. Executable Statements ..
Write (nout,*) 'F11DBF Example Program Results'
Write (nout,*)

!     Skip heading in data file

!     Read order of matrix and number of nonzero entries

la = 2*nnz
liwork = 7*n + 2
Allocate (a(la),x(n),y(n),icol(la),idiag(n),ipivp(n),ipivq(n),irow(la),  &
istr(n+1),iwork(liwork))

Do i = 1, nnz
End Do

!     Calculate LU factorization

lfill = -1
dtol = 0.E0_nag_wp
pstrat = 'C'
milu = 'N'

!     ifail: behaviour on error exit
!             =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call f11daf(n,nnz,a,la,irow,icol,lfill,dtol,pstrat,milu,ipivp,ipivq,     &
istr,idiag,nnzc,npivm,iwork,liwork,ifail)

!     Check value of npivm

If (npivm>0) Then

Write (nout,*) 'Factorization is not complete'

Else

!       Solve P L D U x = y

trans = 'N'
check = 'C'

ifail = 0
Call f11dbf(trans,n,a,la,irow,icol,ipivp,ipivq,istr,idiag,check,y,x,   &
ifail)

!       Output results

Write (nout,*) ' Solution of linear system'
Write (nout,'(E16.4)') x(1:n)

End If

End Program f11dbfe
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