Program f07aafe

!     F07AAF Example Program Text

!     Mark 30.0 Release. NAG Copyright 2024.

!     .. Use Statements ..
      Use nag_library, Only: dgesv, nag_wp, x04caf
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
      Integer                          :: i, ifail, info, lda, ldb, n
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: a(:,:), b(:)
      Integer, Allocatable             :: ipiv(:)
!     .. Executable Statements ..
      Write (nout,*) 'F07AAF Example Program Results'
      Write (nout,*)
!     Skip heading in data file
      Read (nin,*)
      Read (nin,*) n
      lda = n
      ldb = n
      Allocate (a(lda,n),b(ldb),ipiv(n))

!     Read A and B from data file

      Read (nin,*)(a(i,1:n),i=1,n)
      Read (nin,*) b(1:n)

!     Solve the equations Ax = b for x

!     The NAG name equivalent of dgesv is f07aaf
      Call dgesv(n,1,a,lda,ipiv,b,ldb,info)

      If (info==0) Then

!       Print solution

        Write (nout,*) 'Solution'
        Write (nout,99999) b(1:n)

!       Print details of factorization

        Write (nout,*)
        Flush (nout)

!       ifail: behaviour on error exit
!              =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
        ifail = 0
        Call x04caf('General',' ',n,n,a,lda,'Details of factorization',ifail)

!       Print pivot indices

        Write (nout,*)
        Write (nout,*) 'Pivot indices'
        Write (nout,99998) ipiv(1:n)

      Else
        Write (nout,99997) 'The (', info, ',', info, ')',                      &
          ' element of the factor U is zero'
      End If

99999 Format ((3X,7F11.4))
99998 Format ((3X,7I11))
99997 Format (1X,A,I3,A,I3,A,A)
    End Program f07aafe