Program f07befe

!     F07BEF Example Program Text

!     Mark 27.3 Release. NAG Copyright 2021.

!     .. Use Statements ..
      Use nag_library, Only: dgbtrf, dgbtrs, nag_wp, x04caf
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nin = 5, nout = 6
      Character (1), Parameter         :: trans = 'N'
!     .. Local Scalars ..
      Integer                          :: i, ifail, info, j, k, kl, ku, ldab,  &
                                          ldb, n, nrhs
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: ab(:,:), b(:,:)
      Integer, Allocatable             :: ipiv(:)
!     .. Intrinsic Procedures ..
      Intrinsic                        :: max, min
!     .. Executable Statements ..
      Write (nout,*) 'F07BEF Example Program Results'
!     Skip heading in data file
      Read (nin,*)
      Read (nin,*) n, nrhs, kl, ku
      ldab = 2*kl + ku + 1
      ldb = n
      Allocate (ab(ldab,n),b(ldb,nrhs),ipiv(n))

!     Read A and B from data file

      k = kl + ku + 1
      Read (nin,*)((ab(k+i-j,j),j=max(i-kl,1),min(i+ku,n)),i=1,n)
      Read (nin,*)(b(i,1:nrhs),i=1,n)

!     Factorize A
!     The NAG name equivalent of dgbtrf is f07bdf
      Call dgbtrf(n,n,kl,ku,ab,ldab,ipiv,info)

      Write (nout,*)
      Flush (nout)
      If (info==0) Then

!       Compute solution
!       The NAG name equivalent of dgbtrs is f07bef
        Call dgbtrs(trans,n,kl,ku,nrhs,ab,ldab,ipiv,b,ldb,info)

!       Print solution

!       ifail: behaviour on error exit
!              =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
        ifail = 0
        Call x04caf('General',' ',n,nrhs,b,ldb,'Solution(s)',ifail)

      Else
        Write (nout,*) 'The factor U is singular'
      End If

    End Program f07befe