Program f07vefe

!     F07VEF Example Program Text

!     Mark 30.2 Release. NAG Copyright 2024.

!     .. Use Statements ..
      Use nag_library, Only: dtbtrs, nag_wp, x04caf
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Integer, Parameter               :: nin = 5, nout = 6
      Character (1), Parameter         :: diag = 'N', trans = 'N'
!     .. Local Scalars ..
      Integer                          :: i, ifail, info, j, kd, ldab, ldb, n, &
                                          nrhs
      Character (1)                    :: uplo
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: ab(:,:), b(:,:)
!     .. Intrinsic Procedures ..
      Intrinsic                        :: max, min
!     .. Executable Statements ..
      Write (nout,*) 'F07VEF Example Program Results'
!     Skip heading in data file
      Read (nin,*)
      Read (nin,*) n, kd, nrhs
      ldab = kd + 1
      ldb = n
      Allocate (ab(ldab,n),b(ldb,nrhs))

!     Read A and B from data file

      Read (nin,*) uplo
      If (uplo=='U') Then
        Do i = 1, n
          Read (nin,*)(ab(kd+1+i-j,j),j=i,min(n,i+kd))
        End Do
      Else If (uplo=='L') Then
        Do i = 1, n
          Read (nin,*)(ab(1+i-j,j),j=max(1,i-kd),i)
        End Do
      End If
      Read (nin,*)(b(i,1:nrhs),i=1,n)

!     Compute solution
!     The NAG name equivalent of dtbtrs is f07vef
      Call dtbtrs(uplo,trans,diag,n,kd,nrhs,ab,ldab,b,ldb,info)

!     Print solution

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

!       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,*) 'A is singular'
      End If

    End Program f07vefe