Program f07befe
! F07BEF Example Program Text
! Mark 29.2 Release. NAG Copyright 2023.
! .. 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