Program f07bsfe
! F07BSF Example Program Text
! Mark 27.3 Release. NAG Copyright 2021.
! .. Use Statements ..
Use nag_library, Only: nag_wp, x04dbf, zgbtrf, zgbtrs
! .. 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 ..
Complex (Kind=nag_wp), Allocatable :: ab(:,:), b(:,:)
Integer, Allocatable :: ipiv(:)
Character (1) :: clabs(1), rlabs(1)
! .. Intrinsic Procedures ..
Intrinsic :: max, min
! .. Executable Statements ..
Write (nout,*) 'F07BSF 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 zgbtrf is f07brf
Call zgbtrf(n,n,kl,ku,ab,ldab,ipiv,info)
Write (nout,*)
Flush (nout)
If (info==0) Then
! Compute solution
! The NAG name equivalent of zgbtrs is f07bsf
Call zgbtrs(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 x04dbf('General',' ',n,nrhs,b,ldb,'Bracketed','F7.4', &
'Solution(s)','Integer',rlabs,'Integer',clabs,80,0,ifail)
Else
Write (nout,*) 'The factor U is singular'
End If
End Program f07bsfe