Program f07bgfe ! F07BGF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dgbcon, dgbtrf, dlangb => f06rbf, nag_wp, x02ajf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 Character (1), Parameter :: norm = '1' ! .. Local Scalars .. Real (Kind=nag_wp) :: anorm, rcond Integer :: i, info, j, k, kl, ku, ldab, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: ab(:,:), work(:) Integer, Allocatable :: ipiv(:), iwork(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout,*) 'F07BGF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n, kl, ku ldab = 2*kl + ku + 1 Allocate (ab(ldab,n),work(3*n),ipiv(n),iwork(n)) ! Read A 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) ! Compute norm of A ! f06rbf is the NAG name equivalent of the LAPACK auxiliary dlangb anorm = dlangb(norm,n,kl,ku,ab(kl+1,1),ldab,work) ! Factorize A ! The NAG name equivalent of dgbtrf id f07bdf Call dgbtrf(n,n,kl,ku,ab,ldab,ipiv,info) Write (nout,*) If (info==0) Then ! Estimate condition number ! The NAG name equivalent of dgbcon is f07bgf Call dgbcon(norm,n,kl,ku,ab,ldab,ipiv,anorm,rcond,work,iwork,info) If (rcond>=x02ajf()) Then Write (nout,99999) 'Estimate of condition number =', & 1.0_nag_wp/rcond Else Write (nout,*) 'A is singular to working precision' End If Else Write (nout,*) 'The factor U is singular' End If 99999 Format (1X,A,1P,E10.2) End Program f07bgfe