Program f07jgfe ! F07JGF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dlanst => f06rpf, dptcon, dpttrf, nag_wp, x02ajf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=nag_wp) :: anorm, rcond Integer :: info, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: d(:), e(:), work(:) ! .. Executable Statements .. Write (nout,*) 'F07JGF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) Read (nin,*) n Allocate (d(n),e(n-1),work(n)) ! Read the lower bidiagonal part of the tridiagonal matrix A from ! data file Read (nin,*) d(1:n) Read (nin,*) e(1:n-1) ! Compute the 1-norm of A ! f06rpf is the NAG name equivalent of the LAPACK auxiliary dlanst anorm = dlanst('1-norm',n,d,e) ! Factorize the tridiagonal matrix A ! The NAG name equivalent of dpttrf is f07jdf Call dpttrf(n,d,e,info) If (info==0) Then ! Estimate the condition number of A ! The NAG name equivalent of dptcon is f07jgf Call dptcon(n,d,e,anorm,rcond,work,info) ! Print the estimated condition number If (rcond>=x02ajf()) Then Write (nout,99999) 'Estimate of condition number = ', & 1.0_nag_wp/rcond Else Write (nout,99999) 'A is singular to working precision. RCOND = ', & rcond End If Else Write (nout,99998) 'The leading minor of order ', info, & ' is not positive definite' End If 99999 Format (1X,A,1P,E10.2) 99998 Format (1X,A,I3,A) End Program f07jgfe