Program f07jufe ! F07JUF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: nag_wp, x02ajf, zlanht => f06upf, zptcon, zpttrf ! .. 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 .. Complex (Kind=nag_wp), Allocatable :: e(:) Real (Kind=nag_wp), Allocatable :: d(:), rwork(:) ! .. Executable Statements .. Write (nout,*) 'F07JUF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) Read (nin,*) n Allocate (e(n-1),d(n),rwork(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 ! f06upf is the NAG name equivalent of the LAPACK auxiliary zlanht anorm = zlanht('1-norm',n,d,e) ! Factorize the tridiagonal matrix A ! The NAG name equivalent of zpttrf is f07jrf Call zpttrf(n,d,e,info) If (info==0) Then ! Estimate the condition number of A ! The NAG name equivalent of zptcon is f07juf Call zptcon(n,d,e,anorm,rcond,rwork,info) ! Print the estimated condition number If (rcond>=x02ajf()) Then Write (nout,99999) 'Estimate of condition number = ', & 1.0E0_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 f07jufe