Program f07cufe ! F07CUF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: nag_wp, x02ajf, zgtcon, zgttrf, zlangt => f06unf ! .. 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 :: d(:), dl(:), du(:), du2(:), work(:) Integer, Allocatable :: ipiv(:) ! .. Executable Statements .. Write (nout,*) 'F07CUF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) Read (nin,*) n Allocate (d(n),dl(n-1),du(n-1),du2(n-2),work(2*n),ipiv(n)) ! Read the tridiagonal matrix A from data file Read (nin,*) du(1:n-1) Read (nin,*) d(1:n) Read (nin,*) dl(1:n-1) ! Compute the 1-norm of A ! f06unf is the NAG name equivalent of the LAPACK auxiliary zlangt anorm = zlangt('1-norm',n,dl,d,du) ! Factorize the tridiagonal matrix A ! The NAG name equivalent of zgttrf is f07crf Call zgttrf(n,dl,d,du,du2,ipiv,info) If (info==0) Then ! Estimate the condition number of A ! The NAG name equivalent of zgtcon is f07cuf Call zgtcon('1-norm',n,dl,d,du,du2,ipiv,anorm,rcond,work,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 (', info, ',', info, ')', & ' element of the factor U is zero' End If 99999 Format (1X,A,1P,E10.2) 99998 Format (1X,A,I3,A,I3,A,A) End Program f07cufe