Program f08jcfe ! F08JCF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dnrm2, dstevd, nag_wp, x04caf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=nag_wp) :: norm Integer :: i, ifail, info, ldz, liwork, lwork, n Character (1) :: job ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: d(:), e(:), work(:), z(:,:) Integer, Allocatable :: iwork(:) ! .. Executable Statements .. Write (nout,*) 'F08JCF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n ldz = n liwork = 5*n + 3 lwork = n*n + 4*n + 1 Allocate (d(n),e(n-1),work(lwork),z(ldz,n),iwork(liwork)) ! Read T from data file Read (nin,*) d(1:n) Read (nin,*) e(1:n-1) Read (nin,*) job ! Calculate all the eigenvalues and eigenvectors of T ! The NAG name equivalent of dstevd is f08jcf Call dstevd(job,n,d,e,z,ldz,work,lwork,iwork,liwork,info) Write (nout,*) If (info>0) Then Write (nout,*) 'Failure to converge.' Else ! Print eigenvalues and eigenvectors Write (nout,*) 'Eigenvalues' Write (nout,99999) d(1:n) Write (nout,*) Flush (nout) ! Normalize the eigenvectors Do i = 1, n ! The NAG name equivalent of dnrm2 is f06ejf norm = dnrm2(n,z(1,i),1) If (z(1,i)<0.0_nag_wp) norm = -norm z(1:n,i) = z(1:n,i)/norm End Do ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call x04caf('General',' ',n,n,z,ldz,'Eigenvectors',ifail) End If 99999 Format (3X,(8F8.4)) End Program f08jcfe