Program f08hsfe ! F08HSF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: nag_wp, x04dbf, zhbtrd, zsteqr ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: i, ifail, info, j, kd, ldab, ldq, n Character (1) :: uplo ! .. Local Arrays .. Complex (Kind=nag_wp), Allocatable :: ab(:,:), q(:,:), work(:) Real (Kind=nag_wp), Allocatable :: d(:), e(:), rwork(:) Character (1) :: clabs(1), rlabs(1) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout,*) 'F08HSF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n, kd ldab = kd + 1 ldq = n Allocate (ab(ldab,n),q(ldq,n),work(n),d(n),e(n-1),rwork(2*n-2)) ! Read A from data file Read (nin,*) uplo If (uplo=='U') Then Do i = 1, n Read (nin,*)(ab(kd+1+i-j,j),j=i,min(n,i+kd)) End Do Else If (uplo=='L') Then Do i = 1, n Read (nin,*)(ab(1+i-j,j),j=max(1,i-kd),i) End Do End If ! Reduce A to tridiagonal form T = (Q**H)*A*Q (and form Q) ! The NAG name equivalent of zhbtrd is f08hsf Call zhbtrd('V',uplo,n,kd,ab,ldab,d,e,q,ldq,work,info) ! Calculate all the eigenvalues and eigenvectors of A ! The NAG name equivalent of zsteqr is f08jsf Call zsteqr('V',n,d,e,q,ldq,rwork,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 q(1:n,i) = q(1:n,i)/q(1,i) End Do ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call x04dbf('General',' ',n,n,q,ldq,'Bracketed','F7.4','Eigenvectors', & 'Integer',rlabs,'Integer',clabs,80,0,ifail) End If 99999 Format (8X,4(F7.4,11X:)) End Program f08hsfe