Program f08hqfe ! F08HQF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: nag_wp, x04daf, zhbevd ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: i, ifail, info, j, kd, ldab, ldz, & liwork, lrwork, lwork, n Character (1) :: job, uplo ! .. Local Arrays .. Complex (Kind=nag_wp), Allocatable :: ab(:,:), work(:), z(:,:) Real (Kind=nag_wp), Allocatable :: rwork(:), w(:) Integer, Allocatable :: iwork(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout,*) 'F08HQF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n, kd ldab = n ldz = n liwork = 5*n + 3 lrwork = 2*n*n + 5*n + 1 lwork = 2*n*n Allocate (ab(ldab,n),work(lwork),z(ldz,n),rwork(lrwork),w(n), & iwork(liwork)) ! 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 Read (nin,*) job ! Calculate all the eigenvalues and eigenvectors of A ! The NAG name equivalent of zhbevd is f08hqf Call zhbevd(job,uplo,n,kd,ab,ldab,w,z,ldz,work,lwork,rwork,lrwork,iwork, & liwork,info) Write (nout,*) If (info>0) Then Write (nout,*) 'Failure to converge.' Else ! Print eigenvalues and eigenvectors Write (nout,*) 'Eigenvalues' Do i = 1, n Write (nout,99999) i, w(i) End Do Write (nout,*) Flush (nout) ! Normalize the eigenvectors Do i = 1, n z(1:n,i) = z(1:n,i)/z(1,i) End Do ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call x04daf('General',' ',n,n,z,ldz,'Eigenvectors',ifail) End If 99999 Format (3X,I5,5X,2F8.4) End Program f08hqfe