PROGRAM f08hcfe ! F08HCF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dsbevd, nag_wp, x04caf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. INTEGER :: i, ifail, info, j, kd, ldab, ldz, & liwork, lwork, n CHARACTER (1) :: job, uplo ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: ab(:,:), w(:), work(:), z(:,:) INTEGER, ALLOCATABLE :: iwork(:) ! .. Intrinsic Functions .. INTRINSIC max, min ! .. Executable Statements .. WRITE (nout,*) 'F08HCF Example Program Results' ! Skip heading in data file READ (nin,*) READ (nin,*) n, kd ldab = kd + 1 ldz = n liwork = 5*n + 3 lwork = 2*n*n + 5*n + 1 ALLOCATE (ab(ldab,n),w(n),work(lwork),z(ldz,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 dsbevd is f08hcf CALL dsbevd(job,uplo,n,kd,ab,ldab,w,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) w(1:n) 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 x04caf('General',' ',n,n,z,ldz,'Eigenvectors',ifail) END IF 99999 FORMAT (3X,(8F8.4)) END PROGRAM f08hcfe