PROGRAM f08jefe ! F08JEF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dsteqr, nag_wp, x04caf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. INTEGER :: i, ifail, info, ldz, n ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: d(:), e(:), work(:), z(:,:) ! .. Executable Statements .. WRITE (nout,*) 'F08JEF Example Program Results' ! Skip heading in data file READ (nin,*) READ (nin,*) n ldz = n ALLOCATE (d(n),e(n-1),work(2*n-2),z(ldz,n)) ! Read T from data file READ (nin,*) d(1:n) READ (nin,*) e(1:n-1) ! Calculate all the eigenvalues and eigenvectors of T ! The NAG name equivalent of dsteqr is f08jef CALL dsteqr('I',n,d,e,z,ldz,work,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 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 f08jefe