PROGRAM f08jufe ! F08JUF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : f06tff, nag_wp, x04dbf, zhetrd, zpteqr, zungtr ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. INTEGER :: i, ifail, info, lda, ldz, lwork, n CHARACTER (1) :: uplo ! .. Local Arrays .. COMPLEX (KIND=nag_wp), ALLOCATABLE :: a(:,:), tau(:), work(:), z(:,:) REAL (KIND=nag_wp), ALLOCATABLE :: d(:), e(:), rwork(:) CHARACTER (1) :: clabs(1), rlabs(1) ! .. Executable Statements .. WRITE (nout,*) 'F08JUF Example Program Results' ! Skip heading in data file READ (nin,*) READ (nin,*) n lda = n ldz = n lwork = 64*n ALLOCATE (a(lda,n),tau(n),work(lwork),z(ldz,n),d(n),e(n),rwork(4*n)) ! Read A from data file READ (nin,*) uplo IF (uplo=='U') THEN READ (nin,*) (a(i,i:n),i=1,n) ELSE IF (uplo=='L') THEN READ (nin,*) (a(i,1:i),i=1,n) END IF ! Reduce A to tridiagonal form T = (Q**H)*A*Q ! The NAG name equivalent of zhetrd is f08fsf CALL zhetrd(uplo,n,a,lda,d,e,tau,work,lwork,info) ! Copy A into Z CALL f06tff(uplo,n,n,a,lda,z,ldz) ! Form Q explicitly, storing the result in Z ! The NAG name equivalent of zungtr is f08ftf CALL zungtr(uplo,n,z,ldz,tau,work,lwork,info) ! Calculate all the eigenvalues and eigenvectors of A ! The NAG name equivalent of zpteqr is f08juf CALL zpteqr('V',n,d,e,z,ldz,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 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 x04dbf('General',' ',n,n,z,ldz,'Bracketed','F7.4', & 'Eigenvectors','Integer',rlabs,'Integer',clabs,80,0,ifail) END IF 99999 FORMAT (8X,4(F7.4,11X:)) END PROGRAM f08jufe