```      SUBROUTINE CHPEV( JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, RWORK,
\$                  INFO )
*
*  -- LAPACK driver routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
CHARACTER          JOBZ, UPLO
INTEGER            INFO, LDZ, N
*     ..
*     .. Array Arguments ..
REAL               RWORK( * ), W( * )
COMPLEX            AP( * ), WORK( * ), Z( LDZ, * )
*     ..
*
*  Purpose
*  =======
*
*  CHPEV computes all the eigenvalues and, optionally, eigenvectors of a
*  complex Hermitian matrix in packed storage.
*
*  Arguments
*  =========
*
*  JOBZ    (input) CHARACTER*1
*          = 'N':  Compute eigenvalues only;
*          = 'V':  Compute eigenvalues and eigenvectors.
*
*  UPLO    (input) CHARACTER*1
*          = 'U':  Upper triangle of A is stored;
*          = 'L':  Lower triangle of A is stored.
*
*  N       (input) INTEGER
*          The order of the matrix A.  N >= 0.
*
*  AP      (input/output) COMPLEX array, dimension (N*(N+1)/2)
*          On entry, the upper or lower triangle of the Hermitian matrix
*          A, packed columnwise in a linear array.  The j-th column of A
*          is stored in the array AP as follows:
*          if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
*          if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n.
*
*          On exit, AP is overwritten by values generated during the
*          reduction to tridiagonal form.  If UPLO = 'U', the diagonal
*          and first superdiagonal of the tridiagonal matrix T overwrite
*          the corresponding elements of A, and if UPLO = 'L', the
*          diagonal and first subdiagonal of T overwrite the
*          corresponding elements of A.
*
*  W       (output) REAL array, dimension (N)
*          If INFO = 0, the eigenvalues in ascending order.
*
*  Z       (output) COMPLEX array, dimension (LDZ, N)
*          If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal
*          eigenvectors of the matrix A, with the i-th column of Z
*          holding the eigenvector associated with W(i).
*          If JOBZ = 'N', then Z is not referenced.
*
*  LDZ     (input) INTEGER
*          The leading dimension of the array Z.  LDZ >= 1, and if
*          JOBZ = 'V', LDZ >= max(1,N).
*
*  WORK    (workspace) COMPLEX array, dimension (max(1, 2*N-1))
*
*  RWORK   (workspace) REAL array, dimension (max(1, 3*N-2))
*
*  INFO    (output) INTEGER
*          = 0:  successful exit.
*          < 0:  if INFO = -i, the i-th argument had an illegal value.
*          > 0:  if INFO = i, the algorithm failed to converge; i
*                off-diagonal elements of an intermediate tridiagonal
*                form did not converge to zero.
*
*  =====================================================================
*
*     .. Parameters ..
REAL               ZERO, ONE
PARAMETER          ( ZERO = 0.0E0, ONE = 1.0E0 )
*     ..
*     .. Local Scalars ..
LOGICAL            WANTZ
INTEGER            IINFO, IMAX, INDE, INDRWK, INDTAU, INDWRK,
\$                   ISCALE
REAL               ANRM, BIGNUM, EPS, RMAX, RMIN, SAFMIN, SIGMA,
\$                   SMLNUM
*     ..
*     .. External Functions ..
LOGICAL            LSAME
REAL               CLANHP, SLAMCH
EXTERNAL           LSAME, CLANHP, SLAMCH
*     ..
*     .. External Subroutines ..
EXTERNAL           CHPTRD, CSSCAL, CSTEQR, CUPGTR, SSCAL, SSTERF,
\$                   XERBLA
*     ..
*     .. Intrinsic Functions ..
INTRINSIC          SQRT
*     ..
*     .. Executable Statements ..
*
*     Test the input parameters.
*
WANTZ = LSAME( JOBZ, 'V' )
*
INFO = 0
IF( .NOT.( WANTZ .OR. LSAME( JOBZ, 'N' ) ) ) THEN
INFO = -1
ELSE IF( .NOT.( LSAME( UPLO, 'L' ) .OR. LSAME( UPLO, 'U' ) ) )
\$          THEN
INFO = -2
ELSE IF( N.LT.0 ) THEN
INFO = -3
ELSE IF( LDZ.LT.1 .OR. ( WANTZ .AND. LDZ.LT.N ) ) THEN
INFO = -7
END IF
*
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'CHPEV ', -INFO )
RETURN
END IF
*
*     Quick return if possible
*
IF( N.EQ.0 )
\$   RETURN
*
IF( N.EQ.1 ) THEN
W( 1 ) = AP( 1 )
RWORK( 1 ) = 1
IF( WANTZ )
\$      Z( 1, 1 ) = ONE
RETURN
END IF
*
*     Get machine constants.
*
SAFMIN = SLAMCH( 'Safe minimum' )
EPS = SLAMCH( 'Precision' )
SMLNUM = SAFMIN / EPS
BIGNUM = ONE / SMLNUM
RMIN = SQRT( SMLNUM )
RMAX = SQRT( BIGNUM )
*
*     Scale matrix to allowable range, if necessary.
*
ANRM = CLANHP( 'M', UPLO, N, AP, RWORK )
ISCALE = 0
IF( ANRM.GT.ZERO .AND. ANRM.LT.RMIN ) THEN
ISCALE = 1
SIGMA = RMIN / ANRM
ELSE IF( ANRM.GT.RMAX ) THEN
ISCALE = 1
SIGMA = RMAX / ANRM
END IF
IF( ISCALE.EQ.1 ) THEN
CALL CSSCAL( ( N*( N+1 ) ) / 2, SIGMA, AP, 1 )
END IF
*
*     Call CHPTRD to reduce Hermitian packed matrix to tridiagonal form.
*
INDE = 1
INDTAU = 1
CALL CHPTRD( UPLO, N, AP, W, RWORK( INDE ), WORK( INDTAU ),
\$             IINFO )
*
*     For eigenvalues only, call SSTERF.  For eigenvectors, first call
*     CUPGTR to generate the orthogonal matrix, then call CSTEQR.
*
IF( .NOT.WANTZ ) THEN
CALL SSTERF( N, W, RWORK( INDE ), INFO )
ELSE
INDWRK = INDTAU + N
CALL CUPGTR( UPLO, N, AP, WORK( INDTAU ), Z, LDZ,
\$                WORK( INDWRK ), IINFO )
INDRWK = INDE + N
CALL CSTEQR( JOBZ, N, W, RWORK( INDE ), Z, LDZ,
\$                RWORK( INDRWK ), INFO )
END IF
*
*     If matrix was scaled, then rescale eigenvalues appropriately.
*
IF( ISCALE.EQ.1 ) THEN
IF( INFO.EQ.0 ) THEN
IMAX = N
ELSE
IMAX = INFO - 1
END IF
CALL SSCAL( IMAX, ONE / SIGMA, W, 1 )
END IF
*
RETURN
*
*     End of CHPEV
*
END

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