zhpevd.f.html

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      DOUBLE PRECISION   ANRM, BIGNUM, EPS, RMAX, RMIN, SAFMIN, SIGMA,
     $                   SMLNUM
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.142"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      DOUBLE PRECISION   <a name="DLAMCH.143"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="ZLANHP.143"></a><a href="zlanhp.f.html#ZLANHP.1">ZLANHP</a>
      EXTERNAL           <a name="LSAME.144"></a><a href="lsame.f.html#LSAME.1">LSAME</a>, <a name="DLAMCH.144"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="ZLANHP.144"></a><a href="zlanhp.f.html#ZLANHP.1">ZLANHP</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           DSCAL, <a name="DSTERF.147"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>, <a name="XERBLA.147"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>, ZDSCAL, <a name="ZHPTRD.147"></a><a href="zhptrd.f.html#ZHPTRD.1">ZHPTRD</a>, <a name="ZSTEDC.147"></a><a href="zstedc.f.html#ZSTEDC.1">ZSTEDC</a>,
     $                   <a name="ZUPMTR.148"></a><a href="zupmtr.f.html#ZUPMTR.1">ZUPMTR</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          SQRT
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Executable Statements ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Test the input parameters.
</span><span class="comment">*</span><span class="comment">
</span>      WANTZ = <a name="LSAME.157"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      LQUERY = ( LWORK.EQ.-1 .OR. LRWORK.EQ.-1 .OR. LIWORK.EQ.-1 )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( .NOT.( WANTZ .OR. <a name="LSAME.161"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'N'</span> ) ) ) THEN
         INFO = -1
      ELSE IF( .NOT.( <a name="LSAME.163"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> ) .OR. <a name="LSAME.163"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> ) ) )
     $          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
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.EQ.0 ) THEN
         IF( N.LE.1 ) THEN
            LWMIN = 1
            LIWMIN = 1
            LRWMIN = 1
         ELSE
            IF( WANTZ ) THEN
               LWMIN = 2*N
               LRWMIN = 1 + 5*N + 2*N**2
               LIWMIN = 3 + 5*N
            ELSE
               LWMIN = N
               LRWMIN = N
               LIWMIN = 1
            END IF
         END IF
         WORK( 1 ) = LWMIN
         RWORK( 1 ) = LRWMIN
         IWORK( 1 ) = LIWMIN
<span class="comment">*</span><span class="comment">
</span>         IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -9
         ELSE IF( LRWORK.LT.LRWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -11
         ELSE IF( LIWORK.LT.LIWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -13
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.202"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="ZHPEVD.202"></a><a href="zhpevd.f.html#ZHPEVD.1">ZHPEVD</a>'</span>, -INFO )
         RETURN
      ELSE IF( LQUERY ) THEN
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Quick return if possible
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.0 )
     $   RETURN
<span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.1 ) THEN
         W( 1 ) = AP( 1 )
         IF( WANTZ )
     $      Z( 1, 1 ) = CONE
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Get machine constants.
</span><span class="comment">*</span><span class="comment">
</span>      SAFMIN = <a name="DLAMCH.222"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Safe minimum'</span> )
      EPS = <a name="DLAMCH.223"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'Precision'</span> )
      SMLNUM = SAFMIN / EPS
      BIGNUM = ONE / SMLNUM
      RMIN = SQRT( SMLNUM )
      RMAX = SQRT( BIGNUM )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Scale matrix to allowable range, if necessary.
</span><span class="comment">*</span><span class="comment">
</span>      ANRM = <a name="ZLANHP.231"></a><a href="zlanhp.f.html#ZLANHP.1">ZLANHP</a>( <span class="string">'M'</span>, 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 ZDSCAL( ( N*( N+1 ) ) / 2, SIGMA, AP, 1 )
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Call <a name="ZHPTRD.244"></a><a href="zhptrd.f.html#ZHPTRD.1">ZHPTRD</a> to reduce Hermitian packed matrix to tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span>      INDE = 1
      INDTAU = 1
      INDRWK = INDE + N
      INDWRK = INDTAU + N
      LLWRK = LWORK - INDWRK + 1
      LLRWK = LRWORK - INDRWK + 1
      CALL <a name="ZHPTRD.252"></a><a href="zhptrd.f.html#ZHPTRD.1">ZHPTRD</a>( UPLO, N, AP, W, RWORK( INDE ), WORK( INDTAU ),
     $             IINFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     For eigenvalues only, call <a name="DSTERF.255"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>.  For eigenvectors, first call
</span><span class="comment">*</span><span class="comment">     <a name="ZUPGTR.256"></a><a href="zupgtr.f.html#ZUPGTR.1">ZUPGTR</a> to generate the orthogonal matrix, then call <a name="ZSTEDC.256"></a><a href="zstedc.f.html#ZSTEDC.1">ZSTEDC</a>.
</span><span class="comment">*</span><span class="comment">
</span>      IF( .NOT.WANTZ ) THEN
         CALL <a name="DSTERF.259"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>( N, W, RWORK( INDE ), INFO )
      ELSE
         CALL <a name="ZSTEDC.261"></a><a href="zstedc.f.html#ZSTEDC.1">ZSTEDC</a>( <span class="string">'I'</span>, N, W, RWORK( INDE ), Z, LDZ, WORK( INDWRK ),
     $                LLWRK, RWORK( INDRWK ), LLRWK, IWORK, LIWORK,
     $                INFO )
         CALL <a name="ZUPMTR.264"></a><a href="zupmtr.f.html#ZUPMTR.1">ZUPMTR</a>( <span class="string">'L'</span>, UPLO, <span class="string">'N'</span>, N, N, AP, WORK( INDTAU ), Z, LDZ,
     $                WORK( INDWRK ), IINFO )
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     If matrix was scaled, then rescale eigenvalues appropriately.
</span><span class="comment">*</span><span class="comment">
</span>      IF( ISCALE.EQ.1 ) THEN
         IF( INFO.EQ.0 ) THEN
            IMAX = N
         ELSE
            IMAX = INFO - 1
         END IF
         CALL DSCAL( IMAX, ONE / SIGMA, W, 1 )
      END IF
<span class="comment">*</span><span class="comment">
</span>      WORK( 1 ) = LWMIN
      RWORK( 1 ) = LRWMIN
      IWORK( 1 ) = LIWMIN
      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="ZHPEVD.284"></a><a href="zhpevd.f.html#ZHPEVD.1">ZHPEVD</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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