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来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 243 行 · 第 1/2 页

<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.109"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      LOWER = <a name="LSAME.110"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> )
      LQUERY = ( LWORK.EQ.-1 )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( .NOT.( WANTZ .OR. <a name="LSAME.114"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'N'</span> ) ) ) THEN
         INFO = -1
      ELSE IF( .NOT.( LOWER .OR. <a name="LSAME.116"></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( LDA.LT.MAX( 1, N ) ) THEN
         INFO = -5
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.EQ.0 ) THEN
         NB = <a name="ILAENV.125"></a><a href="hfy-index.html#ILAENV">ILAENV</a>( 1, <span class="string">'<a name="CHETRD.125"></a><a href="chetrd.f.html#CHETRD.1">CHETRD</a>'</span>, UPLO, N, -1, -1, -1 )
         LWKOPT = MAX( 1, ( NB+1 )*N )
         WORK( 1 ) = LWKOPT
<span class="comment">*</span><span class="comment">
</span>         IF( LWORK.LT.MAX( 1, 2*N-1 ) .AND. .NOT.LQUERY )
     $      INFO = -8
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.134"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="CHEEV.134"></a><a href="cheev.f.html#CHEEV.1">CHEEV</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 ) THEN
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.1 ) THEN
         W( 1 ) = A( 1, 1 )
         WORK( 1 ) = 1
         IF( WANTZ )
     $      A( 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="SLAMCH.156"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>( <span class="string">'Safe minimum'</span> )
      EPS = <a name="SLAMCH.157"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</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="CLANHE.165"></a><a href="clanhe.f.html#CLANHE.1">CLANHE</a>( <span class="string">'M'</span>, UPLO, N, A, LDA, 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 )
     $   CALL <a name="CLASCL.175"></a><a href="clascl.f.html#CLASCL.1">CLASCL</a>( UPLO, 0, 0, ONE, SIGMA, N, N, A, LDA, INFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Call <a name="CHETRD.177"></a><a href="chetrd.f.html#CHETRD.1">CHETRD</a> to reduce Hermitian matrix to tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span>      INDE = 1
      INDTAU = 1
      INDWRK = INDTAU + N
      LLWORK = LWORK - INDWRK + 1
      CALL <a name="CHETRD.183"></a><a href="chetrd.f.html#CHETRD.1">CHETRD</a>( UPLO, N, A, LDA, W, RWORK( INDE ), WORK( INDTAU ),
     $             WORK( INDWRK ), LLWORK, IINFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     For eigenvalues only, call <a name="SSTERF.186"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>.  For eigenvectors, first call
</span><span class="comment">*</span><span class="comment">     <a name="CUNGTR.187"></a><a href="cungtr.f.html#CUNGTR.1">CUNGTR</a> to generate the unitary matrix, then call <a name="CSTEQR.187"></a><a href="csteqr.f.html#CSTEQR.1">CSTEQR</a>.
</span><span class="comment">*</span><span class="comment">
</span>      IF( .NOT.WANTZ ) THEN
         CALL <a name="SSTERF.190"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>( N, W, RWORK( INDE ), INFO )
      ELSE
         CALL <a name="CUNGTR.192"></a><a href="cungtr.f.html#CUNGTR.1">CUNGTR</a>( UPLO, N, A, LDA, WORK( INDTAU ), WORK( INDWRK ),
     $                LLWORK, IINFO )
         INDWRK = INDE + N
         CALL <a name="CSTEQR.195"></a><a href="csteqr.f.html#CSTEQR.1">CSTEQR</a>( JOBZ, N, W, RWORK( INDE ), A, LDA,
     $                RWORK( INDWRK ), INFO )
      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 SSCAL( IMAX, ONE / SIGMA, W, 1 )
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Set WORK(1) to optimal complex workspace size.
</span><span class="comment">*</span><span class="comment">
</span>      WORK( 1 ) = LWKOPT
<span class="comment">*</span><span class="comment">
</span>      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="CHEEV.216"></a><a href="cheev.f.html#CHEEV.1">CHEEV</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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