ssyevd.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 298 行 · 第 1/2 页

<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.133"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      INTEGER            <a name="ILAENV.134"></a><a href="hfy-index.html#ILAENV">ILAENV</a>
      REAL               <a name="SLAMCH.135"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>, <a name="SLANSY.135"></a><a href="slansy.f.html#SLANSY.1">SLANSY</a>
      EXTERNAL           <a name="ILAENV.136"></a><a href="hfy-index.html#ILAENV">ILAENV</a>, <a name="LSAME.136"></a><a href="lsame.f.html#LSAME.1">LSAME</a>, <a name="SLAMCH.136"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>, <a name="SLANSY.136"></a><a href="slansy.f.html#SLANSY.1">SLANSY</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           <a name="SLACPY.139"></a><a href="slacpy.f.html#SLACPY.1">SLACPY</a>, <a name="SLASCL.139"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>, <a name="SORMTR.139"></a><a href="sormtr.f.html#SORMTR.1">SORMTR</a>, SSCAL, <a name="SSTEDC.139"></a><a href="sstedc.f.html#SSTEDC.1">SSTEDC</a>, <a name="SSTERF.139"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>,
     $                   <a name="SSYTRD.140"></a><a href="ssytrd.f.html#SSYTRD.1">SSYTRD</a>, <a name="XERBLA.140"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          MAX, 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.149"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      LOWER = <a name="LSAME.150"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> )
      LQUERY = ( LWORK.EQ.-1 .OR. LIWORK.EQ.-1 )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( .NOT.( WANTZ .OR. <a name="LSAME.154"></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.156"></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
         IF( N.LE.1 ) THEN
            LIWMIN = 1
            LWMIN = 1
            LOPT = LWMIN
            LIOPT = LIWMIN
         ELSE
            IF( WANTZ ) THEN
               LIWMIN = 3 + 5*N
               LWMIN = 1 + 6*N + 2*N**2
            ELSE
               LIWMIN = 1
               LWMIN = 2*N + 1
            END IF
            LOPT = MAX( LWMIN, 2*N +
     $                  <a name="ILAENV.179"></a><a href="hfy-index.html#ILAENV">ILAENV</a>( 1, <span class="string">'<a name="SSYTRD.179"></a><a href="ssytrd.f.html#SSYTRD.1">SSYTRD</a>'</span>, UPLO, N, -1, -1, -1 ) )
            LIOPT = LIWMIN
         END IF
         WORK( 1 ) = LOPT
         IWORK( 1 ) = LIOPT
<span class="comment">*</span><span class="comment">
</span>         IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -8
         ELSE IF( LIWORK.LT.LIWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -10
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.193"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="SSYEVD.193"></a><a href="ssyevd.f.html#SSYEVD.1">SSYEVD</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 ) = A( 1, 1 )
         IF( WANTZ )
     $      A( 1, 1 ) = ONE
         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.213"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>( <span class="string">'Safe minimum'</span> )
      EPS = <a name="SLAMCH.214"></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="SLANSY.222"></a><a href="slansy.f.html#SLANSY.1">SLANSY</a>( <span class="string">'M'</span>, UPLO, N, A, LDA, WORK )
      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="SLASCL.232"></a><a href="slascl.f.html#SLASCL.1">SLASCL</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="SSYTRD.234"></a><a href="ssytrd.f.html#SSYTRD.1">SSYTRD</a> to reduce symmetric matrix to tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span>      INDE = 1
      INDTAU = INDE + N
      INDWRK = INDTAU + N
      LLWORK = LWORK - INDWRK + 1
      INDWK2 = INDWRK + N*N
      LLWRK2 = LWORK - INDWK2 + 1
<span class="comment">*</span><span class="comment">
</span>      CALL <a name="SSYTRD.243"></a><a href="ssytrd.f.html#SSYTRD.1">SSYTRD</a>( UPLO, N, A, LDA, W, WORK( 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.246"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>.  For eigenvectors, first call
</span><span class="comment">*</span><span class="comment">     <a name="SSTEDC.247"></a><a href="sstedc.f.html#SSTEDC.1">SSTEDC</a> to generate the eigenvector matrix, WORK(INDWRK), of the
</span><span class="comment">*</span><span class="comment">     tridiagonal matrix, then call <a name="SORMTR.248"></a><a href="sormtr.f.html#SORMTR.1">SORMTR</a> to multiply it by the
</span><span class="comment">*</span><span class="comment">     Householder transformations stored in A.
</span><span class="comment">*</span><span class="comment">
</span>      IF( .NOT.WANTZ ) THEN
         CALL <a name="SSTERF.252"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>( N, W, WORK( INDE ), INFO )
      ELSE
         CALL <a name="SSTEDC.254"></a><a href="sstedc.f.html#SSTEDC.1">SSTEDC</a>( <span class="string">'I'</span>, N, W, WORK( INDE ), WORK( INDWRK ), N,
     $                WORK( INDWK2 ), LLWRK2, IWORK, LIWORK, INFO )
         CALL <a name="SORMTR.256"></a><a href="sormtr.f.html#SORMTR.1">SORMTR</a>( <span class="string">'L'</span>, UPLO, <span class="string">'N'</span>, N, N, A, LDA, WORK( INDTAU ),
     $                WORK( INDWRK ), N, WORK( INDWK2 ), LLWRK2, IINFO )
         CALL <a name="SLACPY.258"></a><a href="slacpy.f.html#SLACPY.1">SLACPY</a>( <span class="string">'A'</span>, N, N, WORK( INDWRK ), N, A, LDA )
      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 )
     $   CALL SSCAL( N, ONE / SIGMA, W, 1 )
<span class="comment">*</span><span class="comment">
</span>      WORK( 1 ) = LOPT
      IWORK( 1 ) = LIOPT
<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="SSYEVD.271"></a><a href="ssyevd.f.html#SSYEVD.1">SSYEVD</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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