dsbgvd.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 296 行 · 第 1/2 页

</span><span class="comment">*</span><span class="comment">             &lt;= N:  the algorithm failed to converge:
</span><span class="comment">*</span><span class="comment">                    i off-diagonal elements of an intermediate
</span><span class="comment">*</span><span class="comment">                    tridiagonal form did not converge to zero;
</span><span class="comment">*</span><span class="comment">             &gt; N:   if INFO = N + i, for 1 &lt;= i &lt;= N, then <a name="DPBSTF.133"></a><a href="dpbstf.f.html#DPBSTF.1">DPBSTF</a>
</span><span class="comment">*</span><span class="comment">                    returned INFO = i: B is not positive definite.
</span><span class="comment">*</span><span class="comment">                    The factorization of B could not be completed and
</span><span class="comment">*</span><span class="comment">                    no eigenvalues or eigenvectors were computed.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Further Details
</span><span class="comment">*</span><span class="comment">  ===============
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Based on contributions by
</span><span class="comment">*</span><span class="comment">     Mark Fahey, Department of Mathematics, Univ. of Kentucky, USA
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Parameters ..
</span>      DOUBLE PRECISION   ONE, ZERO
      PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            LQUERY, UPPER, WANTZ
      CHARACTER          VECT
      INTEGER            IINFO, INDE, INDWK2, INDWRK, LIWMIN, LLWRK2,
     $                   LWMIN
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.157"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      EXTERNAL           <a name="LSAME.158"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           DGEMM, <a name="DLACPY.161"></a><a href="dlacpy.f.html#DLACPY.1">DLACPY</a>, <a name="DPBSTF.161"></a><a href="dpbstf.f.html#DPBSTF.1">DPBSTF</a>, <a name="DSBGST.161"></a><a href="dsbgst.f.html#DSBGST.1">DSBGST</a>, <a name="DSBTRD.161"></a><a href="dsbtrd.f.html#DSBTRD.1">DSBTRD</a>, <a name="DSTEDC.161"></a><a href="dstedc.f.html#DSTEDC.1">DSTEDC</a>,
     $                   <a name="DSTERF.162"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>, <a name="XERBLA.162"></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">     .. 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.168"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      UPPER = <a name="LSAME.169"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> )
      LQUERY = ( LWORK.EQ.-1 .OR. LIWORK.EQ.-1 )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( N.LE.1 ) THEN
         LIWMIN = 1
         LWMIN = 1
      ELSE IF( WANTZ ) THEN
         LIWMIN = 3 + 5*N
         LWMIN = 1 + 5*N + 2*N**2
      ELSE
         LIWMIN = 1
         LWMIN = 2*N
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( .NOT.( WANTZ .OR. <a name="LSAME.184"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'N'</span> ) ) ) THEN
         INFO = -1
      ELSE IF( .NOT.( UPPER .OR. <a name="LSAME.186"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> ) ) ) THEN
         INFO = -2
      ELSE IF( N.LT.0 ) THEN
         INFO = -3
      ELSE IF( KA.LT.0 ) THEN
         INFO = -4
      ELSE IF( KB.LT.0 .OR. KB.GT.KA ) THEN
         INFO = -5
      ELSE IF( LDAB.LT.KA+1 ) THEN
         INFO = -7
      ELSE IF( LDBB.LT.KB+1 ) THEN
         INFO = -9
      ELSE IF( LDZ.LT.1 .OR. ( WANTZ .AND. LDZ.LT.N ) ) THEN
         INFO = -12
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.EQ.0 ) THEN
         WORK( 1 ) = LWMIN
         IWORK( 1 ) = LIWMIN
<span class="comment">*</span><span class="comment">
</span>         IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -14
         ELSE IF( LIWORK.LT.LIWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -16
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.214"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="DSBGVD.214"></a><a href="dsbgvd.f.html#DSBGVD.1">DSBGVD</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><span class="comment">*</span><span class="comment">     Form a split Cholesky factorization of B.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="DPBSTF.227"></a><a href="dpbstf.f.html#DPBSTF.1">DPBSTF</a>( UPLO, N, KB, BB, LDBB, INFO )
      IF( INFO.NE.0 ) THEN
         INFO = N + INFO
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Transform problem to standard eigenvalue problem.
</span><span class="comment">*</span><span class="comment">
</span>      INDE = 1
      INDWRK = INDE + N
      INDWK2 = INDWRK + N*N
      LLWRK2 = LWORK - INDWK2 + 1
      CALL <a name="DSBGST.239"></a><a href="dsbgst.f.html#DSBGST.1">DSBGST</a>( JOBZ, UPLO, N, KA, KB, AB, LDAB, BB, LDBB, Z, LDZ,
     $             WORK( INDWRK ), IINFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Reduce to tridiagonal form.
</span><span class="comment">*</span><span class="comment">
</span>      IF( WANTZ ) THEN
         VECT = <span class="string">'U'</span>
      ELSE
         VECT = <span class="string">'N'</span>
      END IF
      CALL <a name="DSBTRD.249"></a><a href="dsbtrd.f.html#DSBTRD.1">DSBTRD</a>( VECT, UPLO, N, KA, AB, LDAB, W, WORK( INDE ), Z, LDZ,
     $             WORK( INDWRK ), IINFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     For eigenvalues only, call <a name="DSTERF.252"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>. For eigenvectors, call <a name="SSTEDC.252"></a><a href="sstedc.f.html#SSTEDC.1">SSTEDC</a>.
</span><span class="comment">*</span><span class="comment">
</span>      IF( .NOT.WANTZ ) THEN
         CALL <a name="DSTERF.255"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>( N, W, WORK( INDE ), INFO )
      ELSE
         CALL <a name="DSTEDC.257"></a><a href="dstedc.f.html#DSTEDC.1">DSTEDC</a>( <span class="string">'I'</span>, N, W, WORK( INDE ), WORK( INDWRK ), N,
     $                WORK( INDWK2 ), LLWRK2, IWORK, LIWORK, INFO )
         CALL DGEMM( <span class="string">'N'</span>, <span class="string">'N'</span>, N, N, N, ONE, Z, LDZ, WORK( INDWRK ), N,
     $               ZERO, WORK( INDWK2 ), N )
         CALL <a name="DLACPY.261"></a><a href="dlacpy.f.html#DLACPY.1">DLACPY</a>( <span class="string">'A'</span>, N, N, WORK( INDWK2 ), N, Z, LDZ )
      END IF
<span class="comment">*</span><span class="comment">
</span>      WORK( 1 ) = LWMIN
      IWORK( 1 ) = LIWMIN
<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="DSBGVD.269"></a><a href="dsbgvd.f.html#DSBGVD.1">DSBGVD</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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