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来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 213 行 · 第 1/2 页

</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  INFO    (output) INTEGER
</span><span class="comment">*</span><span class="comment">          = 0:  successful exit
</span><span class="comment">*</span><span class="comment">          &lt; 0:  if INFO = -i, the i-th argument had an illegal value
</span><span class="comment">*</span><span class="comment">          &gt; 0:  if INFO = i, and i is:
</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="SPBSTF.97"></a><a href="spbstf.f.html#SPBSTF.1">SPBSTF</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">  =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            UPPER, WANTZ
      CHARACTER          VECT
      INTEGER            IINFO, INDE, INDWRK
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.110"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      EXTERNAL           <a name="LSAME.111"></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           <a name="SPBSTF.114"></a><a href="spbstf.f.html#SPBSTF.1">SPBSTF</a>, <a name="SSBGST.114"></a><a href="ssbgst.f.html#SSBGST.1">SSBGST</a>, <a name="SSBTRD.114"></a><a href="ssbtrd.f.html#SSBTRD.1">SSBTRD</a>, <a name="SSTEQR.114"></a><a href="ssteqr.f.html#SSTEQR.1">SSTEQR</a>, <a name="SSTERF.114"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>, <a name="XERBLA.114"></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.120"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      UPPER = <a name="LSAME.121"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( .NOT.( WANTZ .OR. <a name="LSAME.124"></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.126"></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
      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.142"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="SSBGV.142"></a><a href="ssbgv.f.html#SSBGV.1">SSBGV</a> '</span>, -INFO )
         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="SPBSTF.153"></a><a href="spbstf.f.html#SPBSTF.1">SPBSTF</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
      CALL <a name="SSBGST.163"></a><a href="ssbgst.f.html#SSBGST.1">SSBGST</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="SSBTRD.173"></a><a href="ssbtrd.f.html#SSBTRD.1">SSBTRD</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="SSTERF.176"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>.  For eigenvectors, call <a name="SSTEQR.176"></a><a href="ssteqr.f.html#SSTEQR.1">SSTEQR</a>.
</span><span class="comment">*</span><span class="comment">
</span>      IF( .NOT.WANTZ ) THEN
         CALL <a name="SSTERF.179"></a><a href="ssterf.f.html#SSTERF.1">SSTERF</a>( N, W, WORK( INDE ), INFO )
      ELSE
         CALL <a name="SSTEQR.181"></a><a href="ssteqr.f.html#SSTEQR.1">SSTEQR</a>( JOBZ, N, W, WORK( INDE ), Z, LDZ, WORK( INDWRK ),
     $                INFO )
      END IF
      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="SSBGV.186"></a><a href="ssbgv.f.html#SSBGV.1">SSBGV</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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