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来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 322 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="ZPBSTF.151"></a><a href="zpbstf.f.html#ZPBSTF.1">ZPBSTF</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>      COMPLEX*16         CONE, CZERO
      PARAMETER          ( CONE = ( 1.0D+0, 0.0D+0 ),
     $                   CZERO = ( 0.0D+0, 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, LLRWK,
     $                   LLWK2, LRWMIN, LWMIN
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.176"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      EXTERNAL           <a name="LSAME.177"></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="DSTERF.180"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>, <a name="XERBLA.180"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>, ZGEMM, <a name="ZHBGST.180"></a><a href="zhbgst.f.html#ZHBGST.1">ZHBGST</a>, <a name="ZHBTRD.180"></a><a href="zhbtrd.f.html#ZHBTRD.1">ZHBTRD</a>, <a name="ZLACPY.180"></a><a href="zlacpy.f.html#ZLACPY.1">ZLACPY</a>,
     $                   <a name="ZPBSTF.181"></a><a href="zpbstf.f.html#ZPBSTF.1">ZPBSTF</a>, <a name="ZSTEDC.181"></a><a href="zstedc.f.html#ZSTEDC.1">ZSTEDC</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.187"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      UPPER = <a name="LSAME.188"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> )
      LQUERY = ( LWORK.EQ.-1 .OR. LRWORK.EQ.-1 .OR. LIWORK.EQ.-1 )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( N.LE.1 ) THEN
         LWMIN = 1
         LRWMIN = 1
         LIWMIN = 1
      ELSE IF( WANTZ ) THEN
         LWMIN = 2*N**2
         LRWMIN = 1 + 5*N + 2*N**2
         LIWMIN = 3 + 5*N
      ELSE
         LWMIN = N
         LRWMIN = N
         LIWMIN = 1
      END IF
      IF( .NOT.( WANTZ .OR. <a name="LSAME.205"></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.207"></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
         RWORK( 1 ) = LRWMIN
         IWORK( 1 ) = LIWMIN
<span class="comment">*</span><span class="comment">
</span>         IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -14
         ELSE IF( LRWORK.LT.LRWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -16
         ELSE IF( LIWORK.LT.LIWMIN .AND. .NOT.LQUERY ) THEN
            INFO = -18
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.238"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="ZHBGVD.238"></a><a href="zhbgvd.f.html#ZHBGVD.1">ZHBGVD</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="ZPBSTF.251"></a><a href="zpbstf.f.html#ZPBSTF.1">ZPBSTF</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 = 1 + N*N
      LLWK2 = LWORK - INDWK2 + 2
      LLRWK = LRWORK - INDWRK + 2
      CALL <a name="ZHBGST.264"></a><a href="zhbgst.f.html#ZHBGST.1">ZHBGST</a>( JOBZ, UPLO, N, KA, KB, AB, LDAB, BB, LDBB, Z, LDZ,
     $             WORK, RWORK( INDWRK ), IINFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Reduce Hermitian band matrix 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="ZHBTRD.274"></a><a href="zhbtrd.f.html#ZHBTRD.1">ZHBTRD</a>( VECT, UPLO, N, KA, AB, LDAB, W, RWORK( INDE ), Z,
     $             LDZ, WORK, IINFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     For eigenvalues only, call <a name="DSTERF.277"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>.  For eigenvectors, call <a name="ZSTEDC.277"></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.280"></a><a href="dsterf.f.html#DSTERF.1">DSTERF</a>( N, W, RWORK( INDE ), INFO )
      ELSE
         CALL <a name="ZSTEDC.282"></a><a href="zstedc.f.html#ZSTEDC.1">ZSTEDC</a>( <span class="string">'I'</span>, N, W, RWORK( INDE ), WORK, N, WORK( INDWK2 ),
     $                LLWK2, RWORK( INDWRK ), LLRWK, IWORK, LIWORK,
     $                INFO )
         CALL ZGEMM( <span class="string">'N'</span>, <span class="string">'N'</span>, N, N, N, CONE, Z, LDZ, WORK, N, CZERO,
     $               WORK( INDWK2 ), N )
         CALL <a name="ZLACPY.287"></a><a href="zlacpy.f.html#ZLACPY.1">ZLACPY</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
      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="ZHBGVD.295"></a><a href="zhbgvd.f.html#ZHBGVD.1">ZHBGVD</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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