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来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 318 行 · 第 1/2 页

</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  IWORK   (workspace) INTEGER array, dimension (5*N)
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  IFAIL   (output) INTEGER array, dimension (N)
</span><span class="comment">*</span><span class="comment">          If JOBZ = 'V', then if INFO = 0, the first M elements of
</span><span class="comment">*</span><span class="comment">          IFAIL are zero.  If INFO &gt; 0, then IFAIL contains the
</span><span class="comment">*</span><span class="comment">          indices of the eigenvectors that failed to converge.
</span><span class="comment">*</span><span class="comment">          If JOBZ = 'N', then IFAIL is not referenced.
</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:  <a name="ZPPTRF.153"></a><a href="zpptrf.f.html#ZPPTRF.1">ZPPTRF</a> or <a name="ZHPEVX.153"></a><a href="zhpevx.f.html#ZHPEVX.1">ZHPEVX</a> returned an error code:
</span><span class="comment">*</span><span class="comment">             &lt;= N:  if INFO = i, <a name="ZHPEVX.154"></a><a href="zhpevx.f.html#ZHPEVX.1">ZHPEVX</a> failed to converge;
</span><span class="comment">*</span><span class="comment">                    i eigenvectors failed to converge.  Their indices
</span><span class="comment">*</span><span class="comment">                    are stored in array IFAIL.
</span><span class="comment">*</span><span class="comment">             &gt; N:   if INFO = N + i, for 1 &lt;= i &lt;= n, then the leading
</span><span class="comment">*</span><span class="comment">                    minor of order i of 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">     .. Local Scalars ..
</span>      LOGICAL            ALLEIG, INDEIG, UPPER, VALEIG, WANTZ
      CHARACTER          TRANS
      INTEGER            J
<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="XERBLA.180"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>, <a name="ZHPEVX.180"></a><a href="zhpevx.f.html#ZHPEVX.1">ZHPEVX</a>, <a name="ZHPGST.180"></a><a href="zhpgst.f.html#ZHPGST.1">ZHPGST</a>, <a name="ZPPTRF.180"></a><a href="zpptrf.f.html#ZPPTRF.1">ZPPTRF</a>, ZTPMV, ZTPSV
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          MIN
<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.189"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'V'</span> )
      UPPER = <a name="LSAME.190"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'U'</span> )
      ALLEIG = <a name="LSAME.191"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( RANGE, <span class="string">'A'</span> )
      VALEIG = <a name="LSAME.192"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( RANGE, <span class="string">'V'</span> )
      INDEIG = <a name="LSAME.193"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( RANGE, <span class="string">'I'</span> )
<span class="comment">*</span><span class="comment">
</span>      INFO = 0
      IF( ITYPE.LT.1 .OR. ITYPE.GT.3 ) THEN
         INFO = -1
      ELSE IF( .NOT.( WANTZ .OR. <a name="LSAME.198"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBZ, <span class="string">'N'</span> ) ) ) THEN
         INFO = -2
      ELSE IF( .NOT.( ALLEIG .OR. VALEIG .OR. INDEIG ) ) THEN
         INFO = -3
      ELSE IF( .NOT.( UPPER .OR. <a name="LSAME.202"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( UPLO, <span class="string">'L'</span> ) ) ) THEN
         INFO = -4
      ELSE IF( N.LT.0 ) THEN
         INFO = -5
      ELSE 
         IF( VALEIG ) THEN
            IF( N.GT.0 .AND. VU.LE.VL ) THEN
               INFO = -9
            END IF
         ELSE IF( INDEIG ) THEN
            IF( IL.LT.1 ) THEN
               INFO = -10
            ELSE IF( IU.LT.MIN( N, IL ) .OR. IU.GT.N ) THEN
               INFO = -11
            END IF
         END IF
      END IF
      IF( INFO.EQ.0 ) THEN
         IF( LDZ.LT.1 .OR. ( WANTZ .AND. LDZ.LT.N ) ) THEN
            INFO = -16
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.226"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="ZHPGVX.226"></a><a href="zhpgvx.f.html#ZHPGVX.1">ZHPGVX</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 Cholesky factorization of B.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="ZPPTRF.237"></a><a href="zpptrf.f.html#ZPPTRF.1">ZPPTRF</a>( UPLO, N, BP, 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 and solve.
</span><span class="comment">*</span><span class="comment">
</span>      CALL <a name="ZHPGST.245"></a><a href="zhpgst.f.html#ZHPGST.1">ZHPGST</a>( ITYPE, UPLO, N, AP, BP, INFO )
      CALL <a name="ZHPEVX.246"></a><a href="zhpevx.f.html#ZHPEVX.1">ZHPEVX</a>( JOBZ, RANGE, UPLO, N, AP, VL, VU, IL, IU, ABSTOL, M,
     $             W, Z, LDZ, WORK, RWORK, IWORK, IFAIL, INFO )
<span class="comment">*</span><span class="comment">
</span>      IF( WANTZ ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Backtransform eigenvectors to the original problem.
</span><span class="comment">*</span><span class="comment">
</span>         IF( INFO.GT.0 )
     $      M = INFO - 1
         IF( ITYPE.EQ.1 .OR. ITYPE.EQ.2 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           For A*x=(lambda)*B*x and A*B*x=(lambda)*x;
</span><span class="comment">*</span><span class="comment">           backtransform eigenvectors: x = inv(L)'*y or inv(U)*y
</span><span class="comment">*</span><span class="comment">
</span>            IF( UPPER ) THEN
               TRANS = <span class="string">'N'</span>
            ELSE
               TRANS = <span class="string">'C'</span>
            END IF
<span class="comment">*</span><span class="comment">
</span>            DO 10 J = 1, M
               CALL ZTPSV( UPLO, TRANS, <span class="string">'Non-unit'</span>, N, BP, Z( 1, J ),
     $                     1 )
   10       CONTINUE
<span class="comment">*</span><span class="comment">
</span>         ELSE IF( ITYPE.EQ.3 ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">           For B*A*x=(lambda)*x;
</span><span class="comment">*</span><span class="comment">           backtransform eigenvectors: x = L*y or U'*y
</span><span class="comment">*</span><span class="comment">
</span>            IF( UPPER ) THEN
               TRANS = <span class="string">'C'</span>
            ELSE
               TRANS = <span class="string">'N'</span>
            END IF
<span class="comment">*</span><span class="comment">
</span>            DO 20 J = 1, M
               CALL ZTPMV( UPLO, TRANS, <span class="string">'Non-unit'</span>, N, BP, Z( 1, J ),
     $                     1 )
   20       CONTINUE
         END IF
      END IF
<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="ZHPGVX.291"></a><a href="zhpgvx.f.html#ZHPGVX.1">ZHPGVX</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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