[BACK]Return to dlaed5.f CVS log [TXT] [DIR] Up to [local] / rpl / lapack / lapack

Diff for /rpl/lapack/lapack/dlaed5.f between versions 1.2 and 1.18

version 1.2, 2010/04/21 13:45:16 version 1.18, 2023/08/07 08:38:53
Line 1 Line 1
   *> \brief \b DLAED5 used by DSTEDC. Solves the 2-by-2 secular equation.
   *
   *  =========== DOCUMENTATION ===========
   *
   * Online html documentation available at
   *            http://www.netlib.org/lapack/explore-html/
   *
   *> \htmlonly
   *> Download DLAED5 + dependencies
   *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlaed5.f">
   *> [TGZ]</a>
   *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlaed5.f">
   *> [ZIP]</a>
   *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlaed5.f">
   *> [TXT]</a>
   *> \endhtmlonly
   *
   *  Definition:
   *  ===========
   *
   *       SUBROUTINE DLAED5( I, D, Z, DELTA, RHO, DLAM )
   *
   *       .. Scalar Arguments ..
   *       INTEGER            I
   *       DOUBLE PRECISION   DLAM, RHO
   *       ..
   *       .. Array Arguments ..
   *       DOUBLE PRECISION   D( 2 ), DELTA( 2 ), Z( 2 )
   *       ..
   *
   *
   *> \par Purpose:
   *  =============
   *>
   *> \verbatim
   *>
   *> This subroutine computes the I-th eigenvalue of a symmetric rank-one
   *> modification of a 2-by-2 diagonal matrix
   *>
   *>            diag( D )  +  RHO * Z * transpose(Z) .
   *>
   *> The diagonal elements in the array D are assumed to satisfy
   *>
   *>            D(i) < D(j)  for  i < j .
   *>
   *> We also assume RHO > 0 and that the Euclidean norm of the vector
   *> Z is one.
   *> \endverbatim
   *
   *  Arguments:
   *  ==========
   *
   *> \param[in] I
   *> \verbatim
   *>          I is INTEGER
   *>         The index of the eigenvalue to be computed.  I = 1 or I = 2.
   *> \endverbatim
   *>
   *> \param[in] D
   *> \verbatim
   *>          D is DOUBLE PRECISION array, dimension (2)
   *>         The original eigenvalues.  We assume D(1) < D(2).
   *> \endverbatim
   *>
   *> \param[in] Z
   *> \verbatim
   *>          Z is DOUBLE PRECISION array, dimension (2)
   *>         The components of the updating vector.
   *> \endverbatim
   *>
   *> \param[out] DELTA
   *> \verbatim
   *>          DELTA is DOUBLE PRECISION array, dimension (2)
   *>         The vector DELTA contains the information necessary
   *>         to construct the eigenvectors.
   *> \endverbatim
   *>
   *> \param[in] RHO
   *> \verbatim
   *>          RHO is DOUBLE PRECISION
   *>         The scalar in the symmetric updating formula.
   *> \endverbatim
   *>
   *> \param[out] DLAM
   *> \verbatim
   *>          DLAM is DOUBLE PRECISION
   *>         The computed lambda_I, the I-th updated eigenvalue.
   *> \endverbatim
   *
   *  Authors:
   *  ========
   *
   *> \author Univ. of Tennessee
   *> \author Univ. of California Berkeley
   *> \author Univ. of Colorado Denver
   *> \author NAG Ltd.
   *
   *> \ingroup auxOTHERcomputational
   *
   *> \par Contributors:
   *  ==================
   *>
   *>     Ren-Cang Li, Computer Science Division, University of California
   *>     at Berkeley, USA
   *>
   *  =====================================================================
       SUBROUTINE DLAED5( I, D, Z, DELTA, RHO, DLAM )        SUBROUTINE DLAED5( I, D, Z, DELTA, RHO, DLAM )
 *  *
 *  -- LAPACK routine (version 3.2) --  *  -- LAPACK computational routine --
 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --  *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--  *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
 *     November 2006  
 *  *
 *     .. Scalar Arguments ..  *     .. Scalar Arguments ..
       INTEGER            I        INTEGER            I
Line 13 Line 118
       DOUBLE PRECISION   D( 2 ), DELTA( 2 ), Z( 2 )        DOUBLE PRECISION   D( 2 ), DELTA( 2 ), Z( 2 )
 *     ..  *     ..
 *  *
 *  Purpose  
 *  =======  
 *  
 *  This subroutine computes the I-th eigenvalue of a symmetric rank-one  
 *  modification of a 2-by-2 diagonal matrix  
 *  
 *             diag( D )  +  RHO *  Z * transpose(Z) .  
 *  
 *  The diagonal elements in the array D are assumed to satisfy  
 *  
 *             D(i) < D(j)  for  i < j .  
 *  
 *  We also assume RHO > 0 and that the Euclidean norm of the vector  
 *  Z is one.  
 *  
 *  Arguments  
 *  =========  
 *  
 *  I      (input) INTEGER  
 *         The index of the eigenvalue to be computed.  I = 1 or I = 2.  
 *  
 *  D      (input) DOUBLE PRECISION array, dimension (2)  
 *         The original eigenvalues.  We assume D(1) < D(2).  
 *  
 *  Z      (input) DOUBLE PRECISION array, dimension (2)  
 *         The components of the updating vector.  
 *  
 *  DELTA  (output) DOUBLE PRECISION array, dimension (2)  
 *         The vector DELTA contains the information necessary  
 *         to construct the eigenvectors.  
 *  
 *  RHO    (input) DOUBLE PRECISION  
 *         The scalar in the symmetric updating formula.  
 *  
 *  DLAM   (output) DOUBLE PRECISION  
 *         The computed lambda_I, the I-th updated eigenvalue.  
 *  
 *  Further Details  
 *  ===============  
 *  
 *  Based on contributions by  
 *     Ren-Cang Li, Computer Science Division, University of California  
 *     at Berkeley, USA  
 *  
 *  =====================================================================  *  =====================================================================
 *  *
 *     .. Parameters ..  *     .. Parameters ..
Line 120 Line 181
       END IF        END IF
       RETURN        RETURN
 *  *
 *     End OF DLAED5  *     End of DLAED5
 *  *
       END        END
Removed from v.1.2  
changed lines
  Added in v.1.18

CVSweb interface <joel.bertrand@systella.fr>