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-version 1.2, 2010/04/21 13:45:25
+version 1.18, 2023/08/07 08:39:07
  Line 1
+ *> \brief \b DSTERF
+ *
+ *  =========== DOCUMENTATION ===========
+ *
+ * Online html documentation available at
+ *            http://www.netlib.org/lapack/explore-html/
+ *
+ *> \htmlonly
+ *> Download DSTERF + dependencies
+ *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dsterf.f">
+ *> [TGZ]</a>
+ *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dsterf.f">
+ *> [ZIP]</a>
+ *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dsterf.f">
+ *> [TXT]</a>
+ *> \endhtmlonly
+ *
+ *  Definition:
+ *  ===========
+ *
+ *       SUBROUTINE DSTERF( N, D, E, INFO )
+ *
+ *       .. Scalar Arguments ..
+ *       INTEGER            INFO, N
+ *       ..
+ *       .. Array Arguments ..
+ *       DOUBLE PRECISION   D( * ), E( * )
+ *       ..
+ *
+ *
+ *> \par Purpose:
+ *  =============
+ *>
+ *> \verbatim
+ *>
+ *> DSTERF computes all eigenvalues of a symmetric tridiagonal matrix
+ *> using the Pal-Walker-Kahan variant of the QL or QR algorithm.
+ *> \endverbatim
+ *
+ *  Arguments:
+ *  ==========
+ *
+ *> \param[in] N
+ *> \verbatim
+ *>          N is INTEGER
+ *>          The order of the matrix.  N >= 0.
+ *> \endverbatim
+ *>
+ *> \param[in,out] D
+ *> \verbatim
+ *>          D is DOUBLE PRECISION array, dimension (N)
+ *>          On entry, the n diagonal elements of the tridiagonal matrix.
+ *>          On exit, if INFO = 0, the eigenvalues in ascending order.
+ *> \endverbatim
+ *>
+ *> \param[in,out] E
+ *> \verbatim
+ *>          E is DOUBLE PRECISION array, dimension (N-1)
+ *>          On entry, the (n-1) subdiagonal elements of the tridiagonal
+ *>          matrix.
+ *>          On exit, E has been destroyed.
+ *> \endverbatim
+ *>
+ *> \param[out] INFO
+ *> \verbatim
+ *>          INFO is INTEGER
+ *>          = 0:  successful exit
+ *>          < 0:  if INFO = -i, the i-th argument had an illegal value
+ *>          > 0:  the algorithm failed to find all of the eigenvalues in
+ *>                a total of 30*N iterations; if INFO = i, then i
+ *>                elements of E have not converged to zero.
+ *> \endverbatim
+ *
+ *  Authors:
+ *  ========
+ *
+ *> \author Univ. of Tennessee
+ *> \author Univ. of California Berkeley
+ *> \author Univ. of Colorado Denver
+ *> \author NAG Ltd.
+ *
+ *> \ingroup auxOTHERcomputational
+ *
+ *  =====================================================================
        SUBROUTINE DSTERF( N, D, E, INFO )
  *
- *  -- LAPACK routine (version 3.2) --
+ *  -- LAPACK computational routine --
  *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
  *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
- *     November 2006
  *
  *     .. Scalar Arguments ..
        INTEGER            INFO, N
- Line 12
+ Line 95
        DOUBLE PRECISION   D( * ), E( * )
  *     ..
  *
- *  Purpose
- *  =======
- *
- *  DSTERF computes all eigenvalues of a symmetric tridiagonal matrix
- *  using the Pal-Walker-Kahan variant of the QL or QR algorithm.
- *
- *  Arguments
- *  =========
- *
- *  N       (input) INTEGER
- *          The order of the matrix.  N >= 0.
- *
- *  D       (input/output) DOUBLE PRECISION array, dimension (N)
- *          On entry, the n diagonal elements of the tridiagonal matrix.
- *          On exit, if INFO = 0, the eigenvalues in ascending order.
- *
- *  E       (input/output) DOUBLE PRECISION array, dimension (N-1)
- *          On entry, the (n-1) subdiagonal elements of the tridiagonal
- *          matrix.
- *          On exit, E has been destroyed.
- *
- *  INFO    (output) INTEGER
- *          = 0:  successful exit
- *          < 0:  if INFO = -i, the i-th argument had an illegal value
- *          > 0:  the algorithm failed to find all of the eigenvalues in
- *                a total of 30*N iterations; if INFO = i, then i
- *                elements of E have not converged to zero.
- *
  *  =====================================================================
  *
  *     .. Parameters ..
- Line 54
+ Line 109
       $                   NMAXIT
        DOUBLE PRECISION   ALPHA, ANORM, BB, C, EPS, EPS2, GAMMA, OLDC,
       $                   OLDGAM, P, R, RT1, RT2, RTE, S, SAFMAX, SAFMIN,
-      $                   SIGMA, SSFMAX, SSFMIN
+      $                   SIGMA, SSFMAX, SSFMIN, RMAX
  *     ..
  *     .. External Functions ..
        DOUBLE PRECISION   DLAMCH, DLANST, DLAPY2
- Line 90
+ Line 145
        SAFMAX = ONE / SAFMIN
        SSFMAX = SQRT( SAFMAX ) / THREE
        SSFMIN = SQRT( SAFMIN ) / EPS2
+       RMAX = DLAMCH( 'O' )
  *
  *     Compute the eigenvalues of the tridiagonal matrix.
  *
- Line 128
+ Line 184
  *
  *     Scale submatrix in rows and columns L to LEND
  *
-       ANORM = DLANST( 'I', LEND-L+1, D( L ), E( L ) )
+       ANORM = DLANST( 'M', LEND-L+1, D( L ), E( L ) )
        ISCALE = 0
-       IF( ANORM.GT.SSFMAX ) THEN
+       IF( ANORM.EQ.ZERO )
+      $   GO TO 10
+       IF( (ANORM.GT.SSFMAX) ) THEN
           ISCALE = 1
           CALL DLASCL( 'G', 0, 0, ANORM, SSFMAX, LEND-L+1, 1, D( L ), N,
       $                INFO )

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