DLAED6 (3lapack)

compute the positive or negative root (closest to the origin) of z(1) z(2) z(3) f(x) = rho + (3lapack)
-------- + ---------- + --------- d(1)-x d(2)-x d(3)-x It is assumed that if ORGATI = .true



SYNOPSIS

  SUBROUTINE DLAED6( KNITER, ORGATI, RHO, D, Z, FINIT, TAU, INFO )

      LOGICAL        ORGATI

      INTEGER        INFO, KNITER

      DOUBLE         PRECISION FINIT, RHO, TAU

      DOUBLE         PRECISION D( 3 ), Z( 3 )

PURPOSE

  DLAED6 computes the positive or negative root (closest to the origin) of
                   z(1)        z(2)        z(3) f(x) =   rho + --------- +
  ---------- + ---------
                  d(1)-x      d(2)-x      d(3)-x
        otherwise it is between d(1) and d(2)

  This routine will be called by DLAED4 when necessary. In most cases, the
  root sought is the smallest in magnitude, though it might not be in some
  extremely rare situations.

ARGUMENTS

  KNITER       (input) INTEGER
               Refer to DLAED4 for its significance.

  ORGATI       (input) LOGICAL
               If ORGATI is true, the needed root is between d(2) and d(3);
               otherwise it is between d(1) and d(2).  See DLAED4 for further
               details.

  RHO          (input) DOUBLE PRECISION
               Refer to the equation f(x) above.

  D            (input) DOUBLE PRECISION array, dimension (3)
               D satisfies d(1) < d(2) < d(3).

  Z            (input) DOUBLE PRECISION array, dimension (3)
               Each of the elements in z must be positive.

  FINIT        (input) DOUBLE PRECISION
               The value of f at 0. It is more accurate than the one
               evaluated inside this routine (if someone wants to do so).

  TAU          (output) DOUBLE PRECISION
               The root of the equation f(x).

  INFO         (output) INTEGER
               = 0: successful exit
               > 0: if INFO = 1, failure to converge



CXML Home Page

Index of CXML Routines