slaed6(3F)

NAME
     SLAED6 - compute 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  It is assumed that   if ORGATI = .true

SYNOPSIS
     SUBROUTINE SLAED6( KNITER, ORGATI, RHO, D, Z, FINIT, TAU, INFO )

         LOGICAL        ORGATI

         INTEGER        INFO, KNITER

         REAL           FINIT, RHO, TAU

         REAL           D( 3 ), Z( 3 )

PURPOSE
     SLAED6 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 SLAED4 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 SLAED4 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 SLAED4 for
                  further details.

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

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

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

     FINIT        (input) REAL
                  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) REAL
                  The root of the equation f(x).

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