
SLAED6(l) ) SLAED6(l)
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 It is assumed that if
ORGATI = .true. the root is between d(2) and d(3); 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
FURTHER DETAILS
Based on contributions by
RenCang Li, Computer Science Division, University of California
at Berkeley, USA
LAPACK version 3.0 15 June 2000 SLAED6(l) 
