
DLAED6(l) ) DLAED6(l)
NAME
DLAED6  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 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 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 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
FURTHER DETAILS
Based on contributions by
RenCang Li, Computer Science Division, University of California
at Berkeley, USA
LAPACK version 3.0 15 June 2000 DLAED6(l) 
