# dlaed6.f man page

dlaed6.f

## Synopsis

### Functions/Subroutines

subroutine dlaed6 (KNITER, ORGATI, RHO, D, Z, FINIT, TAU, INFO)
DLAED6 used by sstedc. Computes one Newton step in solution of the secular equation.

## Function/Subroutine Documentation

### subroutine dlaed6 (integer KNITER, logical ORGATI, double precision RHO, double precision, dimension( 3 ) D, double precision, dimension( 3 ) Z, double precision FINIT, double precision TAU, integer INFO)

DLAED6 used by sstedc. Computes one Newton step in solution of the secular equation.

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.```
Parameters:

KNITER

```          KNITER is INTEGER
Refer to DLAED4 for its significance.```

ORGATI

```          ORGATI is 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

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

D

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

Z

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

FINIT

```          FINIT is 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

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

INFO

```          INFO is INTEGER
= 0: successful exit
> 0: if INFO = 1, failure to converge```
Author:

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

December 2016

Further Details:

```  10/02/03: This version has a few statements commented out for thread
safety (machine parameters are computed on each entry). SJH.

05/10/06: Modified from a new version of Ren-Cang Li, use
Gragg-Thornton-Warner cubic convergent scheme for better stability.```
Contributors:

Ren-Cang Li, Computer Science Division, University of California at Berkeley, USA

Definition at line 142 of file dlaed6.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dlaed6(3) is an alias of dlaed6.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK