slaed6.f(3) LAPACK slaed6.f(3)
NAME
slaed6.f -
SYNOPSIS
Functions/Subroutines
subroutine slaed6 (KNITER, ORGATI, RHO, D, Z, FINIT, TAU, INFO)
SLAED6
Function/Subroutine Documentation
subroutine slaed6 (integerKNITER, logicalORGATI, realRHO, real, dimension( 3 )D, real, dimension( 3 )Z, realFINIT, realTAU, integerINFO)
SLAED6
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.
Parameters:
KNITER
KNITER is INTEGER
Refer to SLAED4 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
SLAED4 for further details.
RHO
RHO is REAL
Refer to the equation f(x) above.
D
D is REAL array, dimension (3)
D satisfies d(1) < d(2) < d(3).
Z
Z is REAL array, dimension (3)
Each of the elements in z must be positive.
FINIT
FINIT is 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
TAU is REAL
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
Univ. of Colorado Denver
NAG Ltd.
Date:
April 2012
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 141 of file slaed6.f.
Author
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Version 3.4.1 Sun May 26 2013 slaed6.f(3)
