dlaed6.f (3)  Linux Man Pages
NAME
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 (integerKNITER, logicalORGATI, double precisionRHO, double precision, dimension( 3 )D, double precision, dimension( 3 )Z, double precisionFINIT, double precisionTAU, integerINFO)
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.
ORGATIORGATI 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.
RHORHO is DOUBLE PRECISION Refer to the equation f(x) above.
DD is DOUBLE PRECISION array, dimension (3) D satisfies d(1) < d(2) < d(3).
ZZ is DOUBLE PRECISION array, dimension (3) Each of the elements in z must be positive.
FINITFINIT 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).
TAUTAU is DOUBLE PRECISION The root of the equation f(x).
INFOINFO 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:
 September 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 RenCang Li, use GraggThorntonWarner cubic convergent scheme for better stability.
Contributors:
 RenCang Li, Computer Science Division, University of California at Berkeley, USA
Definition at line 141 of file dlaed6.f.
Author
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