slaed6.f (3)  Linux Manuals
NAME
slaed6.f 
SYNOPSIS
Functions/Subroutines
subroutine slaed6 (KNITER, ORGATI, RHO, D, Z, FINIT, TAU, INFO)
SLAED6 used by sstedc. Computes one Newton step in solution of the secular equation.
Function/Subroutine Documentation
subroutine slaed6 (integerKNITER, logicalORGATI, realRHO, real, dimension( 3 )D, real, dimension( 3 )Z, realFINIT, realTAU, integerINFO)
SLAED6 used by sstedc. Computes one Newton step in solution of the secular equation.
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.
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 SLAED4 for further details.
RHORHO is REAL Refer to the equation f(x) above.
DD is REAL array, dimension (3) D satisfies d(1) < d(2) < d(3).
ZZ is REAL array, dimension (3) Each of the elements in z must be positive.
FINITFINIT 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).
TAUTAU is REAL 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 slaed6.f.
Author
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