LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

Go to the source code of this file.
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. 
subroutine slaed6  (  integer  KNITER, 
logical  ORGATI,  
real  RHO,  
real, dimension( 3 )  D,  
real, dimension( 3 )  Z,  
real  FINIT,  
real  TAU,  
integer  INFO  
) 
SLAED6 used by sstedc. Computes one Newton step in solution of the secular equation.
Download SLAED6 + dependencies [TGZ] [ZIP] [TXT]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.
[in]  KNITER  KNITER is INTEGER Refer to SLAED4 for its significance. 
[in]  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. 
[in]  RHO  RHO is REAL Refer to the equation f(x) above. 
[in]  D  D is REAL array, dimension (3) D satisfies d(1) < d(2) < d(3). 
[in]  Z  Z is REAL array, dimension (3) Each of the elements in z must be positive. 
[in]  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). 
[out]  TAU  TAU is REAL The root of the equation f(x). 
[out]  INFO  INFO is INTEGER = 0: successful exit > 0: if INFO = 1, failure to converge 
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.
Definition at line 141 of file slaed6.f.