NAME

slasq3 - SLASQ3 is the workhorse of the whole bidiagonal SVD algorithm

SYNOPSIS

SUBROUTINE SLASQ3( N, Q, E, QQ, EE, SUP, SIGMA, KEND, OFF, IPHASE, ICONV, EPS, TOL2, SMALL2 )

INTEGER ICONV, IPHASE, KEND, N, OFF

REAL EPS, SIGMA, SMALL2, SUP, TOL2

REAL E( ∗ ), EE( ∗ ), Q( ∗ ), QQ( ∗ )

#include <sunperf.h>

void slasq3(int ∗n, float ∗q, float ∗e, float ∗qq, float ∗ee, float ∗sup, float ∗sigma, int ∗kend, int ∗off, int ∗iphase, int iconv, float eps, float tol2, float small2) ;

PURPOSE

SLASQ3 is the workhorse of the whole bidiagonal SVD algorithm.  This can be described as the differential qd with shifts. 
 

ARGUMENTS

N (input/output) INTEGER
On entry, N specifies the number of rows and columns in the matrix. N must be at least 3. On exit N is non-negative and less than the input value.

Q (input/output) REAL array, dimension (N)
Q array in ping (see IPHASE below)

E (input/output) REAL array, dimension (N)
E array in ping (see IPHASE below)

QQ (input/output) REAL array, dimension (N)
Q array in pong (see IPHASE below)

EE (input/output) REAL array, dimension (N)
E array in pong (see IPHASE below)

SUP (input/output) REAL
Upper bound for the smallest eigenvalue

SIGMA (input/output) REAL
Accumulated shift for the present submatrix

KEND (input/output) INTEGER
Index where minimum D(i) occurs in recurrence for splitting criterion

OFF (input/output) INTEGER
Offset for arrays

IPHASE (input/output) INTEGER
If IPHASE = 1 (ping) then data is in Q and E arrays If IPHASE = 2 (pong) then data is in QQ and EE arrays

ICONV (input) INTEGER
If ICONV = 0 a bottom part of a matrix (with a split) If ICONV =-3 a top part of a matrix (with a split)

EPS (input) REAL
Machine epsilon

TOL2 (input) REAL
Square of the relative tolerance TOL as defined in SLASQ1

SMALL2 (input) REAL
A threshold value as defined in SLASQ1

SunOS 5.0  —  Last change: 10 Dec 1998