DLASQ3(3F)DLASQ3(3F)NAME
DLASQ3 - DLASQ3 is the workhorse of the whole bidiagonal SVD algorithm
SYNOPSIS
SUBROUTINE DLASQ3( N, Q, E, QQ, EE, SUP, SIGMA, KEND, OFF, IPHASE, ICONV,
EPS, TOL2, SMALL2 )
INTEGER ICONV, IPHASE, KEND, N, OFF
DOUBLE PRECISION EPS, SIGMA, SMALL2, SUP, TOL2
DOUBLE PRECISION E( * ), EE( * ), Q( * ), QQ( * )
PURPOSE
DLASQ3 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) DOUBLE PRECISION array, dimension (N)
Q array in ping (see IPHASE below)
E (input/output) DOUBLE PRECISION array, dimension (N)
E array in ping (see IPHASE below)
QQ (input/output) DOUBLE PRECISION array, dimension (N)
Q array in pong (see IPHASE below)
EE (input/output) DOUBLE PRECISION array, dimension (N)
E array in pong (see IPHASE below)
SUP (input/output) DOUBLE PRECISION
Upper bound for the smallest eigenvalue
SIGMA (input/output) DOUBLE PRECISION
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
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DLASQ3(3F)DLASQ3(3F)
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) DOUBLE PRECISION
Machine epsilon
TOL2 (input) DOUBLE PRECISION
Square of the relative tolerance TOL as defined in DLASQ1
SMALL2 (input) DOUBLE PRECISION
A threshold value as defined in DLASQ1
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