| SRC/dlasq4.f(3) | Library Functions Manual | SRC/dlasq4.f(3) |
NAME
SRC/dlasq4.f
SYNOPSIS
Functions/Subroutines
subroutine dlasq4 (i0, n0, z, pp, n0in, dmin, dmin1, dmin2,
dn, dn1, dn2, tau, ttype, g)
DLASQ4 computes an approximation to the smallest eigenvalue using
values of d from the previous transform. Used by sbdsqr.
Function/Subroutine Documentation
subroutine dlasq4 (integer i0, integer n0, double precision, dimension( * ) z, integer pp, integer n0in, double precision dmin, double precision dmin1, double precision dmin2, double precision dn, double precision dn1, double precision dn2, double precision tau, integer ttype, double precision g)
DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.
Purpose:
DLASQ4 computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform.
Parameters
I0
I0 is INTEGER
First index.
N0
N0 is INTEGER
Last index.
Z
Z is DOUBLE PRECISION array, dimension ( 4*N0 )
Z holds the qd array.
PP
PP is INTEGER
PP=0 for ping, PP=1 for pong.
N0IN
N0IN is INTEGER
The value of N0 at start of EIGTEST.
DMIN
DMIN is DOUBLE PRECISION
Minimum value of d.
DMIN1
DMIN1 is DOUBLE PRECISION
Minimum value of d, excluding D( N0 ).
DMIN2
DMIN2 is DOUBLE PRECISION
Minimum value of d, excluding D( N0 ) and D( N0-1 ).
DN
DN is DOUBLE PRECISION
d(N)
DN1
DN1 is DOUBLE PRECISION
d(N-1)
DN2
DN2 is DOUBLE PRECISION
d(N-2)
TAU
TAU is DOUBLE PRECISION
This is the shift.
TTYPE
TTYPE is INTEGER
Shift type.
G
G is DOUBLE PRECISION
G is passed as an argument in order to save its value between
calls to DLASQ4.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Further Details:
CNST1 = 9/16
Definition at line 149 of file dlasq4.f.
Author
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