NAME¶

DLAZQ4 - an approximation TAU to the smallest eigenvalue using values of d from the previous transform

SYNOPSIS¶

SUBROUTINE DLAZQ4(

I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU, TTYPE, G )

INTEGER I0, N0, N0IN, PP, TTYPE DOUBLE PRECISION DMIN, DMIN1, DMIN2, DN, DN1, DN2, G, TAU DOUBLE PRECISION Z( * )

PURPOSE¶

DLAZQ4 computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform.

I0 (input) INTEGER
First index.

N0 (input) INTEGER
Last index.

Z (input) DOUBLE PRECISION array, dimension ( 4*N )
Z holds the qd array.

PP (input) INTEGER
PP=0 for ping, PP=1 for pong.

N0IN (input) INTEGER
The value of N0 at start of EIGTEST.

DMIN (input) DOUBLE PRECISION
Minimum value of d.

DMIN1 (input) DOUBLE PRECISION
Minimum value of d, excluding D( N0 ).

DMIN2 (input) DOUBLE PRECISION
Minimum value of d, excluding D( N0 ) and D( N0-1 ).

DN (input) DOUBLE PRECISION
d(N)

DN1 (input) DOUBLE PRECISION
d(N-1)

DN2 (input) DOUBLE PRECISION
d(N-2)

TAU (output) DOUBLE PRECISION
This is the shift.

TTYPE (output) INTEGER
Shift type.

G (input/output) DOUBLE PRECISION
G is passed as an argument in order to save its value between
calls to DLAZQ4

FURTHER DETAILS¶

This is a thread safe version of DLASQ4, which passes G through the argument list in place of declaring G in a SAVE statment.