# dlazq4 (l) - Linux Manuals

## dlazq4: an approximation TAU to the smallest eigenvalue using values of d from the previous transform

## 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(

DMIN2 (input) DOUBLE PRECISION

Minimum value of d, excluding D(

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.