man SLAZQ4 (3): an approximation TAU to the smallest eigenvalue using values of d from the previous transform

SYNOPSIS

SUBROUTINE SLAZQ4(: I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU, TTYPE, G )
: INTEGER I0, N0, N0IN, PP, TTYPE
: REAL DMIN, DMIN1, DMIN2, DN, DN1, DN2, G, TAU
: REAL Z( * )

SLAZQ4 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) REAL 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) REAL

Minimum value of d.

DMIN1 (input) REAL

Minimum value of d, excluding D( N0 ).

DMIN2 (input) REAL

Minimum value of d, excluding D( N0 ) and D( N0-1 ).

DN (input) REAL

d(N)

DN1 (input) REAL

d(N-1)

DN2 (input) REAL

d(N-2)

TAU (output) REAL

This is the shift.

TTYPE (output) INTEGER

Shift type.

G (input/output) REAL

G is passed as an argument in order to save its value between
calls to SLAZQ4

This is a thread safe version of SLASQ4, which passes G through the argument list in place of declaring G in a SAVE statment.