NAME¶

SLAZQ4 - 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( * )

PURPOSE¶

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

FURTHER DETAILS¶

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