?lasq4

Computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by ?bdsqr.

Syntax

call slasq4( i0, n0, z, pp, n0in, dmin, dmin1, dmin2, dn, dn1, dn2, tau, ttype, g )

call dlasq4( i0, n0, z, pp, n0in, dmin, dmin1, dmin2, dn, dn1, dn2, tau, ttype, g )

Include Files

The FORTRAN 77 interfaces are specified in the mkl_lapack.fi include file (to be used in Fortran programs) and in the mkl_lapack.h include file (to be used in C programs).

Description

The routine computes an approximation tau to the smallest eigenvalue using values of d from the previous transform.

Input Parameters

i0

INTEGER. First index.

n0

INTEGER. Last index.

z

REAL for slasq4

DOUBLE PRECISION for dlasq4.

Array, DIMENSION (4n).

z holds the qd array.

pp

INTEGER. pp=0 for ping, pp=1 for pong.

n0in

INTEGER. The value of n0 at start of eigtest.

dmin

REAL for slasq4

DOUBLE PRECISION for dlasq4.

Minimum value of d.

dmin1

REAL for slasq4

DOUBLE PRECISION for dlasq4.

Minimum value of d, excluding d(n0).

dmin2

REAL for slasq4

DOUBLE PRECISION for dlasq4.

Minimum value of d, excluding d(n0) and d(n0-1).

dn

REAL for slasq4

DOUBLE PRECISION for dlasq4. Contains d(n).

dn1

REAL for slasq4

DOUBLE PRECISION for dlasq4. Contains d(n-1).

dn2

REAL for slasq4

DOUBLE PRECISION for dlasq4. Contains d(n-2).

g

REAL for slasq4

DOUBLE PRECISION for dlasq4.

A scalar passed as an argument in order to save its value between calls to ?lasq4.

Output Parameters

tau

REAL for slasq4

DOUBLE PRECISION for dlasq4.

Shift.

ttype

INTEGER. Shift type.

g

REAL for slasq4

DOUBLE PRECISION for dlasq4.

A scalar passed as an argument in order to save its value between calls to ?lasq4.