dlasq3(3)

NAME

DLASQ3 - check for deflation, computes a shift (TAU) and

calls dqds

SYNOPSIS

SUBROUTINE  DLASQ3(  I0,  N0,  Z,  PP, DMIN, SIGMA, DESIG,
QMAX, NFAIL, ITER, NDIV, IEEE )
    LOGICAL        IEEE
    INTEGER        I0, ITER, N0, NDIV, NFAIL, PP
    DOUBLE         PRECISION DESIG, DMIN, QMAX, SIGMA
    DOUBLE         PRECISION Z( * )

PURPOSE

DLASQ3 checks for deflation, computes a shift (TAU) and

calls dqds. In case of failure it changes shifts, and tries again

until output is positive.

ARGUMENTS

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.

DMIN (output) DOUBLE PRECISION

Minimum value of d.

SIGMA (output) DOUBLE PRECISION

Sum of shifts used in current segment.

DESIG (input/output) DOUBLE PRECISION

Lower order part of SIGMA

QMAX (input) DOUBLE PRECISION

Maximum value of q.

NFAIL (output) INTEGER

Number of times shift was too big.

ITER (output) INTEGER

Number of iterations.

NDIV (output) INTEGER

Number of divisions.

TTYPE (output) INTEGER

Shift type.

IEEE (input) LOGICAL

Flag for IEEE or non IEEE arithmetic (passed to

DLASQ5).

LAPACK version 3.0 15 June 2000

DLASQ3(3)