slasq3(3)

NAME

SLASQ3 - check for deflation, computes a shift (TAU) and

calls dqds

SYNOPSIS

SUBROUTINE  SLASQ3(  I0,  N0,  Z,  PP, DMIN, SIGMA, DESIG,
QMAX, NFAIL, ITER, NDIV, IEEE )
    LOGICAL        IEEE
    INTEGER        I0, ITER, N0, NDIV, NFAIL, PP
    REAL           DESIG, DMIN, QMAX, SIGMA
    REAL           Z( * )

PURPOSE

SLASQ3 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) REAL array, dimension ( 4*N )

Z holds the qd array.

PP (input) INTEGER

PP=0 for ping, PP=1 for pong.

DMIN (output) REAL

Minimum value of d.

SIGMA (output) REAL

Sum of shifts used in current segment.

DESIG (input/output) REAL

Lower order part of SIGMA

QMAX (input) REAL

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

SLASQ5).

LAPACK version 3.0 15 June 2000

SLASQ3(3)