slasq3 (l) - Linux Man Pages

slasq3: checks for deflation, computes a shift (TAU) and calls dqds

NAME

SLASQ3 - checks for deflation, computes a shift (TAU) and calls dqds

SYNOPSIS

SUBROUTINE SLASQ3(
I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL, ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2, G, TAU )

    
LOGICAL IEEE

    
INTEGER I0, ITER, N0, NDIV, NFAIL, PP

    
REAL DESIG, DMIN, DMIN1, DMIN2, DN, DN1, DN2, G, QMAX, SIGMA, TAU

    
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/output) INTEGER
PP=0 for ping, PP=1 for pong. PP=2 indicates that flipping was applied to the Z array and that the initial tests for deflation should not be performed.
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.
IEEE (input) LOGICAL
Flag for IEEE or non IEEE arithmetic (passed to SLASQ5).
TTYPE (input/output) INTEGER
Shift type. DMIN1, DMIN2, DN, DN1, DN2, G, TAU (input/output) REAL These are passed as arguments in order to save their values between calls to SLASQ3.