CXML

LAPACK version 3.0

slasq3(3)

PURPOSE

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

SYNTAX

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( * )

DESCRIPTION

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).

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