Developer Reference

  • 2020.2
  • 07/15/2020
  • Public Content
Contents

?lasq3

Checks for deflation, computes a shift and calls
dqds
. Used by
?bdsqr
.

Syntax

call slasq3
(
i0
,
n0
,
z
,
pp
,
dmin
,
sigma
,
desig
,
qmax
,
nfail
,
iter
,
ndiv
,
ieee
,
ttype
,
dmin1
,
dmin2
,
dn
,
dn1
,
dn2
,
g
,
tau
)
call dlasq3
(
i0
,
n0
,
z
,
pp
,
dmin
,
sigma
,
desig
,
qmax
,
nfail
,
iter
,
ndiv
,
ieee
,
ttype
,
dmin1
,
dmin2
,
dn
,
dn1
,
dn2
,
g
,
tau
)
Include Files
  • mkl.fi
Description
The routine
?lasq3
checks for deflation, computes a shift
tau
, and calls
dqds
. In case of failure, it changes shifts, and tries again until output is positive.
Input Parameters
i0
INTEGER
. First index.
n0
INTEGER
. Last index.
z
REAL
for
slasq3
DOUBLE PRECISION
for
dlasq3
.
Array,
DIMENSION
(4
n
).
z
holds the
qd
array.
pp
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.
desig
REAL
for
slasq3
DOUBLE PRECISION
for
dlasq3
.
Lower order part of
sigma
.
qmax
REAL
for
slasq3
DOUBLE PRECISION
for
dlasq3
.
Maximum value of
q
.
ieee
LOGICAL
.
Flag for
ieee
or non-
ieee
arithmetic (passed to
?lasq5
).
ttype
INTEGER
.
Shift type.
dmin1
,
dmin2
,
dn
,
dn1
,
dn2
,
g
,
tau
REAL
for
slasq3
DOUBLE PRECISION
for
dlasq3
.
These scalars are passed as arguments in order to save their values between calls to
?lasq3
.
Output Parameters
dmin
REAL
for
slasq3
DOUBLE PRECISION
for
dlasq3
.
Minimum value of
d
.
pp
INTEGER
.
pp
=0
for ping,
pp
=1
for pong.