Contents

?lasd9

Finds the square roots of the roots of the secular equation, and stores, for each element in
D
, the distance to its two nearest poles. Used by
?bdsdc
.

Syntax

Include Files
• mkl.h
Description
The routine
?lasd9
finds the square roots of the roots of the secular equation, as defined by the values in
dsigma
and
z
. It makes the appropriate calls to
?lasd4
, and stores, for each element in
d
, the distance to its two nearest poles (elements in
dsigma
). It also updates the arrays
vf
and
vl
, the first and last components of all the right singular vectors of the original bidiagonal matrix.
?lasd9
is called from
?lasd7
.
Input Parameters
icompq
Specifies whether singular vectors are to be computed in factored form in the calling routine:
If
icompq
= 0
, compute singular values only;
If
icompq
= 1
, compute singular vector matrices in factored form also.
k
The number of terms in the rational function to be solved by
slasd4
.
k
1
.
dsigma
Array,
DIMENSION
(
k
).
The first
k
elements of this array contain the old roots of the deflated updating problem. These are the poles of the secular equation.
z
Array,
DIMENSION
(
k
). The first
k
elements of this array contain the components of the deflation-adjusted updating row vector.
vf
Array,
DIMENSION
(
k
). On entry,
vf
contains information passed through
sbede8
.
vl
Array,
DIMENSION
(
k
). On entry,
vl
contains information passed through
sbede8
.
work
Workspace array,
DIMENSION
at least (3
k
).
Output Parameters
d
Array,
DIMENSION
(
k
).
d
(
i
) contains the updated singular values.
vf
On exit,
vf
contains the first
k
components of the first components of all right singular vectors of the bidiagonal matrix.
vl
On exit,
vl
contains the first
k
components of the last components of all right singular vectors of the bidiagonal matrix.
difl
Array,
DIMENSION
(
k
).
On exit,
difl
(
i
) =
d
(
i
) -
dsigma
(
i
)
.
difr
Array,
DIMENSION
(
ldu
, 2) if
icompq
=1
and
DIMENSION
(
k
) if
icompq
= 0
.
On exit,
difr
(
i
, 1) =
d
(
i
) -
dsigma
(
i
+1)
,
difr
(
k
, 1) is not defined and will not be referenced.
If
icompq
= 1
,
difr
(1:
k
, 2)
is an array containing the normalizing factors for the right singular vector matrix.
info
= 0: successful exit.
< 0: if
info
= -
i
, the
i
-th argument had an illegal value.
> 0: If
info
= 1
, an singular value did not converge

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804