Developer Reference

  • 0.9
  • 09/09/2020
  • Public Content
Contents

?lacn2

Estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.

Syntax

C:
lapack_int
LAPACKE_slacn2
(
lapack_int
n
,
float
*
v
,
float
*
x
,
lapack_int
*
isgn
,
float
*
est
,
lapack_int
*
kase
,
lapack_int
*
isave
);
lapack_int
LAPACKE_clacn2
(
lapack_int
n
,
lapack_complex_float
*
v
,
lapack_complex_float
*
x
,
float
*
est
,
lapack_int
*
kase
,
lapack_int
*
isave
);
lapack_int
LAPACKE_dlacn2
(
lapack_int
n
,
double
*
v
,
double
*
x
,
lapack_int
*
isgn
,
double
*
est
,
lapack_int
*
kase
,
lapack_int
*
isave
);
lapack_int
LAPACKE_zlacn2
(
lapack_int
n
,
lapack_complex_double
*
v
,
lapack_complex_double
*
x
,
double
*
est
,
lapack_int
*
kase
,
lapack_int
*
isave
);
Include Files
  • mkl.h
Description
The routine estimates the 1-norm of a square, real or complex matrix
A
. Reverse communication is used for evaluating matrix-vector products.
Input Parameters
n
The order of the matrix
A
(
n
1
).
v
,
x
Arrays, size (
n
) each.
v
is a workspace array.
x
is used as input after an intermediate return.
isgn
Workspace array, size (
n
), used with real flavors only.
est
On entry with
kase
set to 1 or 2, and
isave
(1) = 1
,
est
must be unchanged from the previous call to the routine.
kase
On the initial call to the routine,
kase
must be set to 0.
isave
Array, size (
3
).
Contains variables from the previous call to the routine.
Output Parameters
est
An estimate (a lower bound) for norm(
A
).
kase
On an intermediate return,
kase
is set to 1 or 2, indicating whether
x
is overwritten by
A
*
x
or
A
T
*
x
for real flavors and
A
*
x
or
A
H
*
x
for complex flavors.
On the final return,
kase
is set to 0.
v
On the final return,
v
=
A
*
w
, where
est
= norm(
v
)/norm(
w
)
(
w
is not returned).
x
On an intermediate return,
x
is overwritten by
A
*
x
, if
kase
= 1
,
A
T
*
x
, if
kase
= 2
(for real flavors),
A
H
*
x
, if
kase
= 2
(for complex flavors),
and the routine must be re-called with all the other parameters unchanged.
isave
This parameter is used to save variables between calls to the routine.
Return Values
This function returns a value
info
.
If
info
= 0
, the execution is successful.
If
info
=
-i
, the
i
-th parameter had an illegal value.

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