Developer Reference

Contents

?stev

Computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix.

Syntax

lapack_int
LAPACKE_sstev
(
int
matrix_layout
,
char
jobz
,
lapack_int
n
,
float
*
d
,
float
*
e
,
float
*
z
,
lapack_int
ldz
);
lapack_int
LAPACKE_dstev
(
int
matrix_layout
,
char
jobz
,
lapack_int
n
,
double
*
d
,
double
*
e
,
double
*
z
,
lapack_int
ldz
);
Include Files
  • mkl.h
Description
The routine computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix
A
.
Input Parameters
matrix_layout
Specifies whether matrix storage layout is row major (
LAPACK_ROW_MAJOR
) or column major (
LAPACK_COL_MAJOR
).
jobz
Must be
'N'
or
'V'
.
If
jobz
=
'N'
, then only eigenvalues are computed.
If
jobz
=
'V'
, then eigenvalues and eigenvectors are computed.
n
The order of the matrix
A
(
n
0
).
d
,
e
Arrays:
Array
d
contains the
n
diagonal elements of the tridiagonal matrix
A
.
The size of
d
must be at least max(1,
n
).
Array
e
contains the
n
-1 subdiagonal elements of the tridiagonal matrix
A
.
The size of
e
must be at least max(1,
n
). The
n
-th element of this array is used as workspace.
ldz
The leading dimension of the output array
z
;
ldz
1
. If
jobz
=
'V'
then
ldz
max
(1,
n
).
Output Parameters
d
On exit, if
info
= 0
, contains the eigenvalues of the matrix
A
in ascending order.
z
Array, size
(size max(1,
ldz
*
n
))
.
If
jobz
=
'V'
, then if
info
= 0
,
z
contains the orthonormal eigenvectors of the matrix
A
, with the
i
-th column of
z
holding the eigenvector associated with the eigenvalue returned in
d
[
i
- 1]
.
If
job
=
'N'
, then
z
is not referenced.
e
On exit, this array is overwritten with intermediate results.
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.
If
info
=
i
, then the algorithm failed to converge;
i
elements of
e
did not converge to zero.

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