Developer Reference for Intel® oneAPI Math Kernel Library - C

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

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.