Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

  • 2021.1
  • 12/04/2020
  • Public Content
Contents

?spev

Computes all eigenvalues and, optionally, eigenvectors of a real symmetric matrix in packed storage.

Syntax

lapack_int
LAPACKE_sspev
(
int
matrix_layout
,
char
jobz
,
char
uplo
,
lapack_int
n
,
float
*
ap
,
float
*
w
,
float
*
z
,
lapack_int
ldz
);
lapack_int
LAPACKE_dspev
(
int
matrix_layout
,
char
jobz
,
char
uplo
,
lapack_int
n
,
double
*
ap
,
double
*
w
,
double
*
z
,
lapack_int
ldz
);
Include Files
  • mkl.h
Description
The routine computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix
A
 in packed storage.
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
job
 =
'N'
, then only eigenvalues are computed.
If
job
 =
'V'
, then eigenvalues and eigenvectors are computed.
uplo
Must be
'U'
 or
'L'
.
If
uplo
 =
'U'
,
ap
 stores the packed upper triangular part of
A
.
If
uplo
 =
'L'
,
ap
 stores the packed lower triangular part of
A
.
n
The order of the matrix
A
 (
n
≥
 0
).
ap
Array
ap
 contains the packed upper or lower triangle of symmetric matrix
A
, as specified by
uplo
.
The size of
ap
 must be at least max(1,
n
*(
n
+1)/2).
ldz
The leading dimension of the output array
z
. Constraints:
if
jobz
 =
'N'
, then
ldz
≥
 1
;
if
jobz
 =
'V'
, then
ldz
≥
 max(1,
n
)
.
Output Parameters
w
,
z
Arrays:
w
, size at least max(1,
n
).
If
info
 = 0
,
w
 contains the eigenvalues of the matrix
A
 in ascending order.
z
(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
w
[
i
 - 1]
.
If
jobz
 =
'N'
, then
z
 is not referenced.
ap
On exit, this array is overwritten by the values generated during the reduction to tridiagonal form. The elements of the diagonal and the off-diagonal of the tridiagonal matrix overwrite the corresponding elements of
A
.
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
 indicates the number of elements of an intermediate tridiagonal form which 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.