?stev

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 12/16/2022

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?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.

Parent topic: Symmetric Eigenvalue Problems: LAPACK Driver Routines

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?stev