?stev

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 4/28/2026

Version

Public

?stev

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

Syntax

lapack_intLAPACKE_sstev ( intmatrix_layout , charjobz , lapack_intn , float*d , float*e , float*z , lapack_intldz );

lapack_intLAPACKE_dstev ( intmatrix_layout , charjobz , lapack_intn , double*d , double*e , double*z , lapack_intldz );

Include Files

mkl.h

Description

sstev dstev stev

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 , work: REAL for sstev DOUBLE PRECISION for dstev . 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. work (*) is a workspace array. The dimension of work must be at least max(1, 2 n -2). If jobz = 'N' , work is not referenced.

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

REAL for sstev DOUBLE PRECISION for dstev

Array, size (size max(1, ldz * n )) .

The second dimension of z must be at least max(1, 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)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.

LAPACK 95 Interface Notes

There exist FORTRAN 77 and FORTRAN 95 interfaces for this routine. See the Intel® oneMKL Fortran Developer Reference for details.

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Developer Reference for Intel® oneAPI Math Kernel Library for C

?stev

Syntax

Include Files

Description

Input Parameters

Output Parameters

Return Values

LAPACK 95 Interface Notes