?sbev

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 4/28/2026

Version

Public

?sbev

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

Syntax

lapack_intLAPACKE_ssbev ( intmatrix_layout , charjobz , charuplo , lapack_intn , lapack_intkd , float*ab , lapack_intldab , float*w , float*z , lapack_intldz );

lapack_intLAPACKE_dsbev ( intmatrix_layout , charjobz , charuplo , lapack_intn , lapack_intkd , double*ab , lapack_intldab , double*w , double*z , lapack_intldz );

Include Files

mkl.h

Description

ssbev dsbev sbev

The routine computes all eigenvalues and, optionally, eigenvectors of a real symmetric band 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.

uplo

Must be ‘U’ or ‘L’ .

If uplo = 'U' , ab stores the upper triangular part of A . If uplo = 'L' , ab stores the lower triangular part of A .

n

The order of the matrix A ( n≥ 0 ).

kd

The number of super- or sub-diagonals in A

( kd≥ 0 ).

ab , work

REAL for ssbev DOUBLE PRECISION for dsbev . Arrays:

ab (size at least max(1, ldab * n ) for column major layout and at least max(1, ldab *( kd + 1)) for row major layout) is an array containing either upper or lower triangular part of the symmetric matrix A (as specified by uplo ) in band storage format.

The second dimension of ab must be at least max(1, n ). work (*) is a workspace array. The dimension of work must be at least max(1, 3 n -2).

ldab

The leading dimension of ab ; must be at least kd +1 for column major layout and n for row major layout .

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

REAL for ssbev DOUBLE PRECISION for dsbev Arrays:

w , size at least max(1, n ).

If info = 0 , contains the eigenvalues of the matrix A in ascending order.

z (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 w(i)w[i - 1] . If jobz = 'N' , then z is not referenced.

ab

On exit, this array is overwritten by the values generated during the reduction to tridiagonal form (see the description of ?sbtrd ).

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.

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

?sbev

Syntax

Include Files

Description

Input Parameters

Output Parameters

Return Values

LAPACK 95 Interface Notes