?spev

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 4/28/2026

Version

Public

?spev

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

Syntax

lapack_intLAPACKE_sspev ( intmatrix_layout , charjobz , charuplo , lapack_intn , float*ap , float*w , float*z , lapack_intldz );

lapack_intLAPACKE_dspev ( intmatrix_layout , charjobz , charuplo , lapack_intn , double*ap , double*w , double*z , lapack_intldz );

Include Files

mkl.h

Description

sspev dspev spev

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 , work: REAL for sspev DOUBLE PRECISION for dspev Arrays: 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). work (*) is a workspace array, size at least max(1, 3 n ).

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 sspev DOUBLE PRECISION for dspev 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)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.

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

?spev

Syntax

Include Files

Description

Input Parameters

Output Parameters

Return Values

LAPACK 95 Interface Notes