Intel® oneAPI Math Kernel Library Developer Reference - C
Computes all eigenvalues and, optionally, eigenvectors of a real symmetric matrix in packed storage.
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);
The routine computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage.
Specifies whether matrix storage layout is row major (LAPACK_ROW_MAJOR) or column major (LAPACK_COL_MAJOR).
Must be 'N' or 'V'.
If job = 'N', then only eigenvalues are computed.
If job = 'V', then eigenvalues and eigenvectors are computed.
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.
The order of the matrix A (n≥ 0).
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).
The leading dimension of the output array z. Constraints:
if jobz = 'N', then ldz≥ 1;
if jobz = 'V', then ldz≥ max(1, n).
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.
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.
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.