scipy.linalg.lapack.dstemr

scipy.linalg.lapack.dstemr(d, e, range, vl, vu, il, iu, compute_v=1, lwork=18 * n, liwork=10 * n, overwrite_d=0, overwrite_e=0) = <flapack function dstemr>

Compute selected eigenvalues and optionally eigenvectors of a symmetric tridiagonal matrix by the MRRR algorithm (LAPACK dstemr).

Parameters:

dndarray

Diagonal elements of the symmetric tridiagonal matrix, length n.

endarray

Off-diagonal elements in the leading n - 1 entries, length n. The final entry need not be set; LAPACK uses it as workspace.

rangeint

Which eigenvalues to compute: 0 for all, 1 for those in (vl, vu], 2 for those with indices il through iu.

vlfloat

Lower bound of the half-open interval; used only when range is 1.

vufloat

Upper bound of the half-open interval; used only when range is 1.

ilint

Index of the smallest eigenvalue to return, 1-based; used only when range is 2.

iuint

Index of the largest eigenvalue to return, 1-based; used only when range is 2.

compute_vint, optional

If nonzero, eigenvectors are computed. Default is 1.

lworkint, optional

Size of the workspace. Default is 18 * n when compute_v is nonzero and 12 * n otherwise. Use stemr_lwork for the optimal value.

liworkint, optional

Size of the integer workspace. Default is 10 * n when compute_v is nonzero and 8 * n otherwise. Use stemr_lwork for the optimal value.

overwrite_dint, optional

If nonzero, d may be overwritten in place. Default is 0.

overwrite_eint, optional

If nonzero, e may be overwritten in place. Default is 0.

Returns:

mint

Number of eigenvalues found; only w[:m] and z[:, :m] are meaningful.

wndarray

The computed eigenvalues in ascending order, length n.

zndarray

Orthonormal eigenvectors as columns, shape (n, n). Not referenced when compute_v is 0.

infoint

0 on success; if negative, the -info-th argument had an illegal value; if positive, the algorithm failed to converge.