scipy.linalg.lapack.dsyevr

scipy.linalg.lapack.dsyevr(a, compute_v=1, range='A', lower=0, vl=0.0, vu=1.0, il=1, iu=n, abstol=0.0, lwork=..., liwork=..., overwrite_a=0) = <flapack function dsyevr>

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

Parameters:

andarray

real symmetric matrix of shape (n, n).

compute_vint, optional

If nonzero, eigenvectors are computed as well as eigenvalues. Default is 1.

rangestr, optional

'A' for all eigenvalues, 'V' for those in (vl, vu], 'I' for those indexed il through iu. Default is 'A'.

lowerint, optional

If nonzero, the lower triangle of a is referenced; otherwise the upper. Default is 0.

vlfloat, optional

Lower bound of the interval; used only when range is 'V'. Default is 0.0.

vufloat, optional

Upper bound of the interval; used only when range is 'V'. Default is 1.0.

ilint, optional

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

iuint, optional

Index of the largest eigenvalue to return, 1-based; used only when range is 'I'. Default is n.

abstolfloat, optional

Absolute error tolerance for the eigenvalues. Default is 0.0.

lworkint, optional

Default is max(26 * n, 1) for the real flavors, max(2 * n, 1) for the complex.

liworkint, optional

Size of the integer workspace. Default is max(10 * n, 1).

overwrite_aint, optional

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

Returns:

wndarray

Eigenvalues in ascending order, length n. Real for every flavor.

zndarray

The m computed eigenvectors as columns, or empty when compute_v is 0.

mint

Number of eigenvalues found.

isuppzndarray

Support of each eigenvector: rows isuppz[2*i] through isuppz[2*i+1] are nonzero, 1-based. Length 2 * n when range is 'A', when range is 'I' spanning the whole index range, or when n == 1; empty otherwise, those being the only cases LAPACK writes it.

infoint

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