scipy.linalg._flapack:dsbevx

Parameters

ab : ndarray

The band of the symmetric/Hermitian matrix, shape (kd + 1, n): the order n and the bandwidth kd are both read off ab itself. It is consumed rather than returned.

vl : float

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

vu : float

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

il : int

Index of the smallest eigenvalue to return, 1-based; used only when range is 2. This group keeps Fortran indexing, deliberately.

iu : int

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

ldab : int, optional

Leading dimension of ab. It must equal ab.shape[0]; the argument exists only because the .pyf exposed it. Default is ab.shape[0].

compute_v : int, optional

If nonzero, eigenvectors are computed and z is sized for them; otherwise z comes back as a 1x1 placeholder. Default is 1.

range : int, optional

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

lower : int, optional

If nonzero, ab holds the lower band; otherwise the upper. Default is 0.

abstol : float, optional

Absolute error tolerance. Accuracy is best at twice the underflow threshold, 2 * lamch('S'), rather than at 0. Default is 0.0.

mmax : int, optional

How many eigenvectors z has room for. With range == 1 the count is not known until the call returns, so the default is the whole spectrum; pass a tighter bound to avoid allocating for eigenvectors you will not get.

overwrite_ab : int, optional

If nonzero, ab may be overwritten in place -- and it is consumed either way, never returned. Unlike the rest of this module, the default is 1; pass 0 to keep your array intact.