`scipy.linalg._flapack:zpteqr`

Signature

def zpteqr(d, e, z, compute_z = 0, overwrite_d = 0, overwrite_e = 0, overwrite_z = 0)

Compute the eigenvalues and optionally the eigenvectors of a positive definite tridiagonal matrix, to high relative accuracy (LAPACK zpteqr).

d : ndarray: Diagonal of the matrix, length n. Real for every flavor.
e : ndarray: Off-diagonal, length max(0, n - 1). Real for every flavor.
z : ndarray: Required even when unused. With compute_z=1 it is the matrix whose eigenvectors are wanted, of shape (max(1, n), n) and complex; with compute_z=2 its contents are ignored and the eigenvectors of the tridiagonal matrix itself are returned; with compute_z=0 it is not referenced at all and any shape is accepted.
compute_z : int, optional: 0 for eigenvalues only, 1 to compute eigenvectors of the original matrix from the z supplied, 2 for eigenvectors of the tridiagonal matrix. Default is 0.
overwrite_d : int, optional: If nonzero, d may be overwritten in place. Default is 0.
overwrite_e : int, optional: If nonzero, e may be overwritten in place. Default is 0.
overwrite_z : int, optional: If nonzero, z may be overwritten in place. Default is 0.

d : ndarray: Eigenvalues in descending order.
e : ndarray: Destroyed by the computation; the contents are not meaningful.
z : ndarray: Orthonormal eigenvectors as columns, or z unchanged when compute_z is 0.
info : int: 0 on success; if negative, the -info-th argument had an illegal value; if 0 < info <= n, the leading minor of order info is not positive definite; if info > n, that many off-diagonal elements failed to converge to zero.