`scipy.linalg._flapack:dtgsen`

source: build-install/usr/lib/python3.14/site-packages/scipy/linalg/_flapack.cpython-314-x86_64-linux-gnu.so

Signature

def dtgsen(select, a, b, q, z, ijob = 4, wantq = 1, wantz = 1, lwork = Ellipsis, liwork = Ellipsis, overwrite_a = 0, overwrite_b = 0, overwrite_q = 0, overwrite_z = 0)

Summary

Reorder a generalized Schur decomposition to gather selected eigenvalues into a leading cluster (LAPACK dtgsen).

Parameters

select : ndarray: Boolean mask of length n: the eigenvalues it marks are gathered into the leading block. A bool array works; LAPACK reads it as a Fortran LOGICAL.
a : ndarray: Upper (quasi-)triangular factor of the pencil, shape (n, n).
b : ndarray: Upper triangular factor of the pencil, shape (n, n).
q : ndarray: Left Schur vectors; updated when wantq is nonzero.
z : ndarray: Right Schur vectors; updated when wantz is nonzero.
ijob : int, optional: What to compute besides the reordering, 0 through 5; 0 reorders only. Default is 4.
wantq : int, optional: If nonzero, the left transformation is accumulated into q. Default is 1.
wantz : int, optional: If nonzero, the right transformation is accumulated into z. Default is 1.
lwork : int, optional: Workspace size; -1 requests the query. Default is 4 * n + 16. The default is a bare minimum for the cheapest job only -- what is actually needed depends on the cluster size, so query the matching _lwork routine.
liwork : int, optional: Integer workspace size; -1 requests the query. Default is n + 6.
overwrite_a : int, optional: If nonzero, a may be overwritten in place. Default is 0.
overwrite_b : int, optional: If nonzero, b may be overwritten in place. Default is 0.
overwrite_q : int, optional: If nonzero, q may be overwritten in place. Default is 0.
overwrite_z : int, optional: If nonzero, z may be overwritten in place. Default is 0.

Returns

as : ndarray: The reordered first factor.
bs : ndarray: The reordered second factor.
alphar : ndarray: Real parts of the eigenvalue numerators, length n.
alphai : ndarray: Imaginary parts of the eigenvalue numerators, length n.
beta : ndarray: Denominators of the reordered eigenvalues, length n.
qs : ndarray: The updated left Schur vectors.
zs : ndarray: The updated right Schur vectors.
m : int: Size of the selected cluster.
pl : float: Lower bound on the reciprocal condition number of the left cluster.
pr : float: Lower bound on the reciprocal condition number of the right cluster.
dif : ndarray: Two estimates of the Difu and Difl separations.
info : int: 0 on success; if negative, the -info-th argument had an illegal value.

Aliases

scipy.linalg._flapack.dtgsen