`scipy.linalg._flapack:ctgexc`

Signature

def ctgexc(a, b, q, z, ifst, ilst, wantq = 1, wantz = 1, overwrite_a = 0, overwrite_b = 0, overwrite_q = 0, overwrite_z = 0)

Reorder a generalized Schur decomposition by moving one diagonal block (LAPACK ctgexc).

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.
ifst : int: Current position of the diagonal block to move, 1-based.
ilst : int: Position to move it to, 1-based. LAPACK adjusts both when a block turns out to be 2x2; the adjusted values are not returned.
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.
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.

a : ndarray: The reordered first factor.
b : ndarray: The reordered second factor.
q : ndarray: The updated left Schur vectors.
z : ndarray: The updated right Schur vectors.
info : int: 0 on success; if negative, the -info-th argument had an illegal value.