`scipy.linalg._flapack:ctrexc`

Signature

def ctrexc(a, q, ifst, ilst, wantq = 1, overwrite_a = 0, overwrite_q = 0)

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

a : ndarray: Upper (quasi-)triangular Schur form of shape (n, n).
q : ndarray: Matrix of Schur vectors; updated when wantq 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 transformation is accumulated into q. Default is 1.
overwrite_a : int, optional: If nonzero, a may be overwritten in place. Default is 0.
overwrite_q : int, optional: If nonzero, q may be overwritten in place. Default is 0.

a : ndarray: The reordered Schur form.
q : ndarray: The updated Schur vectors.
info : int: 0 on success; if negative, the -info-th argument had an illegal value.