1996年にCardosoとSoulomiacによって公開された、ギブンス回転に基づく非常にシンプルで非常にエレガントな同時対角化アルゴリズムがあります。
Cardoso、J.、およびSouloumiac、A.(1996)。同時対角化のためのヤコビ角。SIAM Journal on Matrix Analysis and Applications、17(1)、161–164。doi:10.1137 / S0895479893259546
この応答の最後に、アルゴリズムの多数の実装を添付しました。警告:同時対角化は、グローバルな収束を保証するアルゴリズムがない(私の知る限りでは)、少しトリッキーな数値問題であることがわかりました。ただし、それが機能しない場合(論文を参照)は退化しており、実際には、Jacobi角度アルゴリズムが失敗したことはありません。
#!/usr/bin/env python2.7
# -*- coding: utf-8 -*-
"""
Routines for simultaneous diagonalization
Arun Chaganty <arunchaganty@gmail.com>
"""
import numpy as np
from numpy import zeros, eye, diag
from numpy.linalg import norm
def givens_rotate( A, i, j, c, s ):
"""
Rotate A along axis (i,j) by c and s
"""
Ai, Aj = A[i,:], A[j,:]
A[i,:], A[j,:] = c * Ai + s * Aj, c * Aj - s * Ai
return A
def givens_double_rotate( A, i, j, c, s ):
"""
Rotate A along axis (i,j) by c and s
"""
Ai, Aj = A[i,:], A[j,:]
A[i,:], A[j,:] = c * Ai + s * Aj, c * Aj - s * Ai
A_i, A_j = A[:,i], A[:,j]
A[:,i], A[:,j] = c * A_i + s * A_j, c * A_j - s * A_i
return A
def jacobi_angles( *Ms, **kwargs ):
r"""
Simultaneously diagonalize using Jacobi angles
@article{SC-siam,
HTML = "ftp://sig.enst.fr/pub/jfc/Papers/siam_note.ps.gz",
author = "Jean-Fran\c{c}ois Cardoso and Antoine Souloumiac",
journal = "{SIAM} J. Mat. Anal. Appl.",
title = "Jacobi angles for simultaneous diagonalization",
pages = "161--164",
volume = "17",
number = "1",
month = jan,
year = {1995}}
(a) Compute Givens rotations for every pair of indices (i,j) i < j
- from eigenvectors of G = gg'; g = A_ij - A_ji, A_ij + A_ji
- Compute c, s as \sqrt{x+r/2r}, y/\sqrt{2r(x+r)}
(b) Update matrices by multiplying by the givens rotation R(i,j,c,s)
(c) Repeat (a) until stopping criterion: sin theta < threshold for all ij pairs
"""
assert len(Ms) > 0
m, n = Ms[0].shape
assert m == n
sweeps = kwargs.get('sweeps', 500)
threshold = kwargs.get('eps', 1e-8)
rank = kwargs.get('rank', m)
R = eye(m)
for _ in xrange(sweeps):
done = True
for i in xrange(rank):
for j in xrange(i+1, m):
G = zeros((2,2))
for M in Ms:
g = np.array([ M[i,i] - M[j,j], M[i,j] + M[j,i] ])
G += np.outer(g,g) / len(Ms)
# Compute the eigenvector directly
t_on, t_off = G[0,0] - G[1,1], G[0,1] + G[1,0]
theta = 0.5 * np.arctan2( t_off, t_on + np.sqrt( t_on*t_on + t_off * t_off) )
c, s = np.cos(theta), np.sin(theta)
if abs(s) > threshold:
done = False
# Update the matrices and V
for M in Ms:
givens_double_rotate(M, i, j, c, s)
#assert M[i,i] > M[j, j]
R = givens_rotate(R, i, j, c, s)
if done:
break
R = R.T
L = np.zeros((m, len(Ms)))
err = 0
for i, M in enumerate(Ms):
# The off-diagonal elements of M should be 0
L[:,i] = diag(M)
err += norm(M - diag(diag(M)))
return R, L, err