test_extmath.py 文件源码

def test_randomized_svd_sign_flip_with_transpose():
    # Check if the randomized_svd sign flipping is always done based on u
    # irrespective of transpose.
    # See https://github.com/scikit-learn/scikit-learn/issues/5608
    # for more details.
    def max_loading_is_positive(u, v):
        """
        returns bool tuple indicating if the values maximising np.abs
        are positive across all rows for u and across all columns for v.
        """
        u_based = (np.abs(u).max(axis=0) == u.max(axis=0)).all()
        v_based = (np.abs(v).max(axis=1) == v.max(axis=1)).all()
        return u_based, v_based

    mat = np.arange(10 * 8).reshape(10, -1)

    # Without transpose
    u_flipped, _, v_flipped = randomized_svd(mat, 3, flip_sign=True)
    u_based, v_based = max_loading_is_positive(u_flipped, v_flipped)
    assert_true(u_based)
    assert_false(v_based)

    # With transpose
    u_flipped_with_transpose, _, v_flipped_with_transpose = randomized_svd(
        mat, 3, flip_sign=True, transpose=True)
    u_based, v_based = max_loading_is_positive(
        u_flipped_with_transpose, v_flipped_with_transpose)
    assert_true(u_based)
    assert_false(v_based)