factory.py 文件源码

def eye(sites, ldim):
    """Returns a MPA representing the identity matrix

    :param sites: Number of sites
    :param ldim: Int-like local dimension or iterable of local dimensions
    :returns: Representation of the identity matrix as MPA

    >>> I = eye(4, 2)
    >>> I.ranks, I.shape
    ((1, 1, 1), ((2, 2), (2, 2), (2, 2), (2, 2)))
    >>> I = eye(3, (3, 4, 5))
    >>> I.shape
    ((3, 3), (4, 4), (5, 5))
    """
    if isinstance(ldim, collections.Iterable):
        ldim = tuple(ldim)
        assert len(ldim) == sites
    else:
        ldim = it.repeat(ldim, sites)
    return mp.MPArray.from_kron(map(np.eye, ldim))