core.py 文件源码

def nvecs(X, n, rank, do_flipsign=True, dtype=np.float):
    """
    Eigendecomposition of mode-n unfolding of a tensor
    """
    Xn = X.unfold(n)
    if issparse_mat(Xn):
        Xn = csr_matrix(Xn, dtype=dtype)
        Y = Xn.dot(Xn.T)
        _, U = eigsh(Y, rank, which='LM')
    else:
        Y = Xn.dot(Xn.T)
        N = Y.shape[0]
        _, U = eigh(Y, eigvals=(N - rank, N - 1))
        #_, U = eigsh(Y, rank, which='LM')
    # reverse order of eigenvectors such that eigenvalues are decreasing
    U = array(U[:, ::-1])
    # flip sign
    if do_flipsign:
        U = flipsign(U)
    return U