def nalu(x, depth, epsilon=1e-30, name=None, reuse=None):
  """NALU as in https://arxiv.org/abs/1808.00508."""
  with tf.variable_scope(name, default_name="nalu", values=[x], reuse=reuse):
    x_shape = shape_list(x)
    x_flat = tf.reshape(x, [-1, x_shape[-1]])
    gw = tf.get_variable("w", [x_shape[-1], depth])
    g = tf.nn.sigmoid(tf.matmul(x_flat, gw))
    g = tf.reshape(g, x_shape[:-1] + [depth])
    a = nac(x, depth, name="nac_lin")
    log_x = tf.log(tf.abs(x) + epsilon)
    m = nac(log_x, depth, name="nac_log")
    return g * a + (1 - g) * tf.exp(m)