Before revision:  In terms of both computational efficiency and ease of learning, it is preferable to dynamically vary the numbers of computations according to the hardness of the input words. However, how to find a suitable estimation for such hardness , then explicitly modeling adaptive computation depths are still not investigated.
After revision:  In terms of both computational efficiency and ease of learning, it is preferable to dynamically vary the numbers of computations according to the hardness of input words , then explicitly modeling adaptive computation depths are still not investigated.