We assign a normalized weight to each sentence according to the criterion that can be given as: Further, weighted sampling without any replacement was used to select a small subset, such as 80% 1 of the entire corpus, as the corpus D i+1 ws to perform the subsequent iteration.
the updated objective function using weighted sampling J ws can be formulated as follows: only 80% of the entire corpus is used to perform the NMt training during each iteration (for the first two iteration, all of the sentences should be sampled).