Though with the help of GPU, BLSTM-RNN is still slower than the other methods.
it should be noted that the speed of our approach is acceptable compared with previous neural network language model based methods, including (Bengio et al., 2003;Mikolov et al., 2010;Mnih and Hinton, 2007), as our model uses a much simpler output layer which only has two nodes, avoiding the time consuming computation of the big softmax output layer in language model.