Inspired by previous work that has demonstrated that additional inputs to decoder models can effectively control the characteristics of the output (Wen et al., 2015;Li et al., 2016b), this model provides information about the length in the form of an additional input to the net.
the model uses an embedding e 2 (l t ) ∈ R D for each potential desired length, which is parameterized by a length embedding matrix W le ∈ R D×L where L is the number of length types.