However, in the case of vocabulary size |V |, which is much larger order than sample size T , it has been observed empirically that the prediction performance of l 1 -penalized regression, the Lasso is dominated by the l 2 -penalized one.
we employ the Elastic Net (Zou and Hastie, 2005), which combines the l 1 -penalty and l 2 -penalty 2 ), where α is called l 1 ratio.