2. The non-transitory storage medium of claim 1 wherein the penalty Ω(W) comprises l p T (w)=Σ jε ∥g(w,j)ƒ p where ∥•∥ p denotes the l p -norm, g(w,j) is the sub-vector of w associated with the subtree rooted at node j of the suffix trie of a language sample of the corpus, and is an ordered set of nodes of the suffix trie.
3. The non-transitory storage medium of claim 2 wherein the penalty Ω(W) comprises 4(w)=Σ jε ∥g(w,j)∥ 2 where ∥•∥ 2 denotes the l 2 -norm.