it's a good history of kind of where these methods came from so you know since we're talking about NLP and language models is one of the core workhorses here kind of how do you evaluate and interpret a language model well probabilities are often within running or of 0 since language is a huge discrete space in the sentence might you know or a document might just be very long and so the most common way of evaluating these models and saying how well does it do is we use a quantity that's not dependent on the length so we