This is a follow-up on the hashing for linear functions post. It’s based on the HashCoFi paper that Markus Weimer, Alexandros Karatzoglou and I wrote for AISTATS'10. It deals with the issue of running out of memory when you want to use collaborative filtering for very large problems. Here’s the setting: Assume you want to do Netflix-style collaborative filtering, i.e. you want to estimate entries