Annoy – now without Boost dependencies and with Python 3 Support
Annoy is a C++/Python package I built for fast approximate nearest neighbor search in high dimensional spaces. Spotify uses it a lot to find similar items. First, matrix factorization gives a low dimensional representation of each item (artist/album/track/user) so that every item is a k-dimensional vector, where k is typically 40-100. This is then loaded into an Annoy index for a number of things: fast similar items, personal music recommendations, etc.
Annoy stands for Approximate Nearest Neighbors something something and was originally open sourced back in 2013, although it wasn't entirely well-supported until last year when I fixed a couple of crucial bugs. Subsequently, Dirk Eddelbuettel released RCppAnnoy, an R version of Annoy.
The key feature of Annoy is that it supports file-based indexes that can be mmapped very quickly. This makes it very easy to share indexes across multiple processes, load/save indexes, etc.
Last weekend I decided to fix it. I have something to confess. I've been meaning to address the Boost dependency for a long time, but never found the time to do it. Finally I just put up an ad on Odesk and outsourced the whole project. I found a great developer who built it all in a few hours.
It might seem ironic to outsource open source projects since I don't get payed for it. But I spend time working on open source projects because it gives me things back in many ways – networking, recognition, some sort of fuzzy altruistic feeling of having contributed. I don't mind spending a few bucks on it, same way as I don't mind spending time on it.