Erik Bernhardsson    About

Welcome Echo Nest!

In case you missed it, we just acquired a company called Echo Nest in Boston. These people have been obsessed with understanding music for the past 8 years since it was founded by Brian Whitman and Tristan Jehan out of MIT Medialab. We ...

Luigi success

So Luigi, our open sourced workflow engine in Python, just recently passed 1,000 stars on Github, then shortly after passed mrjob as (I think) the most popular Python package to do Hadoop stuff. This is exciting! A fun anecdote from l...

Momentum strategies

Haven’t posted anything in ages, so here’s a quick hack I threw together in Python on a Sunday night. Basically I wanted to know whether momentum strategies work well for international stock indexes. I spent a bit of time putting togethe...

Ratio metrics

We run a ton of A/B tests at Spotify and we look at a ton of metrics. Defining metrics is a little bit of an art form. Ideally you want to define success metrics before you run a test to avoid cherry picking metrics. You also want to def...

Benchmarking nearest neighbor libraries in Python

Radim Rehurek has put together an excellent summary of approximate nearest neighbor libraries in Python. This is exciting, because one of the libraries he’s covering, annoy, was built by me. After introducing the problem, he goes throug...

More recommender algorithms

I wanted to share some more insight into the algorithms we use at Spotify. One matrix factorization algorithm we have used for a while assumes that we have user vectors and item vectors . The next track for a user is now given by th...

Microsoft’s new marketing strategy: give up

I think it’s funny how MS at some point realized they are not the cool kids and there’s no reason to appeal to that target audience. Their new marketing strategy finally admits what’s been long known: the correlation between “business ca...