Find similar things on tumblr

The things that you're likely to like are the things that are liked by the people who like the things that you like.

• Initialize an empty map of posts to a list of users: M
• Accept post from some blog: P
• Find every user who has left a note on that post (either a like or reblog) U0 - Un
• For each user U0-Un: U
  • For each note that U wrote to some post Q:
    • Append U to the list M[Q]
• (TODO: somehow normalize this map so that some peoples' counts mean more than others -- not yet implemented)
• Initialize a second empty map of posts Q to counts of users liking each post: C
• For each key Q in M:
  • Set C[Q] to the length of the list in M[Q]
• Now, the largest values in C have the most similar keys (posts) to P

It's in Go. It uses websockets, bootstrap, jQuery and the gorilla web toolkit.