A place to discuss the science of computers and programs, from algorithms to computability.

Formal proofs preferred.

Moderators: phlip, Moderators General, Prelates

So yeah, does anyone have any idea about the nature of the algorithm that determines which 10 friends Facebook chooses to display on your profile? It certainly isn't random every visit, as multiple refreshes simply result in the order of the friends being shuffled.

Now, facebook itself has mentioned this in their FAQs - http://www.facebook.com/help/?page=810 - but the description seems fairly limited; how, for example, can we account for the times when people I've had no interaction with appear on the list of friends?

Obviously only an actual facebook employee could give us a real insight into how the friends are selected, but it'd be interesting to see what people think here.
Mincewind

Posts: 10
Joined: Thu Dec 10, 2009 7:54 pm UTC

Pretty much all of my facebook friends who don't start a sentence with, "So yeah," are on my top 10. Hope that helps!
Moose Hole

Posts: 400
Joined: Fri Jul 09, 2010 1:34 pm UTC

What an intelligent and erudite observation, and one with such an incisive topical comment appended onto it! I applaud you, Sir, and I would like to subscribe to your newsletter!
Mincewind

Posts: 10
Joined: Thu Dec 10, 2009 7:54 pm UTC

You're right about the lack of information here, so all we can really provide are wild guesses. You say that people appear who you have had no interaction whatsoever with, which leaves me with two (similar) ideas.

1) It shows the top 10 after a non-stable sort based on (number of interactions), and you don't have ten friends you've interacted with. Example: you interact with seven, all the rest have equivalent values (zero), and since it's a non-stable sort, different zeros will appear. It may then shuffle the final ten too maybe, to obscure the ranking.

2) It shows the top 10 after a sort based on (number of interactions plus a random number between 0 and max/10), thus giving more or less stable results, but also showing less interacted-with people sometimes.
Ambeco

Posts: 102
Joined: Thu Mar 03, 2011 12:17 am UTC