

Determining hot items with exponentially decaying likes - jules
http://julesjacobs.github.io/2015/05/06/exponentially-decaying-likes.html

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karmakaze
This can also be achieved by giving newer likes more value than older ones.
Equivalent with opportunity for efficiencies in precomputing older sums. Is it
HN or reddit ranking algo that does this?

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jules
Yes, that's exactly what this is doing :) But it's doing that in a specific
way to keep the sort order equal to exponential decay, and make sure that the
numbers don't cause floating point overflow and rounding errors.

Reddit does boost the score of newer posts. It doesn't do that for the value
of votes though. Reddit simply adds the (scaled) timestamp when the post was
created to the score of a post. This way newer posts get a higher score than
old ones. Reference: [http://www.outofscope.com/reddits-empire-no-longer-
founded-o...](http://www.outofscope.com/reddits-empire-no-longer-founded-on-a-
flawed-algorithm/)

