

Is it hot or not? Ranking of user modded content. - ivankirigin

Reddit and News.YC share a feature: hotness. Users mod up and down -- but hotness is more than total points.<p>How should I do it?<p>Positive correlation with number of votes.
Negative correlation with submit time.
Perhaps negative correlation with time since mean or median time of mods.
Perhaps adjust for rates -- a surge implies extra hotness.<p>How do you make the front page efficiently? I hope not to recalculate hotness for each page view -- but a naive approach might think it necessary given the continuous time decay.<p>A parallel service could periodically troll through the entries from the past N days and calculate their hotness -- which serves the front page. That could be updated and chached in memory inependent of front pageview count.
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pg
The way I do it is points divided by age in hours (plus two) to the 1.25th
power. This is probably not optimal, but it's simple.

    
    
     (= gravity* 1.25 timebase* 120)
    
     (def hotness (s (o gravity gravity*))
       (/ (- (realscore s) 1)
          (expt (/ (+ (story-age s) timebase*) 60) gravity)))
    

I avoid reranking all the stories by keeping them in sorted order, and
whenever I generate a frontpage for someone logged in, reinserting one
randomly chosen story near the top (where all the change is). I also reinsert
any story that gets voted on.

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run4yourlives
Thanks for sharing that Paul. Most people guard that knowledge like it's the
lost grail.

Kudo to you for being open about it.

~~~
ivankirigin
Indeed

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palish
Speaking of karma, I wrote a little micro-essay about it at
<http://news.ycombinator.com/item?id=38605> .. I don't know if you'd want to
experiment with karma quite like that, but it would be interesting.

