Ask HN: algorithm used in Hacker News, that determines the front page news

https://news.ycombinator.com/item?id=4824698

by coderhs • 14 years ago

2 4 14 years ago

news.ycombinator.com

Whats the algorithm used in Hacker News, that determines which post gets to the front page.

zio99• 14 years ago

Gravity.

Score decreases over time, so interesting news bubble up, and older/no-longer-relevant news gradually decline.

    (= gravity* 1.8 timebase* 120 front-threshold* 1
       nourl-factor* .4 lightweight-factor* .17 gag-factor* .1)

    (def frontpage-rank (s (o scorefn realscore) (o gravity gravity*))
      (* (/ (let base (- (scorefn s) 1)
              (if (> base 0) (expt base .8) base))
            (expt (/ (+ (item-age s) timebase*) 60) gravity))
         (if (no (in s!type 'story 'poll))  .8
             (blank s!url)                  nourl-factor*
             (mem 'bury s!keys)             .001
                                            (* (contro-factor s)
                                               (if (mem 'gag s!keys)
                                                    gag-factor*
                                                   (lightweight s)
                                                    lightweight-factor*
                                                   1)))))

coderhs• 14 years ago

is there any relation to the vote given by people with higher karma or who is more active in the website?

pizza• 14 years ago

direct copy from http://news.ycombinator.com/item?id=4746566

According to the link in dmgrow's comment, it's

    Score = (P-1) / (T+2)^G

where P is the number of votes, T is the time in hours since submission, and G is a power that controls the steepness/rate of decline in ranking, so popularity is decreases exponentially over time. I'm sure that YC-affiliated posts have a different ranking algorithm, considering you can't vote on them.

Some other cool algorithms are:

del.icio.us / delicious.com 's: ranked by upvotes in the last hour. I like the elegance of this solution a lot :)

reddit's "best" feature: compares the rates at which comments are upvoted to generate the probability that a comment is a good one, which is how posts with fewer votes can be ranked better than posts with more votes. It works well, in my opinion.

bravoyankee• 14 years ago

I think there's more to it than what the other two comments described. No doubt there is human moderation on HN (beyond users flagging submissions I mean), and maybe a list of domains and keywords to keep some stories from ever hitting front page, even when the submission gets a lot of votes in a short amount of time.

Who knows what the reasons why they'd keep a story off the front page. The moderation is emo at times, even resorting to hellbanning, slowbanning etc.

Slashdot moderation is way better. It's a better overall system over there.

Ask HN: algorithm used in Hacker News, that determines the front page news

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