Fixing ranking algorithm.

This commit is contained in:
Dessalines 2019-04-21 10:15:40 -07:00
parent 18e239789f
commit 535231f800
4 changed files with 8 additions and 4 deletions

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@ -30,6 +30,9 @@ This is a **very early beta version**, and a lot of features are currently broke
- Server is written in rust.
- Front end is `~80kB` gzipped.
## About
Lemmy is similar to sites like Reddit, lobste.rs, Raddle, or Hacker News. Behind the scenes, it is very different; It allows anyone to run a server (instance), and all instances are federated, and similar to Mastodon, connected to the same universe. For a link aggregator, this means a user registered on one server can subscribe to forums on any other Lemmy instance, and can have discussions with users registered on any number of instances.
## Why's it called Lemmy?
- Lead singer from [motorhead](https://invidio.us/watch?v=pWB5JZRGl0U).
- The old school [video game](https://en.wikipedia.org/wiki/Lemmings_(video_game)).

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@ -12,14 +12,15 @@ The [Hacker New's ranking algorithm](https://medium.com/hacking-and-gonzo/how-ha
## My Algorithm
```
Rank = ScaleFactor * sign(3 + Score) * log(abs(3 + Score)) / (Time + 2)^Gravity
Rank = ScaleFactor * log(Max(1, 3 + Score)) / (Time + 2)^Gravity
Score = Upvotes - Downvotes
Time = time since submission (in hours)
Gravity = Decay gravity, 1.8 is default
```
- Add 3 to the score, so that even minimally downvoted comments will be affected by time decay. Otherwise all new comments would stay at zero, near the bottom.
- Use Max(1, score) to make sure all comments are affected by time decay.
- Add 3 to the score, so that everything that has less than 3 downvotes will seem new. Otherwise all new comments would stay at zero, near the bottom.
- The sign and abs of the score are necessary for dealing with the log of negative scores.
- A scale factor of 10k gets the rank in integer form.

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@ -5,7 +5,7 @@ create or replace function hot_rank(
returns integer as $$
begin
-- hours_diff:=EXTRACT(EPOCH FROM (timezone('utc',now()) - published))/3600
return floor(10000*sign(3+score)*log(abs(3+score)) / power(((EXTRACT(EPOCH FROM (timezone('utc',now()) - published))/3600) + 2), 1.8))::integer;
return floor(10000*log(greatest(1,score+3)) / power(((EXTRACT(EPOCH FROM (timezone('utc',now()) - published))/3600) + 2), 1.8))::integer;
end; $$
LANGUAGE plpgsql;

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@ -21,7 +21,7 @@ export function hotRank(comment: Comment): number {
let now: Date = new Date();
let hoursElapsed: number = (now.getTime() - date.getTime()) / 36e5;
let rank = (10000 * Math.sign(3+comment.score) * Math.log10(Math.abs(3+comment.score))) / Math.pow(hoursElapsed + 2, 1.8);
let rank = (10000 * Math.log10(Math.max(1, 3 + comment.score))) / Math.pow(hoursElapsed + 2, 1.8);
// console.log(`Comment: ${comment.content}\nRank: ${rank}\nScore: ${comment.score}\nHours: ${hoursElapsed}`);