问题
I'm trying to come up with a way to determine how "hot" certain threads are in a forum. What criteria would you use and why? How would these come together to give a hotness score?
The criteria I'm thinking of include:
- how many replies
- how long since the last reply
- average time between replies
The problems this algorithm must solve:
- A thread which has 500 replies is clearly hot, unless the last reply was over a year ago.
- A thread with 500 replies that was replied to a second ago is clearly hot, unless it's taken 4 years to reach 500 replies.
- A thread with 15 replies in the last 4 minutes is really hot!
Any ideas, thoughts or complete solutions out there?
回答1:
this might be what you are looking for:
Popularity algorithm
回答2:
Jeff Atwood has a nice question about this with a ton of information on other "hot" algorithms. I suggest using one of those and adapting it to your liking.
回答3:
Simplest algorithm: If there have been greater than X replies since Y, it is hot.
If you prefer something that scales, just count how many replies since time y. More replies means more hotness.
回答4:
I was thinking you could probably model it with diminishing waves here, using amplitude (or root mean square) to measure hotness. As time goes, the wave diminishes, and so a late reply will only cause a little stir.
In practice, I think this requires a lot of calculation. You could make good use of caching to speed up the calculation.
Just my two cents.
回答5:
In short I've found logarithmic decay of "hotness" to be the most natural.
回答6:
Thanks to those who posted the links to the other questions/answers. Unfortunately, those equations take a lot more things into consideration than what's possible with my setup (eg: voting, reputation of author, etc)
After playing around with it, I've come up with this equation which I'll use for the time being:
log10($numOfReplies * 20000 / pow($timeSinceLastPost, 1.3))
It still could use some work. For example, if there's a really really popular but old thread, it'll be low on the hotness, but if one person replies to it that'll put it right back to the top for a few days/weeks.
回答7:
Why not just use a sort of exponential decay model. Hotness of thread = sum( k^(time since posting) ) for all posts. This has the advantage of being really easy to update and calculate. You'd have to play around with k and your unit of time measurement (k should be < 1, but fairly close to it)
Current hotness = hotness at time of last post * k^(time since last post).
Hotness after new post = current hotness + 1
回答8:
One thing you should pay some attention to is whether people might want to "game" the algorithm in order to make/keep their threads "hot". Actually, you can pretty much assume that they will.
The minimum you should do to discourage this is to only consider replies from different people.
来源：https://stackoverflow.com/questions/381138/algorithm-to-determine-thread-hotness