Performance drops off a cliff after ~50 teams?

[downhiller]

I'm trying to implement this for a sporting event, which could have anything up to 1000 competitors.

I find with 20/30/40/50 competitors it works perfectly, and speedily - typically less than 0.2 second.

But as soon as I go to 60 competitors, it takes over 30 seconds and times out.

Do you have any idea why this would be? Any pointers appreciated, many thanks!

[downhiller]

That'll be the problem then. That's counting loops of

https://github.com/moserware/PHPSkills/blob/master/src/TrueSkill/Factors/GaussianWeightedSumFactor.php#L129

(I counted those simply because that's the line that timed out).

I feel there must be something about the number 26 or 52 in the code, but I can't find it. Coincidence that that's how many letters are in the alphabet..?

[downhiller]

I found http://disq.us/p/vreqdi, which gave me a pointer.

Changing $initialMaxDelta to 0.1 or even 1 seems to hardly change the order of ranked players after 100 match-ups of 20 player from a large pool at all, or their sigma, but it does significantly inflate their mu.

I've put a base mu of 1000, and with initialMaxDelta as 0.0001 I end up with players on 1200. With 0.1 some are as high as 1350, and with 1 they go right up to 1510.

Sigma is relatively unaffected, and ordering is almost identical.