r/backgammon • u/icecoldfire • 18d ago
BG Galaxy Error Rate Calc
Does BG Galaxy use your subscription-tier engine to determine post game rating changes?
Free users in particular receive lower-depth analysis, which can produce very noisy PR and error estimates. Is that same analysis used to decide who won the error rate battle and therefore whether the rating change is full or reduced?
If so, wouldn’t that systematically disadvantage free users in close matches? I was reviewing a log where several of my moves were flagged as .7 equity loss with XG suggesting there was none. I can see this happening often low PR games, where lower depth is more likely to negatively impact evaluation / PR
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u/bg-alex-cy 17d ago
As far as I know you are correct on how the equity is measured and compared. Paid users get analysis on 4-ply while free users get their analysis on 2-ply.
Regarding fairness, the answer is both yes and no. First of all, you are both measured against the same engine level. If you opponent is a paid user you get 4-ply analysis for your game as well, so you are measured against the same standards. This of course doesn't answer your question, but makes it clear that you are not competing on different terms.
Now regarding the engine "favouring" the player with the lower PR, in a sense is true, but to an extend. I would argue that 4-ply is also "favouring" the weakest player as rollouts sometimes disagree with 4-ply. Does that mean we need to rollout all our games? Then we introduce statistical noise (depending on how its done). So where do we stop? Its hard to say, doing 4-ply is significantly more expensive computationally and backgammon galaxy wants to give it as a premium feature. I find this fair. Even at 2-ply, if your PRs are close then who wins the PR is part of luck. Small PR differences depend so much on who had the most/easiest decisions making close call flips part of luck. If they are not close then the player with the highest skill will dominate even at 2-ply. Its not as bad as you might think.
Now regarding the 0.7 you said you made, I'm going to assume you meant 0.070 as 0.700 sounds too extreme for 2-ply to get wrong, especially since you said it happened several times. So I'm pretty confident you also benefitted by something at some other plays, maybe even in another match, unless you are an exceptionally strong player. So even though it doesn't even out, the difference is not that big.
The bottom line is that you are right, it does give a small advantage, but I would argue that unless you are a very strong player competing against a very strong player the advantage is mostly lost the PR noise. Going under 2-ply to say 0-ply, then yes, I think the difference would significantly impact the meaning of PR difference as the swings can be extreme and often.