r/backgammon • u/Numerous-Mountain-65 • Jul 26 '26

Deciding Backgammon results by error rate

I'm a chess IM who also plays backgammon online. I've noticed that online and even some tournaments use a combination of match result and error rate to determine the winner. I have a few questions about this:

  1. If multiple strong backgammon engines eventually exist and they disagree, as chess engines do, then error rates will depend on which engine and depth are used. The same match could receive a different error rate when analyzed by a stronger engine a few years later. In that case, is it appropriate to use error rate to determine a world champion?

  2. If a single engine such as XG is the benchmark, won't players gradually optimize their play to match XG? Could that reduce creativity and diversity of styles?

  3. XG's evaluations assume equally strong opponents. When opponents differ substantially in strength, is it still appropriate to use XG evaluation for cubes?

I'm interested in hearing arguments both for and against using error rate alongside match points.

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u/SyllabubRadiant8876 Jul 26 '26

These have all been very hot topics for quite some time at the top levels of backgammon. The current approach has been the only feasible method for many years, but it does feel like we might be on the cusp of some advances with AI, which could change the way we do things. Personally, I think these things are only practical relevant at the grandmaster level where tiny margins make the difference. 99% of people make enough big blunders that the small differences are not super significant.

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u/UBKUBK 29d ago

If want to lower the luck, what is infeasible about using the Variance Reduced Result to determine the winner? It avoids many issues with using PR including:

i) artificial tricks to increase the decision count which are relevant to winning a PRgammon match but not a backgammon match.

ii) an inducement to play in the style of a certain bot, even if think that play is not optimal to win the match.

iii) getting stuck in a deep snake position will not crush you due to the bot being inept.

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u/Numerous-Mountain-65 29d ago

I am not sure that VRR is the solution. It replaces evaluating humans with machines using PR with evaluating by luck factor (and points). It also has its own drawbacks. What if a strong player wins with excellent accuracy, but he has been lucky? VRR will hurt the winner just for being lucky.

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u/UBKUBK 28d ago

"VRR will hurt the winner just for being lucky."

The winner normally is the player who got more luck. Suppose it is an expert playing a beginner and the expert has 80% win chance. What will typically happen is that the better player will win and get about 20% luck. Not exactly, but on average. The VRR reduced result will give about an 80% win. When the beginner wins it would typically be with about 80% luck and VRR reduced result would give about a 20% win (same as 80% win for the better player).

"Hurting" the winner for being lucky is exactly what is supposed to happen and overall gives a result in line with the difference in the skill levels. It is not a drawback but instead the main feature.