How does the rating system handle handicap games?

How does the rating system take handicap/komi settings into account, if at all?

komi is not used during calculation at all.

Adding handicap stones increases your effective rank by 1 per stone (In a 1:1 manner).

So if you are an 11kyu and you take a 1 stone handicap when playing a 10kyu. The final point calculation will be performed as though you played an even game 10k vs. 10k but with the delta applied to your existing rating.

When you say “1 stone handicap”, isn’t that just a reduced komi?

I’m just giving an example there @Jamada … if you are an 11kyu and you play a 10kyu under automatic handicap you’ll get one stone plus komi. If you are a 10kyu and you play a 10kyu under automatic handicap settings you’ll get 0 stones plus komi. Under both scenarios the net points awarded or deducted will be the same.

  • Ninja Edit… it should go without saying here that if you play an even game as an 11kyu vs a 10kyu and win you will get more points than if you played a handicapped game against the same rank.

But you wouldn’t get the handicap and the komi would you? I thought Komi were to negate the advantage of playing last - and handicap stones are always black - aren’t they?

What exactly does one stone plus komi mean?

I thought the following was typical for handicap games:

  • 10 kyu vs 10 kyu: even game (no handicap stones, 6.5 komi, black plays first), either can play as black (usually decided randomly)
  • 10 kyu vs 11 kyu: “one stone handicap”, no actual handicap stones, weaker player plays first as black (may play anywhere), reduced komi points (typically 0.5), just effectively a game without komi.
  • 10 kyu vs (10+n) kyu, where n > 1: n stone handicap (at traditionally fixed locations for 2 to 9 stones), stronger player plays first as white (after handicap stones placed), reduced komi points (typically 0.5).

That’s correcct, komi will change to 0.5 for handicapped games however that’s still komi…

The only difference between an “even game” and “one stone handicap” is the komi setting (6.5 versus 0.5), correct? So, in order to recognize the difference between these two cases, the system must take into account the komi when performing the rating calculations?

komi by itself is never taken into account when calculating rating… only the handicap itself.

Ok, I just tried playing around with the game settings, and now I see the crucial aspect that makes this make sense: ranked games force players to use “automatic” for the komi setting, which sets it appropriately from the handicap setting.

If this were not the case, it could lead to some problems if one adjusts the komi setting inapproriately. Consider these example games:

Game 1: Handicap = none, Komi = auto, results in an “even game” with 6.5 komi
Game 2: Handicap = 1, Komi = auto, results in a “one stone handicap” (no actual handicap stones, but white only gets 0.5 komi)
Game 3: Handicap = 1, Komi = 6.5, results in an “even game” with 6.5 komi

Game 3 has the handicap set to “one stone”, but it’s really no different than playing the “even” Game 1. It doesn’t really make much sense to allow a player to set handicap to 1 while also being able to adjust the komi. “One handicap stone” is really just an artificial notion to mean “no komi” (the half point is just to break ties).

In general, if komi were ignored and freely adjustable for ranked games, it could be abused to create unbalance that is not accounted for by the rating system. For example, http://online-go.com/game/688792.

… however since we restrict what can be done in that situation then everything is accounted for so no issue.