Life In 19x19 :: Question regarding AGA vs Territory/Area scoring

EdLee wrote:

snorri wrote:

We don't do komi = 0.5, which would change the winner.

snorri, this is exactly my confusion. When komi = 0.0, and when komi = 0.5, Chinese scoring and Japanese scoring give different winners (for the above final board position).

Yes, this is a general issue. With no komi, black has one more point than white in 1/2 of games (dame polarity). And whenever white has a fixed komi, black will still have one more point under area scoring than under territory scoring in 1/2 of games. But in fact, China has historically tended to offer one more point of komi (well, an extra 0.5 zi) in komi than the Japanese and Koreans do, so in practice it is white who has an extra point in 1/2 of games when people use area rules.

In effect, white's extra pass under AGA rules is a way to give back one point of the Chinese-style 7.5 komi (if I understand correctly). I'm sure I will swiftly corrected by someone who is better at arithmetic...

Author:	Magicwand [ Wed Aug 14, 2013 5:43 pm ]
Post subject:	Re: Question regarding AGA vs Territory/Area scoring
RobertJasiek wrote: MJK wrote: I've never ever seen a single Korean discussing or maybe arguing with baduk rules The good news is: just recently, I have discussed about rules with an influential Korean for 3 hours. They are interested not only in Western pairing programs but also in Western input for the sake of correcting their own rules, because they have realised that they cannot solve this problem alone. More later. really??? do you even read what you write? if i say any more i might be banned from this place... so i will stop. word of advice: read what you write and try to figure out why it is wrong.

Author:	Mef [ Wed Aug 14, 2013 8:20 pm ]
Post subject:	Re: Re:
jts wrote: EdLee wrote: snorri wrote: We don't do komi = 0.5, which would change the winner. snorri, this is exactly my confusion. When komi = 0.0, and when komi = 0.5, Chinese scoring and Japanese scoring give different winners (for the above final board position). Yes, this is a general issue. With no komi, black has one more point than white in 1/2 of games (dame polarity). And whenever white has a fixed komi, black will still have one more point under area scoring than under territory scoring in 1/2 of games. But in fact, China has historically tended to offer one more point of komi (well, an extra 0.5 zi) in komi than the Japanese and Koreans do, so in practice it is white who has an extra point in 1/2 of games when people use area rules. In effect, white's extra pass under AGA rules is a way to give back one point of the Chinese-style 7.5 komi (if I understand correctly). I'm sure I will swiftly corrected by someone who is better at arithmetic... I think you might be trying to overcomplicate things (= The extra point of komi under chinese rules is a relatively recent thing. For a long time komi was 5.5 for both Japanese and Chinese rules. The problem is that under area counting only odd komi (+0.5) really makes sense. This means that even though Japan could raise their komi to 6.5 to balance the game, China had to go all the way to 7.5. You see when you have an odd number of points on the board and want to score area style, 0.5 komi is essentially the same as no komi. A board position where white would lose by 1 instead becomes a loss by 0.5. To have 0.5 komi alter the outcome requires a game with an odd number of dame (very rare). Beyond this score differences will almost always be by twos because for white to score one more point, black will also score one less. AGA rules are area scoring just like Chinese so it's natural for AGA to use 7.5 komi (even though they can be counted using territory counting). The third pass is for bookkeeping to maintain the correct difference in prisoners (which are only relevant in territory counting. Under chinese-style counting all the prisoners are ignored). It also has a side-effect of avoiding a scenario known as a "pass fight" (which also only applies to territory counting, and we don't need to get into details of here).

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