Message from discussion
Handicap = komi?
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NNTP-Posting-Date: Sun, 21 Jun 2009 09:49:21 -0500
From: jazzerci...@hotmail.com (-)
Newsgroups: rec.games.go
Subject: Re: Handicap = komi?
Date: Sun, 21 Jun 2009 14:45:23 GMT
Message-ID: <4a3e41dc.718769025@news3.isomedia.com>
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"Joel Olson" <joel_ol...@sbcglobal.net> wrote:
> Heard just last night that under AGA rules, when counting up a
> handicap game, Black has to give back the handicap stones. Is
> this correct? Is it common knowledge?
via:
http://www.usgo.org/resources/internet.html
"4) Handicaps: [ ... ]
If the players have agreed to use area counting to score
the game (Rule 12), White receives an additional point of
compensation for each Black handicap stone after the first."
[ ... ]
"12) Counting. There are two methods for counting the
score at the end of the game. One is based on terriroty, the
other on area. Although players' scores may differ under the
two methods, the difference in their scores, and the game
result, will be the same."
( AGA Concise Rules of Go, April 1, 1991 )
http://www.usgo.org/resources/downloads/conciserules.pdf
One might think there seems to be a contradiction. The AGA
Rules state that game result will be the same under either method,
and yet you report someone's insistence upon selecting an
optional rule which would threaten to alter the game result. This
may be resolved by the characterization of player agreement.
If players have not agreed to compensate White for Black's
handicap stones by means of Area Counting then agreements
cannot be in effect. They must revert to Territory Counting.
The "complete rules" states a similar procedure:
http://www.usgo.org/resources/downloads/completerules.pdf
Here is an argument that payback for handicap stones
makes no difference:
http://www-2.cs.cmu.edu/~wjh/go/rules/AGA.commentary.html
------------------------------ begin insert --------
"Finally, in a handicap game, the additional points of compensation
paid by Black to White can be thought of as "reverse pass stones"
ensuring that both players have, in effect, still played exactly the
same number of stones.
If we assume that the two players have played the same number
of stones, with no neutral points left on the board, and that the
score in equation [1] is equal to k, we have:
(Ab + Tb) - (Aw + Tw) = k
But
(Ab + Tb) + (Aw + Tw) = 361 [2]
So k must be odd!
This implies that if such a game is even on the board by
traditional territorial counting (without pass stones), Black must
have made the last move! At one time, the Chinese rules compensated
White with an extra point when Black got the last move. If Black's
last move was to fill a ko he or she had won, however, it was
deemed unfair to penalize him or her, so eventually the Chinese
removed this proviso. Requiring that White always have the last move
and using pass stones removes the possibility of a "pass fight" over
who gets the very last move.
If there are neutral points on the board at the end of the game
(presumably in seki, since the players would naturally fill all
dame under the area system), the same argument still shows that
the two systems give the same result if the players have played the
same number of stones, but the parity of k will depend on the number
of neutral points; if there are an odd number of neutral points, k
will be even, and vice versa. This may explain why some rule
systems go to great lengths to award all points in seki.
Finally, note that in the confirmation phase, by our rules, the
final result remains the same (that is, the "same" as would be
calculated before playing out the confirmation phase if the status
of all groups were taken to be whatever it proves to be through
the confirmation process!) Since the game is over, we can assume
that all empty points belong to the territory of one or the other
of the players. Under area counting, stones of either color played
into one's own territory or into the opponent's territory will not
change the score--nor will the "pass" stones. Under territorial
counting, every stone played into one's own or the opponent's
territory will cost a point--but by requiring that the players make
the same number of moves, and by insuring that even passes
cost a point (the "pass" stones), we insure that the end result
is still the same.
[ ... ]
Scoring the Game: The rules allows the use of either "area" or
"territory" counting, by prior agreement. The use of pass stones
and the requirement that the two players each make the same
number of moves insures that the two methods will give the same
result in all even games. The requirement that Black compensate
White for any handicap stones given insures the same result in
handicap games as well. (This could equally well have been
achieved by treating White's first n-1 moves in an n-stone handicap
game as passes, requiring White to pass Black n-1 pass stones.
The results would then be the same, but the value of a handicap
stone would then change from what we are used to; New Zealand
effectively uses this system (they only count by area), but most
other Chinese-style (area counting) rules seem to compensate
White as we do.)
-------------------------------- end insert --------
This last paragraph in the "rules explanation" incorrectly suggests
that prior agreement is necessary for the choice of either method
of counting. Clearly the AGA Rules stipulate that prior agreement
is necessary only when asking for Area Counting.
- regards
- jb
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