Lesson 100: Difference in Counting Rules (2)
By Nam Chi-hyung
As we’ve seen in the last lesson, the main difference between the two existing counting rules_Area Counting and Territory Counting,_is what is counted. While the latter takes into account the number of captured stones, the former considers the stones left on the board instead. Since the number of stones on the board is the number of moves each player played minus the number of captured stones, the results taken through these two counting rules are usually the same.
However, in certain situations, the application of the two rules can result in a big difference. Let’s start with some notable features of Area Counting.
• First, in Area Counting, a player returns his prisoners to the opponent because they are not counted.
• Second, there is no neutral point as in Territory Counting because it is a two-point-difference whether a black stone is on a certain intersection or a white stone is.
• Third, it is not a loss at all that a player adds his stones inside his already-built territory, because both the empty intersections and the stones on the board are treated in the same way.
• Fourth, the intersections inside a dual-life situation are also counted. These characteristics, which are closely related each other, produce several situations considered differently under Area Counting and Territory Counting.
Diagram 1
The white and the black groups on the upper side are in a dual-life situation. As you already know, in Territory Counting, the stones and intersections belonging to a dual-life are not taken into account, while in Area Counting, they are treated as the same as the other stones and intersections on the board. Usually this doesn’t make any serious difference, because normally the groups of both sides in a dual-life share only two intersections, and they are divided equally for both players.
However, here, Black can leave the three x-marked points untouched until all the other meaningful moves played out, and then get three more points than White by playing the x’s while White can only play inside his own territory.
Diagram 2
Bent four in the corner is the example presented most often for showing the difference between the two counting rules. Here, the black group in the upper left corner is a bent four. Bent four in the corner is considered dead under the Korean and Japanese rule, which uses Territory Counting. This is because of the rule ‘when only one player can start a ko and the other can do nothing but kill himself, the group of the latter is considered to be dead without further play.’
On the contrary, under Area Counting, the player who can start a ko in the situation can actually do so after erasing all the possible ko threats of the opponent, since the ko-threat-erasing-move played inside his own territory will cost him nothing. That is, in this situation, assuming there is no dual-life in the upper right corner, White can play A first to erase a ko threat of Black, and start a ko in the corner. This result would be exactly the same as the one under Territory Counting. But, in this case, because of the dual-life, there is a ko threat which White cannot remove beforehand, namely B.
Therefore, if White plays A and then starts a ko, Black will play B as a ko threat, and White has to give up the three stones in the right corner to win the ko, which would make a serious difference in the result of the game.
The writer is a Baduk professor at Myongji University and a professional player of the game.