By the time you read this, the results of ...
By Rob Van Zeijst
By the time you read this, the results of the 28th World Amateur Go Championship will be in. At the time I write this, Japan, China, South Korea and Taiwan are leading the field with four wins each after four rounds. Amazingly, the player from China is 13 years old, but what is even more amazing is that the player from Hong Kong is 14 but already has two championships under his belt, which means he participated for the first time when he was only 12.
Last year, we saw a Japanese winner when Satoshi Hiraoka made a comeback after losing in the fourth round. In the first few years of this yearly championship, the Chinese did not have an official professional system and just selected their strongest player. This explains why of the first seven tournaments, six were won by the Chinese.
Only on one occasion, in 1986, was the winner not from mainland China, South Korea or Japan. That eighth championship was won by Ka Yui Chan from Hong Kong. You can find more information and results at: www.nihonkiin.or.jp/amakisen/worldama/28/.
Diagram 1: It is a misconception to think that a certain given board position has only one answer. Especially in the beginning of the game, there is room for many different "correct" moves. The main differences in style are playing for profit and playing for influence, the realists versus the dreamers. Last week, we started a game by O Meien, born in Taiwan but among the strongest players in Japan where he has lived since the age of 14. He exemplifies the dreamers, but when it comes to fighting he is anything but dreamy. He plays the black stones while Mimura Tomoyasu plays the white.
Black 1 was last week's final move. Black cuts off White's center group up to 11 while turning the left side into territory. However, White counterattacks with 8, 12, 14 and 16. This starts a ko that Black wins with 17, 19 and 21. In the meantime, White captures the two marked stones with 18 and 20. However, Black is leading because of his huge territory on the lower left. In addition, White's stones in the top right are in danger.
Diagram 2: In this diagram, Black pulls the rabbit out of his hat when he sacrifices all of his marked stones in the center, while making moves on the outside. If you look at White's moves in this diagram, they only accomplish the capture of Black's center stones. This is large, but White only caught an additional five stones, worth less than 20 points in real terms. On the other hand, Black's stones are all on the outside to make territory on the right, worth at least 10 points, and surround the territory around the lower edge, which has a value of at least 20 points. A more important issue might be that Black has no weak stones anymore because he sacrificed them. Because of this, Black is clearly leading, but White plays on for some hundred moves before resigning.
Ko
In this game, a situation appears that we have not discussed yet, namely "ko."
Diagram 3: The marked white stone is in atari--it has one liberty and is in danger of being captured. Because the marked stone is where the ko arises, this stone is sometimes referred to as a "hot" stone.
Diagram 4: Black can now capture White's marked stone by playing at 1.
Diagram 5: This is the new situation. As you can see, the marked black stone is in atari now. So can't White just capture this marked stone on his next turn? No, he cannot, because the ko rule prohibits this. The ko rule states that a board position cannot be repeated.
Diagram 6: So after Black played the marked stone, White must play somewhere else before he can recapture the marked stone. For example, if White plays at 2, he threatens to kill Black's group. Should Black answer with 3 to keep his group alive, the board situation has changed. Since that is the case, now White can capture Black's marked stone. Incidentally, white 2, which was played as a threat that needs to be answered in order to recapture the ko, is called a ko threat. After white 4, it is Black's turn to think about where to play a ko threat.
Solutions to last week's problems
Solution 1:
Case A: Black 1 is the vital point. White 2 is the other vital point, but black 3 kills White's group. Because of a lack of liberties, White cannot play at A. Compare with case C.
Case B: Black 1 is correct. White's best response is 2, which starts a ko for the life of his group.
Case C: Compare with case A. Because of the extra liberty at B, Black's best move is 1, the other vital point. This time, White can force a ko with 2 and 4. Black takes the ko first with 5. If he wins the ko and connects at 4, White can capture, which leads to a situation similar to Case B.
Case D: Black 1 and 3 are the vital points. After white 4, the situation is a bit complicated. According to the Japanese rules, this shape is dead. However, the Chinese rules offer a different view. We will discuss this next week.
New problem
Problem 1: In each case, A through D, Black can make a ko. How should he play in each case?
Van Zeijst is a four-time European go champion and European representative at the Fujitsu World Championship.