Important decisions are often ...

By Rob Van Zeijst

Important decisions are often made on the basis of personal feelings, with objectivity thrown by the wayside.To determine the better of two options, some books recommend a system where the pros and cons are given a certain number of points depending on their "value" and the option with the most points wins. Others suggest listing the pros and cons irrespective of the weight of each individual item and making a decision on the list containing more items. In go, a system called tewari allows players to analyze basic structures by changing the order of moves and removing superfluous stones.

On Dec. 23, we started a game between O Meien (White) and Satoru Kobayashi for the NEC Cup, a tournament that permits only 30 seconds per move--although players are allowed to take one minute for 10 of the moves. The time may be short but the speed required makes the games exciting and the first prize of \15 million is a good incentive.

Diagram 1 (1-34 represent moves 75-108): Black 1 kills the marked white stone and prepares for an interesting invasion technique of 11 through 19. After this combination, Black can still aim at starting a ko with A, so White's territory at the top is not as extensive as it seems after white 22. Black 5 aims at ensuring life on the left side by using the aji (potential) of his marked stone in combination with 23 through 29. If this group survives without problems, Black is ahead (see Reference 1). However, White strikes with 30, 32 and 34, completely confusing the issue. This was White's intention all along when he played at 20 and 22. In retrospect, after 10 Black should have played around A.

Reference 1: After black 1, if White blocks with 2, the sequence through 10 is almost forced, allowing Black to comfortably live up to 13. After 14, White can switch elsewhere.

Diagram 2 (35-59 represent moves 109-133): Black 35 and 37 are forced and White goes for broke with 42 through 46, cutting off Black's marked stones. After 47, Black's only way out seems to be the ko at A, followed by white B and black 56. However, White could win it with C and D, and follow with a good move at E. Therefore, there would be no point in playing a ko at this time. However, Black finds another way with 51, 53 and 55, preparing huge ko threats in the process at C (white D), E (white F) and G (with more complications). White solves the ko with 56 and Black ensures life with 57 and 59. The game is very close at this point, but Black eventually wins it by 1.5 points.

Tewari

Diagram 3: Most players stronger than 5 kyu are familiar with this joseki. However, instead of obliging with 5, Black has the option of playing elsewhere.

Diagram 4: Black, for example, could play a local move at 5. But what if White played at 6 to take the corner?

Diagram 5: If White had a stone on the 3-3 point, most 5 kyu players would recognize this joseki. Isn't White's position a little low? Actually, the positions are even.

Diagram 6: How do you feel about this 1-2 exchange? This looks rather passive for White and Black is happy with the exchange. Now compare this with Diagram 4 and you'll see that the result is the same but the order of moves is different.

Diagram 7: Because White did not answer at C in Diagram 6, Black 1 becomes a good move. This move can be followed by the sequence black A, white B, black C and white D, putting White in an even lower position. Now what do you think about Diagram 4?

Solution to previous problems

You were asked two weeks ago which was better: Solution 1A or 1B.

Counting the number of stones in Solution 1A, Black used 11 stones (including a stone captured at A) against White's 10. In Solution 1B, White really needs to play at B, so Black used 12 stones (including the captured stone) against White's 12. Therefore, Solution 1A is better as White saves one move, usually worth more than 10 points at this point.

A more important problem in Solution 1B is that the ladder at B must work for White. But as it is Black's turn he can play a ladder breaker somewhere--not a pleasant situation for White.

Solution 2: If White plays a move around 1 or A, the exchange of the marked stones becomes bad for Black, because his stone would die, while White's stone expands his territory.

New problem

Problem 1: Something is wrong in this sequence even if it looks natural. Use tewari to establish what the problem is. A joseki dictionary or research on the Internet may help.

Van Zeijst is a four-time European go champion and European representative at the Fujitsu World Championship.