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Tewari

 

Tewari Example 1
    Keywords: MiddleGame, Tactics, Strategy

Bill Spight: Here is an example from my recent play:

[Diagram]
Not joseki

In two games of mine all players were strong amateurs (U. S. 5-dan plus). In both games the play went the same through B10. White has deviated from joseki. Let's do a tewari analysis after W9.


[Diagram]
Pairing stones

The WS stone was played in response to a black stone at the marked point. Let's eliminate that stone (the black stone is already gone).
Now let's do the hypothetical replay.


[Diagram]
Replay

B6 at a would be joseki, but W7 is clearly bad. Taking the ko, or a, or even b would be better.



Very interesting. I've always wanted to discuss tewari: it is one of the relatively few concepts that approach our western flavour of analysis.

[Diagram]
Replay 2

Now, after the criticized move at W7, Black exchanges B8 for W9 (the "superfluous stones" that were removed). Isn't this a favourable exchange for White? In other words, how unfair have we been to White in criticizing her move, by removing two stones that perhaps weren't that equally superfluous. Or yet in other words, what are the opportunities Black lost with B8 for W9 in Replay 2, with respect to the opportunities White lost by playing W7 in both "replay" diagrams ?

--Dieter

Well, both B8 and W9 are poor moves at this point, but B8 does seem to be worse than W9. Tewari is not exact. You cannot always say that two plays are exactly equal, but often they are nearly so, and that is the case here. Under certain circumstances, depending on ko threats, W9 offers a little extra protection. But if we consider the corner to be White's territory, the difference between B8 and W9 is negligible.

If W9 were worth substantially more than B8, it would be because of the flaw at the marked point. But if White needed to protect that flaw, then W7 would not just be bad, it would be terrible! ;-)

Without tewari, we might think that White's play was OK. It solidified the corner and left Black without a clearly live group. But tewari shows us that, even given that B6 is somewhat doubtful and the pairing of the stones slightly favors Black, White has lost at least half a move.

-- Bill

I don't agree with your argument. In particular But if White needed to protect that flaw, then W7 would not be just bad, it would be terrible! ;-) - there's nothing bad about having to protect that flaw, given that it is going to be protected anyway. Andre Engels

Bill: Since the flaw is going to be protected anyway, the exchange of B8 and W9 is almost equal.



This is a copy of the living page "Tewari Example 1" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.