Tewari analysis.

[snorri]

Is there a method to evaluate a tewari analysis that you have performed? That is, it seems possible to do it the wrong way. I like Shaddy's suggestion regarding playing "normal" moves for one side. Are there any other ways to ensure that your tewari analysis is correct?

IMHO, even allegedly good tewari reorderings leave a lot to experience or imagination in terms of judgment. They are rarely as clean as "one side plays all reasonable moves and the other plays some obvious junk." As John Fairbairn mentions, it's often used to compare a new sequence to one that is already presumed to be even by other methods. So you already have to have some kind of reference point, such as trusting that a joseki really is a joseki. However, old josekis are falling out of favor all the time, so it's hard to be certain of even the reference point.

$$B Old Joseki
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 4 . . . . . . . . . . . . . . . |
$$ | . . 5 . . 2 . . 6 . . . . . . . . . . |
$$ | . . . 1 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |

Click Here To Show Diagram Code

[go]$$B Old Joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 4 . . . . . . . . . . . . . . . |
$$ | . . 5 . . 2 . . 6 . . . . . . . . . . |
$$ | . . . 1 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]

$$B New joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 4 . . . . . . . . . . . . . . . |
$$ | . . 6 . . 2 . . . . . . . . . . . . . |
$$ | . . . 1 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 7 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |

Click Here To Show Diagram Code

[go]$$B New joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 4 . . . . . . . . . . . . . . . |
$$ | . . 6 . . 2 . . . . . . . . . . . . . |
$$ | . . . 1 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 7 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]

elsewhere

$$W Tewari of new joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 7 . . . . . . . . . . . . . . . |
$$ | . . 1 a . 3 . . . . . . . . . . . . . |
$$ | . . . 6 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 2 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 4 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |

Click Here To Show Diagram Code

[go]$$W Tewari of new joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 7 . . . . . . . . . . . . . . . |
$$ | . . 1 a . 3 . . . . . . . . . . . . . |
$$ | . . . 6 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 2 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 4 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]

So here, the claim is that the tewari of the new joseki shows to being a joseki and therefore reasonable for both side, but that somehow in reponse to , is played as a diagonal rather than at 'a' which would clearly be better. This has been given as one of the reasons that black doesn't respond at the 3-3 point in the original variation as much as in the past. Of course, even though is bad, I sort of wonder about as well, so I don't find this analysis terribly convincing. But I guess some pros do, and so we are back to trusting pros.

I personally would like to hope that tewari can help me figure out for myself whether a move is good or bad or whether a result is good or bad. But actually in the end I wind up asking stronger players anyway. I think to use tewari effectively, you often have to already have an accurate sense of how much worse bad move X is than bad move Y, but that seems to be pretty hard even for fairly strong players.

I saw a lecture by Janice Kim 3p not to long ago and she was asked to judge who was ahead in a certain opening. She said it was hard to tell because both players had their stones in the wrong places!

It reminds me of a joke:

What's the difference between a Japanese joseki and a Korean joseki?

A. In a Japanese joseki, white and black get equally good results. In a Korean joseki, black and white get equally bad results.

[mitsun]

Of course, even though is bad, I sort of wonder about as well, so I don't find this analysis terribly convincing.

Yes, this is precisely the problem with most tewari analysis. It is faulty reasoning to say "In answer to , would be a mistake, so W is better here", because there is no guarantee that is a good move. The question needs to be more convoluted: "If W promised to play , and B agreed to reply with the (non-optimal) , who would come out ahead?"

[RobertJasiek]

to use tewari effectively, you often have to already have an accurate sense of how much worse bad move X is than bad move Y

Not that often. E.g., identifying superfluous inside stones is straightforward and counting their difference of numbers possible also for kyu players.

[daal]

$$B New joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 4 . . . . . . . . . . . . . . . |
$$ | . . 6 . . 2 . . . . . . . . . . . . . |
$$ | . . . 1 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 7 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |

Click Here To Show Diagram Code

[go]$$B New joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 4 . . . . . . . . . . . . . . . |
$$ | . . 6 . . 2 . . . . . . . . . . . . . |
$$ | . . . 1 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 3 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 7 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]

elsewhere

$$W Tewari of new joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 7 . . . . . . . . . . . . . . . |
$$ | . . 1 a . 3 . . . . . . . . . . . . . |
$$ | . . . 6 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 2 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 4 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |

Click Here To Show Diagram Code

[go]$$W Tewari of new joseki
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 7 . . . . . . . . . . . . . . . |
$$ | . . 1 a . 3 . . . . . . . . . . . . . |
$$ | . . . 6 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 2 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 4 . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |[/go]

In the "new" joseki, black tenukis at , and in the tewari analysis, it is white who has gotten in a play elsewhere at . Does this not play a role in the evaluation (i.e., serve as justification that the suboptimal is not at a)?