Tedomari Exercise 1


Source of diagrams: Guo Juan, Teaching Go at different Levels, Nov. 2002, (advice for 1-2dan)
The game is Lee Changho (white) vs Cho Hun-hyun in the 34rd Kuksu final, GoGoD 1990-09-07a.

Black to play  

How to play so as to take the last big point

Black loses sente  

Wrong: Black attacks and takes an extension (too wide anyway),
but White gets sente for the last fuseki moves.

Black takes the last Fuseki points  

Correct: Here it is Black who takes the last Fuseki points.
Afterwards e.g. White a and checking-extension black b could end in a normal Gote sequence for White.

Afterwards (!) circle=black+circle is the move which Black wanted to get and now will get.

The professional advice by Guo Juan is colored by the following analysis using Leela Zero

Leela's sequence  

Black makes shape in the centre and then takes a big point with B9.

The "good move"  

The above recommended move leads to this diagram, which loses 10% with respect to LZ's sequence.

The "bad" move  

The above advised against move B1 elicits the defence of W2, which affects Black's weak group as well, and loses 11% with respect to LZ's preference.

As has been commented by the go community, professional advice is still instructive, even if seemingly refuted by bot analysis. So, while these diagrams paint a different picture, the spirit of the example may still apply.

xela: Note that the details of the analysis will vary with the software and hardware used. I'm unable to replicate the exact results above. I get the same ordering of move values, but not the "big" winrate drops of 10 or more percentage points.

Black to play  

Using Leela Zero network number 242, indeed b is the preferred move, with a winrate of 63.9% when I try it. But a is only a 6.5% drop, whereas c is a 9.3% drop, noticeably if not significantly worse. And all three options still leave black with a winrate above 50%.

On an older LZ network, number 157, there's less difference: b is still preferred on 60.0%, a is 2.7% worse, c is 4.8% worse (compared to b), and in fact d now emerges as a second choice move, nearly as good as a (but with fewer playouts, so more uncertainty on the evaluation).

KataGo (20-block network g104-b20c256-s447913472-d241840887) gives b as 69.0% with black 8.2 points up, d again as practically the same (fewer playouts), a as worse by 4.2% or 2 points, and c as worse by 5.8% or 2.3 points.

In all three cases the message is the same even if the details differ a little: the "correct" move isn't best according to the bots (although still good enough to win), and they throw out another option that wasn't mentioned in the human analysis.

Tedomari Exercise 1 last edited by xela on January 1, 2020 - 09:10
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